Android读取系统相册图片并获得绝对地址

public class MainActivity extends Activity {
    private Button btn;
    private ImageView img;
    Bitmap bitmap;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn=(Button)findViewById(R.id.select);
                img=(ImageView)findViewById(R.id.pic);
                //设置监听                
           setlistener();
    }

    private void setlistener() {
        // TODO Auto-generated method stub
        btn.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                Intent intent = new Intent();
                intent.setType("image/*");//set intent type
                intent.setAction(Intent.ACTION_GET_CONTENT);
                //取得图片信息返回MainActivity                
                startActivityForResult(intent,1);
            }
        });
    }
    protected void onActivityResult(int requestCode,int resultCode,Intent data)
    {
        if(resultCode==RESULT_OK)
        {
            Uri uri = data.getData();
            //通过URI获取图片绝对地址            
        String[] proj = { MediaStore.Images.Media.DATA };
            Cursor cursor = managedQuery(uri,proj,null,null,null);
            int actual_image_column_index = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
            //游标跳到首位，防止越界            
        cursor.moveToFirst();
            String img_path = cursor.getString(actual_image_column_index);
            //通过地址获得位图信息            
        bitmap =BitmapFactory.decodeFile(img_path);                
            //设置ImageView资源            
        img.setImageBitmap(bitmap);
         }
        
    

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}