Question

I am currently developing an app in Android which will record sensor data for a fixed length of time for several cycles. For example, I plan to record the data for 10 seconds, and then stop, let the phone rest for 10 seconds, and start record again, … working in this pattern for 1 hour. My question is, how to let the phone automatically execute this plan? I am currently using code below ( from Android: How to collect sensor values for a fixed period of time?) , but it only works for one cycle, I have to manually start new cycles after I am sure the previous cycle has finished.

public void onResume() {
mSensorManager.registerListener(mListener, mSensorAcceleration, SensorManager.SENSOR_DELAY_GAME);
mSensorManager.registerListener(mListener, mSensorMagnetic, SensorManager.SENSOR_DELAY_GAME);
Handler h = new Handler();
h.postDelayed(new Runnable() {

    @Override
    public void run() {
    //    do stuff with sensor values
        mSensorManager.unregisterListener(mListener);               
    }
}, 10000);

…

Any help will be appreciated!!

Answer 1

Step #1: Have your activity implement Runnable, rather than use an anonymous inner class, moving your run() method to be implemented on the activity.

Step #2: In your run() method, schedule yourself (the activity) to run again after a delay using postDelayed(). This, plus your existing call to postDelayed(), will effectively set up a periodic call to run().

Step #3: Keep track of whether you are in “sensors on” or “sensors off” mode, and, in run(), either register or unregister the listeners as appropriate.

Step #4: In onPause(), call removeCallbacks() on your Handler to stop the periodic calls to run().

You will see an example of this sort of schedule-yourself-to-run-again logic in this sample project. Here is the activity:

package com.commonsware.android.post;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class PostDelayedDemo extends Activity implements Runnable {
  private static final int PERIOD=5000;
  private View root=null;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    root=findViewById(android.R.id.content);
  }

  @Override
  public void onResume() {
    super.onResume();

    run();
  }

  @Override
  public void onPause() {
    root.removeCallbacks(this);

    super.onPause();
  }

  @Override
  public void run() {
    Toast.makeText(PostDelayedDemo.this, "Who-hoo!", Toast.LENGTH_SHORT)
         .show();
    root.postDelayed(this, PERIOD);
  }
}