How to get current value of Android's proximity sensor?

Question

Is it possible to get the current value of the Proximity Sensor in Android?

I know that I can use SensorManager and Sensor and register a state changed listener, but I have no need to be notified of every state change, so it would be highly inefficient since this code is being run in a service. Also, my code won't know the value until a state change has occurred (what if the value hasn't changed...how do I know what it is? Instead, rather than registering a listener, I just want to say:

proximitySensor.getCurrentDistance();

Is this possible?

Thanks

Tomsk

Answer 1

After looking through the documentation, it looks like you can get the distance in centimeters by subscribing to the SensorEvent and looking at the data being passed back.

There is a good example of starting to use the Proximity sensor here: Android Proximity Sensor Example

After reading a bit further into the Android docs, it looks like the array values[0] returns a value in centimeters. Note, look at the docs, some sensors only return binary values, meaning that the device is either near or far.

Exorbitant

Yes, but I'm asking how to do it without using those listeners. – Tomsk

From my post: "I know that I can use SensorManager and Sensor and register a state changed listener, but I have no need to be notified of every state change, so it would be highly inefficient since this code is being run in a service. Also, my code won't know the value until a state change has occurred (what if the value hasn't changed...how do I know what it is?" – Tomsk

I apologize, I was multi-tasking while answering, my fault. I don't know that there is really any other way than to listen for the changes. – Exorbitant

There appears to be a behavior difference between real device and an emulator: On real device, as soon as I register the listener, the onSensorChanged callback is called. – Tong

Answer 2

To get access the device sensor using SensorManager, you have to call getSystemService(SENSOR_SERVICE) . Here is the example:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context=".SensorActivity" >

<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/far" />

</RelativeLayout>

Here is the java class:

import android.app.Activity;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.widget.ImageView;

public class SensorActivity extends Activity implements SensorEventListener {
 private SensorManager mSensorManager;
 private Sensor mSensor;
 ImageView iv;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  // TODO Auto-generated method stub
  super.onCreate(savedInstanceState);
  setContentView(R.layout.sensor_screen);
  mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
  mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY);
  iv = (ImageView) findViewById(R.id.imageView1);
 }

 protected void onResume() {
  super.onResume();
  mSensorManager.registerListener(this, mSensor,
    SensorManager.SENSOR_DELAY_NORMAL);
 }

 protected void onPause() {
  super.onPause();
  mSensorManager.unregisterListener(this);
 }

 public void onAccuracyChanged(Sensor sensor, int accuracy) {
 }

 public void onSensorChanged(SensorEvent event) {
  if (event.values[0] == 0) {
   iv.setImageResource(R.drawable.near);
  } else {
   iv.setImageResource(R.drawable.far);
  }
 }
}

Selfexplanatory