Using postDelayed for Sensor Data

Question

I have a working app that I need adjusted. I am trying to get the label to update every 'n' seconds using the postDelayed method but I am only getting it to delay the time in which it first shows versus updating the label every so often. I have tried multiple ways of using the Runnable method with postDelayed but I haven't been able to do anything except, again, delay the initial post. I would appreciate any feedback or advice as to how to get it to work. The "textLightReading.setText" is the label I am trying to delay the update for.

`@Override
public void onSensorChanged(final SensorEvent event) {

    if (event.sensor.getType() == Sensor.TYPE_LIGHT) {
        final Handler mHandler = new Handler();
        mHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                mHandler.postDelayed(this, 1000);
                final float lux = event.values[0];
                final float conversion = Math.round(((1/638f) * lux) * 100.0f)/100.0f;
                textLightReading.setText("Light: " + conversion);
            }
        }, 1000);
    }
}`

This is another attempt...

`@Override
public void onSensorChanged(final SensorEvent event) {

    if (event.sensor.getType() == Sensor.TYPE_LIGHT) {
        float lux = event.values[0];
        final float conversion = Math.round(((1/638f) * lux) * 100.0f)/100.0f;
        final Handler mHandler = new Handler();
        mHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                textLightReading.setText("Light: " + conversion);
                //mHandler.postDelayed(this, 1000);
            }
        }, 1000);
    }
}`

I am sure I just don't understand how to use this. Thanks again in advance.

your first attempt result in recursion since you called it on top, second attempt whenever sensor changed it will create a new Handler so if the sensor changed rapidly result in many instances of handler, Try to Create Single Handler Object and postdelay at bottom. — Rachit Solanki, May 17 '16 at 12:40
So would I only wrap the if statement in the Handler/Runnable? I believe I have tried that as well with only the same result in a delay in the first post of the label. — Chris Panella, May 18 '16 at 03:17

score 0 · Accepted Answer · edited May 21 '16 at 05:58

Try this First approach

  Handler mHandler = new Handler();
  float lux,conversion;// intialize it
  Runnable run=new Runnable() {

    @Override
    public void run() {

            textLightReading.setText("Light: " + conversion);
            //Line to kill runnable before a new one starts
            mHandler.removeCallbacks(run);

    }
};

  //it will update 1 second after onSensorChanged called and when condition true
  //As per your both attempts
  @Override
public void onSensorChanged(final SensorEvent event) {

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

     lux = event.values[0];
     conversion = Math.round(((1/638f) * lux) * 100.0f)/100.0f;
    mHandler.postDelayed(run, 1000);

  }
}

To get the label to update every 'n' seconds doesn't matter if onSensorChanged called

second Approach Part 1 : //Use of Timer

 Timer swipeTimer = new Timer();
 swipeTimer.schedule(new TimerTask() {

            @Override
            public void run() {
                mHandler.post(run);
            }
        }, 500, 500); //put this onCreateView or at initialization

Note : When a timer is no longer needed, users should call cancel, which releases the timer's thread and other resources. Timers not explicitly cancelled may hold resources indefinitely.

second Approach Part 2: Similar approach mention in your question

  Handler mHandler = new Handler();
  Runnable run=new Runnable() {

    @Override
    public void run() {


            textLightReading.setText("Light: " + conversion); //update textView 
              mHandler.postDelayed(run, 1000);
    }
};


              mHandler.post(run); // at initialization or anywhere in your code where you want to start handler

  @Override
public void onSensorChanged(final SensorEvent event) {

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

     lux = event.values[0];
     conversion = Math.round(((1/638f) * lux) * 100.0f)/100.0f;

  }
}

There are many other ways you can do this...

I edited you answer but once I added 'handler.removeCallbacks(run);' to the run Runnable at the end it worked! It killed the current runnable before calling another new one 1sec after! Thank you so much for your help! — Chris Panella, May 21 '16 at 04:34

Using postDelayed for Sensor Data

1 Answers1