如何在android状态栏上写

Question

我试图在我的onCreate()方法中做这样的事情.

@TargetApi(21)
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    getWindow().getDecorView().setBackgroundColor(Color.parseColor("#444444"));
    getWindow().setStatusBarColor(Color.parseColor("#565656"));
    getSupportActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#4d4d4d")));
    writeOnStatusBar("Hello world");
}