android - 如何在 Android 中对图像应用缩放、拖动和旋转

Question

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Answer 1

尝试使用下面的代码，它对我有用。

    float[] lastEvent = null;
    float d = 0f;
    float newRot = 0f;
    private Matrix matrix = new Matrix();
    private Matrix savedMatrix = new Matrix();
    public static String fileNAME;
    public static int framePos = 0;

    private float scale = 0;
    private float newDist = 0;

    // Fields
    private String TAG = this.getClass().getSimpleName();

    // We can be in one of these 3 states
    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    private int mode = NONE;

    // Remember some things for zooming
    private PointF start = new PointF();
    private PointF mid = new PointF();
    float oldDist = 1f;

     public boolean onTouch(View v, MotionEvent event) {
                ImageView view = (ImageView) v;

                // Handle touch events here...
                switch (event.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:
                    savedMatrix.set(matrix);
                    start.set(event.getX(), event.getY());
                    mode = DRAG;
                    lastEvent = null;
                    break;
                case MotionEvent.ACTION_POINTER_DOWN:
                    oldDist = spacing(event);
                    if (oldDist > 10f) {
                        savedMatrix.set(matrix);
                        midPoint(mid, event);
                        mode = ZOOM;
                    }
                    lastEvent = new float[4];
                    lastEvent[0] = event.getX(0);
                    lastEvent[1] = event.getX(1);
                    lastEvent[2] = event.getY(0);
                    lastEvent[3] = event.getY(1);
                    d = rotation(event);
                    break;
                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_POINTER_UP:
                    mode = NONE;
                    lastEvent = null;
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (mode == DRAG) {
                        // ...
                        matrix.set(savedMatrix);
                        matrix.postTranslate(event.getX() - start.x, event.getY()
                                - start.y);
                    } else if (mode == ZOOM && event.getPointerCount() == 2) {
                        float newDist = spacing(event);
                        matrix.set(savedMatrix);
                        if (newDist > 10f) {
                            float scale = newDist / oldDist;
                            matrix.postScale(scale, scale, mid.x, mid.y);
                        }
                        if (lastEvent != null) {
                            newRot = rotation(event);
                            float r = newRot - d;
                            matrix.postRotate(r, view.getMeasuredWidth() / 2,
                                    view.getMeasuredHeight() / 2);
                        }
                    }
                    break;
                }

                view.setImageMatrix(matrix);

                return true;
            }

//用于在多点触控时旋转图像。

private float rotation(MotionEvent event) {
        double delta_x = (event.getX(0) - event.getX(1));
        double delta_y = (event.getY(0) - event.getY(1));
        double radians = Math.atan2(delta_y, delta_x);

        return (float) Math.toDegrees(radians);
    }
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);
    }