package com.example.photowallfallsdemo;import android.content.Context;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Matrix;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;public class ZoomImageView extends View {    public static final int STATUS_INIT = 1;//常量初始化    public static final int STATUS_ZOOM_OUT = 2;//图片放大状态常量    public static final int STATUS_ZOOM_IN = 3;//图片缩小状态常量    public static final int STATUS_MOVE = 4;//图片拖动状态常量    private Matrix matrix = new Matrix();//对图片进行移动和缩放变换的矩阵    private Bitmap sourceBitmap;//待展示的Bitmap对象    private int currentStatus;//记录当前操作的状态，可选值为STATUS_INIT、STATUS_ZOOM_OUT、STATUS_ZOOM_IN和STATUS_MOVE    private int width;//ZoomImageView控件的宽度    private int height;//ZoomImageView控件的高度    private float centerPointX;//记录两指同时放在屏幕上时，中心点的横坐标值    private float centerPointY;//记录两指同时放在屏幕上时，中心点的纵坐标值    private float currentBitmapWidth;//记录当前图片的宽度，图片被缩放时，这个值会一起变动    private float currentBitmapHeight;//记录当前图片的高度，图片被缩放时，这个值会一起变动    private float lastXMove = -1;//记录上次手指移动时的横坐标    private float lastYMove = -1;//记录上次手指移动时的纵坐标    private float movedDistanceX;//记录手指在横坐标方向上的移动距离    private float movedDistanceY;//记录手指在纵坐标方向上的移动距离    private float totalTranslateX;//记录图片在矩阵上的横向偏移值    private float totalTranslateY;//记录图片在矩阵上的纵向偏移值    private float totalRatio;//记录图片在矩阵上的总缩放比例    private float scaledRatio;//记录手指移动的距离所造成的缩放比例    private float initRatio;//记录图片初始化时的缩放比例    private double lastFingerDis;//记录上次两指之间的距离    /**     * ZoomImageView构造函数，将当前操作状态设为STATUS_INIT。     * @param context     * @param attrs     */    public ZoomImageView(Context context, AttributeSet attrs) {        super(context, attrs);        currentStatus = STATUS_INIT;    }    /*将待展示的图片设置进来。     * @param bitmap     * 待展示的Bitmap对象     */    public void setImageBitmap(Bitmap bitmap) {        sourceBitmap = bitmap;        invalidate();    }    @Override    protected void onLayout(boolean changed, int left, int top, int right,            int bottom) {        super.onLayout(changed, left, top, right, bottom);        if (changed) {            // 分别获取到ZoomImageView的宽度和高度            width = getWidth();            height = getHeight();        }    }    @Override    public boolean onTouchEvent(MotionEvent event) {        if (initRatio == totalRatio) {            getParent().requestDisallowInterceptTouchEvent(false);        } else {            getParent().requestDisallowInterceptTouchEvent(true);        }        switch (event.getActionMasked()) {        case MotionEvent.ACTION_POINTER_DOWN:            if (event.getPointerCount() == 2) {                // 当有两个手指按在屏幕上时，计算两指之间的距离                lastFingerDis = distanceBetweenFingers(event);            }            break;        case MotionEvent.ACTION_CANCEL:        case MotionEvent.ACTION_MOVE:            if (event.getPointerCount() == 1) {                // 只有单指按在屏幕上移动时，为拖动状态                float xMove = event.getX();                float yMove = event.getY();                if (lastXMove == -1 && lastYMove == -1) {                    lastXMove = xMove;                    lastYMove = yMove;                }                currentStatus = STATUS_MOVE;                movedDistanceX = xMove - lastXMove;                movedDistanceY = yMove - lastYMove;                // 进行边界检查，不允许将图片拖出边界                if (totalTranslateX + movedDistanceX > 0) {                    movedDistanceX = 0;                } else if (width - (totalTranslateX + movedDistanceX) > currentBitmapWidth) {                    movedDistanceX = 0;                }                if (totalTranslateY + movedDistanceY > 0) {                    movedDistanceY = 0;                } else if (height - (totalTranslateY + movedDistanceY) > currentBitmapHeight) {                    movedDistanceY = 0;                }                // 调用onDraw()方法绘制图片                invalidate();                lastXMove = xMove;                lastYMove = yMove;            } else if (event.getPointerCount() == 2) {                // 有两个手指按在屏幕上移动时，为缩放状态                centerPointBetweenFingers(event);                double fingerDis = distanceBetweenFingers(event);                if (fingerDis > lastFingerDis) {                    currentStatus = STATUS_ZOOM_OUT;                } else {                    currentStatus = STATUS_ZOOM_IN;                }                // 进行缩放倍数检查，最大只允许将图片放大4倍，最小可以缩小到初始化比例                if ((currentStatus == STATUS_ZOOM_OUT && totalRatio < 4 * initRatio)                        || (currentStatus == STATUS_ZOOM_IN && totalRatio > initRatio)) {                    scaledRatio = (float) (fingerDis / lastFingerDis);                    totalRatio = totalRatio * scaledRatio;                    if (totalRatio > 4 * initRatio) {                        totalRatio = 4 * initRatio;                    } else if (totalRatio < initRatio) {                        totalRatio = initRatio;                    }                    // 调用onDraw()方法绘制图片                    invalidate();                    lastFingerDis = fingerDis;                }            }            break;        case MotionEvent.ACTION_POINTER_UP:            if (event.getPointerCount() == 2) {                // 手指离开屏幕时将临时值还原                lastXMove = -1;                lastYMove = -1;            }            break;        case MotionEvent.ACTION_UP:            // 手指离开屏幕时将临时值还原            lastXMove = -1;            lastYMove = -1;            break;        default:            break;        }        return true;    }    /*根据currentStatus的值来决定对图片进行什么样的绘制操作。*/    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        switch (currentStatus) {        case STATUS_ZOOM_OUT:        case STATUS_ZOOM_IN:            zoom(canvas);            break;        case STATUS_MOVE:            move(canvas);            break;        case STATUS_INIT:            initBitmap(canvas);        default:            if (sourceBitmap != null) {                canvas.drawBitmap(sourceBitmap, matrix, null);            }            break;        }    }    /**     * 对图片进行缩放处理。     * @param canvas     */    private void zoom(Canvas canvas) {        matrix.reset();        // 将图片按总缩放比例进行缩放        matrix.postScale(totalRatio, totalRatio);        float scaledWidth = sourceBitmap.getWidth() * totalRatio;        float scaledHeight = sourceBitmap.getHeight() * totalRatio;        float translateX = 0f;        float translateY = 0f;        // 如果当前图片宽度小于屏幕宽度，则按屏幕中心的横坐标进行水平缩放。否则按两指的中心点的横坐标进行水平缩放        if (currentBitmapWidth < width) {            translateX = (width - scaledWidth) / 2f;        } else {            translateX = totalTranslateX * scaledRatio + centerPointX                    * (1 - scaledRatio);            // 进行边界检查，保证图片缩放后在水平方向上不会偏移出屏幕            if (translateX > 0) {                translateX = 0;            } else if (width - translateX > scaledWidth) {                translateX = width - scaledWidth;            }        }        // 如果当前图片高度小于屏幕高度，则按屏幕中心的纵坐标进行垂直缩放。否则按两指的中心点的纵坐标进行垂直缩放        if (currentBitmapHeight < height) {            translateY = (height - scaledHeight) / 2f;        } else {            translateY = totalTranslateY * scaledRatio + centerPointY                    * (1 - scaledRatio);            // 进行边界检查，保证图片缩放后在垂直方向上不会偏移出屏幕            if (translateY > 0) {                translateY = 0;            } else if (height - translateY > scaledHeight) {                translateY = height - scaledHeight;            }        }        // 缩放后对图片进行偏移，以保证缩放后中心点位置不变        matrix.postTranslate(translateX, translateY);        totalTranslateX = translateX;        totalTranslateY = translateY;        currentBitmapWidth = scaledWidth;        currentBitmapHeight = scaledHeight;        canvas.drawBitmap(sourceBitmap, matrix, null);    }    /**     * 对图片进行平移处理     * @param canvas     */    private void move(Canvas canvas) {        matrix.reset();        // 根据手指移动的距离计算出总偏移值        float translateX = totalTranslateX + movedDistanceX;        float translateY = totalTranslateY + movedDistanceY;        // 先按照已有的缩放比例对图片进行缩放        matrix.postScale(totalRatio, totalRatio);        // 再根据移动距离进行偏移        matrix.postTranslate(translateX, translateY);        totalTranslateX = translateX;        totalTranslateY = translateY;        canvas.drawBitmap(sourceBitmap, matrix, null);    }    /**     * 对图片进行初始化操作，包括让图片居中，以及当图片大于屏幕宽高时对图片进行压缩。     * @param canvas     */    private void initBitmap(Canvas canvas) {        if (sourceBitmap != null) {            matrix.reset();            int bitmapWidth = sourceBitmap.getWidth();            int bitmapHeight = sourceBitmap.getHeight();            if (bitmapWidth > width || bitmapHeight > height) {                if (bitmapWidth - width > bitmapHeight - height) {                    // 当图片宽度大于屏幕宽度时，将图片等比例压缩，使它可以完全显示出来                    float ratio = width / (bitmapWidth * 1.0f);                    matrix.postScale(ratio, ratio);                    float translateY = (height - (bitmapHeight * ratio)) / 2f;                    // 在纵坐标方向上进行偏移，以保证图片居中显示                    matrix.postTranslate(0, translateY);                    totalTranslateY = translateY;                    totalRatio = initRatio = ratio;                } else {                    // 当图片高度大于屏幕高度时，将图片等比例压缩，使它可以完全显示出来                    float ratio = height / (bitmapHeight * 1.0f);                    matrix.postScale(ratio, ratio);                    float translateX = (width - (bitmapWidth * ratio)) / 2f;                    // 在横坐标方向上进行偏移，以保证图片居中显示                    matrix.postTranslate(translateX, 0);                    totalTranslateX = translateX;                    totalRatio = initRatio = ratio;                }                currentBitmapWidth = bitmapWidth * initRatio;                currentBitmapHeight = bitmapHeight * initRatio;            } else {                // 当图片的宽高都小于屏幕宽高时，直接让图片居中显示                float translateX = (width - sourceBitmap.getWidth()) / 2f;                float translateY = (height - sourceBitmap.getHeight()) / 2f;                matrix.postTranslate(translateX, translateY);                totalTranslateX = translateX;                totalTranslateY = translateY;                totalRatio = initRatio = 1f;                currentBitmapWidth = bitmapWidth;                currentBitmapHeight = bitmapHeight;            }            canvas.drawBitmap(sourceBitmap, matrix, null);        }    }    /**     * 计算两个手指之间的距离。     * @param event     * @return 两个手指之间的距离     */    private double distanceBetweenFingers(MotionEvent event) {        float disX = Math.abs(event.getX(0) - event.getX(1));        float disY = Math.abs(event.getY(0) - event.getY(1));        return Math.sqrt(disX * disX + disY * disY);    }    /**     * 计算两个手指之间中心点的坐标。     * @param event     */    private void centerPointBetweenFingers(MotionEvent event) {        float xPoint0 = event.getX(0);        float yPoint0 = event.getY(0);        float xPoint1 = event.getX(1);        float yPoint1 = event.getY(1);        centerPointX = (xPoint0 + xPoint1) / 2;        centerPointY = (yPoint0 + yPoint1) / 2;    }}