点击对话框以外的地方，对话框消失

public class DismissDialog extends Activity {
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		showDialog(1);
	}

	@Override
	protected Dialog onCreateDialog(int id) {
		Dialog dd = new AlertDialog.Builder(this)
				.setIcon(android.R.drawable.ic_dialog_alert)
				.setMessage("hello world")
				.setNegativeButton(android.R.string.cancel, null)
				.setPositiveButton(android.R.string.ok,
						new DialogInterface.OnClickListener() {
							@Override
							public void onClick(DialogInterface dialog,
									int which) {
								// TODO Auto-generated method stub
							}

						}).create();
		dd.setCanceledOnTouchOutside(true);
		return dd;
	}
}
public class DismissDialog extends Activity {