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。