自定义View：PullToZoomScrollView

傷城~ 2022-07-13 03:42 163阅读 0赞

![PullToZoomScrollView][]

public class PullToZoomScrollView extends NestedScrollView { 
        private int DEFAULT_PULL_HEIGHT = 100;
        private float distance = 0.0f;
        private boolean isBig;
        private boolean isPreparePull;
        private boolean isTouchOne;
        private boolean isonce;
        private int mCurrentOffset = 0;
        private LinearLayout         mParentView;
        private int                  mScreenHeight;
        private ViewGroup            mTopView;
        private int                  mTopViewHeight;
        private ObjectAnimator       mAnimator;
        private OnPullToZoomListener onPullToZoomListener;
        private float startY = 0.0f;
        private int touchSlop;
    
        public interface OnPullToZoomListener { 
            void onCancelPull();
    
            void onPreparePull();
    
            void onPull();
    
            void onScrollChanged(int i);
    
            void onStartDrag();
        }
    
        public PullToZoomScrollView(Context context, AttributeSet attrs) {
            super(context, attrs);
            setOverScrollMode(View.OVER_SCROLL_NEVER);
            WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
            DisplayMetrics metrics = new DisplayMetrics();
            wm.getDefaultDisplay().getMetrics(metrics);
            this.mScreenHeight = metrics.heightPixels;
            this.mTopViewHeight = ResolutionUtils.getHeight(context, metrics.widthPixels, 3, 2);
            setVerticalScrollBarEnabled(false);
            this.touchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
        }
    
        protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            if (!this.isonce) {
                this.mParentView = (LinearLayout) getChildAt(0);
                this.mTopView = (ViewGroup) this.mParentView.getChildAt(0);
                this.mTopView.getLayoutParams().height = this.mTopViewHeight;
                this.isonce = true;
            }
        }
    
        public boolean onTouchEvent(MotionEvent ev) {
            switch (ev.getAction()) {
                case MotionEvent.ACTION_UP:
                    if (this.isBig) {
                        reset();
                        this.isBig = false;
                    }
                    this.isTouchOne = false;
                    break;
                case MotionEvent.ACTION_MOVE:
                    if (this.mCurrentOffset <= 0) {
                        if (!this.isTouchOne) {
                            this.startY = ev.getY();
                            this.isTouchOne = true;
                        }
                        this.distance = ev.getY() - this.startY;
                        if (this.distance >= ((float) this.touchSlop) && this.distance > 0.0f) {
                            this.isBig = true;
                            setT(((int) (-this.distance)) / 4);
                            break;
                        }
                    }
                    break;
            }
            return super.onTouchEvent(ev);
        }
    
        public void setT(int t) {
            scrollTo(0, 0);
            if (t < 0) {
                this.mTopView.getLayoutParams().height = this.mTopViewHeight - t;
                this.mTopView.requestLayout();
                if ((-t) <= this.DEFAULT_PULL_HEIGHT || !this.isBig) {
                    if (this.onPullToZoomListener != null) {
                        this.onPullToZoomListener.onStartDrag();
                    }
                } else if (this.onPullToZoomListener != null) {
                    this.isPreparePull = true;
                    this.onPullToZoomListener.onPreparePull();
                }
            }
        }
    
        private void reset() {
            if (this.mAnimator == null || !this.mAnimator.isRunning()) {
                this.mAnimator = ObjectAnimator.ofInt(this, "t", new int[]{((int) (-this.distance)) / 4, 0});
                this.mAnimator.setDuration(150);
                this.mAnimator.addListener(new AnimatorListenerAdapter() {
                    public void onAnimationEnd(Animator animation) {
                        super.onAnimationEnd(animation);
                        PullToZoomScrollView.this.isPreparePull = false;
                        if (PullToZoomScrollView.this.distance / aj.hA > ((float) PullToZoomScrollView.this.DEFAULT_PULL_HEIGHT)) {
                            if (PullToZoomScrollView.this.onPullToZoomListener != null) {
                                PullToZoomScrollView.this.onPullToZoomListener.onPull();
                            }
                        } else if (PullToZoomScrollView.this.onPullToZoomListener != null) {
                            PullToZoomScrollView.this.onPullToZoomListener.onCancelPull();
                        }
                    }
                });
                this.mAnimator.start();
            }
        }
    
        protected void onScrollChanged(int l, int t, int oldl, int oldt) {
            super.onScrollChanged(l, t, oldl, oldt);
            this.mCurrentOffset = t;
            if (this.onPullToZoomListener != null) {
                this.onPullToZoomListener.onScrollChanged(t);
            }
            if (t <= this.mTopViewHeight && t >= 0 && !this.isBig) {
                this.mTopView.setTranslationY((float) (t / 2));
            }
            if (this.isBig) {
                scrollTo(0, 0);
            }
        }
    
        public void setOnPullToZoomListener(OnPullToZoomListener onPullToZoomListener) {
            this.onPullToZoomListener = onPullToZoomListener;
        }
    }

[PullToZoomScrollView]: /images/20220713/b1a93691b6f24199a4b6c7a80ddf3e62.png