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トップJavaに関する質問java.lang.NullPointerException　Android studio

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回答編集履歴

17

コード修正

2024/01/25 10:21

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -44,7 +44,7 @@
44
44
 
45
45
  if(savedInstanceState == null) {
46
46
  getSupportFragmentManager().beginTransaction()
47
- .add(R.id.fragment_container, new MonthFragment())
47
+ .replace(R.id.fragment_container, new MonthFragment())
48
48
  .commit();
49
49
  }
50
50
  }

16

MainActivity関係追加(アプリを実行したまま言語を切り替えた際のバグのため)

2024/01/25 06:53

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -28,9 +28,38 @@
28
28
 
29
29
  ---
30
30
  アダプタが分かりませんが想像で追加、フラグメントで完結するようにしました。
31
- アクティビティは onCreate でフラグメントを配置するだけなので省略です。
32
31
  Calendar は扱い難いので LocalDate/YearMonth に変更、年月の表示は Adapter の更新を受ける形とし、年月の国際化対応(?)、曜日名表示の追加、今日の日は描画時に背景色を変えています。
33
32
 
33
+ MainActivity.java
34
+ ```java
35
+ import android.os.Bundle;
36
+
37
+ import androidx.appcompat.app.AppCompatActivity;
38
+
39
+ public class MainActivity extends AppCompatActivity {
40
+ @Override
41
+ protected void onCreate(Bundle savedInstanceState) {
42
+ super.onCreate(savedInstanceState);
43
+ setContentView(R.layout.activity_main);
44
+
45
+ if(savedInstanceState == null) {
46
+ getSupportFragmentManager().beginTransaction()
47
+ .add(R.id.fragment_container, new MonthFragment())
48
+ .commit();
49
+ }
50
+ }
51
+ }
52
+ ```
53
+ res/layout/activity_main.xml
54
+ ```xml
55
+ <?xml version="1.0" encoding="utf-8"?>
56
+ <androidx.fragment.app.FragmentContainerView xmlns:android="http://schemas.android.com/apk/res/android"
57
+ xmlns:tools="http://schemas.android.com/tools"
58
+ android:id="@+id/fragment_container"
59
+ android:layout_width="match_parent"
60
+ android:layout_height="match_parent"
61
+ tools:context=".MainActivity" />
62
+ ```
34
63
  MonthFragment.java
35
64
  ```java
36
65
  import android.graphics.Color;

15

インデント修正

2024/01/24 20:10

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -142,16 +142,16 @@
142
142
  }
143
143
  private int getTextColor(LocalDate date) {
144
144
  return date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
145
- getTextColor(date.getDayOfWeek());
145
+ getTextColor(date.getDayOfWeek());
146
146
  }
147
147
  private int getTextColor(DayOfWeek dayOfWeek) {
148
- return dayOfWeek == DayOfWeek.SUNDAY ? Color.RED : //日曜
148
+ return dayOfWeek == DayOfWeek.SUNDAY ? Color.RED : //日曜
149
- dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
149
+ dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
150
- Color.BLACK;
150
+ Color.BLACK;
151
151
  }
152
152
  private int getBackgroundColor(LocalDate date) {
153
153
  return date.isEqual(LocalDate.now()) ? Color.CYAN : //今日
154
- Color.TRANSPARENT;
154
+ Color.TRANSPARENT;
155
155
  }
156
156
  }
157
157
  }

14

バグ修正・変数名変更

2024/01/24 19:55

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -50,7 +50,7 @@
50
50
  import java.util.function.Consumer;
51
51
 
52
52
  public class MonthFragment extends Fragment {
53
- MonthFragment() {
53
+ public MonthFragment() {
54
54
  super(R.layout.month_fragment);
55
55
  }
56
56
 
@@ -76,7 +76,7 @@
76
76
  }
77
77
 
78
78
  private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
79
- private static final DayOfWeek WEEK_FIRST = WeekFields.of(Locale.getDefault()).getFirstDayOfWeek(); //週の始まり
79
+ private final DayOfWeek firstDayOfWeek = WeekFields.of(Locale.getDefault()).getFirstDayOfWeek(); //週の始まり
80
80
 
81
81
  private final Consumer<YearMonth> dateChangeListener;
82
82
 
@@ -99,7 +99,7 @@
99
99
 
100
100
  private void setYearMonth(YearMonth yearMonth) {
101
101
  this.current = yearMonth;
102
- start = current.atDay(1).with(TemporalAdjusters.previousOrSame(WEEK_FIRST)); //月初直前の週始め
102
+ start = current.atDay(1).with(TemporalAdjusters.previousOrSame(firstDayOfWeek)); //月初直前の週始め
103
103
  notifyItemRangeChanged(7, 6*7); //日付部分
104
104
  if(dateChangeListener != null) dateChangeListener.accept(current);
105
105
  }
@@ -129,7 +129,7 @@
129
129
  }
130
130
  void bind(int position) {
131
131
  if(position < 7) { //曜日名
132
- DayOfWeek dow = WEEK_FIRST.plus(position);
132
+ DayOfWeek dow = firstDayOfWeek.plus(position);
133
133
  day.setTextColor(getTextColor(dow));
134
134
  day.setBackgroundColor(HEADER_BGCOLOR);
135
135
  day.setText(dow.getDisplayName(TextStyle.SHORT_STANDALONE, Locale.getDefault()));

13

修正

2024/01/24 19:39

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -1,5 +1,3 @@
1
- まだコードを見ただけで試していませんが。
2
-
3
1
  MainActivity.java(一部)
4
2
  ```java
5
3
  MonthFragment monthFragment = new MonthFragment();
@@ -47,7 +45,7 @@
47
45
 
48
46
  import java.time.*;
49
47
  import java.time.format.TextStyle;
50
- import java.time.temporal.ChronoField;
48
+ import java.time.temporal.*;
51
49
  import java.util.*;
52
50
  import java.util.function.Consumer;
53
51
 
@@ -78,7 +76,7 @@
78
76
  }
79
77
 
80
78
  private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
81
- private static final DayOfWeek WEEK_FIRST = DayOfWeek.SUNDAY; //週の始まり
79
+ private static final DayOfWeek WEEK_FIRST = WeekFields.of(Locale.getDefault()).getFirstDayOfWeek(); //週の始まり
82
80
 
83
81
  private final Consumer<YearMonth> dateChangeListener;
84
82
 
@@ -101,16 +99,9 @@
101
99
 
102
100
  private void setYearMonth(YearMonth yearMonth) {
103
101
  this.current = yearMonth;
104
- start = calcStart(current);
102
+ start = current.atDay(1).with(TemporalAdjusters.previousOrSame(WEEK_FIRST)); //月初直前の週始め
105
103
  notifyItemRangeChanged(7, 6*7); //日付部分
106
104
  if(dateChangeListener != null) dateChangeListener.accept(current);
107
- }
108
-
109
- //月初直前の週始め
110
- private LocalDate calcStart(YearMonth yearMonth) {
111
- LocalDate start = yearMonth.atDay(1);
112
- LocalDate temp = (LocalDate)WEEK_FIRST.adjustInto(start);
113
- return temp.isAfter(start) ? temp.minusDays(7) : temp;
114
105
  }
115
106
 
116
107
  @NonNull
@@ -151,16 +142,16 @@
151
142
  }
152
143
  private int getTextColor(LocalDate date) {
153
144
  return date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
154
- getTextColor(date.getDayOfWeek());
145
+ getTextColor(date.getDayOfWeek());
155
146
  }
156
147
  private int getTextColor(DayOfWeek dayOfWeek) {
157
148
  return dayOfWeek == DayOfWeek.SUNDAY ? Color.RED : //日曜
158
- dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
149
+ dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
159
- Color.BLACK;
150
+ Color.BLACK;
160
151
  }
161
152
  private int getBackgroundColor(LocalDate date) {
162
153
  return date.isEqual(LocalDate.now()) ? Color.CYAN : //今日
163
- Color.TRANSPARENT;
154
+ Color.TRANSPARENT;
164
155
  }
165
156
  }
166
157
  }

12

修正

2024/01/23 17:22

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -15,7 +15,7 @@
15
15
  }
16
16
  ```
17
17
  これでは、 plus を実行するフラグメントオブジェクトと画面に表示しているフラグメントオブジェクトは **違うモノ** です。
18
- **View は Activity に載せないと onCreateView や onViewCreated 等のライフサイクルメソッドは呼ばれません。** 従って this.activity も null のままですので、 plus() メソッドから処理を続けて activity.findViewById() で activity が null で例外になっています。
18
+ **View は Activity に載せないと onCreateView や onViewCreated 等のライフサイクルメソッドは呼ばれません。** 従って this.activity も null のままですので、 viewCalendar() 内の activity.findViewById() で例外になっています。
19
19
  ```
20
20
  .add(R.id.month_fragment_container, monthFragment)
21
21
  ```

11

修正

2024/01/23 17:20

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -15,6 +15,7 @@
15
15
  }
16
16
  ```
17
17
  これでは、 plus を実行するフラグメントオブジェクトと画面に表示しているフラグメントオブジェクトは **違うモノ** です。
18
+ **View は Activity に載せないと onCreateView や onViewCreated 等のライフサイクルメソッドは呼ばれません。** 従って this.activity も null のままですので、 plus() メソッドから処理を続けて activity.findViewById() で activity が null で例外になっています。
18
19
  ```
19
20
  .add(R.id.month_fragment_container, monthFragment)
20
21
  ```
@@ -34,7 +35,6 @@
34
35
 
35
36
  MonthFragment.java
36
37
  ```java
37
- import android.annotation.SuppressLint;
38
38
  import android.graphics.Color;
39
39
  import android.os.Bundle;
40
40
  import android.text.format.DateUtils;

10

コード修正

2024/01/23 17:07

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -99,11 +99,10 @@
99
99
  setYearMonth(current.minusMonths(1));
100
100
  }
101
101
 
102
- @SuppressLint("NotifyDataSetChanged")
103
102
  private void setYearMonth(YearMonth yearMonth) {
104
103
  this.current = yearMonth;
105
104
  start = calcStart(current);
106
- notifyDataSetChanged();
105
+ notifyItemRangeChanged(7, 6*7); //日付部分
107
106
  if(dateChangeListener != null) dateChangeListener.accept(current);
108
107
  }
109
108
 
@@ -127,7 +126,7 @@
127
126
 
128
127
  @Override
129
128
  public int getItemCount() {
130
- return 7 + 6 * 7;
129
+ return 7 + 6*7;
131
130
  }
132
131
 
133
132
  class ViewHolder extends RecyclerView.ViewHolder {

9

コード修正

2024/01/23 13:03

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -110,8 +110,8 @@
110
110
  //月初直前の週始め
111
111
  private LocalDate calcStart(YearMonth yearMonth) {
112
112
  LocalDate start = yearMonth.atDay(1);
113
- while(start.getDayOfWeek() != WEEK_FIRST) start = start.minusDays(1);
113
+ LocalDate temp = (LocalDate)WEEK_FIRST.adjustInto(start);
114
- return start;
114
+ return temp.isAfter(start) ? temp.minusDays(7) : temp;
115
115
  }
116
116
 
117
117
  @NonNull

8

コード修正

2024/01/23 11:23

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -83,7 +83,7 @@
83
83
  private final Consumer<YearMonth> dateChangeListener;
84
84
 
85
85
  private YearMonth current;
86
- private final List<LocalDate> list = new ArrayList<>();
86
+ private LocalDate start;
87
87
 
88
88
  Adapter(@NonNull Consumer<YearMonth> dateChangeListener) {
89
89
  this.dateChangeListener = dateChangeListener;
@@ -102,20 +102,16 @@
102
102
  @SuppressLint("NotifyDataSetChanged")
103
103
  private void setYearMonth(YearMonth yearMonth) {
104
104
  this.current = yearMonth;
105
- generateDayList(current);
105
+ start = calcStart(current);
106
106
  notifyDataSetChanged();
107
107
  if(dateChangeListener != null) dateChangeListener.accept(current);
108
108
  }
109
109
 
110
- private void generateDayList(YearMonth yearMonth) {
111
- //月初直前の週始め
110
+ //月初直前の週始め
111
+ private LocalDate calcStart(YearMonth yearMonth) {
112
112
  LocalDate start = yearMonth.atDay(1);
113
113
  while(start.getDayOfWeek() != WEEK_FIRST) start = start.minusDays(1);
114
-
115
- LocalDate endExclusive = start.plusDays(6 * 7); //六週間
116
- //start から endExclusive まで
117
- list.clear();
114
+ return start;
118
- for(LocalDate date=start; date.isBefore(endExclusive); date=date.plusDays(1)) list.add(date);
119
115
  }
120
116
 
121
117
  @NonNull
@@ -126,12 +122,12 @@
126
122
 
127
123
  @Override
128
124
  public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
129
- holder.bind(position, position < 7 ? null : list.get(position - 7));
125
+ holder.bind(position);
130
126
  }
131
127
 
132
128
  @Override
133
129
  public int getItemCount() {
134
- return list.size() + 7;
130
+ return 7 + 6 * 7;
135
131
  }
136
132
 
137
133
  class ViewHolder extends RecyclerView.ViewHolder {
@@ -141,13 +137,14 @@
141
137
  super(LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_day, parent, false));
142
138
  day = itemView.findViewById(R.id.day);
143
139
  }
144
- void bind(int position, LocalDate date) {
140
+ void bind(int position) {
145
141
  if(position < 7) { //曜日名
146
142
  DayOfWeek dow = WEEK_FIRST.plus(position);
147
143
  day.setTextColor(getTextColor(dow));
148
144
  day.setBackgroundColor(HEADER_BGCOLOR);
149
145
  day.setText(dow.getDisplayName(TextStyle.SHORT_STANDALONE, Locale.getDefault()));
150
146
  } else {
147
+ LocalDate date = start.plusDays(position - 7);
151
148
  day.setTextColor(getTextColor(date));
152
149
  day.setBackgroundColor(getBackgroundColor(date));
153
150
  day.setText(String.valueOf(date.getDayOfMonth()));

7

コード修正

2024/01/23 11:04

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -30,13 +30,14 @@
30
30
  ---
31
31
  アダプタが分かりませんが想像で追加、フラグメントで完結するようにしました。
32
32
  アクティビティは onCreate でフラグメントを配置するだけなので省略です。
33
- Calendar は扱い難いので LocalDate に変更、年月の表示は Adapter の更新を受ける形とし、今日の日は描画時に背景色を変えています。
33
+ Calendar は扱い難いので LocalDate/YearMonth に変更、年月の表示は Adapter の更新を受ける形とし、年月の国際化対応(?)、曜日名表示の追加、今日の日は描画時に背景色を変えています。
34
34
 
35
35
  MonthFragment.java
36
36
  ```java
37
37
  import android.annotation.SuppressLint;
38
38
  import android.graphics.Color;
39
39
  import android.os.Bundle;
40
+ import android.text.format.DateUtils;
40
41
  import android.view.*;
41
42
  import android.widget.*;
42
43
 
@@ -46,6 +47,7 @@
46
47
 
47
48
  import java.time.*;
48
49
  import java.time.format.TextStyle;
50
+ import java.time.temporal.ChronoField;
49
51
  import java.util.*;
50
52
  import java.util.function.Consumer;
51
53
 
@@ -56,12 +58,11 @@
56
58
 
57
59
  @Override
58
60
  public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
59
- TextView yearText = view.findViewById(R.id.year);
60
61
  TextView monthText = view.findViewById(R.id.month);
61
62
 
62
- Adapter adapter = new Adapter(date -> {
63
+ Adapter adapter = new Adapter(yearMonth -> {
63
- yearText.setText(String.format(Locale.getDefault(), "%d年", date.getYear()));
64
+ long millies = yearMonth.atDay(1).getLong(ChronoField.EPOCH_DAY) * 24 * 60 * 60 * 1000; //epoch[ms]
64
- monthText.setText(date.getMonth().getDisplayName(TextStyle.FULL, Locale.getDefault()));
65
+ monthText.setText(DateUtils.formatDateTime(requireContext(), millies, DateUtils.FORMAT_SHOW_YEAR | DateUtils.FORMAT_NO_MONTH_DAY));
65
66
  });
66
67
 
67
68
  Button prevButton = view.findViewById(R.id.prev);
@@ -72,58 +73,49 @@
72
73
 
73
74
  RecyclerView recyclerView = view.findViewById(R.id.recycler_view);
74
75
  recyclerView.setHasFixedSize(true);
75
- recyclerView.setLayoutManager(new GridLayoutManager(getContext(), 7));
76
+ recyclerView.setLayoutManager(new GridLayoutManager(requireContext(), 7));
76
77
  recyclerView.setAdapter(adapter);
77
78
  }
78
79
 
79
80
  private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
80
- private final DayOfWeek WEEK_FIRST = DayOfWeek.SUNDAY; //週の始まり
81
+ private static final DayOfWeek WEEK_FIRST = DayOfWeek.SUNDAY; //週の始まり
81
-
82
+
82
- private final Consumer<LocalDate> dateChangeListener;
83
+ private final Consumer<YearMonth> dateChangeListener;
83
-
84
+
84
- private LocalDate current;
85
+ private YearMonth current;
85
86
  private final List<LocalDate> list = new ArrayList<>();
86
87
 
87
- Adapter(@NonNull Consumer<LocalDate> dateChangeListener) {
88
+ Adapter(@NonNull Consumer<YearMonth> dateChangeListener) {
88
89
  this.dateChangeListener = dateChangeListener;
89
90
 
90
- setDate(LocalDate.now().withDayOfMonth(1));
91
+ setYearMonth(YearMonth.now());
91
92
  }
92
93
 
93
94
  void next() {
94
- setDate(current.plusMonths(1));
95
+ setYearMonth(current.plusMonths(1));
95
96
  }
96
97
 
97
98
  void prev() {
98
- setDate(current.minusMonths(1));
99
+ setYearMonth(current.minusMonths(1));
99
100
  }
100
101
 
101
102
  @SuppressLint("NotifyDataSetChanged")
102
- private void setDate(LocalDate date) {
103
+ private void setYearMonth(YearMonth yearMonth) {
103
- this.current = date;
104
+ this.current = yearMonth;
104
- generateDayList(current.getYear(), current.getMonthValue());
105
+ generateDayList(current);
105
106
  notifyDataSetChanged();
106
107
  if(dateChangeListener != null) dateChangeListener.accept(current);
107
108
  }
108
109
 
109
- private void generateDayList(int year, int month) {
110
+ private void generateDayList(YearMonth yearMonth) {
110
- LocalDate first = LocalDate.of(year, month, 1);
111
111
  //月初直前の週始め
112
- LocalDate start = first;
112
+ LocalDate start = yearMonth.atDay(1);
113
- while(start.getDayOfWeek() != WEEK_FIRST) {
113
+ while(start.getDayOfWeek() != WEEK_FIRST) start = start.minusDays(1);
114
- start = start.minusDays(1);
114
+
115
- }
116
- //月末直後の週始め
117
- LocalDate endExclusive = first.plusMonths(1);
118
- while(endExclusive.getDayOfWeek() != WEEK_FIRST) {
119
- endExclusive = endExclusive.plusDays(1);
120
- }
121
- endExclusive = endExclusive.plusDays(7); //+一週間
115
+ LocalDate endExclusive = start.plusDays(6 * 7); //六週間
122
116
  //start から endExclusive まで
123
117
  list.clear();
124
- for(LocalDate date=start; date.isBefore(endExclusive); date=date.plusDays(1)) {
118
+ for(LocalDate date=start; date.isBefore(endExclusive); date=date.plusDays(1)) list.add(date);
125
- list.add(date);
126
- }
127
119
  }
128
120
 
129
121
  @NonNull
@@ -134,28 +126,45 @@
134
126
 
135
127
  @Override
136
128
  public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
137
- holder.bind(list.get(position));
129
+ holder.bind(position, position < 7 ? null : list.get(position - 7));
138
130
  }
139
131
 
140
132
  @Override
141
133
  public int getItemCount() {
142
- return list.size();
134
+ return list.size() + 7;
143
135
  }
144
136
 
145
137
  class ViewHolder extends RecyclerView.ViewHolder {
138
+ private final int HEADER_BGCOLOR = Color.rgb(240,240,240);
146
139
  private final TextView day;
147
140
  ViewHolder(ViewGroup parent) {
148
141
  super(LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_day, parent, false));
149
142
  day = itemView.findViewById(R.id.day);
150
143
  }
151
- void bind(LocalDate date) {
144
+ void bind(int position, LocalDate date) {
152
- day.setTextColor(
153
- date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
154
- date.getDayOfWeek() == DayOfWeek.SUNDAY ? Color.RED : //日曜
155
- date.getDayOfWeek() == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
156
- Color.BLACK); //通常
145
+ if(position < 7) { //曜日名
146
+ DayOfWeek dow = WEEK_FIRST.plus(position);
147
+ day.setTextColor(getTextColor(dow));
148
+ day.setBackgroundColor(HEADER_BGCOLOR);
149
+ day.setText(dow.getDisplayName(TextStyle.SHORT_STANDALONE, Locale.getDefault()));
150
+ } else {
151
+ day.setTextColor(getTextColor(date));
157
- day.setBackgroundColor(date.isEqual(LocalDate.now()) ? Color.CYAN : Color.TRANSPARENT); //今日
152
+ day.setBackgroundColor(getBackgroundColor(date));
158
- day.setText(String.valueOf(date.getDayOfMonth()));
153
+ day.setText(String.valueOf(date.getDayOfMonth()));
154
+ }
155
+ }
156
+ private int getTextColor(LocalDate date) {
157
+ return date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
158
+ getTextColor(date.getDayOfWeek());
159
+ }
160
+ private int getTextColor(DayOfWeek dayOfWeek) {
161
+ return dayOfWeek == DayOfWeek.SUNDAY ? Color.RED : //日曜
162
+ dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
163
+ Color.BLACK;
164
+ }
165
+ private int getBackgroundColor(LocalDate date) {
166
+ return date.isEqual(LocalDate.now()) ? Color.CYAN : //今日
167
+ Color.TRANSPARENT;
159
168
  }
160
169
  }
161
170
  }
@@ -164,28 +173,10 @@
164
173
  res/layout/month_fragment.xml
165
174
  ```xml
166
175
  <?xml version="1.0" encoding="utf-8"?>
167
- <androidx.constraintlayout.widget.ConstraintLayout
168
- xmlns:android="http://schemas.android.com/apk/res/android"
176
+ <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
169
177
  xmlns:app="http://schemas.android.com/apk/res-auto"
170
178
  android:layout_width="match_parent"
171
179
  android:layout_height="match_parent">
172
-
173
- <TextView
174
- android:id="@+id/year"
175
- android:layout_width="wrap_content"
176
- android:layout_height="wrap_content"
177
- android:text="year"
178
- app:layout_constraintEnd_toEndOf="parent"
179
- app:layout_constraintStart_toStartOf="parent"
180
- app:layout_constraintTop_toTopOf="parent" />
181
-
182
- <Space
183
- android:id="@+id/year_bottom"
184
- android:layout_width="0dp"
185
- android:layout_height="32dp"
186
- app:layout_constraintEnd_toEndOf="parent"
187
- app:layout_constraintStart_toStartOf="parent"
188
- app:layout_constraintTop_toBottomOf="@id/year" />
189
180
 
190
181
  <Button
191
182
  android:id="@+id/prev"
@@ -196,21 +187,20 @@
196
187
  android:text="prev"
197
188
  android:textColor="@color/black"
198
189
  android:textSize="24sp"
199
- app:layout_constraintBottom_toTopOf="@id/header_bottom"
200
- app:layout_constraintEnd_toStartOf="@id/month"
190
+ app:layout_constraintBaseline_toBaselineOf="@id/month"
201
- app:layout_constraintTop_toBottomOf="@id/year_bottom" />
191
+ app:layout_constraintStart_toStartOf="parent" />
202
192
 
203
193
  <TextView
204
194
  android:id="@+id/month"
205
- android:layout_width="100dp"
195
+ android:layout_width="0dp"
206
- android:layout_height="wrap_content"
196
+ android:layout_height="wrap_content"
197
+ android:layout_marginTop="32dp"
207
198
  android:text="month"
199
+ android:textAlignment="center"
208
200
  android:textSize="24sp"
209
- android:textAlignment="center"
210
- app:layout_constraintBottom_toTopOf="@id/header_bottom"
211
201
  app:layout_constraintEnd_toEndOf="parent"
212
202
  app:layout_constraintStart_toStartOf="parent"
213
- app:layout_constraintTop_toBottomOf="@id/year_bottom" />
203
+ app:layout_constraintTop_toTopOf="parent" />
214
204
 
215
205
  <Button
216
206
  android:id="@+id/next"
@@ -221,16 +211,8 @@
221
211
  android:text="next"
222
212
  android:textColor="@color/black"
223
213
  android:textSize="24sp"
224
- app:layout_constraintBottom_toTopOf="@id/header_bottom"
225
- app:layout_constraintStart_toEndOf="@id/month"
214
+ app:layout_constraintBaseline_toBaselineOf="@id/month"
226
- app:layout_constraintTop_toBottomOf="@id/year_bottom"/>
215
+ app:layout_constraintEnd_toEndOf="parent" />
227
-
228
- <androidx.constraintlayout.widget.Barrier
229
- android:id="@+id/header_bottom"
230
- android:layout_width="0dp"
231
- android:layout_height="0dp"
232
- app:barrierDirection="bottom"
233
- app:constraint_referenced_ids="prev, month, next" />
234
216
 
235
217
  <androidx.recyclerview.widget.RecyclerView
236
218
  android:id="@+id/recycler_view"
@@ -239,7 +221,7 @@
239
221
  app:layout_constraintBottom_toBottomOf="parent"
240
222
  app:layout_constraintEnd_toEndOf="parent"
241
223
  app:layout_constraintStart_toStartOf="parent"
242
- app:layout_constraintTop_toBottomOf="@id/header_bottom" />
224
+ app:layout_constraintTop_toBottomOf="@id/month" />
243
225
 
244
226
  </androidx.constraintlayout.widget.ConstraintLayout>
245
227
  ```
@@ -250,9 +232,12 @@
250
232
  android:id="@+id/day"
251
233
  android:layout_width="match_parent"
252
234
  android:layout_height="wrap_content"
235
+ android:autoSizeTextType="uniform"
236
+ android:ellipsize="end"
237
+ android:maxLines="1"
253
238
  android:text="21"
254
- android:textSize="30sp"
255
- android:textAlignment="center" />
239
+ android:textAlignment="center"
240
+ android:textSize="30sp" />
256
- ```
241
+ ```
257
- ![起動時(1月)スクリーンショット](https://ddjkaamml8q8x.cloudfront.net/questions/2024-01-23/70f2e1ae-47cf-4f77-8e7f-1214a9bf932e.png)
242
+ ![起動時(1月)スクリーンショット](https://ddjkaamml8q8x.cloudfront.net/questions/2024-01-23/01a37e83-2801-41aa-b9ce-7307f19fc88c.png)
258
- ![next押下時(2月)スクリーンショット](https://ddjkaamml8q8x.cloudfront.net/questions/2024-01-23/149202ea-11d4-4838-8109-eed338dd84e7.png)
243
+ ![next押下時(2月)スクリーンショット](https://ddjkaamml8q8x.cloudfront.net/questions/2024-01-23/fa1137d9-47fd-4e18-b79a-9b5e10ed53c4.png)

6

行数削減のためレイアウトを簡略化

2024/01/22 20:06

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -246,23 +246,13 @@
246
246
  res/layout/grid_day.xml
247
247
  ```xml
248
248
  <?xml version="1.0" encoding="utf-8"?>
249
- <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
249
+ <TextView xmlns:android="http://schemas.android.com/apk/res/android"
250
+ android:id="@+id/day"
250
251
  android:layout_width="match_parent"
251
252
  android:layout_height="wrap_content"
252
- xmlns:app="http://schemas.android.com/apk/res-auto">
253
-
254
- <TextView
255
- android:id="@+id/day"
256
- android:layout_width="0dp"
257
- android:layout_height="wrap_content"
258
- android:text="21"
253
+ android:text="21"
259
- android:textSize="30sp"
254
+ android:textSize="30sp"
260
- android:textAlignment="center"
255
+ android:textAlignment="center" />
261
- app:layout_constraintEnd_toEndOf="parent"
262
- app:layout_constraintStart_toStartOf="parent"
263
- app:layout_constraintTop_toTopOf="parent" />
264
-
265
- </androidx.constraintlayout.widget.ConstraintLayout>
266
256
  ```
267
257
  ![起動時(1月)スクリーンショット](https://ddjkaamml8q8x.cloudfront.net/questions/2024-01-23/70f2e1ae-47cf-4f77-8e7f-1214a9bf932e.png)
268
258
  ![next押下時(2月)スクリーンショット](https://ddjkaamml8q8x.cloudfront.net/questions/2024-01-23/149202ea-11d4-4838-8109-eed338dd84e7.png)

5

コードのワーニング等修正

2024/01/22 19:32

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -45,6 +45,7 @@
45
45
  import androidx.recyclerview.widget.*;
46
46
 
47
47
  import java.time.*;
48
+ import java.time.format.TextStyle;
48
49
  import java.util.*;
49
50
  import java.util.function.Consumer;
50
51
 
@@ -59,8 +60,8 @@
59
60
  TextView monthText = view.findViewById(R.id.month);
60
61
 
61
62
  Adapter adapter = new Adapter(date -> {
62
- yearText.setText(date.getYear() + "年");
63
+ yearText.setText(String.format(Locale.getDefault(), "%d年", date.getYear()));
63
- monthText.setText(date.getMonthValue() + "月");
64
+ monthText.setText(date.getMonth().getDisplayName(TextStyle.FULL, Locale.getDefault()));
64
65
  });
65
66
 
66
67
  Button prevButton = view.findViewById(R.id.prev);
@@ -76,11 +77,12 @@
76
77
  }
77
78
 
78
79
  private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
80
+ private final DayOfWeek WEEK_FIRST = DayOfWeek.SUNDAY; //週の始まり
81
+
79
- private Consumer<LocalDate> dateChangeListener;
82
+ private final Consumer<LocalDate> dateChangeListener;
80
-
81
- private DayOfWeek weekFirst = DayOfWeek.SUNDAY; //日曜日始まり
83
+
82
84
  private LocalDate current;
83
- private List<LocalDate> list = new ArrayList<>();
85
+ private final List<LocalDate> list = new ArrayList<>();
84
86
 
85
87
  Adapter(@NonNull Consumer<LocalDate> dateChangeListener) {
86
88
  this.dateChangeListener = dateChangeListener;
@@ -106,21 +108,21 @@
106
108
 
107
109
  private void generateDayList(int year, int month) {
108
110
  LocalDate first = LocalDate.of(year, month, 1);
109
- //月初の直前の週始め
111
+ //月初直前の週始め
110
112
  LocalDate start = first;
111
- while(start.getDayOfWeek() != weekFirst) {
113
+ while(start.getDayOfWeek() != WEEK_FIRST) {
112
114
  start = start.minusDays(1);
113
115
  }
114
- //最終日直後の週始め
116
+ //月末直後の週始め
115
117
  LocalDate endExclusive = first.plusMonths(1);
116
- while(endExclusive.getDayOfWeek() != weekFirst) {
118
+ while(endExclusive.getDayOfWeek() != WEEK_FIRST) {
117
119
  endExclusive = endExclusive.plusDays(1);
118
120
  }
119
121
  endExclusive = endExclusive.plusDays(7); //+一週間
120
122
  //start から endExclusive まで
121
123
  list.clear();
122
- for(LocalDate target=start; target.compareTo(endExclusive) < 0; target=target.plusDays(1)) {
124
+ for(LocalDate date=start; date.isBefore(endExclusive); date=date.plusDays(1)) {
123
- list.add(target);
125
+ list.add(date);
124
126
  }
125
127
  }
126
128
 
@@ -141,7 +143,7 @@
141
143
  }
142
144
 
143
145
  class ViewHolder extends RecyclerView.ViewHolder {
144
- private TextView day;
146
+ private final TextView day;
145
147
  ViewHolder(ViewGroup parent) {
146
148
  super(LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_day, parent, false));
147
149
  day = itemView.findViewById(R.id.day);
@@ -151,9 +153,9 @@
151
153
  date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
152
154
  date.getDayOfWeek() == DayOfWeek.SUNDAY ? Color.RED : //日曜
153
155
  date.getDayOfWeek() == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
154
- Color.BLACK); //通常
156
+ Color.BLACK); //通常
155
- day.setBackgroundColor(date.compareTo(LocalDate.now()) == 0 ? Color.CYAN : Color.WHITE); //今日
157
+ day.setBackgroundColor(date.isEqual(LocalDate.now()) ? Color.CYAN : Color.TRANSPARENT); //今日
156
- day.setText("" + date.getDayOfMonth());
158
+ day.setText(String.valueOf(date.getDayOfMonth()));
157
159
  }
158
160
  }
159
161
  }

4

ログ入れっぱなしだったので削除

2024/01/22 19:07

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -37,7 +37,6 @@
37
37
  import android.annotation.SuppressLint;
38
38
  import android.graphics.Color;
39
39
  import android.os.Bundle;
40
- import android.util.Log;
41
40
  import android.view.*;
42
41
  import android.widget.*;
43
42
 
@@ -56,7 +55,6 @@
56
55
 
57
56
  @Override
58
57
  public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
59
- Log.d("MonthFragment", "onViewCreated");
60
58
  TextView yearText = view.findViewById(R.id.year);
61
59
  TextView monthText = view.findViewById(R.id.month);
62
60
 
@@ -75,7 +73,6 @@
75
73
  recyclerView.setHasFixedSize(true);
76
74
  recyclerView.setLayoutManager(new GridLayoutManager(getContext(), 7));
77
75
  recyclerView.setAdapter(adapter);
78
- Log.d("MonthFragment", "onViewCreated end");
79
76
  }
80
77
 
81
78
  private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
@@ -121,11 +118,8 @@
121
118
  }
122
119
  endExclusive = endExclusive.plusDays(7); //+一週間
123
120
  //start から endExclusive まで
124
- Log.d("MonthFragment", "start="+start);
125
- Log.d("MonthFragment", "endExclusive="+endExclusive);
126
121
  list.clear();
127
122
  for(LocalDate target=start; target.compareTo(endExclusive) < 0; target=target.plusDays(1)) {
128
- Log.d("MonthFragment", "target="+target);
129
123
  list.add(target);
130
124
  }
131
125
  }

3

コード追加

2024/01/22 19:01

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -26,3 +26,247 @@
26
26
  フラグメントの onViewCreated の第一パラメータ view が onCreateView が返した View そのものですので、そのビューから findViewById で得なければならないでしょう。(`view.findViewById(R.id.year);`)
27
27
 
28
28
  アクティビティにアタッチしていればビュー階層的にはアクティビティにも属している形になるのでこれでも動くようですが、本来フラグメントはそれ単体で完結するものです。ボタンのクリック処理もフラグメントに書くべきです。
29
+
30
+ ---
31
+ アダプタが分かりませんが想像で追加、フラグメントで完結するようにしました。
32
+ アクティビティは onCreate でフラグメントを配置するだけなので省略です。
33
+ Calendar は扱い難いので LocalDate に変更、年月の表示は Adapter の更新を受ける形とし、今日の日は描画時に背景色を変えています。
34
+
35
+ MonthFragment.java
36
+ ```java
37
+ import android.annotation.SuppressLint;
38
+ import android.graphics.Color;
39
+ import android.os.Bundle;
40
+ import android.util.Log;
41
+ import android.view.*;
42
+ import android.widget.*;
43
+
44
+ import androidx.annotation.*;
45
+ import androidx.fragment.app.*;
46
+ import androidx.recyclerview.widget.*;
47
+
48
+ import java.time.*;
49
+ import java.util.*;
50
+ import java.util.function.Consumer;
51
+
52
+ public class MonthFragment extends Fragment {
53
+ MonthFragment() {
54
+ super(R.layout.month_fragment);
55
+ }
56
+
57
+ @Override
58
+ public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
59
+ Log.d("MonthFragment", "onViewCreated");
60
+ TextView yearText = view.findViewById(R.id.year);
61
+ TextView monthText = view.findViewById(R.id.month);
62
+
63
+ Adapter adapter = new Adapter(date -> {
64
+ yearText.setText(date.getYear() + "年");
65
+ monthText.setText(date.getMonthValue() + "月");
66
+ });
67
+
68
+ Button prevButton = view.findViewById(R.id.prev);
69
+ prevButton.setOnClickListener(v -> adapter.prev());
70
+
71
+ Button nextButton = view.findViewById(R.id.next);
72
+ nextButton.setOnClickListener(v -> adapter.next());
73
+
74
+ RecyclerView recyclerView = view.findViewById(R.id.recycler_view);
75
+ recyclerView.setHasFixedSize(true);
76
+ recyclerView.setLayoutManager(new GridLayoutManager(getContext(), 7));
77
+ recyclerView.setAdapter(adapter);
78
+ Log.d("MonthFragment", "onViewCreated end");
79
+ }
80
+
81
+ private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
82
+ private Consumer<LocalDate> dateChangeListener;
83
+
84
+ private DayOfWeek weekFirst = DayOfWeek.SUNDAY; //日曜日始まり
85
+ private LocalDate current;
86
+ private List<LocalDate> list = new ArrayList<>();
87
+
88
+ Adapter(@NonNull Consumer<LocalDate> dateChangeListener) {
89
+ this.dateChangeListener = dateChangeListener;
90
+
91
+ setDate(LocalDate.now().withDayOfMonth(1));
92
+ }
93
+
94
+ void next() {
95
+ setDate(current.plusMonths(1));
96
+ }
97
+
98
+ void prev() {
99
+ setDate(current.minusMonths(1));
100
+ }
101
+
102
+ @SuppressLint("NotifyDataSetChanged")
103
+ private void setDate(LocalDate date) {
104
+ this.current = date;
105
+ generateDayList(current.getYear(), current.getMonthValue());
106
+ notifyDataSetChanged();
107
+ if(dateChangeListener != null) dateChangeListener.accept(current);
108
+ }
109
+
110
+ private void generateDayList(int year, int month) {
111
+ LocalDate first = LocalDate.of(year, month, 1);
112
+ //月初の直前の週始め
113
+ LocalDate start = first;
114
+ while(start.getDayOfWeek() != weekFirst) {
115
+ start = start.minusDays(1);
116
+ }
117
+ //最終日直後の週始め
118
+ LocalDate endExclusive = first.plusMonths(1);
119
+ while(endExclusive.getDayOfWeek() != weekFirst) {
120
+ endExclusive = endExclusive.plusDays(1);
121
+ }
122
+ endExclusive = endExclusive.plusDays(7); //+一週間
123
+ //start から endExclusive まで
124
+ Log.d("MonthFragment", "start="+start);
125
+ Log.d("MonthFragment", "endExclusive="+endExclusive);
126
+ list.clear();
127
+ for(LocalDate target=start; target.compareTo(endExclusive) < 0; target=target.plusDays(1)) {
128
+ Log.d("MonthFragment", "target="+target);
129
+ list.add(target);
130
+ }
131
+ }
132
+
133
+ @NonNull
134
+ @Override
135
+ public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
136
+ return new ViewHolder(parent);
137
+ }
138
+
139
+ @Override
140
+ public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
141
+ holder.bind(list.get(position));
142
+ }
143
+
144
+ @Override
145
+ public int getItemCount() {
146
+ return list.size();
147
+ }
148
+
149
+ class ViewHolder extends RecyclerView.ViewHolder {
150
+ private TextView day;
151
+ ViewHolder(ViewGroup parent) {
152
+ super(LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_day, parent, false));
153
+ day = itemView.findViewById(R.id.day);
154
+ }
155
+ void bind(LocalDate date) {
156
+ day.setTextColor(
157
+ date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
158
+ date.getDayOfWeek() == DayOfWeek.SUNDAY ? Color.RED : //日曜
159
+ date.getDayOfWeek() == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
160
+ Color.BLACK); //通常
161
+ day.setBackgroundColor(date.compareTo(LocalDate.now()) == 0 ? Color.CYAN : Color.WHITE); //今日
162
+ day.setText("" + date.getDayOfMonth());
163
+ }
164
+ }
165
+ }
166
+ }
167
+ ```
168
+ res/layout/month_fragment.xml
169
+ ```xml
170
+ <?xml version="1.0" encoding="utf-8"?>
171
+ <androidx.constraintlayout.widget.ConstraintLayout
172
+ xmlns:android="http://schemas.android.com/apk/res/android"
173
+ xmlns:app="http://schemas.android.com/apk/res-auto"
174
+ android:layout_width="match_parent"
175
+ android:layout_height="match_parent">
176
+
177
+ <TextView
178
+ android:id="@+id/year"
179
+ android:layout_width="wrap_content"
180
+ android:layout_height="wrap_content"
181
+ android:text="year"
182
+ app:layout_constraintEnd_toEndOf="parent"
183
+ app:layout_constraintStart_toStartOf="parent"
184
+ app:layout_constraintTop_toTopOf="parent" />
185
+
186
+ <Space
187
+ android:id="@+id/year_bottom"
188
+ android:layout_width="0dp"
189
+ android:layout_height="32dp"
190
+ app:layout_constraintEnd_toEndOf="parent"
191
+ app:layout_constraintStart_toStartOf="parent"
192
+ app:layout_constraintTop_toBottomOf="@id/year" />
193
+
194
+ <Button
195
+ android:id="@+id/prev"
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+ style="?android:attr/borderlessButtonStyle"
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+ android:layout_width="wrap_content"
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+ android:layout_height="wrap_content"
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+ android:backgroundTint="@color/white"
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+ android:text="prev"
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+ android:textColor="@color/black"
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+ android:textSize="24sp"
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+ app:layout_constraintBottom_toTopOf="@id/header_bottom"
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+ app:layout_constraintEnd_toStartOf="@id/month"
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+ app:layout_constraintTop_toBottomOf="@id/year_bottom" />
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+
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+ <TextView
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+ android:id="@+id/month"
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+ android:layout_width="100dp"
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+ android:layout_height="wrap_content"
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+ android:text="month"
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+ android:textSize="24sp"
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+ android:textAlignment="center"
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+ app:layout_constraintBottom_toTopOf="@id/header_bottom"
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+ app:layout_constraintEnd_toEndOf="parent"
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+ app:layout_constraintStart_toStartOf="parent"
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+ app:layout_constraintTop_toBottomOf="@id/year_bottom" />
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+
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+ <Button
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+ android:id="@+id/next"
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+ style="?android:attr/borderlessButtonStyle"
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+ android:layout_width="wrap_content"
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+ android:layout_height="wrap_content"
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+ android:backgroundTint="@color/white"
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+ android:text="next"
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+ android:textColor="@color/black"
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+ android:textSize="24sp"
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+ app:layout_constraintBottom_toTopOf="@id/header_bottom"
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+ app:layout_constraintStart_toEndOf="@id/month"
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+ app:layout_constraintTop_toBottomOf="@id/year_bottom"/>
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+
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+ <androidx.constraintlayout.widget.Barrier
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+ android:id="@+id/header_bottom"
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+ android:layout_width="0dp"
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+ android:layout_height="0dp"
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+ app:barrierDirection="bottom"
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+ app:constraint_referenced_ids="prev, month, next" />
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+
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+ <androidx.recyclerview.widget.RecyclerView
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+ android:id="@+id/recycler_view"
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+ android:layout_width="0dp"
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+ android:layout_height="wrap_content"
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+ app:layout_constraintBottom_toBottomOf="parent"
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+ app:layout_constraintEnd_toEndOf="parent"
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+ app:layout_constraintStart_toStartOf="parent"
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+ app:layout_constraintTop_toBottomOf="@id/header_bottom" />
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+
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+ </androidx.constraintlayout.widget.ConstraintLayout>
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+ ```
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+ res/layout/grid_day.xml
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+ ```xml
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+ <?xml version="1.0" encoding="utf-8"?>
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+ <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
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+ android:layout_width="match_parent"
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+ android:layout_height="wrap_content"
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+ xmlns:app="http://schemas.android.com/apk/res-auto">
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+
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+ <TextView
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+ android:id="@+id/day"
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+ android:layout_width="0dp"
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+ android:layout_height="wrap_content"
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+ android:text="21"
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+ android:textSize="30sp"
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+ android:textAlignment="center"
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+ app:layout_constraintEnd_toEndOf="parent"
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+ app:layout_constraintStart_toStartOf="parent"
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+ app:layout_constraintTop_toTopOf="parent" />
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+
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+ </androidx.constraintlayout.widget.ConstraintLayout>
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+ ```
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+ ![起動時(1月)スクリーンショット](https://ddjkaamml8q8x.cloudfront.net/questions/2024-01-23/70f2e1ae-47cf-4f77-8e7f-1214a9bf932e.png)
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+ ![next押下時(2月)スクリーンショット](https://ddjkaamml8q8x.cloudfront.net/questions/2024-01-23/149202ea-11d4-4838-8109-eed338dd84e7.png)

2

追記

2024/01/22 15:57

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -20,3 +20,9 @@
20
20
  ```
21
21
  としなければならないでしょう。
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22
 
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+ ---
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+ 動作確認しようとコードをコピペして見ていますが…フラグメントのレイアウトなのに
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+ アクティビティで findViewById しています。(`activity.findViewById(R.id.year);`)
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+ フラグメントの onViewCreated の第一パラメータ view が onCreateView が返した View そのものですので、そのビューから findViewById で得なければならないでしょう。(`view.findViewById(R.id.year);`)
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+
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+ アクティビティにアタッチしていればビュー階層的にはアクティビティにも属している形になるのでこれでも動くようですが、本来フラグメントはそれ単体で完結するものです。ボタンのクリック処理もフラグメントに書くべきです。

1

マークダウン修正

2024/01/22 15:25

投稿

jimbe
jimbe

スコア12744

test CHANGED
@@ -14,7 +14,7 @@
14
14
  monthFragment.plus();
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15
  }
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16
  ```
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- これでは、 plus を実行するフラグメントオブジェクトと画面に表示しているフラグメントオブジェクトは *違うモノ* です。
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+ これでは、 plus を実行するフラグメントオブジェクトと画面に表示しているフラグメントオブジェクトは **違うモノ** です。
18
18
  ```
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  .add(R.id.month_fragment_container, monthFragment)
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  ```