Android - 每 5 秒循环部分代码
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/21726055/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Android - loop part of the code every 5 seconds
提问by Damijan
I would like to start repeating two lines of code every 5 seconds when I press the button START and end it, when I press the button STOP. I was trynig with a TimerTask and Handles, but couldn't figure it out how.
当我按下按钮 START 时，我想每 5 秒开始重复两行代码，当我按下按钮 STOP 时结束它。我正在尝试使用 TimerTask 和 Handles，但不知道怎么做。
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//final int i;
final TextView textView = (TextView) findViewById(R.id.textView);
final Button START_STOP = (Button) findViewById(R.id.START_STOP);
final ImageView random_note = (ImageView) findViewById(R.id.random_note);
final int min = 0;
final int max = 2;
final Integer[] image = { R.drawable.a0, R.drawable.a1,R.drawable.a2 };
START_STOP.setTag(1);
START_STOP.setText("START");
START_STOP.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
int status = (Integer) v.getTag();
if (status ==1) {
textView.setText("Hello");
START_STOP.setText("STOP");
v.setTag(0);
final Random random = new Random();
//************************************************************
// I would like to loop next 2 lines of code every 5 seconds.//
int i = random.nextInt(2 - 0 + 1) + 0;
random_note.setImageResource(image[i]);
//************************************************************
}
else
{
textView.setText("Bye");
START_STOP.setText("Let's PLAY!");
v.setTag(1);
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
回答by britzl
Using a CountDownTimer as in one of the other answers is one way to do it. Another would be to use a Handler and the postDelayedmethod:
在其他答案之一中使用 CountDownTimer 是一种方法。另一种方法是使用 Handler 和postDelayed方法：
private boolean started = false;
private Handler handler = new Handler();
private Runnable runnable = new Runnable() {
@Override
public void run() {
final Random random = new Random();
int i = random.nextInt(2 - 0 + 1) + 0;
random_note.setImageResource(image[i]);
if(started) {
start();
}
}
};
public void stop() {
started = false;
handler.removeCallbacks(runnable);
}
public void start() {
started = true;
handler.postDelayed(runnable, 2000);
}
Here's an example using a Timer and a TimerTask:
下面是一个使用 Timer 和 TimerTask 的示例：
private Timer timer;
private TimerTask timerTask = new TimerTask() {
@Override
public void run() {
final Random random = new Random();
int i = random.nextInt(2 - 0 + 1) + 0;
random_note.setImageResource(image[i]);
}
};
public void start() {
if(timer != null) {
return;
}
timer = new Timer();
timer.scheduleAtFixedRate(timerTask, 0, 2000);
}
public void stop() {
timer.cancel();
timer = null;
}
回答by Giacomoni
You can use CountDownTimeras the following method:
您可以使用CountDownTimer以下方法：
private CountDownTimer timer;
timer = new CountDownTimer(5000, 20) {
@Override
public void onTick(long millisUntilFinished) {
}
@Override
public void onFinish() {
try{
yourMethod();
}catch(Exception e){
Log.e("Error", "Error: " + e.toString());
}
}
}.start();
And then to call the timer again:
然后再次调用计时器：
public void yourMethod(){
//do what you want
timer.start();
}
To cancel the timer, you can call timer.cancel();
要取消计时器，您可以调用 timer.cancel();
Hope it helps!
希望能帮助到你！
回答by db80
You can use RxJava2/RxAndroid2 and create an Observable that emits a message every second (or whatever you want), example with pseudo code:
您可以使用 RxJava2/RxAndroid2 并创建一个 Observable 每秒（或任何您想要的）发出一条消息，例如带有伪代码：
Disposable timer = Observable.interval(1000L, TimeUnit.MILLISECONDS)
.timeInterval()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Consumer<Timed<Long>>() {
@Override
public void accept(@NonNull Timed<Long> longTimed) throws Exception {
//your code here.
Log.d(TAG, new DateTime());
}
});
When you want to stop it, you can simply call:
当你想停止它时，你可以简单地调用：
timer.dispose();
I find this code much more readable than the other options.
我发现此代码比其他选项更具可读性。
回答by db80
I don't have much more to add, other than to mention the differences between using Handler, CountDownTimer, and regular Timer. As britzl mentioned, the CountDownTimer uses a Handler internally, so that is equivalent to using the handler directly. A handler is used for running Ui stuff, for very short periods of time. An example would be setText for a text view. For computationally intensive tasks, handlers may cause a lag. A timer also can only run short tasks, but it is not necessarily only for UI stuff. For more complicated tasks, a new Thread should be used.
除了提到使用Handler、CountDownTimer 和常规Timer 之间的区别之外，我没有更多要补充的了。正如britzl提到的，CountDownTimer内部使用了一个Handler，所以相当于直接使用了Handler。处理程序用于在很短的时间内运行 Ui 内容。一个例子是文本视图的 setText 。对于计算密集型任务，处理程序可能会导致延迟。计时器也只能运行短期任务，但不一定只用于 UI 内容。对于更复杂的任务，应该使用新的线程。
