Android

Question

所以我有下面的代码，它基本上获取初始电池电量，等待一定时间，然后在 calculateHelper 中获取结束电池电量，然后找到差异并打印它。

    // Get the initial battery level
    IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
    Intent batteryStatus = this.registerReceiver(null, ifilter);
    int level = batteryStatus.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
    System.out.println("Initial battery level is: " + level);
    int scale = batteryStatus.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
    final float batteryPctTemp0 = level / (float) scale;
    final float batteryPct0 = batteryPctTemp0 * 100;

    int waitTime = 60000 * interval; // 1 minute is 60000 miliseconds
    System.out.println("Wait time is " + waitTime);
    Runnable r = new Runnable() {
        @Override
        public void run(){
            calculateHelper(batteryPct0,startButton);
        }
    };
    Handler h = new Handler();
    h.postDelayed(r, waitTime);

我想无限循环（直到程序退出）整个过程，以便在每个后续线程完成后，下一个线程开始，每次获取一个新的初始电池电量并将其传递给 calculateHelper 函数以计算新的区别。我不想让线程堆积起来。我一次想要一个线程。换句话说，循环需要等待线程完成才能开始另一个线程。

我这辈子都不知道该怎么做！如果我把整个事情放到一段时间里，它只会反复打开线程，导致 phone.

崩溃

如果有人能为我指出正确的方向，我将不胜感激。此外，如果需要更多代码来解决问题，只需发表评论，我会在将其添加到我的问题后立即回复。

谢谢。

感谢Whooper，我在循环中添加了这种调节执行顺序的方法。但是，由于某种原因，我的 postExecute() 方法从未被执行，也没有发生任何事情。

    private class BatteryLifeTask extends AsyncTask<Void, Void, Void> {

    // Member variables
    Context appContext;
    float batteryPct0;
    Button startButton;

    public BatteryLifeTask(Context context, Button start) {
        super();
        appContext = context;
        startButton = start;
    }

    protected Void doInBackground(Void... params) {
        // Get the initial battery level
        IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
        Intent batteryStatus = appContext.registerReceiver(null, ifilter);
        int level = batteryStatus.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
        System.out.println("Initial battery level is: " + level);
        int scale = batteryStatus.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
        final float batteryPctTemp0 = level / (float) scale;
        batteryPct0 = batteryPctTemp0 * 100;
        return null;
    }

    protected void onPostExecute() {
        int waitTime = 60000 * interval; // 1 minute is 60000 miliseconds
        System.out.println("In postExecute. waitTime is" + waitTime);
        Runnable r = new Runnable() {
            @Override
            public void run(){
                System.out.println("An interval has passed.");
                calculateHelper(batteryPct0,startButton);
                new BatteryLifeTask(appContext,startButton).execute();
            }
        };
        Handler h = new Handler();
        h.postDelayed(r, waitTime);
    }
}

以及我对执行方法的调用：

    // Start the task loop
    new BatteryLifeTask(getApplicationContext(), startButton).execute();

我发现了问题：

我忘记设置 @Override 注释，这个答案：状态：

"If your params of onPostExecute(Param param) don't match the one you defined with extends AsyncTask<...,...,Param> and you didn't use the @Override annotation, it will never be executed and you don't get a warning from Eclipse."

所以我已将 postExecute 方法更正为：

        @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        int waitTime = 60000 * interval; // 1 minute is 60000 miliseconds
        System.out.println("In postExecute. waitTime is " + waitTime);
        Runnable r = new Runnable() {
            @Override
            public void run(){
                System.out.println("An interval has passed.");
                calculateHelper(batteryPct0,startButton);
                new BatteryLifeTask(appContext,startButton).execute();
            }
        };
        Handler h = new Handler();
        h.postDelayed(r, waitTime);
    }

所有问题现已解决。

Answer 1

尝试使用 AsyncTask。 http://developer.android.com/reference/android/os/AsyncTask.html

这样就可以在onPostExecute()被调用时再次执行任务

像这样：

private class BatteryLifeTask extends AsyncTask<Void, Void, Void> {
         protected void doInBackground(Void... params) {
             // Get the initial battery level
            IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
            Intent batteryStatus = this.registerReceiver(null, ifilter);
            int level = batteryStatus.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
            System.out.println("Initial battery level is: " + level);
            int scale = batteryStatus.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
            final float batteryPctTemp0 = level / (float) scale;
            final float batteryPct0 = batteryPctTemp0 * 100;
         }

         protected void onPostExecute() {
            int waitTime = 60000 * interval; // 1 minute is 60000 miliseconds
            Runnable r = new Runnable() {
                @Override
                public void run(){
                   new BatteryLifeTask.execute();
                }
            };
            Handler h = new Handler();
            h.postDelayed(r, waitTime);
         }
 }

请注意，此代码未经测试。但我希望它能给你一个想法:-)

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