利用Snackbar实现双重退出提示信息

private Timer tExit;
private static Boolean isExit = false;
private static final String TAG_EXIT = "exit";

private void showSnackBar(View view, String text) {
       if (snackbar == null) {
           snackbar = Snackbar.make(view, text, Snackbar.LENGTH_SHORT);
       } else {
           snackbar.setText(text);
           snackbar.setDuration(Snackbar.LENGTH_SHORT);
       }
       snackbar.show();
   }

使用快捷键ctrl+o  快速找到其方法并生成对应方法以及内容

if (keyCode == KeyEvent.KEYCODE_BACK) {
          tExit = null;
          if (!isExit) {
              isExit = true; // 准备退出
              showSnackBar(titleBar, getString(R.string.click_exit));
              tExit = new Timer();
              tExit.schedule(new TimerTask() {
                  @Override
                  public void run() {
                      isExit = false; // 取消退出
                  }
              }, 2000); 
	} else {
              Intent intent = new Intent(this, MainActivity.class);
              intent.putExtra(MainActivity.TAG_EXIT, true);
              startActivity(intent);
          }

          return true;
      }