Custom Dialog in full screen?

Give its constructor a non-dialog theme, such as android.R.style.Theme or android.R.style.Theme_Light.

Code by @Bob.

Dialog dialog = new Dialog(context, android.R.style.Theme_Light); 
dialog.requestWindowFeature(Window.FEATURE_NO_TITLE); 
dialog.setContentView(R.layout.MyCustomDialogLayout); 
dialog.show();

Following code works in my case :

dialog.requestWindowFeature(Window.FEATURE_NO_TITLE); 
dialog.setContentView(R.layout.mydialog2);
dialog.getWindow().setLayout(WindowManager.LayoutParams.MATCH_PARENT, WindowManager.LayoutParams.MATCH_PARENT);