Android应用开发提高篇（5）-----Camera使用

一、概述

      Camera是手机的一个很重要的设备，可以说现在的每一部手机上都有。回想当时在Linux搞摄像头编程真的要捏一把汗。有人会说在Linux下装个opencv就可以通过它的函数来使用摄像头啦，但我并没有这么做，我还是用最原始的方法（V4L2）实现了。之前研究过Android关于摄像头这部分的源码，毫无疑问，Android关于摄像头底层的实现用的也是V4L2。

二、实现

     新建工程MyCamera，修改/res/layout/main.xml文件，使用RelativeLayout布局，并添加一个SurfaceView和一个Button，完整的main.xml如下：

1 <?xml version="1.0" encoding="utf-8"?>
2 <RelativeLayout 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
8     <SurfaceView
9         android:id="@+id/surfaceview"
10         android:layout_width="fill_parent"
11         android:layout_height="wrap_content"
12         android:layout_alignParentTop="true"
13         android:layout_above="@+id/button"
14         />
15
16     <Button
17         android:id="@+id/button"
18         android:layout_width="fill_parent"
19         android:layout_height="wrap_content"
20         android:layout_alignParentBottom="true"
21         android:text="拍照"
22         />
23
24 </RelativeLayout>

接着，修改MyCameraActivity.java文件，实现了SurfaceHolder.Callback接口，用于初始化、释放摄像头和Camera.PictureCallback接口，用于保存图片数据到文件里。完整的内容如下：

 

1 package com.nan.camera;
2
3 import java.io.File;
4 import java.io.FileNotFoundException;
5 import java.io.FileOutputStream;
6 import java.io.IOException;
7
8 import android.app.Activity;
9 import android.graphics.Bitmap;
10 import android.graphics.BitmapFactory;
11 import android.graphics.PixelFormat;
12 import android.hardware.Camera;
13 import android.os.Bundle;
14 import android.os.Environment;
15 import android.view.SurfaceHolder;
16 import android.view.SurfaceView;
17 import android.view.View;
18 import android.widget.Button;
19 import android.widget.Toast;
20
21 public class MyCameraActivity extends Activity
22 {
23     private SurfaceView mSurfaceView = null;
24     private SurfaceHolder mSurfaceHolder = null;
25     private Button takePictureButton = null;
26     private Camera mCamera;
27     //记录保存的是第几张图片
28     private int whichPicture = 0;
29
30     /** Called when the activity is first created. */
31     @Override
32     public void onCreate(Bundle savedInstanceState)
33     {
34         super.onCreate(savedInstanceState);
35         setContentView(R.layout.main);
36
37         takePictureButton = (Button)this.findViewById(R.id.button);
38         mSurfaceView = (SurfaceView)this.findViewById(R.id.surfaceview);
39         mSurfaceHolder = mSurfaceView.getHolder();
40         mSurfaceHolder.addCallback(new SurfaceHolderCallback());
41         //设置缓冲区类型
42         mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
43         //拍照按钮监听
44         takePictureButton.setOnClickListener(new View.OnClickListener()
45         {
46
47             @Override
48             public void onClick(View v)
49             {
50                 // TODO Auto-generated method stub
51                 //拍照
52                 mCamera.takePicture(null, null, pictureCallback);
53             }
54         });
55
56     }
57
58     private class SurfaceHolderCallback implements SurfaceHolder.Callback
59     {
60
61         @Override
62         public void surfaceChanged(SurfaceHolder holder, int format, int width,
63                 int height) {
64             // TODO Auto-generated method stub
65
66         }
67
68         @Override
69         public void surfaceCreated(SurfaceHolder holder)
70         {
71             // TODO Auto-generated method stub
72             //打开摄像头
73             mCamera = Camera.open();
74             try {
75                 mCamera.setPreviewDisplay(mSurfaceHolder);
76             } catch (IOException e) {
77                 // TODO Auto-generated catch block
78                 e.printStackTrace();
79             }
80             //获取摄像头参数
81             Camera.Parameters mParameters = mCamera.getParameters();
82             //设置图片格式
83             mParameters.setPictureFormat(PixelFormat.JPEG);
84             mCamera.setParameters(mParameters);
85             //开始预览
86             mCamera.startPreview();
87         }
88
89         @Override
90         public void surfaceDestroyed(SurfaceHolder holder)
91         {
92             // TODO Auto-generated method stub
93             if(mCamera!=null)
94             {
95                 //停止预览
96                 mCamera.stopPreview();
97                 //释放摄像头
98                 mCamera.release();
99                 mCamera = null;
100             }
101         }
102
103     }
104
105     //拍照回调
106     private Camera.PictureCallback pictureCallback = new Camera.PictureCallback()
107     {
108
109         @Override
110         public void onPictureTaken(byte[] data, Camera camera)
111         {
112             // TODO Auto-generated method stub
113             //停止预览
114             mCamera.stopPreview();
115             Bitmap mBitmap;
116             mBitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
117             //文件路径和文件名
118             File pictureFile = new File(Environment.getExternalStorageDirectory(),"camera"+Integer.toString(whichPicture)+".jpg");
119
120             try
121             {
122                 FileOutputStream mFileOutputStream = new FileOutputStream(pictureFile);
123                 //将图像数据压入文件
124                 mBitmap.compress(Bitmap.CompressFormat.JPEG, 75, mFileOutputStream);
125                 try {
126                     //关闭输出流
127                     mFileOutputStream.close();
128                 } catch (IOException e) {
129                     // TODO Auto-generated catch block
130                     e.printStackTrace();
131                 }
132             }
133             catch (FileNotFoundException e)
134             {
135                 // TODO Auto-generated catch block
136                 e.printStackTrace();
137             }
138             displayToast("保存成功！");
139             whichPicture++;
140             //开始预览
141             mCamera.startPreview();
142         }
143
144     };
145
146     //显示Toast函数
147     private void displayToast(String s)
148     {
149         Toast.makeText(this, s, Toast.LENGTH_SHORT).show();
150     }
151
152 }

在真机上运行该程序：

 



按一下“拍照”按钮：

 



图片会被保存到sd卡的根目录下面。