Android应用开发提高篇（3）-----传感器（Sensor）编程

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一、概述

Android支持的传感器种类越来越多了，这确实是一件可喜的事情，两年前在单片机上玩过加速度传感器模块，当时做的是一个摔倒检测的项目，利用相关的算法对三轴数据进行采集、处理、判断来实现检测，既然是摔倒检测，那肯定是一个便携式设备吧，没错，当时做出来的设备是小到可以放进口袋里的。庆幸的是，今天这些东西完全可以在手机上完成了，而且不用涉及到硬件设计的问题，不过今天不是讲如何去移植那个项目，而是讲讲Android上的传感器编程。Android，再一次让我看到你的强大！再一次坚定了我学习你的信心！

二、要求

了解、熟悉传感器的编程方法。

三、实现

新建工程MySensor，修改/res/layout/main.xml文件，在里面添加一个SurfaceView，完整的main.xml文件如下：

1 <?xml version="1.0" encoding="utf-8"?>
2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3     android:layout_width="fill_parent"
4     android:layout_height="fill_parent"
5     android:orientation="vertical" >
6
7     <SurfaceView
8         android:id="@+id/surfaceview"
9         android:layout_width="fill_parent"
10         android:layout_height="180dip"
11         />
12
13
14 </LinearLayout>

接着，修改MySensorActivity.java文件，代码中有详细注释，完整的MySensorActivity.java文件如下：

1 package com.nan.sensor;
2
3 import android.app.Activity;
4 import android.graphics.Canvas;
5 import android.graphics.Color;
6 import android.graphics.Paint;
7 import android.graphics.Rect;
8 import android.hardware.Sensor;
9 import android.hardware.SensorEvent;
10 import android.hardware.SensorEventListener;
11 import android.hardware.SensorManager;
12 import android.os.Bundle;
13 import android.view.SurfaceHolder;
14 import android.view.SurfaceView;
15
16 public class MySensorActivity extends Activity
17 {
18     private float acceValusX = 0f;
19     private float acceValusY = 0f;
20     private float acceValusZ = 0f;
21     private int x = 0;
22
23     private SurfaceView mSurfaceView = null;
24     private SurfaceHolder mSurfaceHolder = null;
25     private Paint mPaint = null;
26
27     private SensorManager mSensorManager;
28     private Sensor mAccelerometer;
29     private OnSensorEventListener mOnSensorEventListener = new OnSensorEventListener();
30
31     /** Called when the activity is first created. */
32     @Override
33     public void onCreate(Bundle savedInstanceState)
34
35     {
36         super.onCreate(savedInstanceState);
37         setContentView(R.layout.main);
38
39         mSurfaceView = (SurfaceView)findViewById(R.id.surfaceview);
40         mSurfaceHolder = mSurfaceView.getHolder();
41         mSurfaceHolder.addCallback(new MyHolder());
42
43         mPaint = new Paint();
44         //画笔的粗细
45         mPaint.setStrokeWidth(1.0f);
46         //从系统服务中获得传感器管服务
47         mSensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
48         mAccelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
49         //注册传感器监听
50         mSensorManager.registerListener(mOnSensorEventListener, mAccelerometer, SensorManager.SENSOR_DELAY_GAME);
51     }
52
53
54     private class OnSensorEventListener implements SensorEventListener
55     {
56
57         @Override
58         public void onAccuracyChanged(Sensor sensor, int accuracy)
59         {
60             // TODO Auto-generated method stub
61
62         }
63
64         @Override
65         public void onSensorChanged(SensorEvent event)
66         {
67             // TODO Auto-generated method stub
68
69             //获得x轴的值
70             acceValusX = event.values[0];
71             //获得y轴的值
72             acceValusY = event.values[1];
73             //获得z轴的值
74             acceValusZ = event.values[2];
75
76             //锁定整个SurfaceView
77             Canvas mCanvas = mSurfaceHolder.lockCanvas();
78             try
79             {
80                 if(mCanvas!=null)
81                 {
82                     //画笔的颜色(红)
83                     mPaint.setColor(Color.RED);
84                     //画X轴的点
85                     mCanvas.drawPoint(x, (int)(30 + acceValusX), mPaint);
86                     //画笔的颜色(绿)
87                     mPaint.setColor(Color.GREEN);
88                     //画Y轴的点
89                     mCanvas.drawPoint(x, (int)(60 + acceValusY), mPaint);
90                     //画笔的颜色(蓝)
91                     mPaint.setColor(Color.BLUE);
92                     //画Z轴的点
93                     mCanvas.drawPoint(x, (int)(90 + acceValusZ), mPaint);
94                     //横坐标+1
95                     x++;
96                     //如果已经画到了屏幕的最右边
97                     if(x > getWindowManager().getDefaultDisplay().getWidth())
98                     {
99                         x = 0;
100                         //清屏
101                         mCanvas.drawColor(Color.BLACK);
102                     }
103                     //绘制完成，提交修改
104                     mSurfaceHolder.unlockCanvasAndPost(mCanvas);
105                 }
106             }
107             catch(Exception e)
108             {
109                 e.printStackTrace();
110             }
111             finally
112             {
113                 if(mCanvas!=null)
114                 {
115                     //重新锁一次
116                     mSurfaceHolder.lockCanvas(new Rect(0, 0, 0, 0));
117                     mSurfaceHolder.unlockCanvasAndPost(mCanvas);
118                 }
119             }
120
121         }
122
123     }
124
125
126       //定义一个类，实现Callback接口
127       public class MyHolder implements SurfaceHolder.Callback
128       {
129
130           public void surfaceChanged(SurfaceHolder holder, int format, int width,
131                   int height)
132           {
133               // TODO Auto-generated method stub
134               //add your code
135           }
136
137           public void surfaceCreated(SurfaceHolder holder)
138           {
139               // TODO Auto-generated method stub
140               //add your code
141           }
142
143           public void surfaceDestroyed(SurfaceHolder holder)
144           {
145               // TODO Auto-generated method stub
146               //add your code
147           }
148
149       }
150
151     @Override
152     public void onDestroy()
153     {
154         super.onDestroy();
155         //注销传感器监听
156         mSensorManager.unregisterListener(mOnSensorEventListener, mAccelerometer);
157     }
158
159 }

好了，在真机上运行它，效果如下：



晃动手机几下，效果如下：



完成。