解析下拉图片放大

╰半橙微兮° 2022-07-25 16:39 138阅读 0赞

原理：

生成一个FrameLayout，然后装载ImageView，在手指按下的时候设置初始值mLastMotionY、mActivePointerId、mMaxScale、mLastScale；在手指移动的时候动态的改变localLayoutParams.height；当手指抬起时，生成一个Runnable，设置缩放动画，更改localLayoutParams.height

public class PullToZoomListView extends ListView implements AbsListView.OnScrollListener {
        private static final int INVALID_VALUE = -1;
        private static final String TAG = "PullToZoomListView";
        private static final Interpolator sInterpolator = new Interpolator() {
      //缩放减速
            public float getInterpolation(float paramAnonymousFloat) {
                float f = paramAnonymousFloat - 1.0F;//下拉-1 - 0
                Log.e("getInterpolation", "f | " + f);
                return 1.0F + f * (f * (f * (f * f)));
            }
        };
        int mActivePointerId = -1;
        private FrameLayout mHeaderContainer;//头部布局容器
        private int mHeaderHeight;//头部控件的高度
        private ImageView mHeaderImage;
        float mLastMotionY = -1.0F;//监听手指在Y轴的移动
        float mLastScale = -1.0F;//下拉：-1 - 2
        float mMaxScale = -1.0F;//3
        private AbsListView.OnScrollListener mOnScrollListener;
        private ScalingRunnalable mScalingRunnalable;//缩放动画
        private int mScreenHeight;//屏幕高度
        private ImageView mShadow;
    
        public PullToZoomListView(Context paramContext) {
            super(paramContext);
            init(paramContext);
        }
    
        public PullToZoomListView(Context paramContext,
                                  AttributeSet paramAttributeSet) {
            super(paramContext, paramAttributeSet);
            init(paramContext);
        }
    
        public PullToZoomListView(Context paramContext, AttributeSet paramAttributeSet, int paramInt) {
            super(paramContext, paramAttributeSet, paramInt);
            init(paramContext);
        }
    
        //手抬起时，设置缩放动画时间
        private void endScraling() {
            Log.e(TAG, "endScraling");
            if (this.mHeaderContainer.getBottom() >= this.mHeaderHeight)
                this.mScalingRunnalable.startAnimation(200L);
        }
    
        private void init(Context paramContext) {
            DisplayMetrics localDisplayMetrics = new DisplayMetrics();
            ((Activity) paramContext).getWindowManager().getDefaultDisplay().getMetrics(localDisplayMetrics);
            this.mScreenHeight = localDisplayMetrics.heightPixels;
            this.mHeaderContainer = new FrameLayout(paramContext);//生成一个FrameLayout，装载下面两个ImageView
    
            this.mHeaderImage = new ImageView(paramContext);
            int i = localDisplayMetrics.widthPixels;//屏幕宽度（像素）
            setHeaderViewSize(i, (int) (9.0F * (i / 16.0F)));
            this.mShadow = new ImageView(paramContext);
            FrameLayout.LayoutParams localLayoutParams = new FrameLayout.LayoutParams(-1, -2);
            localLayoutParams.gravity = 80;
            this.mShadow.setLayoutParams(localLayoutParams);
    
            this.mHeaderContainer.addView(this.mHeaderImage);
            this.mHeaderContainer.addView(this.mShadow);
            addHeaderView(this.mHeaderContainer);
    
            this.mScalingRunnalable = new ScalingRunnalable();//生成一个缩放动画
            super.setOnScrollListener(this);
        }
    
    
        private void onSecondaryPointerUp(MotionEvent paramMotionEvent) {
            Log.e(TAG, "onSecondaryPointerUp = " + paramMotionEvent.getAction() + "");
            int i = (paramMotionEvent.getAction()) >> 8;
            if (paramMotionEvent.getPointerId(i) == this.mActivePointerId)
                if (i != 0) {
                    int j = 1;
                    this.mLastMotionY = paramMotionEvent.getY(0);
                    this.mActivePointerId = paramMotionEvent.getPointerId(0);
                    return;
                }
        }
    
        //重置参数
        private void reset() {
            this.mActivePointerId = -1;
            this.mLastMotionY = -1.0F;
            this.mMaxScale = -1.0F;
            this.mLastScale = -1.0F;
        }
    
        public ImageView getHeaderView() {
            return this.mHeaderImage;
        }
    
        public boolean onInterceptTouchEvent(MotionEvent paramMotionEvent) {
            return super.onInterceptTouchEvent(paramMotionEvent);
        }
    
        //
        protected void onLayout(boolean paramBoolean, int paramInt1, int paramInt2, int paramInt3, int paramInt4) {
            super.onLayout(paramBoolean, paramInt1, paramInt2, paramInt3, paramInt4);
            Log.e(TAG, "onLayout " + " mHeaderHeight == " + this.mHeaderContainer.getHeight());
            if (this.mHeaderHeight == 0)
                this.mHeaderHeight = this.mHeaderContainer.getHeight();
        }
    
        //正在滚动 ; 上滑启动
        @Override
        public void onScroll(AbsListView paramAbsListView, int paramInt1, int paramInt2, int paramInt3) {
            Log.e(TAG, "onScroll");
            float f = this.mHeaderHeight - this.mHeaderContainer.getBottom();
            Log.e(TAG, "f|" + f + " mHeaderContainer.getBottom()|" + this.mHeaderContainer.getBottom());
            if ((f > 0.0F) && (f < this.mHeaderHeight)) {
                Log.e(TAG, "1");
                int i = (int) (0.65D * f);
                this.mHeaderImage.scrollTo(0, -i);
            } else if (this.mHeaderImage.getScrollY() != 0) {
                Log.e(TAG, "2");
                this.mHeaderImage.scrollTo(0, 0);
            }
            if (this.mOnScrollListener != null) {
                this.mOnScrollListener.onScroll(paramAbsListView, paramInt1, paramInt2, paramInt3);
            }
        }
    
        //滚动状态完成后
        public void onScrollStateChanged(AbsListView paramAbsListView, int paramInt) {
            if (this.mOnScrollListener != null)
                this.mOnScrollListener.onScrollStateChanged(paramAbsListView, paramInt);
        }
    
        public boolean onTouchEvent(MotionEvent ev) {
            Log.e(TAG, "MotionEvent == " + (0xFF & ev.getAction()));
    
            switch (ev.getAction() & MotionEvent.ACTION_MASK) {
                case MotionEvent.ACTION_OUTSIDE:
                case MotionEvent.ACTION_DOWN:
                    if (!this.mScalingRunnalable.mIsFinished) {
                        this.mScalingRunnalable.abortAnimation();
                    }
                    this.mLastMotionY = ev.getY();//触摸时y轴的点
                    this.mActivePointerId = ev.getPointerId(0);//0
                    this.mMaxScale = (this.mScreenHeight / this.mHeaderHeight);//屏幕高度/头部控件的高度
                    this.mLastScale = (this.mHeaderContainer.getBottom() / this.mHeaderHeight);//504/504
                    break;
                case MotionEvent.ACTION_MOVE:
                    int j = ev.findPointerIndex(this.mActivePointerId);//id永远为0
                    if (j == -1) {
                        Log.e(TAG, "Invalid pointerId=" + this.mActivePointerId + " in onTouchEvent");
                    } else {
                        if (this.mLastMotionY == -1.0F)
                            this.mLastMotionY = ev.getY(j);
    
                        if (this.mHeaderContainer.getBottom() >= this.mHeaderHeight) {
      //mHeaderHeight = 405
                            ViewGroup.LayoutParams localLayoutParams = this.mHeaderContainer.getLayoutParams();
                            float f = ((ev.getY(j) - this.mLastMotionY + this.mHeaderContainer.getBottom()) / this.mHeaderHeight - this.mLastScale) / 2.0F + this.mLastScale;
                            //下拉：f从1.0 - 2.0
                            Log.e(TAG, "localLayoutParams.height = " + localLayoutParams.height + " localLayoutParams.width = " + localLayoutParams.width + " f = " + f);
    
                            if ((this.mLastScale <= 1.0D) && (f < this.mLastScale)) {
                                localLayoutParams.height = this.mHeaderHeight;
                                this.mHeaderContainer.setLayoutParams(localLayoutParams);
                                return super.onTouchEvent(ev);
                            }
                            this.mLastScale = Math.min(Math.max(f, 1.0F), this.mMaxScale);
                            localLayoutParams.height = ((int) (this.mHeaderHeight * this.mLastScale));
                            if (localLayoutParams.height < this.mScreenHeight)
                                this.mHeaderContainer.setLayoutParams(localLayoutParams);
                            this.mLastMotionY = ev.getY(j);
                            return true;
                        }
                        this.mLastMotionY = ev.getY(j);
                    }
                    break;
                case MotionEvent.ACTION_UP:
                    reset();
                    endScraling();
                    break;
                case MotionEvent.ACTION_CANCEL:
                    int i = ev.getActionIndex();
                    this.mLastMotionY = ev.getY(i);
                    this.mActivePointerId = ev.getPointerId(i);
                    break;
                case MotionEvent.ACTION_POINTER_DOWN://设置多点触控
                    onSecondaryPointerUp(ev);
                    this.mLastMotionY = ev.getY(ev.findPointerIndex(this.mActivePointerId));
                    break;
                case MotionEvent.ACTION_POINTER_UP:
            }
            return super.onTouchEvent(ev);
        }
    
        //初始化头部控件的布局
        public void setHeaderViewSize(int paramInt1, int paramInt2) {
            Object localObject = this.mHeaderContainer.getLayoutParams();
            if (localObject == null)
                localObject = new AbsListView.LayoutParams(paramInt1, paramInt2);
            ((ViewGroup.LayoutParams) localObject).width = paramInt1;
            ((ViewGroup.LayoutParams) localObject).height = paramInt2;
            this.mHeaderContainer.setLayoutParams((ViewGroup.LayoutParams) localObject);
            this.mHeaderHeight = paramInt2;
        }
    
        //设置接收通知的侦听器，监听列表每次滚动。
        public void setOnScrollListener(
                AbsListView.OnScrollListener paramOnScrollListener) {
            this.mOnScrollListener = paramOnScrollListener;
        }
    
    
        //用线程缩放
        class ScalingRunnalable implements Runnable {
            long mDuration;//持续时间
            boolean mIsFinished = true;//动画是否结束
            float mScale;//缩放比例
            long mStartTime;//开始时间
    
            ScalingRunnalable() {
            }
    
            //终止动画
            public void abortAnimation() {
                this.mIsFinished = true;
            }
    
            //开始缩放
            public void run() {
                float f2;
                ViewGroup.LayoutParams localLayoutParams;
                if ((!this.mIsFinished) && (this.mScale > 1.0D)) {
                    float f1 = ((float) SystemClock.currentThreadTimeMillis() - (float) this.mStartTime) / (float) this.mDuration;
                    Log.e(TAG, "mTime" + " mStartTime = " + mStartTime + " ---- SystemClock.currentThreadTimeMillis() = " + SystemClock.currentThreadTimeMillis());
                    f2 = this.mScale - (this.mScale - 1.0F) * PullToZoomListView.sInterpolator.getInterpolation(f1);
                    localLayoutParams = PullToZoomListView.this.mHeaderContainer.getLayoutParams();
                    if (f2 > 1.0F) {
      //下拉：f2==2 - 1   f1==0 - 1
                        Log.e(TAG, "f2>1.0" + " f2 = " + f2 + " ---- f1 = " + f1);
                        localLayoutParams.height = ((int) (f2 * PullToZoomListView.this.mHeaderHeight));//动态的控制这个参数，改变图片的变化
                        PullToZoomListView.this.mHeaderContainer.setLayoutParams(localLayoutParams);
                        PullToZoomListView.this.post(this);
                        return;
                    }
                    this.mIsFinished = true;
                }
            }
    
            //记录抬起手指的坐标，设置动画属性
            public void startAnimation(long paramLong) {
                this.mStartTime = SystemClock.currentThreadTimeMillis();
                this.mDuration = paramLong;
                this.mScale = ((float) (PullToZoomListView.this.mHeaderContainer.getBottom()) / PullToZoomListView.this.mHeaderHeight);
                Log.e("startAnimation", "--------------->mScale + " + mScale + "\nBottom = " + PullToZoomListView.this.mHeaderContainer.getBottom() + "\nmHeaderHeight = " + PullToZoomListView.this.mHeaderHeight);
                this.mIsFinished = false;
                PullToZoomListView.this.post(this);
            }
        }
    }