如何获取系统图片

private static int RESULT_LOAD_IMAGE = 1;
	private ImageView img;
	private Button btn;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		img =(ImageView) findViewById(R.id.img);
		btn =(Button) findViewById(R.id.btn);
		btn.setOnClickListener(new OnClickListener() {
			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
			
				Intent intent = new Intent(
						Intent.ACTION_PICK,
						   android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
				 startActivityForResult(intent, RESULT_LOAD_IMAGE);
			}
		});
	}
	
	@Override
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		// TODO Auto-generated method stub
		super.onActivityResult(requestCode, resultCode, data);
		if (requestCode==RESULT_LOAD_IMAGE &&resultCode==RESULT_OK && null!=data) {
			Uri selectedImage =data.getData();
			String[] filepathcolumn ={MediaStore.Images.Media.DATA};
			
			Cursor cursor =getContentResolver().query(selectedImage, filepathcolumn, null, null, null);
			cursor.moveToFirst();
			int columnIndex =cursor.getColumnIndex(filepathcolumn[0]);
			String picturePath =cursor.getString(columnIndex);
			cursor.close();
			
			ImageView imageView =(ImageView) findViewById(R.id.img);
			imageView.setImageBitmap(BitmapFactory.decodeFile(picturePath));
			
		}
		
	}