public class MainActivity extends AppCompatActivity {
private RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private List<Person> persons;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
mRecyclerView.setHasFixedSize(true);
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);
initializeData();
mAdapter = new MyAdapter(persons);
mRecyclerView.setAdapter(mAdapter);
}
public class Person
{
String name;
String age;
int photoId;
Person(String name, String age, int photoId)
{
this.name = name;
this.age = age;
this.photoId = photoId;
}
}
private void initializeData()//initializing the person class
{
persons = new ArrayList<>();
persons.add(new Person("Emma Wilson", "23 years old", R.drawable.ic_action_name));
persons.add(new Person("Lavery Maiss", "25 years old", R.drawable.ic_action_name2));
persons.add(new Person("Lillie Watts", "35 years old", R.drawable.logo));
}
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private List<Person> mDataset;
public class ViewHolder extends RecyclerView.ViewHolder {
CardView cv;
TextView personName;
TextView personAge;
ImageView personPhoto;
public ViewHolder(View v) {
super(v);
cv = (CardView)findViewById(R.id.cv);
personName = (TextView)findViewById(R.id.person_name);
personAge = (TextView)findViewById(R.id.person_age);
personPhoto = (ImageView)findViewById(R.id.person_photo);
}
}
public MyAdapter(List<Person> myDataset) {
this.mDataset = myDataset;
}
@Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType) {
View v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.card_example, parent, false);
ViewHolder vh = new ViewHolder(v);
return vh;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
Person p = mDataset.get(position);
//here i get an exception indicating holder is null exception
holder.personName.setText(p.name);
holder.personAge.setText(p.age);
holder.personPhoto.setImageResource(p.photoId);
}
@Override
public int getItemCount() {
return mDataset.size();
}
@Override
public void onAttachedToRecyclerView(RecyclerView recyclerView) {
super.onAttachedToRecyclerView(recyclerView);
}
}
}
尝试使用cardview实现基本的回收站视图。 Person类为将使用卡的人保存数据并显示在recycleler视图中，但在onBindViewHolder中它会抛出零点异常。
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: FATAL EXCEPTION: main
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: Process: com.wolf.vivekverma.vedio, PID: 1518
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at com.wolf.vivekverma.vedio.MainActivity$MyAdapter.onBindViewHolder(MainActivity.java:97)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at com.wolf.vivekverma.vedio.MainActivity$MyAdapter.onBindViewHolder(MainActivity.java:61)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:5277)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:5310)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4568)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4461)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1962)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1371)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1334)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:563)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2847)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3145)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.View.layout(View.java:15614)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewGroup.layout(ViewGroup.java:4968)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.View.layout(View.java:15614)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewGroup.layout(ViewGroup.java:4968)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.View.layout(View.java:15614)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewGroup.layout(ViewGroup.java:4968)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.View.layout(View.java:15614)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewGroup.layout(ViewGroup.java:4968)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.View.layout(View.java:15614)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewGroup.layout(ViewGroup.java:4968)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.LinearLayout.onLayout(LinearLayout.java:1466)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.View.layout(View.java:15614)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewGroup.layout(ViewGroup.java:4968)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.View.layout(View.java:15614)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewGroup.layout(ViewGroup.java:4968)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2102)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1859)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1077)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5884)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.Choreographer.doCallbacks(Choreographer.java:580)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.Choreographer.doFrame(Choreographer.java:550)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.os.Handler.handleCallback(Handler.java:739)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:95)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.os.Looper.loop(Looper.java:135)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5312)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:372)
03-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
-08 01:59:28.771 1518-1518/com.wolf.vivekverma.vedio E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.j