public class myFloatView extends Activity {
/** Called when the activity is first created. */
@Override public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button bb=new Button(getApplicationContext());
WindowManager wm=(WindowManager)getApplicationContext().getSystemService("window");
WindowManager.LayoutParams wmParams = new WindowManager.LayoutParams(); 
/** *以下都是WindowManager.LayoutParams的相关属性 * 具体用途请参考SDK文档 */
wmParams.type=2002; //这里是关键，你也可以试试2003
wmParams.format=1; /** *这里的flags也很关键 *代码实际是wmParams.flags |= FLAG_NOT_FOCUSABLE; *40的由来是wmParams的默认属性（32）+ FLAG_NOT_FOCUSABLE（8） */
wmParams.flags=40;
wmParams.width=40;
wmParams.height=40;
wm.addView(bb, wmParams);//创建View
}
}

/** * Window type: phone. These are non-application windows providing * user interaction with the phone (in particular incoming calls). * These windows are normally placed above all applications, but behind * the status bar. */
public static final int TYPE_PHONE = FIRST_SYSTEM_WINDOW+2;
/** * Window type: system window, such as low power alert. These windows * are always on top of application windows. */
public static final int TYPE_SYSTEM_ALERT = FIRST_SYSTEM_WINDOW+3;