带有处理程序的顺序倒数计时器不会正确更新 textView

Question

我试图建立某种顺序倒计时。意思是，我建立了一个“练习”队列，每个练习都包含一个特定的持续时间，即倒计时时间。在自定义倒计时课程中，我将这些练习从队列中弹出，并将持续时间用作倒计时。 我希望这些倒计时一个接一个地运行。为此，我基于抽象类CountDownTimer 的代码基础构建了一个Countdown 类。

import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Locale;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.os.SystemClock;
import android.widget.Button;
import android.widget.TextView;

    public class ExerciseMeCountDownTimer {

    private static final int MSG_COUNTDOWN = 100;
    private static final int MSG_FINISH = 99;
    private ArrayDeque<Exercise> eq;
    private long mMillisInFuture;
    private int mCountdownInterval;
    private String name;
    private long mStopTimeInFuture;
    CountdownHandler cHandler;

    public ExerciseMeCountDownTimer(ArrayList<Exercise> elist,
            Button startStopButton, TextView countdownText,
            CountdownHandler cHandler) {

        this.cHandler = cHandler;
        eq = new ArrayDeque<Exercise>(elist);
        this.start();
    }

    public final void cancel() {
        mHandler.removeMessages(MSG);
    }

    private synchronized final ExerciseMeCountDownTimer start() {
        if (!eq.isEmpty()) {
            Exercise e = eq.pop();
            this.mMillisInFuture = Long.parseLong(e.getDuration());
            this.mCountdownInterval = 30;
            this.name = e.getName();
        } else {
            onFinish();
            return this;
        }

        if (mMillisInFuture <= 0) {
            onFinish();
            return this;
        }
        mStopTimeInFuture = SystemClock.elapsedRealtime() + mMillisInFuture;
        mHandler.sendMessage(mHandler.obtainMessage(MSG));
        return this;
    }

    public void onTick(long millisUntilFinished) {
        Message msg = cHandler.obtainMessage(MSG_COUNTDOWN);
        Bundle data = new Bundle();
        String text = String.format(Locale.GERMANY, "%02d:%02d:%03d",
                millisUntilFinished / 100000, millisUntilFinished / 1000,
                millisUntilFinished % 1000);
        data.putString("countdown", text);
        msg.setData(data);
        cHandler.sendMessage(msg);

    }

    public void onFinish() {
        if (!eq.isEmpty()) {
            this.start();
        }

        Message msg = cHandler.obtainMessage(MSG_FINISH);
        Bundle data = new Bundle();
        String text = String.format(Locale.GERMANY, "00:00:000");
        data.putString("finish", text);
        msg.setData(data);
        cHandler.sendMessage(msg);
    }

    private static final int MSG = 1;

    // handles counting down
    private Handler mHandler = new Handler() {

        @Override
        public void handleMessage(Message msg) {

            final long millisLeft = mStopTimeInFuture
                    - SystemClock.elapsedRealtime();

            if (millisLeft <= 0) {
                onFinish();
            } else if (millisLeft < mCountdownInterval) {
                // no tick, just delay until done
                sendMessageDelayed(obtainMessage(MSG), millisLeft);
            } else {
                long lastTickStart = SystemClock.elapsedRealtime();
                onTick(millisLeft);

                // take into account user's onTick taking time to
                // execute
                long delay = lastTickStart + mCountdownInterval
                        - SystemClock.elapsedRealtime();

                // special case: user's onTick took more than interval
                // to
                // complete, skip to next interval
                while (delay < 0)
                    delay += mCountdownInterval;

                sendMessageDelayed(obtainMessage(MSG), delay);
            }
        }

    };

    @Override
    public String toString() {
        return this.name;
    }
}

重要的部分是sendMessage 部分，我将倒计时剩余的时间发送到我的MainActivity 的handler，然后应该更新一个文本视图。

import android.os.Handler;
import android.os.Message;

class CountdownHandler extends Handler {
private static final int MSG_COUNTDOWN = 100;
private static final int MSG_FINISH = 99;
private MainActivity mActivity;

CountdownHandler(MainActivity activity) {
    this.mActivity = activity;
}

@Override
public void handleMessage(Message msg) {
    if (msg.what == MSG_COUNTDOWN) {
        String text = msg.getData().getString("countdown");
        this.mActivity.sayLog(text);
    }
    if (msg.what == MSG_FINISH) {
        String text = msg.getData().getString("finish");
        this.mActivity.sayLog(text);
    }

}

最后更新MainActivty中的textView

public void sayLog(String text) {
    countdown.setText(text);
}

ExerciseMeCountDownTimer 被调用

new ExerciseMeCountDownTimer(elist, cHandler); 

在一些 onClick() 上。

问题是，有时（实际上大部分时间）textView 没有正确更新。它会在 00:05:211 等随机时间停止更新。 有人介意告诉我为什么会一直这样吗？也许还添加一个解决方案或至少一些我应该阅读以理解问题的文献（也许指出一些部分）？我也对替代方法持开放态度，因为我对 android 中的这个“处理程序”、“线程”东西不熟悉。

编辑

• 文本视图正在更新，但文本视图是可点击的。每当我单击 textview 时，它就会停止更新！
• 正如接受的答案所示，我决定使用直接方法在onTick() 方法中更新适当的文本视图。

Answer 1

在这种情况下使用Handler 会使事情变得过于复杂。

CountDownTimers onTick() 和 onFinish() 都在 UI Thread 上运行，因此从任一方法更新 TextViews 和其他 Views 只需将 View 的引用传递给即可轻松完成类的构造函数，就像你已经在做的那样。然后你只需在所需的方法中更新它。

// could create a member variable for the TextView with your other member variables
...
mTV;

然后在你的构造函数中分配它 // 删除了对 Handler 的引用——你已经在这里引用了 TextView 公共ExerciseMeCountDownTimer（ArrayList elist， 按钮 startStopButton, TextView countdownText) { mTV = 倒计时文字；

然后在需要的任何方法中更新

public void onTick(long millisUntilFinished) {

    String text = String.format(Locale.GERMANY, "%02d:%02d:%03d",
            millisUntilFinished / 100000, millisUntilFinished / 1000,
            millisUntilFinished % 1000);
    mTV.setText(text);  // set the text here


}

public void onFinish() {
    if (!eq.isEmpty()) {
        this.start();
    }