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Getting NullPointerException in a custom ListView

I get errors like this when I launch my application:

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)

And my source code:

 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; } }
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4 answers

I think you are looking for your lines in the wrong place. Try to find them in your inflated view line (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);
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Change to ViewHolder ids, you need to get these identifiers from convertView(the view passed in) as follows:

 viewHolder.subjectName = (TextView) row.findViewById(R.id.myPlanListSubNameTextViewId);

Do the same for others.

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Make these changes to your getView() method:

  @Override public View getView(final int position, View convertView, ViewGroup parent) { final PlanViewHolder viewHolder; if (row == null) { LayoutInflater inflater = (LayoutInflater) context .getSystemService(Context.LAYOUT_INFLATER_SERVICE); convertView = inflater.inflate(R.layout.myplan_list_view_entry, parent, false); 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); convertView.setTag(viewHolder); } else viewHolder=(PlanViewHolder)convertView.getTag(); ... return convertView; }
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Since this is the string you get a NullPointerException , you need to figure out what null :

 holder.subjectName.setText( (getAllPlan() .get(position) .getSubjectName()));

This can be a call to getAllPlan() , get(position) or getSubjectName() .

What type getAllPlan() method getAllPlan() ? And are the keys of this type the same values ​​as the positions in the list? By putting the code on different lines, it’s easier to determine where you get zero.

In addition, getAllPlan().get(position) will return the same as getItem(position) in the ArrayAdapter .

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Source: https://habr.com/ru/post/1398632/

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