獲取MediaScanner自動生成的視頻縮略圖

Question

如您所知，android上的內置媒體掃描儀會定期掃描整個文件系統並生成媒體（照片+視頻）預覽縮略圖。這些是Gallery應用程序正在顯示的縮略圖。

在我的應用我有一個旋轉木馬，我想顯示自動生成縮略圖視頻僅。出於速度的原因，因爲他們已經在那裏。不幸的是，這些文檔對於如何實際獲取它們非常缺乏。

public class MainActivity extends Activity { 

    private Cursor cursor; 
    private int columnIndex; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.content_main); 

     // Set up an array of the Thumbnail Image ID column we want 
     String[] projection = {MediaStore.Video.Thumbnails.VIDEO_ID}; 
     // Create the cursor pointing to the SDCard 
     cursor = managedQuery(MediaStore.Video.Thumbnails.EXTERNAL_CONTENT_URI, 
       projection, // Which columns to return 
       null,  // Return all rows 
       null, 
       null); 

     System.err.println("qqq video cnt=" + cursor.getCount()); 

     // Get the column index of the Thumbnails Image ID 
     columnIndex = cursor.getColumnIndexOrThrow(projection[0]); 

     GridView sdcardImages = (GridView) findViewById(R.id.sdcard); 
     sdcardImages.setAdapter(new ImageAdapter(this)); 

     // Set up a click listener 
     sdcardImages.setOnItemClickListener(new OnItemClickListener() { 
      public void onItemClick(AdapterView parent, View v, int position, long id) { 
       // Get the data location of the image 
       String[] projection = {MediaStore.Video.Media.DATA}; 
       cursor = managedQuery(MediaStore.Video.Media.EXTERNAL_CONTENT_URI, 
         projection, // Which columns to return 
         null,  // Return all rows 
         null, 
         null); 
       columnIndex = cursor.getColumnIndexOrThrow(projection[0]); 
       cursor.moveToPosition(position); 
       // Get image filename 
       String imagePath = cursor.getString(columnIndex); 
       // Use this path to do further processing, i.e. full screen display 
       System.err.println("qqq path=" + imagePath); 
      } 
     }); 
    } 

    private class ImageAdapter extends BaseAdapter { 

     private Context context; 

     public ImageAdapter(Context localContext) { 
      context = localContext; 
     } 

     public int getCount() { 
      System.err.println("qqq count " + cursor.getCount()); 
      return cursor.getCount(); 
     } 
     public Object getItem(int position) { 
      return position; 
     } 
     public long getItemId(int position) { 
      return position; 
     } 
     public View getView(int position, View convertView, ViewGroup parent) { 
      ImageView picturesView; 
      if (convertView == null) { 
       picturesView = new ImageView(context); 


       // Move cursor to current position 
       cursor.moveToPosition(position); 
       // Get the current value for the requested column 
       int imageID = cursor.getInt(columnIndex); 

       Uri uri = Uri.withAppendedPath(
         MediaStore.Video.Thumbnails.EXTERNAL_CONTENT_URI, "" + imageID); 
       System.err.println("qqq getview uri="+uri.toString()); 

       // Set the content of the image based on the provided URI 
       picturesView.setImageURI(uri); 
       picturesView.setScaleType(ImageView.ScaleType.FIT_CENTER); 
       picturesView.setPadding(8, 8, 8, 8); 
       picturesView.setLayoutParams(new GridView.LayoutParams(100, 100)); 


       //picturesView.setImageBitmap(BitmapFactory.decodeResource(getResources(), android.R.drawable.ic_btn_speak_now)); 
      } 
      else { 
       picturesView = (ImageView)convertView; 
      } 
      return picturesView; 
     } 
    } 
} 

我得到的日誌如下。它確實顯示了正確數量的視頻（2），但即使縮略圖媒體URL「看起來不錯」，返回的Bitmap對象也是零。有任何想法嗎？

W/System.err: qqq video cnt=2 
W/System.err: qqq count 2 
W/System.err: qqq count 2 
W/System.err: qqq count 2 
W/System.err: qqq getview uri=content://media/external/video/thumbnails/2484 
W/System.err: qqq getview uri=content://media/external/video/thumbnails/2483 
W/System.err: qqq count 2 
W/System.err: qqq getview uri=content://media/external/video/thumbnails/2484 
W/System.err: qqq count 2 

Answer 1

下面是它如何做。請注意，縮略圖路徑可能是null，如果視頻已損壞或使用android無法解析的編解碼器編碼。

public class MainActivity extends Activity { 

    private Cursor cursor; 
    private int columnIndex; 

    ArrayList thumbs = new ArrayList(); 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.content_main); 

     final String[] columns = { 
       BaseColumns._ID, MediaStore.MediaColumns.DATA 
     }; 

     ContentResolver cr = this.getContentResolver(); 
     Cursor cursor = cr.query(MediaStore.Video.Media.EXTERNAL_CONTENT_URI, columns, null, null, null); 

     boolean cancel = false; 
     if(null != cursor){ 
      while(cursor.moveToNext() && !cancel){ 
       String fileName = cursor.getString(cursor.getColumnIndex(MediaStore.MediaColumns.DATA)); 
       int imageId = cursor.getInt(cursor.getColumnIndex(BaseColumns._ID)); 

       thumbs.add(new Integer(imageId)); 
       System.err.println("qqq " + fileName + " " + imageId); 
      } 
     } 

     GridView sdcardImages = (GridView) findViewById(R.id.sdcard); 
     sdcardImages.setAdapter(new ImageAdapter(this)); 
    } 

    private class ImageAdapter extends BaseAdapter { 

     private Context context; 

     public ImageAdapter(Context localContext) { 
      context = localContext; 
     } 

     public int getCount() { 
      System.err.println("qqq count " + thumbs.size());//cursor.getCount()); 
      //return cursor.getCount(); 
      return thumbs.size(); 
     } 
     public Object getItem(int position) { 
      return position; 
     } 
     public long getItemId(int position) { 
      return position; 
     } 
     public View getView(int position, View convertView, ViewGroup parent) { 
      ImageView picturesView; 
      if (convertView == null) { 
       picturesView = new ImageView(context); 
       picturesView.setScaleType(ImageView.ScaleType.FIT_CENTER); 
       picturesView.setPadding(8, 8, 8, 8); 
       picturesView.setLayoutParams(new GridView.LayoutParams(250, 250)); 

       Bitmap myBitmap = BitmapFactory.decodeResource(getResources(), android.R.drawable.ic_menu_camera); 
       Integer t = (Integer)thumbs.get(position); 
       String path= getThumbPath(getContentResolver(), t.intValue()); 
       if (path != null) { 
        System.err.println("qqq getting " + path); 
        File f = new File(path); 
        if (!f.exists()) { 
         System.err.println("qqq invalid file! " + path); 
        } 

        myBitmap = BitmapFactory.decodeFile(path);//imgFile.getAbsolutePath()); 
       } 
       picturesView.setImageBitmap(myBitmap); 

      } 
      else { 
       picturesView = (ImageView)convertView; 
      } 
      return picturesView; 
     } 
    } 


    public String getThumbPath(ContentResolver contentResolver, long photoId) { 
     String path=null; 
     Cursor thumbnails = contentResolver.query(android.provider.MediaStore.Video.Thumbnails.EXTERNAL_CONTENT_URI, 
       null, android.provider.MediaStore.Video.Thumbnails.VIDEO_ID + "=?", new String[]{String.valueOf(photoId)}, null); 

     for (thumbnails.moveToFirst(); !thumbnails.isAfterLast(); thumbnails.moveToNext()) { 

      long thumbnailId = thumbnails.getLong(thumbnails.getColumnIndex(android.provider.MediaStore.Video.Thumbnails._ID)); 
      path = thumbnails.getString(thumbnails.getColumnIndex(android.provider.MediaStore.Video.Thumbnails.DATA)); 
      break; 
     } 

     thumbnails.close(); 
     return path; 
    } 
}