弹性

2019-11-09 15:16:09

字体：大中小

来源：转载

供稿：网友

package com.hou.mask;import android.content.Context;import android.graphics.Rect;import android.support.v4.view.MotionEventCompat;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.view.ViewConfiguration;import android.view.animation.TranslateAnimation;import android.widget.ScrollView;/** * */public class ReboundScrollView extends ScrollView { PRivate static final String TAG = "MaskScrollView"; private static final int INVALID_POINTER = -1; private static final int FACTOR = 2;//因子，阻尼系数 private View childView; private int mActivePointerId; private float mLastMotionY; private float lastDeltaY; private Rect normal = new Rect(); private int mTouchSlop; private static final int ALL = 0; private static final int NONE = 1; private static final int TOP = 2; private static final int BOTTOM = 3; private int elasticity; public ReboundScrollView(Context context) { this(context, null); } public ReboundScrollView(Context context, AttributeSet attrs) { this(context, attrs, 0); } public ReboundScrollView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); final ViewConfiguration configuration = ViewConfiguration.get(context); mTouchSlop = configuration.getScaledTouchSlop(); elasticity = ALL; } @Override protected void onFinishInflate() { super.onFinishInflate(); childView = getChildAt(0); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { int action = ev.getAction(); if (action == MotionEvent.ACTION_MOVE && Math.abs(ev.getY() - mLastMotionY) > mTouchSlop) { return true; } else if (action == MotionEvent.ACTION_DOWN) { if (getChildCount() == 0) { return false; } mLastMotionY = ev.getY(); mActivePointerId = ev.getPointerId(0); lastDeltaY = 0; } return super.onInterceptTouchEvent(ev); } @Override public boolean onTouchEvent(MotionEvent ev) { int actionMasked = MotionEventCompat.getActionMasked(ev); switch (actionMasked) { case MotionEvent.ACTION_DOWN: if (getChildCount() == 0) { return false; } mLastMotionY = ev.getY(); mActivePointerId = ev.getPointerId(0); lastDeltaY = 0; break; case MotionEvent.ACTION_MOVE: int activePointerIndex = ev.findPointerIndex(mActivePointerId); if (activePointerIndex == -1) { Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent"); break; } final float y = ev.getY(activePointerIndex); float deltaY = mLastMotionY - y; //<0只是上边有弹性,>0只是下边有弹性，不加上下都有 if (elasticity == ALL || elasticity == TOP && deltaY < 0 || elasticity == BOTTOM && deltaY > 0) { if (normal.isEmpty()) { //记录原始位置，用来恢复 normal.set(childView.getLeft(), childView.getTop(), childView.getRight(), childView.getBottom()); } int offsetY = (int) ((lastDeltaY - deltaY) / FACTOR); childView.layout(childView.getLeft(), childView.getTop() + offsetY, childView.getRight(), childView.getBottom() + offsetY); lastDeltaY = deltaY; } break; case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: animateToBack(); mActivePointerId = INVALID_POINTER; break; case MotionEvent.ACTION_POINTER_DOWN: int index = ev.getActionIndex(); mLastMotionY = ev.getY(index); mActivePointerId = ev.getPointerId(index); lastDeltaY = 0; break; case MotionEvent.ACTION_POINTER_UP: onSecondaryPointerUp(ev); mLastMotionY = ev.getY(ev.findPointerIndex(mActivePointerId)); final float upY = ev.getY(ev.findPointerIndex(mActivePointerId)); lastDeltaY = mLastMotionY - upY; break; } return super.onTouchEvent(ev); } private void animateToBack() { TranslateAnimation animation = new TranslateAnimation(0, 0, childView.getTop() - getPaddingTop(), normal.top - getPaddingTop()); animation.setDuration(200); childView.startAnimation(animation); childView.offsetTopAndBottom(normal.top - childView.getTop()); normal.setEmpty(); } private void onSecondaryPointerUp(MotionEvent ev) { final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; final int pointerId = ev.getPointerId(pointerIndex); if (pointerId == mActivePointerId) { final int newPointerIndex = pointerIndex == 0 ? 1 : 0; mLastMotionY = ev.getY(newPointerIndex); mActivePointerId = ev.getPointerId(newPointerIndex); } }}

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