Question

I’m trying to launch an activity from a custom lisview. I have hoded the onItemclick method nd called the class by creating a new intent!

public void onItemClick(AdapterView<?> arg0, View arg1, int position, long arg3) {

    if (position == 0) {
        Intent i = new Intent(getApplicationContext(), InstalledApps.class);
        startActivity(i);
    }
}

but when I try to launch it, it gives me a nullpointer exception. what I’m trying to do is, get the position of the clicked item and direct it to the correct activity by an if clause. the following is the log cat output.

07-05 04:39:52.718: W/dalvikvm(3189): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
07-05 04:39:52.758: E/AndroidRuntime(3189): FATAL EXCEPTION: main
07-05 04:39:52.758: E/AndroidRuntime(3189): java.lang.NullPointerException
07-05 04:39:52.758: E/AndroidRuntime(3189):     at com.sliit.droidman.thirdpartyapplist.ListViewAdapter.getView(ListViewAdapter.java:69)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.AbsListView.obtainView(AbsListView.java:2267)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.ListView.measureHeightOfChildren(ListView.java:1244)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.ListView.onMeasure(ListView.java:1156)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.View.measure(View.java:15172)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at     android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.View.measure(View.java:15172)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.View.measure(View.java:15172)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:833)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.View.measure(View.java:15172)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2148)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.View.measure(View.java:15172)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1848)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1100)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1273)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.Choreographer.doCallbacks(Choreographer.java:555)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.Choreographer.doFrame(Choreographer.java:525)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.os.Handler.handleCallback(Handler.java:615)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.os.Handler.dispatchMessage(Handler.java:92)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.os.Looper.loop(Looper.java:137)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at android.app.ActivityThread.main(ActivityThread.java:4745)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at java.lang.reflect.Method.invokeNative(Native Method)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at java.lang.reflect.Method.invoke(Method.java:511)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
07-05 04:39:52.758: E/AndroidRuntime(3189):     at dalvik.system.NativeStart.main(Native Method)

please let me know what I’m doing wrong here!

the adapter class.

 package com.sliit.droidman.thirdpartyapplist;
 import com.sliit.droidman.R;

 import android.app.Activity;  
 import android.graphics.drawable.Drawable;
 import android.view.LayoutInflater;  
 import android.view.View;  
 import android.view.ViewGroup;  
 import android.widget.BaseAdapter;  
 import android.widget.ImageView;
 import android.widget.TextView;  

 public class ListViewAdapter extends BaseAdapter  
 {  
Activity context;  
String title[];  
String description[];
Drawable icon[];

public ListViewAdapter(Activity context, String[] title, String[] description , Drawable[] ico) {  
    super();  
    this.context = context;  
    this.title = title;  
    this.description = description;
    this.icon = ico;
}  

public int getCount() {  
    // TODO Auto-generated method stub  
    return title.length;  
}  

public Object getItem(int position) {  
    // TODO Auto-generated method stub  
    return null;  
}  

public long getItemId(int position) {  
    // TODO Auto-generated method stub  
    return 0;  
}  

private class ViewHolder {  
    TextView txtViewTitle;  
    TextView txtViewDescription;
    ImageView image;
}  

public View getView(int position, View convertView, ViewGroup parent)  
{  
    // TODO Auto-generated method stub  
    ViewHolder holder;  
    LayoutInflater inflater =  context.getLayoutInflater();  

    if (convertView == null)  
    {  
        convertView = inflater.inflate(R.layout.listitem_row, null);  
        holder = new ViewHolder();  
        holder.txtViewTitle = (TextView) convertView.findViewById(R.id.appname);  
        holder.txtViewDescription = (TextView) convertView.findViewById(R.id.packagename);
        holder.image = (ImageView) convertView.findViewById(R.id.avatar);
        convertView.setTag(holder);  
    }  
    else  
    {  
        holder = (ViewHolder) convertView.getTag();  
    }  

    holder.txtViewTitle.setText(title[position]);  
    holder.txtViewDescription.setText(description[position]);
    holder.image.setImageDrawable(icon[position]);

return convertView;  
}  

 }  

Answer 1

07-05 04:39:52.758: E/AndroidRuntime(3189): at com.sliit.droidman.thirdpartyapplist.ListViewAdapter.getView(ListViewAdapter.java:69)

You have a null pointer at line 69 of com.sliit.droidman.thirdpartyapplist.ListViewAdapter‘s getView method. Figure out what’s causing that null pointer and make sure it doesn’t happen.

It appears that line 69 is the following

    holder.txtViewTitle.setText(title[position]);  

Some things that might cause this:

• Perhaps the title array is null. I think if it were just that the position argument were too large, you’d get an ArrayIndexOutOfBoundsException instead.
• The txtViewTitle member of the holder instance is null, possibly because the id R.id.appname is incorrect in line 59.

You can figure this out by putting a breakpoint on line 69 in the debugger and inspecting the values of holder.txtViewTitle and title.