Android 自定义ImageView：一个可以放大缩小拖动集于一体的ImageView

在开发中我们经常遇到展示一个图片需要放大看，滑动看，今天分享一个极其方便的自定义的ImageView 好的废话不说上代码：

第一步编写自定义ImageView

这个使用的时候直接放进你的util包下就可以

/*
 *  Created by Ms on 2020-08-11
 *
 */public class ZoomImageView extends AppCompatImageView implements ViewTreeObserver.OnGlobalLayoutListener {

    private boolean mIsOneLoad = true;

    //初始化的比例,也就是最小比例
    private float mInitScale;
    //图片最大比例
    private float mMaxScale;
    //双击能达到的最大比例
    private float mMidScale;

    private Matrix mScaleMatrix;
    //捕获用户多点触控
    private ScaleGestureDetector mScaleGestureDetector;

    //移动
    private GestureDetector gestureDetector;

    //双击
    private boolean isEnlarge = false;//是否放大
    private ValueAnimator mAnimator; //双击缩放动画

    //滚动
    private OverScroller scroller;
    private int mCurrentX, mCurrentY;
    private ValueAnimator translationAnimation; //惯性移动动画

    //单击
    private OnClickListener onClickListener;//单击监听

    public ZoomImageView(Context context) {
        this(context, null);
    }

    public ZoomImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ZoomImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        //记住，一定要把ScaleType设置成ScaleType.MATRIX，否则无法缩放
        setScaleType(ScaleType.MATRIX);

        scroller = new OverScroller(context);
        mScaleMatrix = new Matrix();
        //手势缩放
        mScaleGestureDetector = new ScaleGestureDetector(context, new ScaleGestureDetector.SimpleOnScaleGestureListener() {
            @Override
            public boolean onScale(ScaleGestureDetector detector) {
                scale(detector);
                return true;
            }

            @Override
            public void onScaleEnd(ScaleGestureDetector detector) {
                scaleEnd(detector);
            }
        });

        //滑动和双击监听
        gestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {

            @Override
            public boolean onScroll(MotionEvent e1, MotionEvent e2, final float distanceX, final float distanceY) {
                //滑动监听
                onTranslationImage(-distanceX, -distanceY);
                return true;
            }

            @Override
            public boolean onDoubleTap(MotionEvent e) {
                //双击监听
                onDoubleDrowScale(e.getX(), e.getY());
                return true;
            }

            @Override
            public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {

                //滑动惯性处理
                mCurrentX = (int) e2.getX();
                mCurrentY = (int) e2.getY();

                RectF rectF = getMatrixRectF();
                if (rectF == null) {
                    return false;
                }
                //startX为当前图片左边界的x坐标
                int startX = mCurrentX;
                int startY = mCurrentY;
                int minX = 0, maxX = 0, minY = 0, maxY = 0;
                int vX = Math.round(velocityX);
                int vY = Math.round(velocityY);

                maxX = Math.round(rectF.width());
                maxY = Math.round(rectF.height());

                if (startX != maxX || startY != maxY) {
                    //调用fling方法，然后我们可以通过调用getCurX和getCurY来获得当前的x和y坐标
                    //这个坐标的计算是模拟一个惯性滑动来计算出来的，我们根据这个x和y的变化可以模拟
                    //出图片的惯性滑动
                    scroller.fling(startX, startY, vX, vY, 0, maxX, 0, maxY, maxX, maxY);
                }

                if (translationAnimation != null && translationAnimation.isStarted())
                    translationAnimation.end();

                translationAnimation = ObjectAnimator.ofFloat(0, 1);
                translationAnimation.setDuration(500);
                translationAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                    @Override
                    public void onAnimationUpdate(ValueAnimator animation) {
                        if (scroller.computeScrollOffset()) {
                            //获得当前的x坐标
                            int newX = scroller.getCurrX();
                            int dx = newX - mCurrentX;
                            mCurrentX = newX;
                            //获得当前的y坐标
                            int newY = scroller.getCurrY();
                            int dy = newY - mCurrentY;
                            mCurrentY = newY;
                            //进行平移操作
                            if (dx != 0 && dy != 0)
                                onTranslationImage(dx, dy);
                        }
                    }
                });
                translationAnimation.start();
                return super.onFling(e1, e2, velocityX, velocityY);
            }

            @Override
            public boolean onSingleTapConfirmed(MotionEvent e) {
                //单击事件
                if(onClickListener != null)
                    onClickListener.onClick(ZoomImageView.this);
                return true;
            }
        });

    }

    @Override
    public void setOnClickListener(OnClickListener onClickListener) {
        this.onClickListener = onClickListener;
    }

    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        getViewTreeObserver().addOnGlobalLayoutListener(this);
    }

    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        getViewTreeObserver().removeOnGlobalLayoutListener(this);
    }

    /**
     * imageView加载完成后调用，获取imageView加载完成后的图片大小
     */
    @Override
    public void onGlobalLayout() {
        if (mIsOneLoad) {

            //得到控件的宽和高
            int width = getWidth();
            int height = getHeight();

            //获取图片,如果没有图片则直接退出
            Drawable d = getDrawable();
            if (d == null)
                return;
            //获取图片的宽和高
            int dw = d.getIntrinsicWidth();
            int dh = d.getIntrinsicHeight();

            float scale = 1.0f;
            if (dw > width && dh <= height) {
                scale = width * 1.0f / dw;
            }
            if (dw <= width && dh > height) {
                scale = height * 1.0f / dh;
            }
            if ((dw <= width && dh <= height) || (dw >= width && dh >= height)) {
                scale = Math.min(width * 1.0f / dw, height * 1.0f / dh);
            }

            //图片原始比例，图片回复原始大小时使用
            mInitScale = scale;
            //图片双击后放大的比例
            mMidScale = mInitScale * 2;
            //手势放大时最大比例
            mMaxScale = mInitScale * 4;

            //设置移动数据,把改变比例后的图片移到中心点
            float translationX = width * 1.0f / 2 - dw / 2;
            float translationY = height * 1.0f / 2 - dh / 2;

            mScaleMatrix.postTranslate(translationX, translationY);
            mScaleMatrix.postScale(mInitScale, mInitScale, width * 1.0f / 2, height * 1.0f / 2);
            setImageMatrix(mScaleMatrix);
            mIsOneLoad = false;
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        return mScaleGestureDetector.onTouchEvent(event)|
                gestureDetector.onTouchEvent(event);
    }

    //手势操作（缩放）
    public void scale(ScaleGestureDetector detector) {

        Drawable drawable = getDrawable();
        if (drawable == null)
            return;

        float scale = getScale();
        //获取手势操作的值,scaleFactor>1说明放大，<1则说明缩小
        float scaleFactor = detector.getScaleFactor();
        //获取手势操作后的比例，当放操作后比例在[mInitScale,mMaxScale]区间时允许放大
        mScaleMatrix.postScale(scaleFactor, scaleFactor, detector.getFocusX(), detector.getFocusY());
        setImageMatrix(mScaleMatrix);
        removeBorderAndTranslationCenter();

    }

    //手势操作结束
    public void scaleEnd(ScaleGestureDetector detector) {
        float scale = getScale();
        scale = detector.getScaleFactor() * scale;
        if (scale < mInitScale) {
            scaleAnimation(mInitScale, getWidth() / 2, getHeight() / 2);
        } else if (scale > mMaxScale) {
            scaleAnimation(mMaxScale, getWidth() / 2, getHeight() / 2);
        }
    }

    //手势操作（移动）
    private void onTranslationImage(float dx, float dy) {

        if (getDrawable() == null)
            return;

        RectF rect = getMatrixRectF();

        //图片宽度小于控件宽度时不允许左右移动
        if (rect.width() <= getWidth())
            dx = 0.0f;
        //图片高度小于控件宽度时，不允许上下移动
        if (rect.height() <= getHeight())
            dy = 0.0f;

        //移动距离等于0，那就不需要移动了
        if (dx == 0.0f && dy == 0.0f)
            return;

        mScaleMatrix.postTranslate(dx, dy);
        setImageMatrix(mScaleMatrix);
        //去除移动边界
        removeBorderAndTranslationCenter();
    }

    //消除控件边界和把图片移动到中间
    private void removeBorderAndTranslationCenter() {
        RectF rectF = getMatrixRectF();
        if (rectF == null)
            return;

        int width = getWidth();
        int height = getHeight();
        float widthF = rectF.width();
        float heightF = rectF.height();
        float left = rectF.left;
        float right = rectF.right;
        float top = rectF.top;
        float bottom = rectF.bottom;
        float translationX = 0.0f, translationY = 0.0f;

        if (left > 0) {
            //左边有边界
            if (widthF > width) {
                //图片宽度大于控件宽度，移动到左边贴边
                translationX = -left;
            } else {
                //图片宽度小于控件宽度，移动到中间
                translationX = width * 1.0f / 2f - (widthF * 1.0f / 2f + left);
            }
        } else if (right < width) {
            //右边有边界
            if (widthF > width) {
                //图片宽度大于控件宽度，移动到右边贴边
                translationX = width - right;
            } else {
                //图片宽度小于控件宽度，移动到中间
                translationX = width * 1.0f / 2f - (widthF * 1.0f / 2f + left);
            }
        }

        if (top > 0) {
            //顶部有边界
            if (heightF > height) {
                //图片高度大于控件高度，去除顶部边界
                translationY = -top;
            } else {
                //图片高度小于控件宽度，移动到中间
                translationY = height * 1.0f / 2f - (top + heightF * 1.0f / 2f);
            }
        } else if (bottom < height) {
            //底部有边界
            if (heightF > height) {
                //图片高度大于控件高度，去除顶部边界
                translationY = height - bottom;
            } else {
                //图片高度小于控件宽度，移动到中间
                translationY = height * 1.0f / 2f - (top + heightF * 1.0f / 2f);
            }
        }

        mScaleMatrix.postTranslate(translationX, translationY);
        setImageMatrix(mScaleMatrix);
    }

    /**
     * 双击改变大小
     *
     * @param x 点击的中心点
     * @param y 点击的中心点
     */
    private void onDoubleDrowScale(float x, float y) {
        //如果缩放动画已经在执行，那就不执行任何事件
        if (mAnimator != null && mAnimator.isRunning())
            return;

        float drowScale = getDoubleDrowScale();
        //执行动画缩放，不然太难看了
        scaleAnimation(drowScale, x, y);
    }

    /**
     * 缩放动画
     *
     * @param drowScale 缩放的比例
     * @param x         中心点
     * @param y         中心点
     */
    private void scaleAnimation(final float drowScale, final float x, final float y) {
        if (mAnimator != null && mAnimator.isRunning())
            return;
        mAnimator = ObjectAnimator.ofFloat(getScale(), drowScale);
        mAnimator.setDuration(300);
        mAnimator.setInterpolator(new AccelerateInterpolator());
        mAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator animation) {
                float value = ((float) animation.getAnimatedValue()) / getScale();
                mScaleMatrix.postScale(value, value, x, y);
                setImageMatrix(mScaleMatrix);
                removeBorderAndTranslationCenter();
            }
        });

        mAnimator.start();
    }


    //返回双击后改变的大小比例(我们希望缩放误差在deviation范围内)
    private float getDoubleDrowScale() {
        float deviation = 0.05f;
        float drowScale = 1.0f;
        float scale = getScale();

        if (Math.abs(mInitScale - scale) < deviation)
            scale = mInitScale;
        if (Math.abs(mMidScale - scale) < deviation)
            scale = mMidScale;
        if (Math.abs(mMaxScale - scale) < deviation)
            scale = mMaxScale;

        if (scale != mMidScale) {
            //当前大小不等于mMidScale,则调整到mMidScale
            drowScale = mMidScale;
            isEnlarge = scale < mMidScale;
        } else {
            //如果等于mMidScale，则判断放大或者缩小
            //判断是放大或者缩小，如果上次是放大，则继续放大，缩小则继续缩小
            if (isEnlarge) {
                //放大
                drowScale = mMaxScale;
            } else {
                //缩小
                drowScale = mInitScale;
            }
        }
        return drowScale;
    }


    //获取图片宽高以及左右上下边界
    private RectF getMatrixRectF() {

        Drawable drawable = getDrawable();
        if (drawable == null) {
            return null;
        }
        RectF rectF = new RectF(0, 0, drawable.getMinimumWidth(), drawable.getMinimumHeight());
        Matrix matrix = getImageMatrix();
        matrix.mapRect(rectF);

        return rectF;
    }


    /**
     * 获取当前图片的缩放值
     *
     * @return
     */
    private float getScale() {
        float[] values = new float[9];
        mScaleMatrix.getValues(values);
        return values[Matrix.MSCALE_X];
    }


    /**
     * 解决和父控件滑动冲突 只要图片边界超过控件边界，返回true
     *
     * @param direction
     * @return true 禁止父控件滑动
     */
    @Override
    public boolean canScrollHorizontally(int direction) {
        RectF rect = getMatrixRectF();
        if (rect == null || rect.isEmpty())
            return false;

        if (direction > 0) {
            return rect.right >= getWidth() + 1;
        } else {
            return rect.left <= 0 - 1;
        }

    }

    /**
     * 同楼上
     *
     * @param direction
     * @return
     */
    @Override
    public boolean canScrollVertically(int direction) {
        RectF rect = getMatrixRectF();
        if (rect == null || rect.isEmpty())
            return false;

        if (direction > 0) {
            return rect.bottom >= getHeight() + 1;
        } else {
            return rect.top <= 0 - 1;
        }
    }
}

第二步，添加XML布局

<com.test.utils.ZoomImageView
            android:id="@+id/ima_photo"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:scaleType="fitXY" />

这样就可以了 当我们给空间放上资源之后就可以正常使用了