adapter.getView
中的NullPointer异常
我不知道原因。
//////////this is the code
package com.example.said.notetoself;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
private NoteAdapter mNoteAdapter;
private boolean mSound;
private int mAnimOption;
private SharedPreferences mPrefs;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
mNoteAdapter = new NoteAdapter();
ListView listNote = (ListView) findViewById(R.id.listView);
listNote.setAdapter(mNoteAdapter);
listNote.setOnItemClickListener(
new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Note tempNote = (Note) mNoteAdapter.getItem(position);
DialogShowNote dialog = new DialogShowNote();
dialog.sendNoteSelected(tempNote);
dialog.show(getFragmentManager(), "");
}
}
);
}
@Override
protected void onResume(){
super.onResume();
mPrefs = getSharedPreferences("Note to self", MODE_PRIVATE);
mSound = mPrefs.getBoolean("sound", true);
mAnimOption = mPrefs.getInt("anim option", SettingsActivity.fast);
}
public void createNewNote(Note n){
mNoteAdapter.addNote(n);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_add) {
DialogNewNote dialog = new DialogNewNote();
dialog.show(getFragmentManager(), "");
return true;
}
if(id == R.id.action_settings){
Intent intent = new Intent(this, SettingsActivity.class);
startActivity(intent);
return true;
}
return super.onOptionsItemSelected(item);
}
public class NoteAdapter extends BaseAdapter{
List<Note> noteList = new ArrayList<>();
@Override
public int getCount() {
return noteList.size();
}
@Override
public Object getItem(int position) {
return noteList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View view, ViewGroup parent) {
if (view == null){
LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);
view = inflater.inflate(R.layout.listitem, parent, false);
}
TextView txtTitle = (TextView) findViewById(R.id.txtTitle);
TextView txtDescription = (TextView) findViewById(R.id.txtDescription);
ImageView ivImportant =(ImageView) findViewById(R.id.imageViewImportant);
ImageView ivTodo = (ImageView) findViewById(R.id.imageViewTodo);
ImageView ivIdea = (ImageView) findViewById(R.id.imageViewIdea);
Note tempNote = noteList.get(position);
if (!tempNote.isImportant()) ivImportant.setVisibility(View.INVISIBLE);
if (!tempNote.isTodo()) ivTodo.setVisibility(View.INVISIBLE);
if (!tempNote.isIdea()) ivIdea.setVisibility(View.INVISIBLE);
txtTitle.setText(tempNote.getTitle());
txtDescription.setText(tempNote.getDescription());
return view;
}
public void addNote(Note n){
noteList.add(n);
notifyDataSetChanged();
}
}
}
/////////这是出现的问题
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.said.notetoself, PID: 1791
java.lang.NullPointerException
at com.example.said.notetoself.MainActivity$NoteAdapter.getView(MainActivity.java:142)
at android.widget.AbsListView.obtainView(AbsListView.java:2255)
at android.widget.ListView.makeAndAddView(ListView.java:1790)
at android.widget.ListView.fillDown(ListView.java:691)
at android.widget.ListView.fillFromTop(ListView.java:752)
at android.widget.ListView.layoutChildren(ListView.java:1616)
at android.widget.AbsListView.onLayout(AbsListView.java:2087)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1055)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.support.design.widget.HeaderScrollingViewBehavior.layoutChild(HeaderScrollingViewBehavior.java:131)
at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1364)
at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:846)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1671)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1525)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
at android.view.View.layout(View.java:14817)
at android.view.ViewGroup.layout(ViewGroup.java:4631)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1983)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1740)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5600)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
at android.view.Choreographer.doCallbacks(Choreographer.java:574)
at android.view.Choreographer.doFrame(Choreographer.java:544)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：1)
来自视图引用的适配器findViewById的side getView方法，如
TextView txtTitle = (TextView) view.findViewById(R.id.txtTitle);
TextView txtDescription = (TextView) view.findViewById(R.id.txtDescription);
ImageView ivImportant =(ImageView) view.findViewById(R.id.imageViewImportant);
ImageView ivTodo = (ImageView) view.findViewById(R.id.imageViewTodo);
ImageView ivIdea = (ImageView) view.findViewById(R.id.imageViewIdea);