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);
}