Question

I have the following method which is called when the value “Edit Class…” is selected in a ListView.:

public void editClassOptionPressed(AdapterView<?> parent,int position,ArrayList<Class>classesArrayList){
    //The line below throws the null pointer exception
    parent.getChildAt(position).setBackgroundColor(Color.BLUE);
    Toast.makeText(getApplicationContext(), "Please Select Class To Edit...",Toast.LENGTH_LONG).show();
    setEditListener(classesArrayList, adapter);
}

This method is called by the following method, which is in turn called in my OnCreate method:

public void setDefaultListener(final ArrayList<Class>classesArrayList){
    ListView lv = getListView();
    lv.setTextFilterEnabled(true);
    lv.setOnItemClickListener(new OnItemClickListener() {
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        if(position==(classesArrayList.size()-3)){
            Intent intent = new Intent(ClassView.this, AddNewClassView.class);
            startActivity(intent);
        }
        else if(position==(classesArrayList.size()-1)){
            deleteClassOptionPressed(parent,position);
        }
        else if(position==(classesArrayList.size()-2)){
            **editClassOptionPressed(parent, position, classesArrayList);** 
        }
        else{
            Intent intent = new Intent(ClassView.this, GradeView.class);
            intent.putExtra("selectedClassName",((TwoLineListItem)view).getText1().getText());
            startActivity(intent);
        }
      }
    });
}

From what I’ve debugged so far, it appears that the parent does not register a child at that location, although the parent itself is non-null. I should also point out that this happens only when I have over a certain number of items in the ListView. Anyone have any ideas? Here is the logcat output:

06-26 18:31:23.373: E/AndroidRuntime(1243): FATAL EXCEPTION: main
06-26 18:31:23.373: E/AndroidRuntime(1243): java.lang.NullPointerException
06-26 18:31:23.373: E/AndroidRuntime(1243): athellolistview.com.ClassView.editClassOptionPressed(ClassView.java:112)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at hellolistview.com.ClassView$4.onItemClick(ClassView.java:266)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at android.widget.AdapterView.performItemClick(AdapterView.java:292)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at android.widget.AbsListView.performItemClick(AbsListView.java:1058)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at android.widget.AbsListView$PerformClick.run(AbsListView.java:2514)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at android.widget.AbsListView$1.run(AbsListView.java:3168)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at android.os.Handler.handleCallback(Handler.java:605)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at android.os.Handler.dispatchMessage(Handler.java:92)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at android.os.Looper.loop(Looper.java:137)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at android.app.ActivityThread.main(ActivityThread.java:4424)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at java.lang.reflect.Method.invokeNative(Native Method)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at java.lang.reflect.Method.invoke(Method.java:511)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-26 18:31:23.373: E/AndroidRuntime(1243):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

position != childPosition

Maybe you should consider using an ExpandableListView, which helps with this problem:

int childPosition = ExpandableListView.getPackedPositionChild(position);