安卓用手指触碰屏幕缩放和移动，三指触碰屏幕旋转图片

电玩女神 2022-09-26 01:51 193阅读 0赞

[原文链接][Link 1]

package com.multitouch.example;
    
    import android.app.Activity;
    import android.graphics.Matrix;
    import android.graphics.PointF;
    import android.os.Bundle;
    import android.util.FloatMath;
    import android.view.MotionEvent;
    import android.view.View;
    import android.view.View.OnTouchListener;
    import android.widget.ImageView;
    
    public class MultiTouch extends Activity implements OnTouchListener {
    
        // these matrices will be used to move and zoom image
        private Matrix matrix = new Matrix();
        private Matrix savedMatrix = new Matrix();
        // 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();
        private float oldDist = 1f;
        private float d = 0f;
        private float newRot = 0f;
        private float[] lastEvent = null;
    
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
            ImageView view = (ImageView) findViewById(R.id.imageView);
            view.setOnTouchListener(this);
        }
    
        public boolean onTouch(View v, MotionEvent event) {
            // handle touch events here
            ImageView view = (ImageView) v;
            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);
                        float dx = event.getX() - start.x;
                        float dy = event.getY() - start.y;
                        matrix.postTranslate(dx, dy);
                    } else if (mode == ZOOM) {
                        float newDist = spacing(event);
                        if (newDist > 10f) {
                            matrix.set(savedMatrix);
                            float scale = (newDist / oldDist);
                            matrix.postScale(scale, scale, mid.x, mid.y);
                        }
                        if (lastEvent != null && event.getPointerCount() == 3) {
                            newRot = rotation(event);
                            float r = newRot - d;
                            float[] values = new float[9];
                            matrix.getValues(values);
                            float tx = values[2];
                            float ty = values[5];
                            float sx = values[0];
                            float xc = (view.getWidth() / 2) * sx;
                            float yc = (view.getHeight() / 2) * sx;
                            matrix.postRotate(r, tx + xc, ty + yc);
                        }
                    }
                    break;
            }
    
            view.setImageMatrix(matrix);
            return true;
        }
    
        /**
         * Determine the space between the first two fingers
         */
        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);
        }
    
        /**
         * Calculate the mid point of the first two fingers
         */
        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);
        }
    
        /**
         * Calculate the degree to be rotated by.
         *
         * @param event
         * @return Degrees
         */
        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);
        }
    }

<?xml version="1.0" encoding="utf-8"?>
    
    <FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    
    <ImageView android:id="@+id/imageView"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:src="@drawable/butterfly"
    android:scaleType="matrix" /> //设置这个属性很关键
    
    </FrameLayout>

[Link 1]: https://judepereira.com/blog/multi-touch-in-android-translate-scale-and-rotate/