Medium Article - zoomview- ZoomView.java

ZoomView.java

package com.theappnerds.zoomview;

import android.graphics.PointF;
import android.view.MotionEvent;
import android.view.View;

public class ZoomView {

    float[] lastEvent = null;
    float d = 0f;
    float newRot = 0f;
    private boolean isZoomAndRotate;
    private boolean isOutSide;
    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    private int mode = NONE;
    private PointF start = new PointF();
    private PointF mid = new PointF();
    float oldDist = 1f;
    private float xCoOrdinate, yCoOrdinate;

    public void setupZoom(View view) {

        view.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View view, MotionEvent event) {
                view.bringToFront();
                doViewTransformation(view, event);
                return true;
            }
        });

    }
        private void doViewTransformation(View view, MotionEvent event) {
            switch (event.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_DOWN:
                    xCoOrdinate = view.getX() - event.getRawX();
                    yCoOrdinate = view.getY() - event.getRawY();

                    start.set(event.getX(), event.getY());
                    isOutSide = false;
                    mode = DRAG;
                    lastEvent = null;
                    break;
                case MotionEvent.ACTION_POINTER_DOWN:
                    oldDist = viewSpacing(event);
                    if (oldDist > 10f) {
                        viewMidPoint(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 = viewRotate(event);
                    break;
                case MotionEvent.ACTION_UP:
                    isZoomAndRotate = false;
                    if (mode == DRAG) {
                        float x = event.getX();
                        float y = event.getY();
                    }
                case MotionEvent.ACTION_OUTSIDE:
                    isOutSide = true;
                    mode = NONE;
                    lastEvent = null;
                case MotionEvent.ACTION_POINTER_UP:
                    mode = NONE;
                    lastEvent = null;
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (!isOutSide) {
                        if (mode == DRAG) {
                            isZoomAndRotate = false;
                            view.animate().x(event.getRawX() + xCoOrdinate).y(event.getRawY() + yCoOrdinate).setDuration(0).start();
                        }
                        if (mode == ZOOM && event.getPointerCount() == 2) {
                            float newDist1 = viewSpacing(event);
                            if (newDist1 > 10f) {
                                float scale = newDist1 / oldDist * view.getScaleX();
                                view.setScaleX(scale);
                                view.setScaleY(scale);
                            }
                            if (lastEvent != null) {
                                newRot = viewRotate(event);
                                view.setRotation((float) (view.getRotation() + (newRot - d)));
                            }
                        }
                    }
                    break;
            }
        }
        private float viewRotate(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 viewSpacing(MotionEvent event) {
            float x = event.getX(0) - event.getX(1);
            float y = event.getY(0) - event.getY(1);
            return (int) Math.sqrt(x * x + y * y);
        }

        private void viewMidPoint(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);
        }

    }