Creating and Displaying a Custom Dialog in Android

In this post I would like to describe the process of creating and displaying a custom dialog. Though the Android documentation describes pretty well the topic, I faced some problems implementing it, and I would like to share my findings.

The final output should look like this:

1. The first issue I have encountered was that I was getting a BadTokenException in the onCreateDialog() method where I was instantiating the Dialog: android.view.WindowManager$BadTokenException: Unable to add window — token null is not for an application, 

Context context=getApplicationContext();
Dialog dialog=new Dialog(context);

Well, though the Android documentation suggests to use getApplicationContext(); actually it turns out that this is not the proper way to do it and most likely it will throw an exception. The correct way is to use this, or “ActivityName”.this instead of getApplicationContext(). For example:

Context context=MainActivity.this;
Dialog dialog=new Dialog(context);

2. The second issue I was facing was that I wanted to get rid off the standard dialog title.
Normally you would set the Dialog title with this:

dialog.setTitle("Dialog Title");

However, if you don’t want to display a standard title for your dialog, not calling the above line most probably won’t meet your expectations, because it will leave an empty space where the title should be.

Hopefully, this is an easy fix. Just call requestWindowFeature(Window.FEATURE_NO_TITLE); and you are done.

dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);

To sum up with a concrete working example, below I presented an implementation of a simple custom dialog.

custom_dialog.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="250dp"
   android:layout_height="match_parent"
   android:background="#8F1A3B"
   android:orientation="vertical" >

<TextView
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:layout_marginBottom="20dp"
   android:text="Custom Dialog"
   android:textSize="18dp" />

<Button
   android:id="@+id/restart"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="Restart Game" />

</LinearLayout>

MainActivity:

public class MainActivity extends Activity {

Dialog dialog;
int DIALOG_GAME_RESTART=100;

@Override
public void onCreate(Bundle savedInstanceState) {
   // ............
}

@Override
protected Dialog onCreateDialog(int id) {
   switch (id) {
   case DIALOG_GAME_RESTART:
     Context context=MainActivity.this;
     dialog=new Dialog(context);
     dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);

     dialog.setContentView(R.layout.custom_dialog);

     Button restart=(Button)dialog.findViewById(R.id.restart);

     restart.setOnClickListener(new OnClickListener() {
     @Override
     public void onClick(View v) {
        dialog.dismiss();

        //whatever code you want to execute on restart
     }
     });
   break;

   default: break;
   }
   return dialog;
}
}