现在的智能手机都配备了各种各样的传感器，本文将介绍Android SDK提供的传感器开发接口，并通过简单实例展示如何使用这些接口。

Andriod SDK传感器相关类

android SDK提供的与传感器相关的类有(位于android.hardware包)：

Sensor： 表示传感器的类，它保存有传感器名称，厂商，版本，精确度等信息；

SensorEvent：表示传感器事件，它可以保存传感器的值，传感器类型，时间戳等信息；

SensorEventListener：用于接收传感器来自SensorManager的通知，当传感器发生变化时，它包含两个回调函数。

SensorManager：SensorManager让你可以访问设备（手机）的全部传感器。lets you access the device‘s sensors.
可通过以android.content.Context.SENSOR_SERVICE为参数调用Context.getSystemService()获取一个该类的实例。
注意：应当始终保证在不需要使用传感器的时候禁用传感器，特别是当你的activity暂停的时候。没有这样做将会导致电池只能使用很少几个小时。记住，系统不会在屏幕关闭的时候自动禁用传感器。

SensorListener：已废除，不再介绍。

SensorEvent API 定义的坐标系统

Android的SensorEvent API定义的坐标系统是：X轴水平向右，Y轴垂直向上，Z轴沿屏幕向外。在这个坐标系统里，屏幕后面的Z值为负。如下图所示：

下面介绍Android Sensor相关API如何使用。

Demo

来自doc的demo

SensorManager的doc里给出了一个简单的demo：

 public class SensorActivity extends Activity, implements SensorEventListener {
     private final SensorManager mSensorManager;
     private final Sensor mAccelerometer;

     public SensorActivity() {
         mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
         mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
     }

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

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

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

     public void onSensorChanged(SensorEvent event) {
     }
 }

另一个demo——SensorTest

下面是一个传感器测试demo，可以测试你android手机支持那些传感器，并能实时显示传感器的值。

布局文件如下：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.sensortest.MainActivity" >

    <Button
        android:id="@+id/btnNext"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Next" />

    <Button
        android:id="@+id/btnPause"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/btnNext"
        android:layout_alignBottom="@+id/btnNext"
        android:layout_toRightOf="@+id/btnNext"
        android:text="Pause" />

    <TextView
        android:id="@+id/txtInfo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/btnNext"
        android:layout_below="@+id/btnNext"
        android:layout_marginLeft="15dp"
        android:layout_marginTop="18dp"
        android:text="Sensor Informations" />

    <TextView
        android:id="@+id/txtDetails"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/txtInfo"
        android:layout_below="@+id/txtInfo"
        android:layout_marginTop="14dp"
        android:text="Sensor Values" />

</RelativeLayout>

Activity代码如下：

package com.example.sensortest;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

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

public class MainActivity extends ActionBarActivity {
	private final String TAG = "SensorTest";

	SensorManager sensorManager;
	SensorEventListener listener;
	
	List<Sensor> allSensors;
	volatile int currentIndex = -1;

	Button btnNext;
	Button btnPause;

	TextView txtInfo;
	TextView txtValues;

	AtomicInteger showDetail = new AtomicInteger(1);

	private void init() {
		sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
		allSensors = sensorManager.getSensorList(Sensor.TYPE_ALL);
		initViews();
		initSensorsListener();
	}

	private void initViews() {
		btnNext = (Button) findViewById(R.id.btnNext);
		btnPause = (Button) findViewById(R.id.btnPause);

		txtInfo = (TextView) findViewById(R.id.txtInfo);
		txtValues = (TextView) findViewById(R.id.txtDetails);

		btnNext.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				currentIndex = (currentIndex + 1) % allSensors.size();
				Sensor sensor = allSensors.get(currentIndex);
				int type = sensor.getType();
				txtInfo.setText(String.format("%d: %s, %s", currentIndex + 1,
						sensorTypeToString(sensor.getType()), sensor.toString()));
				Log.d(TAG,
						String.format("%d: %s, %s", currentIndex + 1,
								sensorTypeToString(sensor.getType()),
								sensor.toString()));
			}
		});

		btnPause.setOnClickListener(new View.OnClickListener() {
			@Override
			public void onClick(View v) {
				showDetail.incrementAndGet();
				Log.d(TAG, "showDetails: " + showDetail + ", idx: " + currentIndex);
				if(showDetail.get() % 2 == 1) {
					btnPause.setText("Pause");
				}
				else {
					btnPause.setText("Start");
				}
			}
		});
	}

	private void initSensorsListener() {
		if (allSensors.size() > 0) {
			listener = new SensorEventListener() {
				long lastTime = System.currentTimeMillis();
				long time;

				@Override
				public void onSensorChanged(SensorEvent event) {
					time = System.currentTimeMillis();
					if (showDetail.get() % 2 == 1) 
					{
						Sensor sensor = event.sensor;
						if(currentIndex >= 0 
						&& sensor.getType() == allSensors.get(currentIndex).getType()) {
							StringBuffer str = new StringBuffer();
//							for (int i=0; i<event.values.length; i++) {
//								float value = event.values[i];
							for (float value : event.values) {
								str.append(value + "\n");
							}
							txtValues.setText(str);
							
							if (time - lastTime > 1000)
							{ // true ||

								Log.d(TAG, "type: " + sensorTypeToString( event.sensor.getType() )
										+ ", values: " + str.toString() 
										+ ", time: " + time);

							}
						}
					}
					lastTime = time;
				}

				@Override
				public void onAccuracyChanged(Sensor sensor, int accuracy) {
					Log.d(TAG, "onAccuracyChanged sensor: " + sensor
							+ ", accracy: " + accuracy);
				}
			};
			
			for (Sensor sensor : allSensors) {
				sensorManager.registerListener(listener, sensor, SensorManager.SENSOR_DELAY_NORMAL);
			}
		}
	}

	String sensorTypeToString(int type) {
		String res = null;
		switch (type) {
		case Sensor.TYPE_ACCELEROMETER:
			res = "ACCELEROMETER";
			break;
		case Sensor.TYPE_AMBIENT_TEMPERATURE:
			res = "AMBIENT_TEMPERATURE";
			break;
		case Sensor.TYPE_GAME_ROTATION_VECTOR:
			res = "GAME_ROTATION_VECTOR";
			break;
		case Sensor.TYPE_GEOMAGNETIC_ROTATION_VECTOR:
			res = "GEOMAGNETIC_ROTATION_VECTOR";
			break;
		case Sensor.TYPE_GRAVITY:
			res = "GRAVITY";
			break;
		case Sensor.TYPE_GYROSCOPE:
			res = "GYROSCOPE";
			break;
		case Sensor.TYPE_GYROSCOPE_UNCALIBRATED:
			res = "GYROSCOPE_UNCALIBRATED";
			break;
		case Sensor.TYPE_HEART_RATE:
			res = "HEART_RATE";
			break;
		case Sensor.TYPE_LIGHT:
			res = "LIGHT";
			break;
		case Sensor.TYPE_LINEAR_ACCELERATION:
			res = "LINEAR_ACCELERATION";
			break;
		case Sensor.TYPE_MAGNETIC_FIELD:
			res = "MAGNETIC_FIELD";
			break;
		case Sensor.TYPE_MAGNETIC_FIELD_UNCALIBRATED:
			res = "MAGNETIC_FIELD_UNCALIBRATED";
			break;
		case Sensor.TYPE_ORIENTATION:
			res = "ORIENTATION";
			break;
		case Sensor.TYPE_PRESSURE:
			res = "PRESSURE";
			break;
		case Sensor.TYPE_PROXIMITY:
			res = "PROXIMITY";
			break;
		case Sensor.TYPE_RELATIVE_HUMIDITY:
			res = "HUMIDITY";
			break;
		case Sensor.TYPE_ROTATION_VECTOR:
			res = "ROTATION_VECTOR";
			break;
		default:
			res = "UNKNOW";
			break;
		}
		return res;
	}

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		init();
	}
	
    protected void onResume() {
        super.onResume();
		for (Sensor sensor : allSensors) {
			sensorManager.registerListener(listener, sensor, SensorManager.SENSOR_DELAY_NORMAL);
		}
	}

    protected void onPause() {
        super.onPause();
		for (Sensor sensor : allSensors) {
			sensorManager.unregisterListener(listener, sensor);
		}
    }	

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	@Override
	public boolean onOptionsItemSelected(MenuItem item) {
		// Handle action bar item clicks here. The action bar will
		// automatically handle clicks on the Home/Up button, so long
		// as you specify a parent activity in AndroidManifest.xml.
		int id = item.getItemId();
		if (id == R.id.action_settings) {
			return true;
		}
		return super.onOptionsItemSelected(item);
	}
}

实际运行效果图如下：