根据Uri获取文件绝对路径

protected String getAbsoluteImagePath(Uri uri)  
   {  
       // can post image  
       String [] proj={MediaStore.Images.Media.DATA};  
       Cursor cursor = managedQuery( uri,  
                       proj,                 // Which columns to return  
                       null,       // WHERE clause; which rows to return (all rows)  
                       null,       // WHERE clause selection arguments (none)  
                       null);                 // Order-by clause (ascending by name)  
        
       int column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);  
       cursor.moveToFirst();  
          
       return cursor.getString(column_index);  
   }