android 雙擊退出

	@Override
	public boolean onKeyDown(int keyCode, KeyEvent event) {

		if (keyCode == KeyEvent.KEYCODE_BACK) {
			if(!exitBy2Click(HomeActivity.this)){
				return false;
			}
			 // 調用雙擊退出函數
		}
		return super.onKeyDown(keyCode, event);
	}
	
	private long time;

	private boolean exitBy2Click(final Context context) {
		if(System.currentTimeMillis()-time>2000){//大於2秒
			Toast.makeText(context, "再按一下退出應用", Toast.LENGTH_SHORT).show();
			time = System.currentTimeMillis();
			Handler handler = new Handler();
			handler.postDelayed(new Runnable() {
				
				@Override
				public void run() {
					time = 0;
					
				}
			}, 2000);
			return false;
		}else{//兩秒內。退出應用
			return true;
		}
		
		
	}

貌似沒有什麼bug 吧