1、聲明變量
private boolean isExist;//退出標誌
2、實現OnKeyDown方法:
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(keyCode==KeyEvent.KEYCODE_BACK){//按鍵是返回鍵
if(!isExist) {//isExist爲false,第一次按返回鍵
isExist = true;
Toast.makeText(MainActivity.this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
//延遲3秒,變更isExist=false
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
isExist = false;
}
}, 3000);
}else{//isExist爲true,第二次按返回鍵
MainActivity.this.finish();
System.exit(0);
}
}
return false;
}