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

編集履歴

回答編集履歴

コード修正

2024/01/25 10:21

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -44,7 +44,7 @@
     if(savedInstanceState == null) {
       getSupportFragmentManager().beginTransaction()
-              .add(R.id.fragment_container, new MonthFragment())
+              .replace(R.id.fragment_container, new MonthFragment())
               .commit();
     }
   }

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

スコア13209

test CHANGED Viewed

@@ -28,9 +28,38 @@
 ---
 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。
-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。
 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。
+MainActivity.java
+```java
+import android.os.Bundle;
+import androidx.appcompat.app.AppCompatActivity;
+public class MainActivity extends AppCompatActivity {
+  @Override
+  protected void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+    setContentView(R.layout.activity_main);
+    if(savedInstanceState == null) {
+      getSupportFragmentManager().beginTransaction()
+              .add(R.id.fragment_container, new MonthFragment())
+              .commit();
+    }
+  }
+}
+```
+res/layout/activity_main.xml
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.fragment.app.FragmentContainerView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/fragment_container"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".MainActivity" />
+```
 MonthFragment.java
 ```java
 import android.graphics.Color;

インデント修正

2024/01/24 20:10

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -142,16 +142,16 @@
       }
       private int getTextColor(LocalDate date) {
         return date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
-                getTextColor(date.getDayOfWeek());
+               getTextColor(date.getDayOfWeek());
       }
       private int getTextColor(DayOfWeek dayOfWeek) {
-        return dayOfWeek == DayOfWeek.SUNDAY ? Color.RED : //日曜
+        return dayOfWeek == DayOfWeek.SUNDAY   ? Color.RED  : //日曜
-                dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
+               dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
-                        Color.BLACK;
+               Color.BLACK;
       }
       private int getBackgroundColor(LocalDate date) {
         return date.isEqual(LocalDate.now()) ? Color.CYAN : //今日
-                Color.TRANSPARENT;
+               Color.TRANSPARENT;
       }
     }
   }

バグ修正・変数名変更

2024/01/24 19:55

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -50,7 +50,7 @@
 import java.util.function.Consumer;
 public class MonthFragment extends Fragment {
-  MonthFragment() {
+  public MonthFragment() {
     super(R.layout.month_fragment);
   }
@@ -76,7 +76,7 @@
   }
   private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
-    private static final DayOfWeek WEEK_FIRST = WeekFields.of(Locale.getDefault()).getFirstDayOfWeek(); //週の始まり
+    private final DayOfWeek firstDayOfWeek = WeekFields.of(Locale.getDefault()).getFirstDayOfWeek(); //週の始まり
     private final Consumer<YearMonth> dateChangeListener;
@@ -99,7 +99,7 @@
     private void setYearMonth(YearMonth yearMonth) {
       this.current = yearMonth;
-      start = current.atDay(1).with(TemporalAdjusters.previousOrSame(WEEK_FIRST)); //月初直前の週始め
+      start = current.atDay(1).with(TemporalAdjusters.previousOrSame(firstDayOfWeek)); //月初直前の週始め
       notifyItemRangeChanged(7, 6*7); //日付部分
       if(dateChangeListener != null) dateChangeListener.accept(current);
     }
@@ -129,7 +129,7 @@
       }
       void bind(int position) {
         if(position < 7) { //曜日名
-          DayOfWeek dow = WEEK_FIRST.plus(position);
+          DayOfWeek dow = firstDayOfWeek.plus(position);
           day.setTextColor(getTextColor(dow));
           day.setBackgroundColor(HEADER_BGCOLOR);
           day.setText(dow.getDisplayName(TextStyle.SHORT_STANDALONE, Locale.getDefault()));

修正

2024/01/24 19:39

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -1,5 +1,3 @@
-まだコードを見ただけで試していませんが。
 MainActivity.java(一部)
 ```java
     MonthFragment monthFragment = new MonthFragment();
@@ -47,7 +45,7 @@
 import java.time.*;
 import java.time.format.TextStyle;
-import java.time.temporal.ChronoField;
+import java.time.temporal.*;
 import java.util.*;
 import java.util.function.Consumer;
@@ -78,7 +76,7 @@
   }
   private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
-    private static final DayOfWeek WEEK_FIRST = DayOfWeek.SUNDAY; //週の始まり
+    private static final DayOfWeek WEEK_FIRST = WeekFields.of(Locale.getDefault()).getFirstDayOfWeek(); //週の始まり
     private final Consumer<YearMonth> dateChangeListener;
@@ -101,16 +99,9 @@
     private void setYearMonth(YearMonth yearMonth) {
       this.current = yearMonth;
-      start = calcStart(current);
+      start = current.atDay(1).with(TemporalAdjusters.previousOrSame(WEEK_FIRST)); //月初直前の週始め
       notifyItemRangeChanged(7, 6*7); //日付部分
       if(dateChangeListener != null) dateChangeListener.accept(current);
-    }
-    //月初直前の週始め
-    private LocalDate calcStart(YearMonth yearMonth) {
-      LocalDate start = yearMonth.atDay(1);
-      LocalDate temp = (LocalDate)WEEK_FIRST.adjustInto(start);
-      return temp.isAfter(start) ? temp.minusDays(7) : temp;
     }
     @NonNull
@@ -151,16 +142,16 @@
       }
       private int getTextColor(LocalDate date) {
         return date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
-               getTextColor(date.getDayOfWeek());
+                getTextColor(date.getDayOfWeek());
       }
       private int getTextColor(DayOfWeek dayOfWeek) {
         return dayOfWeek == DayOfWeek.SUNDAY ? Color.RED : //日曜
-               dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
+                dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
-               Color.BLACK;
+                        Color.BLACK;
       }
       private int getBackgroundColor(LocalDate date) {
         return date.isEqual(LocalDate.now()) ? Color.CYAN : //今日
-               Color.TRANSPARENT;
+                Color.TRANSPARENT;
       }
     }
   }

修正

2024/01/23 17:22

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -15,7 +15,7 @@
     }
 ```
 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。
-**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。
+**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。
 ```
 .add(R.id.month_fragment_container, monthFragment)
 ```

修正

2024/01/23 17:20

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -15,6 +15,7 @@
     }
 ```
 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。
+**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。
 ```
 .add(R.id.month_fragment_container, monthFragment)
 ```
@@ -34,7 +35,6 @@
 MonthFragment.java
 ```java
-import android.annotation.SuppressLint;
 import android.graphics.Color;
 import android.os.Bundle;
 import android.text.format.DateUtils;

コード修正

2024/01/23 17:07

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -99,11 +99,10 @@
       setYearMonth(current.minusMonths(1));
     }
-    @SuppressLint("NotifyDataSetChanged")
     private void setYearMonth(YearMonth yearMonth) {
       this.current = yearMonth;
       start = calcStart(current);
-      notifyDataSetChanged();
+      notifyItemRangeChanged(7, 6*7); //日付部分
       if(dateChangeListener != null) dateChangeListener.accept(current);
     }
@@ -127,7 +126,7 @@
     @Override
     public int getItemCount() {
-      return 7 + 6 * 7;
+      return 7 + 6*7;
     }
     class ViewHolder extends RecyclerView.ViewHolder {

コード修正

2024/01/23 13:03

投稿

jimbe

スコア13209

test CHANGED Viewed

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

コード修正

2024/01/23 11:23

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -83,7 +83,7 @@
     private final Consumer<YearMonth> dateChangeListener;
     private YearMonth current;
-    private final List<LocalDate> list = new ArrayList<>();
+    private LocalDate start;
     Adapter(@NonNull Consumer<YearMonth> dateChangeListener) {
       this.dateChangeListener = dateChangeListener;
@@ -102,20 +102,16 @@
     @SuppressLint("NotifyDataSetChanged")
     private void setYearMonth(YearMonth yearMonth) {
       this.current = yearMonth;
-      generateDayList(current);
+      start = calcStart(current);
       notifyDataSetChanged();
       if(dateChangeListener != null) dateChangeListener.accept(current);
     }
-    private void generateDayList(YearMonth yearMonth) {
-      //月初直前の週始め
+    //月初直前の週始め
+    private LocalDate calcStart(YearMonth yearMonth) {
       LocalDate start = yearMonth.atDay(1);
       while(start.getDayOfWeek() != WEEK_FIRST) start = start.minusDays(1);
-      LocalDate endExclusive = start.plusDays(6 * 7); //六週間
-      //start から endExclusive まで
-      list.clear();
+      return start;
-      for(LocalDate date=start; date.isBefore(endExclusive); date=date.plusDays(1)) list.add(date);
     }
     @NonNull
@@ -126,12 +122,12 @@
     @Override
     public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
-      holder.bind(position, position < 7 ? null : list.get(position - 7));
+      holder.bind(position);
     }
     @Override
     public int getItemCount() {
-      return list.size() + 7;
+      return 7 + 6 * 7;
     }
     class ViewHolder extends RecyclerView.ViewHolder {
@@ -141,13 +137,14 @@
         super(LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_day, parent, false));
         day = itemView.findViewById(R.id.day);
       }
-      void bind(int position, LocalDate date) {
+      void bind(int position) {
         if(position < 7) { //曜日名
           DayOfWeek dow = WEEK_FIRST.plus(position);
           day.setTextColor(getTextColor(dow));
           day.setBackgroundColor(HEADER_BGCOLOR);
           day.setText(dow.getDisplayName(TextStyle.SHORT_STANDALONE, Locale.getDefault()));
         } else {
+          LocalDate date = start.plusDays(position - 7);
           day.setTextColor(getTextColor(date));
           day.setBackgroundColor(getBackgroundColor(date));
           day.setText(String.valueOf(date.getDayOfMonth()));

コード修正

2024/01/23 11:04

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -30,13 +30,14 @@
 ---
 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。
 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。
-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。
+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。
 MonthFragment.java
 ```java
 import android.annotation.SuppressLint;
 import android.graphics.Color;
 import android.os.Bundle;
+import android.text.format.DateUtils;
 import android.view.*;
 import android.widget.*;
@@ -46,6 +47,7 @@
 import java.time.*;
 import java.time.format.TextStyle;
+import java.time.temporal.ChronoField;
 import java.util.*;
 import java.util.function.Consumer;
@@ -56,12 +58,11 @@
   @Override
   public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
-    TextView yearText = view.findViewById(R.id.year);
     TextView monthText = view.findViewById(R.id.month);
-    Adapter adapter = new Adapter(date -> {
+    Adapter adapter = new Adapter(yearMonth -> {
-      yearText.setText(String.format(Locale.getDefault(), "%d年", date.getYear()));
+      long millies = yearMonth.atDay(1).getLong(ChronoField.EPOCH_DAY) * 24 * 60 * 60 * 1000; //epoch[ms]
-      monthText.setText(date.getMonth().getDisplayName(TextStyle.FULL, Locale.getDefault()));
+      monthText.setText(DateUtils.formatDateTime(requireContext(), millies, DateUtils.FORMAT_SHOW_YEAR | DateUtils.FORMAT_NO_MONTH_DAY));
     });
     Button prevButton = view.findViewById(R.id.prev);
@@ -72,58 +73,49 @@
     RecyclerView recyclerView = view.findViewById(R.id.recycler_view);
     recyclerView.setHasFixedSize(true);
-    recyclerView.setLayoutManager(new GridLayoutManager(getContext(), 7));
+    recyclerView.setLayoutManager(new GridLayoutManager(requireContext(), 7));
     recyclerView.setAdapter(adapter);
   }
   private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
-    private final DayOfWeek WEEK_FIRST = DayOfWeek.SUNDAY; //週の始まり
+    private static final DayOfWeek WEEK_FIRST = DayOfWeek.SUNDAY; //週の始まり
-    private final Consumer<LocalDate> dateChangeListener;
+    private final Consumer<YearMonth> dateChangeListener;
-    private LocalDate current;
+    private YearMonth current;
     private final List<LocalDate> list = new ArrayList<>();
-    Adapter(@NonNull Consumer<LocalDate> dateChangeListener) {
+    Adapter(@NonNull Consumer<YearMonth> dateChangeListener) {
       this.dateChangeListener = dateChangeListener;
-      setDate(LocalDate.now().withDayOfMonth(1));
+      setYearMonth(YearMonth.now());
     }
     void next() {
-      setDate(current.plusMonths(1));
+      setYearMonth(current.plusMonths(1));
     }
     void prev() {
-      setDate(current.minusMonths(1));
+      setYearMonth(current.minusMonths(1));
     }
     @SuppressLint("NotifyDataSetChanged")
-    private void setDate(LocalDate date) {
+    private void setYearMonth(YearMonth yearMonth) {
-      this.current = date;
+      this.current = yearMonth;
-      generateDayList(current.getYear(), current.getMonthValue());
+      generateDayList(current);
       notifyDataSetChanged();
       if(dateChangeListener != null) dateChangeListener.accept(current);
     }
-    private void generateDayList(int year, int month) {
+    private void generateDayList(YearMonth yearMonth) {
-      LocalDate first = LocalDate.of(year, month, 1);
       //月初直前の週始め
-      LocalDate start = first;
+      LocalDate start = yearMonth.atDay(1);
-      while(start.getDayOfWeek() != WEEK_FIRST) {
+      while(start.getDayOfWeek() != WEEK_FIRST) start = start.minusDays(1);
-        start = start.minusDays(1);
-      }
-      //月末直後の週始め
-      LocalDate endExclusive = first.plusMonths(1);
-      while(endExclusive.getDayOfWeek() != WEEK_FIRST) {
-        endExclusive = endExclusive.plusDays(1);
-      }
-      endExclusive = endExclusive.plusDays(7); //+一週間
+      LocalDate endExclusive = start.plusDays(6 * 7); //六週間
       //start から endExclusive まで
       list.clear();
-      for(LocalDate date=start; date.isBefore(endExclusive); date=date.plusDays(1)) {
+      for(LocalDate date=start; date.isBefore(endExclusive); date=date.plusDays(1)) list.add(date);
-        list.add(date);
-      }
     }
     @NonNull
@@ -134,28 +126,45 @@
     @Override
     public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
-      holder.bind(list.get(position));
+      holder.bind(position, position < 7 ? null : list.get(position - 7));
     }
     @Override
     public int getItemCount() {
-      return list.size();
+      return list.size() + 7;
     }
     class ViewHolder extends RecyclerView.ViewHolder {
+      private final int HEADER_BGCOLOR = Color.rgb(240,240,240);
       private final TextView day;
       ViewHolder(ViewGroup parent) {
         super(LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_day, parent, false));
         day = itemView.findViewById(R.id.day);
       }
-      void bind(LocalDate date) {
+      void bind(int position, LocalDate date) {
-        day.setTextColor(
-                date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
-                date.getDayOfWeek() == DayOfWeek.SUNDAY ? Color.RED : //日曜
-                date.getDayOfWeek() == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
-                Color.BLACK); //通常
+        if(position < 7) { //曜日名
+          DayOfWeek dow = WEEK_FIRST.plus(position);
+          day.setTextColor(getTextColor(dow));
+          day.setBackgroundColor(HEADER_BGCOLOR);
+          day.setText(dow.getDisplayName(TextStyle.SHORT_STANDALONE, Locale.getDefault()));
+        } else {
+          day.setTextColor(getTextColor(date));
-        day.setBackgroundColor(date.isEqual(LocalDate.now()) ? Color.CYAN : Color.TRANSPARENT); //今日
+          day.setBackgroundColor(getBackgroundColor(date));
-        day.setText(String.valueOf(date.getDayOfMonth()));
+          day.setText(String.valueOf(date.getDayOfMonth()));
+        }
+      }
+      private int getTextColor(LocalDate date) {
+        return date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
+               getTextColor(date.getDayOfWeek());
+      }
+      private int getTextColor(DayOfWeek dayOfWeek) {
+        return dayOfWeek == DayOfWeek.SUNDAY ? Color.RED : //日曜
+               dayOfWeek == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
+               Color.BLACK;
+      }
+      private int getBackgroundColor(LocalDate date) {
+        return date.isEqual(LocalDate.now()) ? Color.CYAN : //今日
+               Color.TRANSPARENT;
       }
     }
   }
@@ -164,28 +173,10 @@
 res/layout/month_fragment.xml
 ```xml
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout
-    xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
-  <TextView
-      android:id="@+id/year"
-      android:layout_width="wrap_content"
-      android:layout_height="wrap_content"
-      android:text="year"
-      app:layout_constraintEnd_toEndOf="parent"
-      app:layout_constraintStart_toStartOf="parent"
-      app:layout_constraintTop_toTopOf="parent" />
-  <Space
-      android:id="@+id/year_bottom"
-      android:layout_width="0dp"
-      android:layout_height="32dp"
-      app:layout_constraintEnd_toEndOf="parent"
-      app:layout_constraintStart_toStartOf="parent"
-      app:layout_constraintTop_toBottomOf="@id/year" />
   <Button
       android:id="@+id/prev"
@@ -196,21 +187,20 @@
       android:text="prev"
       android:textColor="@color/black"
       android:textSize="24sp"
-      app:layout_constraintBottom_toTopOf="@id/header_bottom"
-      app:layout_constraintEnd_toStartOf="@id/month"
+      app:layout_constraintBaseline_toBaselineOf="@id/month"
-      app:layout_constraintTop_toBottomOf="@id/year_bottom" />
+      app:layout_constraintStart_toStartOf="parent" />
   <TextView
       android:id="@+id/month"
-      android:layout_width="100dp"
+      android:layout_width="0dp"
-      android:layout_height="wrap_content"
+      android:layout_height="wrap_content"
+      android:layout_marginTop="32dp"
       android:text="month"
+      android:textAlignment="center"
       android:textSize="24sp"
-      android:textAlignment="center"
-      app:layout_constraintBottom_toTopOf="@id/header_bottom"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
-      app:layout_constraintTop_toBottomOf="@id/year_bottom" />
+      app:layout_constraintTop_toTopOf="parent" />
   <Button
       android:id="@+id/next"
@@ -221,16 +211,8 @@
       android:text="next"
       android:textColor="@color/black"
       android:textSize="24sp"
-      app:layout_constraintBottom_toTopOf="@id/header_bottom"
-      app:layout_constraintStart_toEndOf="@id/month"
+      app:layout_constraintBaseline_toBaselineOf="@id/month"
-      app:layout_constraintTop_toBottomOf="@id/year_bottom"/>
+      app:layout_constraintEnd_toEndOf="parent" />
-  <androidx.constraintlayout.widget.Barrier
-      android:id="@+id/header_bottom"
-      android:layout_width="0dp"
-      android:layout_height="0dp"
-      app:barrierDirection="bottom"
-      app:constraint_referenced_ids="prev, month, next" />
   <androidx.recyclerview.widget.RecyclerView
       android:id="@+id/recycler_view"
@@ -239,7 +221,7 @@
       app:layout_constraintBottom_toBottomOf="parent"
       app:layout_constraintEnd_toEndOf="parent"
       app:layout_constraintStart_toStartOf="parent"
-      app:layout_constraintTop_toBottomOf="@id/header_bottom" />
+      app:layout_constraintTop_toBottomOf="@id/month" />
 </androidx.constraintlayout.widget.ConstraintLayout>
 ```
@@ -250,9 +232,12 @@
     android:id="@+id/day"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
+    android:autoSizeTextType="uniform"
+    android:ellipsize="end"
+    android:maxLines="1"
     android:text="21"
-    android:textSize="30sp"
-    android:textAlignment="center" />
+    android:textAlignment="center"
+    android:textSize="30sp" />
-```
+```
-![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)
+![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)
-![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)
+![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)

行数削減のためレイアウトを簡略化

2024/01/22 20:06

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -246,23 +246,13 @@
 res/layout/grid_day.xml
 ```xml
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/day"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
-    xmlns:app="http://schemas.android.com/apk/res-auto">
-  <TextView
-      android:id="@+id/day"
-      android:layout_width="0dp"
-      android:layout_height="wrap_content"
-      android:text="21"
+    android:text="21"
-      android:textSize="30sp"
+    android:textSize="30sp"
-      android:textAlignment="center"
+    android:textAlignment="center" />
-      app:layout_constraintEnd_toEndOf="parent"
-      app:layout_constraintStart_toStartOf="parent"
-      app:layout_constraintTop_toTopOf="parent" />
-</androidx.constraintlayout.widget.ConstraintLayout>
 ```
 ![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)
 ![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)

コードのワーニング等修正

2024/01/22 19:32

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -45,6 +45,7 @@
 import androidx.recyclerview.widget.*;
 import java.time.*;
+import java.time.format.TextStyle;
 import java.util.*;
 import java.util.function.Consumer;
@@ -59,8 +60,8 @@
     TextView monthText = view.findViewById(R.id.month);
     Adapter adapter = new Adapter(date -> {
-      yearText.setText(date.getYear() + "年");
+      yearText.setText(String.format(Locale.getDefault(), "%d年", date.getYear()));
-      monthText.setText(date.getMonthValue() + "月");
+      monthText.setText(date.getMonth().getDisplayName(TextStyle.FULL, Locale.getDefault()));
     });
     Button prevButton = view.findViewById(R.id.prev);
@@ -76,11 +77,12 @@
   }
   private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
+    private final DayOfWeek WEEK_FIRST = DayOfWeek.SUNDAY; //週の始まり
-    private Consumer<LocalDate> dateChangeListener;
+    private final Consumer<LocalDate> dateChangeListener;
-    private DayOfWeek weekFirst = DayOfWeek.SUNDAY; //日曜日始まり
     private LocalDate current;
-    private List<LocalDate> list = new ArrayList<>();
+    private final List<LocalDate> list = new ArrayList<>();
     Adapter(@NonNull Consumer<LocalDate> dateChangeListener) {
       this.dateChangeListener = dateChangeListener;
@@ -106,21 +108,21 @@
     private void generateDayList(int year, int month) {
       LocalDate first = LocalDate.of(year, month, 1);
-      //月初の直前の週始め
+      //月初直前の週始め
       LocalDate start = first;
-      while(start.getDayOfWeek() != weekFirst) {
+      while(start.getDayOfWeek() != WEEK_FIRST) {
         start = start.minusDays(1);
       }
-      //最終日直後の週始め
+      //月末直後の週始め
       LocalDate endExclusive = first.plusMonths(1);
-      while(endExclusive.getDayOfWeek() != weekFirst) {
+      while(endExclusive.getDayOfWeek() != WEEK_FIRST) {
         endExclusive = endExclusive.plusDays(1);
       }
       endExclusive = endExclusive.plusDays(7); //+一週間
       //start から endExclusive まで
       list.clear();
-      for(LocalDate target=start; target.compareTo(endExclusive) < 0; target=target.plusDays(1)) {
+      for(LocalDate date=start; date.isBefore(endExclusive); date=date.plusDays(1)) {
-        list.add(target);
+        list.add(date);
       }
     }
@@ -141,7 +143,7 @@
     }
     class ViewHolder extends RecyclerView.ViewHolder {
-      private TextView day;
+      private final TextView day;
       ViewHolder(ViewGroup parent) {
         super(LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_day, parent, false));
         day = itemView.findViewById(R.id.day);
@@ -151,9 +153,9 @@
                 date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
                 date.getDayOfWeek() == DayOfWeek.SUNDAY ? Color.RED : //日曜
                 date.getDayOfWeek() == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
-                        Color.BLACK); //通常
+                Color.BLACK); //通常
-        day.setBackgroundColor(date.compareTo(LocalDate.now()) == 0 ? Color.CYAN : Color.WHITE); //今日
+        day.setBackgroundColor(date.isEqual(LocalDate.now()) ? Color.CYAN : Color.TRANSPARENT); //今日
-        day.setText("" + date.getDayOfMonth());
+        day.setText(String.valueOf(date.getDayOfMonth()));
       }
     }
   }

ログ入れっぱなしだったので削除

2024/01/22 19:07

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -37,7 +37,6 @@
 import android.annotation.SuppressLint;
 import android.graphics.Color;
 import android.os.Bundle;
-import android.util.Log;
 import android.view.*;
 import android.widget.*;
@@ -56,7 +55,6 @@
   @Override
   public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
-    Log.d("MonthFragment", "onViewCreated");
     TextView yearText = view.findViewById(R.id.year);
     TextView monthText = view.findViewById(R.id.month);
@@ -75,7 +73,6 @@
     recyclerView.setHasFixedSize(true);
     recyclerView.setLayoutManager(new GridLayoutManager(getContext(), 7));
     recyclerView.setAdapter(adapter);
-    Log.d("MonthFragment", "onViewCreated end");
   }
   private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
@@ -121,11 +118,8 @@
       }
       endExclusive = endExclusive.plusDays(7); //+一週間
       //start から endExclusive まで
-      Log.d("MonthFragment", "start="+start);
-      Log.d("MonthFragment", "endExclusive="+endExclusive);
       list.clear();
       for(LocalDate target=start; target.compareTo(endExclusive) < 0; target=target.plusDays(1)) {
-        Log.d("MonthFragment", "target="+target);
         list.add(target);
       }
     }

コード追加

2024/01/22 19:01

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -26,3 +26,247 @@
 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);`)
 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。
+---
+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。
+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。
+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。
+MonthFragment.java
+```java
+import android.annotation.SuppressLint;
+import android.graphics.Color;
+import android.os.Bundle;
+import android.util.Log;
+import android.view.*;
+import android.widget.*;
+import androidx.annotation.*;
+import androidx.fragment.app.*;
+import androidx.recyclerview.widget.*;
+import java.time.*;
+import java.util.*;
+import java.util.function.Consumer;
+public class MonthFragment extends Fragment {
+  MonthFragment() {
+    super(R.layout.month_fragment);
+  }
+  @Override
+  public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
+    Log.d("MonthFragment", "onViewCreated");
+    TextView yearText = view.findViewById(R.id.year);
+    TextView monthText = view.findViewById(R.id.month);
+    Adapter adapter = new Adapter(date -> {
+      yearText.setText(date.getYear() + "年");
+      monthText.setText(date.getMonthValue() + "月");
+    });
+    Button prevButton = view.findViewById(R.id.prev);
+    prevButton.setOnClickListener(v -> adapter.prev());
+    Button nextButton = view.findViewById(R.id.next);
+    nextButton.setOnClickListener(v -> adapter.next());
+    RecyclerView recyclerView = view.findViewById(R.id.recycler_view);
+    recyclerView.setHasFixedSize(true);
+    recyclerView.setLayoutManager(new GridLayoutManager(getContext(), 7));
+    recyclerView.setAdapter(adapter);
+    Log.d("MonthFragment", "onViewCreated end");
+  }
+  private static class Adapter extends RecyclerView.Adapter<Adapter.ViewHolder> {
+    private Consumer<LocalDate> dateChangeListener;
+    private DayOfWeek weekFirst = DayOfWeek.SUNDAY; //日曜日始まり
+    private LocalDate current;
+    private List<LocalDate> list = new ArrayList<>();
+    Adapter(@NonNull Consumer<LocalDate> dateChangeListener) {
+      this.dateChangeListener = dateChangeListener;
+      setDate(LocalDate.now().withDayOfMonth(1));
+    }
+    void next() {
+      setDate(current.plusMonths(1));
+    }
+    void prev() {
+      setDate(current.minusMonths(1));
+    }
+    @SuppressLint("NotifyDataSetChanged")
+    private void setDate(LocalDate date) {
+      this.current = date;
+      generateDayList(current.getYear(), current.getMonthValue());
+      notifyDataSetChanged();
+      if(dateChangeListener != null) dateChangeListener.accept(current);
+    }
+    private void generateDayList(int year, int month) {
+      LocalDate first = LocalDate.of(year, month, 1);
+      //月初の直前の週始め
+      LocalDate start = first;
+      while(start.getDayOfWeek() != weekFirst) {
+        start = start.minusDays(1);
+      }
+      //最終日直後の週始め
+      LocalDate endExclusive = first.plusMonths(1);
+      while(endExclusive.getDayOfWeek() != weekFirst) {
+        endExclusive = endExclusive.plusDays(1);
+      }
+      endExclusive = endExclusive.plusDays(7); //+一週間
+      //start から endExclusive まで
+      Log.d("MonthFragment", "start="+start);
+      Log.d("MonthFragment", "endExclusive="+endExclusive);
+      list.clear();
+      for(LocalDate target=start; target.compareTo(endExclusive) < 0; target=target.plusDays(1)) {
+        Log.d("MonthFragment", "target="+target);
+        list.add(target);
+      }
+    }
+    @NonNull
+    @Override
+    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
+      return new ViewHolder(parent);
+    }
+    @Override
+    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
+      holder.bind(list.get(position));
+    }
+    @Override
+    public int getItemCount() {
+      return list.size();
+    }
+    class ViewHolder extends RecyclerView.ViewHolder {
+      private TextView day;
+      ViewHolder(ViewGroup parent) {
+        super(LayoutInflater.from(parent.getContext()).inflate(R.layout.grid_day, parent, false));
+        day = itemView.findViewById(R.id.day);
+      }
+      void bind(LocalDate date) {
+        day.setTextColor(
+                date.getMonth() != current.getMonth() ? Color.LTGRAY : //前月・次月
+                date.getDayOfWeek() == DayOfWeek.SUNDAY ? Color.RED : //日曜
+                date.getDayOfWeek() == DayOfWeek.SATURDAY ? Color.BLUE : //土曜
+                        Color.BLACK); //通常
+        day.setBackgroundColor(date.compareTo(LocalDate.now()) == 0 ? Color.CYAN : Color.WHITE); //今日
+        day.setText("" + date.getDayOfMonth());
+      }
+    }
+  }
+}
+```
+res/layout/month_fragment.xml
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+  <TextView
+      android:id="@+id/year"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:text="year"
+      app:layout_constraintEnd_toEndOf="parent"
+      app:layout_constraintStart_toStartOf="parent"
+      app:layout_constraintTop_toTopOf="parent" />
+  <Space
+      android:id="@+id/year_bottom"
+      android:layout_width="0dp"
+      android:layout_height="32dp"
+      app:layout_constraintEnd_toEndOf="parent"
+      app:layout_constraintStart_toStartOf="parent"
+      app:layout_constraintTop_toBottomOf="@id/year" />
+  <Button
+      android:id="@+id/prev"
+      style="?android:attr/borderlessButtonStyle"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:backgroundTint="@color/white"
+      android:text="prev"
+      android:textColor="@color/black"
+      android:textSize="24sp"
+      app:layout_constraintBottom_toTopOf="@id/header_bottom"
+      app:layout_constraintEnd_toStartOf="@id/month"
+      app:layout_constraintTop_toBottomOf="@id/year_bottom" />
+  <TextView
+      android:id="@+id/month"
+      android:layout_width="100dp"
+      android:layout_height="wrap_content"
+      android:text="month"
+      android:textSize="24sp"
+      android:textAlignment="center"
+      app:layout_constraintBottom_toTopOf="@id/header_bottom"
+      app:layout_constraintEnd_toEndOf="parent"
+      app:layout_constraintStart_toStartOf="parent"
+      app:layout_constraintTop_toBottomOf="@id/year_bottom" />
+  <Button
+      android:id="@+id/next"
+      style="?android:attr/borderlessButtonStyle"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:backgroundTint="@color/white"
+      android:text="next"
+      android:textColor="@color/black"
+      android:textSize="24sp"
+      app:layout_constraintBottom_toTopOf="@id/header_bottom"
+      app:layout_constraintStart_toEndOf="@id/month"
+      app:layout_constraintTop_toBottomOf="@id/year_bottom"/>
+  <androidx.constraintlayout.widget.Barrier
+      android:id="@+id/header_bottom"
+      android:layout_width="0dp"
+      android:layout_height="0dp"
+      app:barrierDirection="bottom"
+      app:constraint_referenced_ids="prev, month, next" />
+  <androidx.recyclerview.widget.RecyclerView
+      android:id="@+id/recycler_view"
+      android:layout_width="0dp"
+      android:layout_height="wrap_content"
+      app:layout_constraintBottom_toBottomOf="parent"
+      app:layout_constraintEnd_toEndOf="parent"
+      app:layout_constraintStart_toStartOf="parent"
+      app:layout_constraintTop_toBottomOf="@id/header_bottom" />
+</androidx.constraintlayout.widget.ConstraintLayout>
+```
+res/layout/grid_day.xml
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+  <TextView
+      android:id="@+id/day"
+      android:layout_width="0dp"
+      android:layout_height="wrap_content"
+      android:text="21"
+      android:textSize="30sp"
+      android:textAlignment="center"
+      app:layout_constraintEnd_toEndOf="parent"
+      app:layout_constraintStart_toStartOf="parent"
+      app:layout_constraintTop_toTopOf="parent" />
+</androidx.constraintlayout.widget.ConstraintLayout>
+```
+![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)
+![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)

追記

2024/01/22 15:57

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -20,3 +20,9 @@
 ```
 としなければならないでしょう。
+---
+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
+アクティビティで findViewById しています。(`activity.findViewById(R.id.year);`)
+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);`)
+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。

マークダウン修正

2024/01/22 15:25

投稿

jimbe

スコア13209

test CHANGED Viewed

@@ -14,7 +14,7 @@
         monthFragment.plus();
     }
 ```
-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。
+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。
 ```
 .add(R.id.month_fragment_container, monthFragment)
 ```