如何设置拖动和缩放图像中心到布局？

Question

在我的应用程序中，我想拖动图像并缩放图像。所以我按照下面的链接。

http://www.androidhub4you.com/2013/05/zoom-image-demo-in-android-zoom-image.html

通过使用这一切，每件事都很有效。但我的要求是，当进入活动时，拖动图像是布局的中心。在此示例中，图像是xml布局中的填充父级。并且应用比例类型是矩阵。因此默认情况下图像是左上角的顶部。如果图像是包装内容，则图像在该区域中拖动。但我的要求是图像是布局的中心，并在完整的布局中拖动图像。为此我搜索了很多。那么请指导我如何做到这一点？这是 XML

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" 
android:layout_width="match_parent" 
android:layout_height="match_parent" >
 <ImageView android:id="@+id/imageView1" 
android:layout_width="fill_parent" 
android:layout_height="fill_parent" 
android:scaleType="matrix" 
android:src="@drawable/images" /> </RelativeLayout>

这就是活动

*public class MainActivity extends Activity {
    ImageView imageDetail;
    LinearLayout linear;

    Matrix matrix = new Matrix();
    Matrix savedMatrix = new Matrix();
    PointF startPoint = new PointF();
    PointF midPoint = new PointF();
    float oldDist = 1f;
    static final int NONE = 0;
    static final int DRAG = 1;
    static final int ZOOM = 2;
    int mode = NONE;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        imageDetail = (ImageView) findViewById(R.id.imageView1);
        imageDetail.setScaleType(ImageView.ScaleType.MATRIX);

        ColorFilter filter = new LightingColorFilter(Color.BLUE, Color.BLUE);
        imageDetail.setColorFilter(filter);


        /**
         * set on touch listner on image
         */
        imageDetail.setOnTouchListener(new View.OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {

                    ImageView view = (ImageView) v;
                    System.out.println("matrix=" + savedMatrix.toString());

                    switch (event.getAction() & MotionEvent.ACTION_MASK) {

                    case MotionEvent.ACTION_DOWN:

                        Log.e("action down","down");
                        savedMatrix.set(matrix);
                        startPoint.set(event.getX(), event.getY());
                        mode = DRAG;
                        break;

                    case MotionEvent.ACTION_POINTER_DOWN:

                        oldDist = spacing(event);

                        if (oldDist > 10f) {
                            savedMatrix.set(matrix);
                            midPoint(midPoint, event);
                            mode = ZOOM;
                        }

                        break;

                    case MotionEvent.ACTION_UP:

                    case MotionEvent.ACTION_POINTER_UP:
                        mode = NONE;

                        break;

                    case MotionEvent.ACTION_MOVE:
                        if (mode == DRAG) {
                            matrix.set(savedMatrix);
                            matrix.postTranslate(event.getX() - startPoint.x,
                                    event.getY() - startPoint.y);
                        } else if (mode == ZOOM) {
                            float newDist = spacing(event);
                            if (newDist > 10f) {
                                matrix.set(savedMatrix);
                                float scale = newDist / oldDist;
                                matrix.postScale(scale, scale, midPoint.x,
                                        midPoint.y);
                            }
                        }
                        break;

                    }
                    view.setImageMatrix(matrix);

                    return true;

            }

            @SuppressLint("FloatMath")
            private float spacing(MotionEvent event) {
                float x = event.getX(0) - event.getX(1);
                float y = event.getY(0) - event.getY(1);
                return FloatMath.sqrt(x * x + y * y);
            }

            private void midPoint(PointF point, MotionEvent event) {
                float x = event.getX(0) + event.getX(1);
                float y = event.getY(0) + event.getY(1);
                point.set(x / 2, y / 2);
            }
        });

    }*