前提・実現したいこと
Android StudioでRecyclerViewのみを使ったジャンル別のリストを作っているのですが、上手くいきません。作りたいのは、以下のようなものです。
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コミック・小説・雑誌はレイアウトが同じ(パターンA)で、書籍内容もレイアウトが同じ(パターンB)です。また、ジャンルごとの項目の数はバラバラです。
該当のソースコード
レイアウト
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:padding="3dp" android:background="#FF0000" android:text="New Text" android:id="@+id/textView1" /> <!-- textViewn --> </LinearLayout>
MyAdapter
1package com.example.myapplication; 2 3import android.content.Context; 4import android.support.v7.widget.RecyclerView; 5import android.view.LayoutInflater; 6import android.view.View; 7import android.view.ViewGroup; 8import android.widget.TextView; 9 10import java.util.List; 11 12public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder>{ 13 14 private final LayoutInflater inflater; 15 private final List<SampleItem> data; 16 17 public MyAdapter(Context context, List<SampleItem> data){ 18 this.inflater = LayoutInflater.from(context); 19 this.data = data; 20 } 21 22 @Override 23 public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType){ 24 switch(viewType){ 25 case 1: 26 return new Sample1ItemViewHolder(inflater.inflate(Sample1ItemViewHolder.LAYOUT_ID, parent, false)); 27 case 2: 28 return new Sample2ItemViewHolder(inflater.inflate(Sample2ItemViewHolder.LAYOUT_ID, parent, false)); 29 case 3: 30 return new Sample3ItemViewHolder(inflater.inflate(Sample3ItemViewHolder.LAYOUT_ID, parent, false)); 31 } 32 return null; 33 } 34 35 @Override 36 public void onBindViewHolder(ViewHolder holder, int position){ 37 switch(getItemViewType(position)){ 38 case 1: 39 ((Sample1ItemViewHolder)holder).onBindItemViewHolder(data.get(position)); 40 break; 41 case 2: 42 ((Sample2ItemViewHolder)holder).onBindItemViewHolder(data.get(position)); 43 break; 44 case 3: 45 ((Sample3ItemViewHolder)holder).onBindItemViewHolder(data.get(position)); 46 break; 47 } 48 } 49 50 public int getItemViewType(int position){ 51 return data.get(position).getCategory(); 52 } 53 54 @Override 55 public int getItemCount(){ 56 return data.size(); 57 } 58 59 public class ViewHolder extends RecyclerView.ViewHolder{ 60 public ViewHolder(View itemView){ 61 super(itemView); 62 } 63 } 64 65 public class Sample1ItemViewHolder extends ViewHolder{ 66 public static final int LAYOUT_ID = R.layout.sample_1_item_view; 67 public final TextView textView; 68 69 public Sample1ItemViewHolder(View itemView){ 70 super(itemView); 71 textView = itemView.findViewById(R.id.textView1); 72 } 73 74 public void onBindItemViewHolder(SampleItem data){ 75 this.textView.setText(data.getText()); 76 } 77 } 78 79 public class Sample2ItemViewHolder extends ViewHolder{ 80 public static final int LAYOUT_ID = R.layout.sample_2_item_view; 81 public final TextView textView; 82 83 public Sample2ItemViewHolder(View itemView){ 84 super(itemView); 85 textView = itemView.findViewById(R.id.textView2); 86 } 87 88 public void onBindItemViewHolder(SampleItem data){ 89 this.textView.setText(data.getText()); 90 } 91 } 92 93 public class Sample3ItemViewHolder extends ViewHolder{ 94 public static final int LAYOUT_ID = R.layout.sample_3_item_view; 95 public final TextView textView; 96 97 public Sample3ItemViewHolder(View itemView){ 98 super(itemView); 99 textView = itemView.findViewById(R.id.textView3); 100 } 101 102 public void onBindItemViewHolder(SampleItem data){ 103 this.textView.setText(data.getText()); 104 } 105 } 106 107}
SampleItem
1package com.example.myapplication; 2 3public class SampleItem { 4 5 private String text; 6 private int category; 7 8 public SampleItem(int category, String text){ 9 this.category = category; 10 this.text = text; 11 } 12 13 public String getText(){ 14 return this.text; 15 } 16 17 public int getCategory(){ 18 return this.category; 19 } 20}
MainActivity
1package com.example.myapplication; 2 3import android.support.v7.app.AppCompatActivity; 4import android.support.v7.widget.LinearLayoutManager; 5import android.support.v7.widget.RecyclerView; 6import android.os.Bundle; 7 8import java.util.ArrayList; 9import java.util.List; 10 11 12public class MainActivity extends AppCompatActivity { 13 14 @Override 15 protected void onCreate(Bundle savedInstanceState) { 16 super.onCreate(savedInstanceState); 17 18 RecyclerView recyclerView = findViewById(R.id.recycler_view); 19 recyclerView.setHasFixedSize(true); 20 21 LinearLayoutManager layoutManager = new LinearLayoutManager(this); 22 recyclerView.setLayoutManager(layoutManager); 23 24 List<SampleItem> data = new ArrayList<>(); 25 26 SampleItem item = null; 27 for (int i = 0; i < 30; i++){ 28 switch(i % 10) { 29 case 0: 30 item = new SampleItem(1, "Data" + i); 31 break; 32 case 1: 33 item = new SampleItem(1, "Data" + i); 34 break; 35 case 2: 36 item = new SampleItem(2, "Data" + i); 37 break; 38 case 3: 39 item = new SampleItem(3, "Data" + i); 40 break; 41 case 4: 42 item = new SampleItem(2, "Data" + i); 43 break; 44 case 5: 45 item = new SampleItem(1, "Data" + i); 46 break; 47 case 6: 48 item = new SampleItem(2, "Data" + i); 49 break; 50 case 7: 51 item = new SampleItem(2, "Data" + i); 52 break; 53 case 8: 54 item = new SampleItem(3, "Data" + i); 55 break; 56 case 9: 57 item = new SampleItem(1, "Data" + i); 58 break; 59 } 60 data.add(item); 61 } 62 recyclerView.setAdapter(new MyAdapter(this, data)); 63 } 64 65}
上のよさげなコードを試してみたのですが、アプリが停止します。
Logcatのエラー
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.myapplication, PID: 12165 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setHasFixedSize(boolean)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setHasFixedSize(boolean)' on a null object reference at com.example.myapplication.MainActivity.onCreate(MainActivity.java:19) at android.app.Activity.performCreate(Activity.java:6679) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) at android.app.ActivityThread.-wrap12(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6119) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
お願いします。
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