Android 计时器似乎忽略了 .cancel

Question

我正在构建一个 Android 应用程序，它可以在打开某个 activity 时录制声音。我把录音功能分离在一个服务class中。我一直在使用问题的答案并且有效。然而，我再次停止计时器时遇到了一些麻烦！

ArrayList<Double> decibelList = new ArrayList<>();
private MediaRecorder mRecorder = null;
Timer timer = new Timer();
RecorderTask recorderTask;

public void startRecorder() {
    mRecorder = new MediaRecorder();
    mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    timer = new Timer();
    recorderTask = new RecorderTask(mRecorder);
    timer.scheduleAtFixedRate(recorderTask, 0, 400);
    mRecorder.setOutputFile("/dev/null");

    try {
        System.out.println("--MediaRecorder started--");
        mRecorder.prepare();
        mRecorder.start();
    } catch(IllegalStateException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

private class RecorderTask extends TimerTask {
    private MediaRecorder recorder;

    public RecorderTask(MediaRecorder recorder) {
        this.recorder = recorder;
    }

    public void run() {
        mActivity.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                int amplitude = recorder.getMaxAmplitude();
                double amplitudeDb = 20 * Math.log10((double) Math.abs(amplitude));
                if (!String.valueOf(amplitudeDb).equals("-Infinity")) {
                    decibelList.add(amplitudeDb);
                }
                System.out.println("Current dB: " + amplitudeDb);
            }
        });
    }
}

public void stopRecorder() {
    if (mRecorder != null) {
        if (timer != null) {
            timer.cancel();
            timer.purge();
            timer = null;
        }
        try {
            mRecorder.stop();
            mRecorder.release();
            mRecorder = null;
        } catch (RuntimeException stopException){}
    }
}

然后在我的 activity.

中的 onBackPressed、onPause 和 onStop 中执行 stopRecorder 函数

如您所见，我已尝试通过 timer.cancel(); 停止它；但它继续运行尽管关闭 activity.

Answer 1

解决了我的问题。

原来我的取消确实有效，但我不小心启动了两个计时器！我通过添加检查我的计时器是否为空来解决了这个问题。

public void startRecorder() {
    mRecorder = new MediaRecorder();
    mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
    mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
    mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    mRecorder.setAudioEncodingBitRate(16);
    mRecorder.setAudioSamplingRate(44100);
    if (timer == null) {
        timer = new Timer();
        recorderTask = new RecorderTask(mRecorder);
        timer.scheduleAtFixedRate(recorderTask, 0, 400);
    }
    mRecorder.setOutputFile("/dev/null");

    try {
        System.out.println("--MediaRecorder started--");
        mRecorder.prepare();
        mRecorder.start();
    } catch (IllegalStateException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

以防万一有人想使用代码。

非常感谢您的评论！他们帮助我优化了我的代码。

Android 计时器似乎忽略了 .cancel

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