如何获取Android接近传感器的当前值？

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

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.

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);
  }
 }
}