Android如何实现接近传感器

package com.example.sz.proximitytest;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
 private static final String TAG = "MainActivity";
 private SensorManager mSensorManager=null;
 private Sensor mSensor=null;
 private TextView textView1=null;
 private TextView textView2=null;
 private TextView textView3=null;
 private Button button1=null;
 private Button button2=null;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 textView1 = (TextView) findViewById(R.id.textView1);
 textView2 = (TextView) findViewById(R.id.textView2);
 textView3 = (TextView) findViewById(R.id.textView3);
 /*获取系统服务（SENSOR_SERVICE）返回一个SensorManager对象*/
 mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
 /*通过SensorManager获取相应的（接近传感器）Sensor类型对象*/
 mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_PROXIMITY);
 /*注册相应的SensorService*/
 button1 = (Button) findViewById(R.id.button1);
 button1.setOnClickListener(new Button.OnClickListener() {

  @Override
  public void onClick(View arg0) {
  mSensorManager.registerListener(mSensorEventListener, mSensor
   , SensorManager.SENSOR_DELAY_NORMAL);
  }
 });
 /* 销毁相应的SensorService
  * 很关键的部分，注意，说明文档中提到，即使Activity不可见的时候，感应器依然会继续工作
  * 所以一定要关闭触发器，否则将消耗用户大量电量*/
 button2 = (Button) findViewById(R.id.button2);
 button2.setOnClickListener(new Button.OnClickListener() {

  @Override
  public void onClick(View v) {
  mSensorManager.unregisterListener(mSensorEventListener, mSensor);
  }
 });
 }

 /*声明一个SensorEventListener对象用于侦听Sensor事件，并重载onSensorChanged方法*/
 private final SensorEventListener mSensorEventListener = new SensorEventListener() {

 @Override
 public void onSensorChanged(SensorEvent event) {
  Log.e(TAG, "onSensorChanged: -----0------"+event.values[0]);
  Log.e(TAG, "onSensorChanged: ------1-----"+event.values[1]);
  Log.e(TAG, "onSensorChanged: --------2---"+event.values[2]);




  if (event.sensor.getType() == Sensor.TYPE_PROXIMITY) {
  /*接近传感器检测物体与听筒的距离，单位是厘米。*/
  //这里要注意，正常都是取第一位的值，但我碰到一个取第二位的
  float distance1 = event.values[0];
  float distance2 = event.values[1];
  float distance3 = event.values[2];
  textView1.setText("[0]距离："+String.valueOf(distance1) + "cm");
  textView2.setText("[1]距离："+String.valueOf(distance2) + "cm");
  textView3.setText("[2]距离："+String.valueOf(distance3) + "cm");
  }
 }

 @Override
 public void onAccuracyChanged(Sensor sensor, int accuracy) {

 }
 };


}

<&#63;xml version="1.0" encoding="utf-8"&#63;>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:gravity="center"
 android:orientation="vertical"
 tools:context=".MainActivity">

 <TextView
 android:id="@+id/textView1"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:text="Hello World!" />

 <Button
 android:id="@+id/button1"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_marginTop="20dp"
 android:text="打开" />

 <Button
 android:id="@+id/button2"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:layout_marginTop="20dp"
 android:text="关闭" />
</LinearLayout>