本文介绍了在自定义ListView中获取NullPointerException的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
运行我的应用程序时出现这样的错误:
I'm getting errors like this when I run my app:
02-27 22:59:19.331: E/AndroidRuntime(2060): FATAL EXCEPTION: main
02-27 22:59:19.331: E/AndroidRuntime(2060): java.lang.NullPointerException
02-27 22:59:19.331: E/AndroidRuntime(2060):
at myPlanAdapter.getView(MyPlanActivity.java:145)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.widget.AbsListView.obtainView(AbsListView.java:1315)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.widget.ListView.measureHeightOfChildren(ListView.java:1198)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.widget.ListView.onMeasure(ListView.java:1109)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.View.measure(View.java:8171)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.View.measure(View.java:8171)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.View.measure(View.java:8171)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.View.measure(View.java:8171)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.ViewRoot.performTraversals(ViewRoot.java:801)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.os.Handler.dispatchMessage(Handler.java:99)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.os.Looper.loop(Looper.java:123)
02-27 22:59:19.331: E/AndroidRuntime(2060): at android.app.ActivityThread.main(ActivityThread.java:4627)
02-27 22:59:19.331: E/AndroidRuntime(2060): at java.lang.reflect.Method.invokeNative(Native Method)
02-27 22:59:19.331: E/AndroidRuntime(2060): at java.lang.reflect.Method.invoke(Method.java:521)
02-27 22:59:19.331: E/AndroidRuntime(2060): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
我的源代码是:
public class MyPlanActivity extends Activity implements OnItemClickListener,
OnClickListener {
private String TAG = "MyPlanActivity";
private Button addButton = null;
private ListView listView;
myPlanAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
viewInit();
adapter = new myPlanAdapter(getBaseContext());
listView.setAdapter(adapter);
listView.setOnItemClickListener(this);
}
private void viewInit() {
setContentView(R.layout.myplan);
addButton = (Button) findViewById(R.id.AddMyPlanButtonId);
listView = (ListView) findViewById(R.id.myPlanListViewId);
addButton.setOnClickListener(this);
}
public void onClick(View v) {
switch (v.getId()) {
case R.id.AddMyPlanButtonId:
startActivity(new Intent(this, AddMyPlan.class));
break;
default:
break;
}
}
public void onItemClick(AdapterView<?> paramAdapterView, View paramView,
int paramInt, long paramLong) {
// TODO Auto-generated method stub
}
@Override
protected void onResume() {
super.onResume();
adapter.notifyDataSetChanged();
}
private class myPlanAdapter extends ArrayAdapter<MyPlan> {
Context context;
MyPlanDataSource dataSource;
public myPlanAdapter(Context context) {
super(context, R.layout.myplan_list_view_entry);
this.context = context;
dataSource = new MyPlanDataSource(context);
}
private ArrayList<MyPlan> getAllPlan() {
dataSource.open();
ArrayList<MyPlan> allPlan = dataSource.getAllPlan();
dataSource.close();
Log.d(TAG,allPlan.get(0).getSubjectName());
return allPlan;
}
@Override
public int getCount() {
Log.d(TAG,"Size: "+getAllPlan().size());
return getAllPlan().size();
}
@Override
public MyPlan getItem(int position) {
return getAllPlan().get(position);
}
@Override
public View getView(final int position, View convertView,
ViewGroup parent) {
View row = convertView;
if (row == null)
{
LayoutInflater inflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
row = inflater.inflate(R.layout.myplan_list_view_entry, parent,
false);
final PlanViewHolder viewHolder = new PlanViewHolder();
viewHolder.subjectName = (TextView) findViewById(R.id.myPlanListSubNameTextViewId);
viewHolder.targetGrade = (TextView) findViewById(R.id.myPlanListTargetGradeTextViewId);
viewHolder.duration = (TextView) findViewById(R.id.myPlanListDurationTextViewId);
viewHolder.examDate = (TextView) findViewById(R.id.myPlanListExamDateTextViewId);
viewHolder.daysTogo = (TextView) findViewById(R.id.myplanListDaystogoBoardTextViewId);
viewHolder.delete = (ImageView) findViewById(R.id.myPlanDeleteImageViewId);
Log.d(TAG, "" + position);
row.setTag(viewHolder);
}
final PlanViewHolder holder = (PlanViewHolder) row.getTag();
holder.subjectName.setText((getAllPlan().get(position)
.getSubjectName())); // line 145
holder.targetGrade.setText("Grade : "
+ getAllPlan().get(position).getTargetGrade());
holder.duration.setText(getAllPlan().get(position).getExamTime());
holder.examDate.setText(getAllPlan().get(position).getExamDate());
holder.daysTogo.setText(getAllPlan().get(position).getDaysTogo());
holder.delete.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
AlertDialog.Builder builder = new AlertDialog.Builder(
context);
builder.setTitle("DELETE")
.setMessage(
"Are you sure you want to delete this Subject?")
.setCancelable(false)
.setPositiveButton("Yes",
new DialogInterface.OnClickListener()
{
public void onClick(
DialogInterface dialog, int id)
{
dataSource.open();
dataSource
.deletePlan(getItem(position));
dataSource.close();
notifyDataSetChanged();
}
})
.setNegativeButton("No",
new DialogInterface.OnClickListener()
{
public void onClick(
DialogInterface dialog, int id)
{
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
}
});
return row;
}
}
static class PlanViewHolder {
private TextView subjectName;
private TextView targetGrade;
private TextView duration;
private TextView examDate;
private TextView daysTogo;
private ImageView delete;
}
}
推荐答案
我认为您在错误的位置搜索行视图.尝试在膨胀的行view(在getView()方法中)中找到它们:
I think you are searcing for your row views in the wrong place. Try to find them in your inflated row view(in the getView() method):
viewHolder.subjectName = (TextView) row.findViewById(R.id.myPlanListSubNameTextViewId);
viewHolder.targetGrade = (TextView) row.findViewById(R.id.myPlanListTargetGradeTextViewId);
viewHolder.duration = (TextView) row.findViewById(R.id.myPlanListDurationTextViewId);
viewHolder.examDate = (TextView) row.findViewById(R.id.myPlanListExamDateTextViewId);
viewHolder.daysTogo = (TextView) row.findViewById(R.id.myplanListDaystogoBoardTextViewId);
viewHolder.delete = (ImageView) findViewById(R.id.myPlanDeleteImageViewId);
这篇关于在自定义ListView中获取NullPointerException的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！