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背景：我有一个 IOIO，用于测量光电二极管的输出，然后将其转换为数字输出。我需要找到信号在 1 和 0 之间变化的频率。有人给了我一些可以用来测量频率的代码，但我不知道如何将它集成到我现有的应用程序中。我知道我实现它的方式不起作用，因为更新变量的 UI 线程正在等待另一个计算频率的线程的返回，因此该线程只会在开始运行时获得二极管的值。那么如何使频率线程具有二极管的实时值，并且在计算出频率后将其传递回 UI 线程以显示？

这是我的 UI 线程（FrequencyApp.java）：

    public class FrequencyApp extends IOIOActivity {
private TextView textView_;
private TextView textView2_;
private TextView textView3_;
private ToggleButton toggleButton_;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    textView_ = (TextView)findViewById(R.id.TextView);
    textView2_ = (TextView)findViewById(R.id.TextView2);
    textView3_ = (TextView)findViewById(R.id.FrequencyLabel);
    toggleButton_ = (ToggleButton)findViewById(R.id.ToggleButton);

    enableUi(false);
}

class Looper extends BaseIOIOLooper {
    private AnalogInput input_;
    private DigitalOutput led_;
    volatile int diode;
    private long frequency;


    @Override
    public void setup() throws ConnectionLostException {
        try {
            input_ = ioio_.openAnalogInput(31);
            led_ = ioio_.openDigitalOutput(IOIO.LED_PIN, true);
            enableUi(true);
        } catch (ConnectionLostException e) {
            enableUi(false);
            throw e;
        }
    }

    @Override
    public void loop() throws ConnectionLostException {
        try {
            led_.write(!toggleButton_.isChecked());


            float reading = input_.getVoltage();

            if(reading  > 1){
                diode = 1;
            } else { 
                diode = 0;
            }
            if(toggleButton_.isChecked()){
                FrequencyThread frequencyTaskThread = new FrequencyThread();
                frequencyTaskThread.setPriority(Thread.NORM_PRIORITY-1); //Make the background thread low priority. This way it will not affect the UI performance
                frequencyTaskThread.start();
                frequency = (long) frequencyTaskThread.run(diode);
                frequencyTaskThread.stop();
            }
            setText(Float.toString(reading), Long.toString(diode), Long.toString(frequency));
            Thread.sleep(100);
        } catch (InterruptedException e) {
            ioio_.disconnect();
        } catch (ConnectionLostException e) {
            enableUi(false);
            throw e;
        }
    }
}

@Override
protected IOIOLooper createIOIOLooper() {
    return new Looper();
}

private void enableUi(final boolean enable) {
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            toggleButton_.setEnabled(enable);
        }
    });
}

private void setText(final String str,final String str2,final String str3 ) {
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            textView_.setText(str);
            textView2_.setText(str2);
            textView3_.setText(str3);
        }
    });
}

}

这是计算频率的线程（FrequencyThread.java：

    public class FrequencyThread extends Thread {
public float run(int diode){
// Find frequency to the nearest hz (+/- 10%)
// It's assumed that some other process is responsible for updating the "diode"
// variable.  "diode" must be declared volatile.
long duration = 1000;   // 1 second
final int interval = 100;    // sampling interval = .01 second
int oldState = diode;
int count = 0;
final long startTime = System.currentTimeMillis();
final long endtime = startTime + duration;
while (System.currentTimeMillis() < endtime) {
  // count all transitions, both leading and trailing
  if (diode != oldState) {
    ++count;
    oldState = diode;
  }

    Thread.sleep(interval);
} catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
}
// find the actual duration
duration = System.currentTimeMillis() - startTime;
// Compute frequency. The 0.5 term is because we were counting both leading and
// trailing edges.
float frequency = (float) (0.5 * count / (duration/1000));
return frequency;
}

}

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1 回答 1

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您设置它的最简单方法可能是使用处理程序将消息从频率线程发送到主线程。使用AsyncTask抽象出 Thread / Handler 并使整个情况更容易处理的方式可能更受欢迎。这样做可能需要您将 IOIOLooper 放入 AsyncTask 中，但我没有使用该板或其 Java API 的经验。

此外，您的 setText() 方法中根本不需要“runOnUiThread”或 Runnable。无论如何，这似乎只是从主线程中调用的。

您要做的是覆盖您的处理程序 handleMessage() 以调用 setText()。然后在 FrequencyThread 内部调用 handler.sendMessage() 传回数据和/或消息（即错误）。

我尝试使用您发布的代码作为示例，但我无法诚实地遵循它。

于 2012-05-13T14:11:19.100 回答