android根据图片的uri获取图片的物理路径

Uri uri = Uri.parse("content://media/external/images/media/4");
ContentResolver cr = this.getContentResolver();
Cursor cursor = cr.query(uri, null, null, null, null);
cursor.moveToFirst();
for (int i = 0; i < cursor.getColumnCount(); i++) {
	System.out.println(i+"-----------------"+cursor.getString(i));
}