Question

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。有人给了我一些我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线程正在等待从计算频率的另一个线程返回，因此线程只会在开始运行时获得二极管的值。那么如何让频率线程具有二极管的实时值，并且在计算出频率后又将其传递回要显示的UI线程？

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;
}

}

Answer 1

设置最简单的方法可能是使用Handler将消息从FrequencyThread发送到主线程。可能更倾向于使用AsyncTask抽象出Thread / Handler并使整个情况更容易处理。这样做可能需要您将IOIOLooper事物放入AsyncTask中，但我没有使用该板或其Java API的经验。

此外，您不应该在setText（）方法中使用“runOnUiThread”或Runnable。这似乎只是从主线程调用。

您要做的是覆盖Handler 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，但我无法诚实地跟踪它。

外部光传感器输入频率

1 个答案: