Extends AlertDialog.Builder in Android

Question

I want to create a class which extends AlertDialog.Builder:

public class AlertBuilder extends AlertDialog.Builder {

    private MultiAdapter mAdapter;
    private ListView lv;
    private Activity mActivity;
    private Context mContext;
    private CheckedTxtView checkedItem;

    public AlertBuilder(Context context, Activity activity, final List<CheckedTxtView> mList) {
        super(context);
        this.mActivity = activity;
        this.mContext = context;

        this.setTitle("Test");
        LayoutInflater inflater = activity.getLayoutInflater();
        View dialoglayout = inflater.inflate(R.layout.main_filter, null);
        this.setView(dialoglayout);

        mAdapter = new MultiAdapter(context, mList); 
        lv = (ListView) dialoglayout.findViewById(R.id.list);
        lv.setAdapter(mAdapter);
        lv.setOnItemClickListener(new ItemClick());
    }

    class ItemClick implements OnItemClickListener {
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            checkedItem = mAdapter.mItems.get(position);;
            mAdapter.notifyDataSetChanged();
        }
    }

    private class MultiAdapter extends ArrayAdapter<CheckedTxtView> {

        private List<CheckedTxtView> mItems;

        public MultiAdapter(Context context, List<CheckedTxtView> mList) {
            super(context, R.layout.list2, mList);
            this.mItems = mList;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            View row;

            if (convertView == null)  {
                LayoutInflater inflater = mActivity.getLayoutInflater();
                row = inflater.inflate(R.layout.list2, parent, false);
            } else
                row = convertView;

            CheckedTextView txt = (CheckedTextView) row.findViewById(R.id.label);

            CheckedTxtView c = mItems.get(position); 

            System.out.println(c.item);

            txt.setText(c.item);
            if(checkedItem != null && checkedItem.item != null)
                txt.setChecked(c.item.equals(checkedItem.item));

            return row;
        }
    }

Then I use it in my Activity:

public class MainActivity extends Activity {

    private List<CheckedTxtView> mList;
    private AlertDialog mAlert;
    private AlertDialog.Builder mAlertBuilder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mList = new ArrayList<CheckedTxtView>();
        for(int i=0; i<30; i++) {
            CheckedTxtView c = new CheckedTxtView();
            c.item = "item " + i;
            mList.add(c);
        }

        mAlertBuilder = new AlertBuilder(getApplicationContext(), this, mList);
        mAlert = mAlertBuilder.create();

        Button mButton = (Button) this.findViewById(R.id.mButton);
        mButton.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                mAlert.show();
            }
        });
    }
}

I get this error in the console:

02-07 13:33:05.641: E/AndroidRuntime(12557): FATAL EXCEPTION: main
02-07 13:33:05.641: E/AndroidRuntime(12557): android.view.WindowManager$BadTokenException: Unable to add window -- token null is not for an application
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.view.ViewRoot.setView(ViewRoot.java:566)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:179)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:91)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.app.Dialog.show(Dialog.java:265)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at com.example.testdialog.MainActivity$1.onClick(MainActivity.java:35)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.view.View.performClick(View.java:2533)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.view.View$PerformClick.run(View.java:9320)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.os.Handler.handleCallback(Handler.java:587)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.os.Handler.dispatchMessage(Handler.java:92)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.os.Looper.loop(Looper.java:150)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at android.app.ActivityThread.main(ActivityThread.java:4385)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at java.lang.reflect.Method.invokeNative(Native Method)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at java.lang.reflect.Method.invoke(Method.java:507)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
02-07 13:33:05.641: E/AndroidRuntime(12557):    at dalvik.system.NativeStart.main(Native Method)

I may miss something here. can you help me?

Answer 1

Instead of getApplicationContext() use this or MainActivity.this.

 mAlertBuilder = new AlertBuilder(this, this, mList);

Answer 2

You shouldn't pass application's context here:

 mAlertBuilder = new AlertBuilder(getApplicationContext(), this, mList);

Since Activity is context itself, you should change your constructor to take only one paramater - Activity, which can be used as a Context object later.