public class MainActivity extends Activity implements SensorEventListener{
 public static final String TAG = "SensorTest";
 private SensorManager sensorManager;
 private TextView tv;
 private PowerManager localPowerManager = null;// 电源管理对象
 private WakeLock localWakeLock = null;// 电源锁
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
  tv = (TextView) findViewById(R.id.tv);
  localPowerManager = (PowerManager) getSystemService(POWER_SERVICE);
  // 获取PowerManager.WakeLock对象,后面的参数|表示同时传入两个值,最后的是LogCat里用的Tag
  localWakeLock = this.localPowerManager.newWakeLock(32, "hahaha");// 第一个参数为电源锁级别，第二个是日志tag
 }
 @Override
 protected void onResume() {
  sensorManager.registerListener(this,
    sensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY),
    SensorManager.SENSOR_DELAY_UI);
  super.onResume();
 }
 @Override
 protected void onPause() {
  sensorManager.unregisterListener(this);
  super.onPause();
 }
 @Override
 public void onSensorChanged(SensorEvent event) {
  // TODO Auto-generated method stub
  float[] values = event.values;
  switch (event.sensor.getType()) {
  case Sensor.TYPE_PROXIMITY:
   tv.setText(values[0] + "");
   if (values[0] == 0.0) {// 贴近手机
    System.out.println("hands up");
    Log.d(TAG, "hands up in calling activity");
    if (localWakeLock.isHeld()) {
     return;
    } else {
     localWakeLock.acquire();// 申请设备电源锁
    }
   } else {// 远离手机
    System.out.println("hands moved");
    Log.d(TAG, "hands moved in calling activity");
    if (localWakeLock.isHeld()) {
     return;
    } else {
     localWakeLock.setReferenceCounted(false);
     localWakeLock.release(); // 释放设备电源锁
    }
    break;
   }
  }
 }
 @Override
 public void onAccuracyChanged(Sensor sensor, int accuracy) {
  // TODO Auto-generated method stub
 }
}

<uses-permission android:name="android.permission.DEVICE_POWER"/>
<uses-permission android:name="android.permission.WAKE_LOCK"/>