Android Camera系列開發 (一): 通過Intent拍照

概述

使用Camera有兩種方式：通過Intent使用已有的app和通過Camera構建自己的app。

Camera相關聲明

如果你的應用程序要使用Camera，則必須獲得使用許可，需要在AndroidManifest.xml中加入如下聲明。

<uses-permissionandroid:name="android.permission.CAMERA" />

如果你的應用程序必須有Camera才能使用，則聲明如下：

<uses-featureandroid:name="android.hardware.camera" />

否則應聲明如下：

<uses-featureandroid:name="android.hardware.camera"android:required="false" />

其他相關聲明：

存儲：<uses-permissionandroid:name="android.permission.WRITE_EXTERNAL_STORAGE" />

語音：<uses-permissionandroid:name="android.permission.RECORD_AUDIO" />

位置：<uses-permissionandroid:name="android.permission.ACCESS_FINE_LOCATION" />

核心類

Itent：通過它進行Camera編程更簡單。

Camera：通過它可以控制相機，構建功能更強大的Camera應用。

SurfaceView：提供實時預覽功能。

通過Itent來實現拍照

第一步：在Eclipse中創建一個名為Photo的Android工程，可參見Hello world的例子；

第二步：在AndroidManifest.xml中添加使用Camera相關的聲明如下：

<uses-permissionandroid:name="android.permission.CAMERA"/>

第三步：編寫MainActivity類。

(1) 添加成員變量

(2) 修改OnCreate方法

(3) 增加onActivityResult方法

(4) 新增兩個輔助方法

類的源代碼如下：

[java]
public class MainActivity extends Activity { 
    private static final int MEDIA_TYPE_IMAGE = 1; 
    private static final int CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE = 100; 
     
    private Intent intent  = null; 
    private Uri fileUri    = null; 
 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.activity_main); 
         
        intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);//create a intent to take picture  
        fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE); // create a file to save the image  
        intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri); // set the image file name  
 
        // start the image capture Intent  
        startActivityForResult(intent, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE); 
    } 
 
    @Override 
    protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
        super.onActivityResult(requestCode, resultCode, data); 
         
        if(requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) { 
            if (resultCode == RESULT_OK) { 
                // Image captured and saved to fileUri specified in the Intent  
                Toast.makeText(this, "Image saved to:\n" + 
                         data.getData(),  
                         Toast.LENGTH_LONG).show(); 
            } else if (resultCode == RESULT_CANCELED) { 
                // User cancelled the image capture  
            } else { 
                // Image capture failed, advise user  
            } 
        } 
    } 
     
    /** Create a file Uri for saving an image or video */ 
    private static Uri getOutputMediaFileUri(int type){ 
          return Uri.fromFile(getOutputMediaFile(type)); 
    } 
 
    /** Create a File for saving an image or video */ 
    private static File getOutputMediaFile(int type){ 
        // To be safe, you should check that the SDCard is mounted  
        // using Environment.getExternalStorageState() before doing this.  
        File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory( 
                  Environment.DIRECTORY_PICTURES), "MyCameraApp"); 
        // This location works best if you want the created images to be shared  
        // between applications and persist after your app has been uninstalled.  
 
        if (! mediaStorageDir.exists()){ 
            if (! mediaStorageDir.mkdirs()){ 
                Log.d("MyCameraApp", "failed to create directory"); 
                return null; 
            } 
        } 
 
        // Create a media file name  
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date()); 
        File mediaFile = null; 
        if (type == MEDIA_TYPE_IMAGE){ 
            mediaFile = new File(mediaStorageDir.getPath() + File.separator + 
            "IMG_"+ timeStamp + ".jpg"); 
        } 
 
        return mediaFile; 
    } 
} 

public class MainActivity extends Activity {
 private static final int MEDIA_TYPE_IMAGE = 1;
 private static final int CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE = 100;
 
 private Intent intent  = null;
 private Uri fileUri    = null;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
     intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);//create a intent to take picture
     fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE); // create a file to save the image
     intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri); // set the image file name

     // start the image capture Intent
     startActivityForResult(intent, CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE);
 }

 @Override
 protected void onActivityResult(int requestCode, int resultCode, Intent data) {
  super.onActivityResult(requestCode, resultCode, data);
  
  if(requestCode == CAPTURE_IMAGE_ACTIVITY_REQUEST_CODE) {
   if (resultCode == RESULT_OK) {
             // Image captured and saved to fileUri specified in the Intent
             Toast.makeText(this, "Image saved to:\n" +
                      data.getData(),
                      Toast.LENGTH_LONG).show();
         } else if (resultCode == RESULT_CANCELED) {
             // User cancelled the image capture
         } else {
             // Image capture failed, advise user
         }
  }
 }
 
 /** Create a file Uri for saving an image or video */
 private static Uri getOutputMediaFileUri(int type){
       return Uri.fromFile(getOutputMediaFile(type));
 }

 /** Create a File for saving an image or video */
 private static File getOutputMediaFile(int type){
     // To be safe, you should check that the SDCard is mounted
     // using Environment.getExternalStorageState() before doing this.
     File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(
               Environment.DIRECTORY_PICTURES), "MyCameraApp");
     // This location works best if you want the created images to be shared
     // between applications and persist after your app has been uninstalled.

     if (! mediaStorageDir.exists()){
         if (! mediaStorageDir.mkdirs()){
             Log.d("MyCameraApp", "failed to create directory");
             return null;
         }
     }

     // Create a media file name
     String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
     File mediaFile = null;
     if (type == MEDIA_TYPE_IMAGE){
         mediaFile = new File(mediaStorageDir.getPath() + File.separator +
         "IMG_"+ timeStamp + ".jpg");
     }

     return mediaFile;
 }
}

 
第四步：運行程序。

如果拍完照返回的時候，程序崩潰，查看日志出現如下錯誤：

java.lang.RuntimeException: Failure delivering resultResultInfo{who=null, request=100, result=-1, data=null} to activity

在AndroidManifest.xml中的activity元素加入android:launchMode="singleInstance"屬性即可解決該問題。

拍完照之後，可以在SD卡中的Pictures/MyCameraApp目錄下找到保存的照片。