我正在学习 Android 编程的基础知识。

我有一个简单的 android 测试应用程序，我在其中将加速度计、磁力计和方向数据记录到外部文件，同时还显示它。我通过调用 initLogger 方法在单击 Start 按钮(相关传感器的 registerListener)时启动日志记录过程。

这看起来有点像这个......

public void initLogger(View view)
{
    boolean bFlag = false;

    Button btnStart = (Button)findViewById(R.id.btnStartLog);
    Button btnStop = (Button)findViewById(R.id.btnStopLog);

    btnStart.setEnabled(bFlag);
    btnStop.setEnabled(!bFlag);

    bEnableLogging = true;
    //Start reading the sensor values
    sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD), SensorManager.SENSOR_DELAY_UI);
    sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_UI);

   //so on.... 

还有一个停止按钮，它将停止记录过程(最后通过为每个传感器调用 unregisterListener 来取消注册)

数据检索过程发生在 onSensorChanged 处理程序内，该处理程序应从相关传感器检索数据，将值设置为相应的 UI 元素，最后将数据记录到外部 .csv 文件。

onSensorChanged 事件处理程序看起来像这样......

public void onSensorChanged(SensorEvent event) {


    // TODO Auto-generated method stub
    // accelerometer
    TextView tAX = (TextView) findViewById(R.id.txtViewAxValue);
    TextView tAY = (TextView) findViewById(R.id.txtViewAyValue);
    TextView tAZ = (TextView) findViewById(R.id.txtViewAzValue);

    // magnetic field
    TextView tMX = (TextView) findViewById(R.id.txtViewMx);
    TextView tMY = (TextView) findViewById(R.id.txtViewMy);
    TextView tMZ = (TextView) findViewById(R.id.txtViewMz);

    if (bEnableLogging) {
        if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {

            accelerometerdata = event.values.clone();

            tAX.setText(Double.toString(accelerometerdata[0]));
            tAY.setText(Double.toString(accelerometerdata[1]));
            tAZ.setText(Double.toString(accelerometerdata[2]));


        }

        if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {

            magneticmatrixdata = event.values.clone();

            tMX.setText(Double.toString(magneticmatrixdata[0]));
            tMY.setText(Double.toString(magneticmatrixdata[1]));
            tMZ.setText(Double.toString(magneticmatrixdata[2]));

        }

               // so on ....

虽然我从所有已配置的传感器接收数据，但我无法控制接收数据的速率。即

我知道 SensorChanged 事件会在传感器数据更改时触发。但是我希望以固定速率触发此事件。 例如:每 40 毫秒

问题:

1. 如何确保以恒定速率触发 SensorChanged 事件？
2. Java 中的 TimerTask 类对这种情况有帮助吗？

这里的专家。请帮助我:)

最佳答案

您可以在注册传感器时通过更改延迟来更改间隔。

int SENSOR_DELAY_FASTEST    get sensor data as fast as possible 
int SENSOR_DELAY_GAME       rate suitable for games 
int SENSOR_DELAY_NORMAL     rate (default) suitable for screen orientation changes
int SENSOR_DELAY_UI         rate suitable for the user interface

根据 this ，最快的延迟就是您所需要的，如果它对您来说变化得不够快，那是因为没有变化。没有 getSensorData 方法。

You can specify other data delays, such as SENSOR_DELAY_GAME (20,000 microsecond delay), SENSOR_DELAY_UI (60,000 microsecond delay), or SENSOR_DELAY_FASTEST (0 microsecond delay). As of Android 3.0 (API Level 11) you can also specify the delay as an absolute value (in microseconds).

The delay that you specify is only a suggested delay. The Android system and other applications can alter this delay. As a best practice, you should specify the largest delay that you can because the system typically uses a smaller delay than the one you specify (that is, you should choose the slowest sampling rate that still meets the needs of your application). Using a larger delay imposes a lower load on the processor and therefore uses less power.

关于java - 如何以固定速率从 Android 运动传感器记录数据，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12246942/