Android 自定义ScrollView 支持惯性滑动，惯性回弹效果。支持上拉加载更多
来源：互联网 发布：小学数学网络研修日志 编辑：程序博客网 时间：2024/05/22 04:31
先讲下原理：
ScrollView的子View 主要分为3部分：head头部，滚动内容，fooder底部
我们实现惯性滑动，以及回弹，都是靠超过head或者fooder 就重新滚动到 ，内容的顶部或者底部。
之前看了Pulltorefresh 他是通过不断改变 head或者 fooder的 pading 值来实现 上拉或者 下拉的效果。感觉有点不流畅，而且层次嵌套得比较多。当然他的好处是扩展性好。
因工作需求，需要层次嵌套少，对性能要求非常高。因此重新自定义了ViewGroup实现。
直接上代码：
package com.example.administrator.customscrollview;import android.content.Context;import android.content.res.TypedArray;import android.util.AttributeSet;import android.util.Log;import android.view.Gravity;import android.view.MotionEvent;import android.view.VelocityTracker;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.widget.OverScroller;/** * 自定义 pulltorefresh Layout * TODO: ferris 2015年9月11日 18:52:40 */public class PullTorefreshScrollView extends ViewGroup { private FoodeLayout fooder_layout;// top and buttom private View top_layout; private int desireWidth, desireHeight; private VelocityTracker velocityTracker; private int mPointerId; private float x, y; private OverScroller mScroller; private int maxFlingVelocity, minFlingVelocity; private int mTouchSlop; protected Boolean isMove = false; protected float downX = 0, downY = 0; private int top_hight = 0; private int scrollYButtom = 0; private int nScrollYButtom = 0; private int pullDownMin = 0; private Boolean isEnablePullDown = true; private Boolean isFirst=true; public void setEnablePullDown(Boolean isEnablePullDown) { this.isEnablePullDown = isEnablePullDown; } public PullTorefreshScrollView(Context context) { super(context); init(null, 0); } public PullTorefreshScrollView(Context context, AttributeSet attrs) { super(context, attrs); init(attrs, 0); } public PullTorefreshScrollView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); init(attrs, defStyle); } private void init(AttributeSet attrs, int defStyle) { // Load attributes// final TypedArray a = getContext().obtainStyledAttributes(// attrs, R.styleable.PullTorefreshScrollView, defStyle, 0);////// a.recycle(); mScroller = new OverScroller(getContext()); maxFlingVelocity = ViewConfiguration.get(getContext()).getScaledMaximumFlingVelocity(); minFlingVelocity = ViewConfiguration.get(getContext()).getScaledMinimumFlingVelocity(); mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop(); } @Override protected void onFinishInflate() { super.onFinishInflate(); fooder_layout = (FoodeLayout) findViewById(R.id.fooder_layout); top_layout = findViewById(R.id.top_layout); if (isEnablePullDown) { fooder_layout.showFooderPull(); } else { fooder_layout.hideFooder(); } } public int getScrollYTop() { return top_hight; } public int getScrollYButtom() { return scrollYButtom; } public int getNScrollYTop() { return 0; } public int getNScrollYButtom() { return nScrollYButtom; } public int measureWidth(int widthMeasureSpec) { int result = 0; int measureMode = MeasureSpec.getMode(widthMeasureSpec); int width = MeasureSpec.getSize(widthMeasureSpec); switch (measureMode) { case MeasureSpec.AT_MOST: case MeasureSpec.EXACTLY: result = width; break; default: break; } return result; } public int measureHeight(int heightMeasureSpec) { int result = 0; int measureMode = MeasureSpec.getMode(heightMeasureSpec); int height = MeasureSpec.getSize(heightMeasureSpec); switch (measureMode) { case MeasureSpec.AT_MOST: case MeasureSpec.EXACTLY: result = height; break; default: break; } return result; } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { // 计算所有child view 要占用的空间 int width = measureWidth(widthMeasureSpec); int height = measureHeight(heightMeasureSpec); desireWidth = 0; desireHeight = 0; int count = getChildCount(); for (int i = 0; i < count; ++i) { View v = getChildAt(i); if (v.getVisibility() != View.GONE) { LayoutParams lp = (LayoutParams) v.getLayoutParams(); measureChildWithMargins(v, widthMeasureSpec, 0, heightMeasureSpec, 0); //只是在这里增加了垂直或者水平方向的判断 if (v.getId() == R.id.top_layout) { top_hight = v.getMeasuredHeight(); } desireWidth = Math.max(desireWidth, v.getMeasuredWidth() + lp.leftMargin + lp.rightMargin); desireHeight += v.getMeasuredHeight() + lp.topMargin + lp.bottomMargin; } } // count with padding desireWidth += getPaddingLeft() + getPaddingRight(); desireHeight += getPaddingTop() + getPaddingBottom(); // see if the size is big enough desireWidth = Math.max(desireWidth, getSuggestedMinimumWidth()); desireHeight = Math.max(desireHeight, getSuggestedMinimumHeight()); //处理内容比较少的时候，就添加一定的高度 int scrollHight = height + top_hight * 2; if (scrollHight > desireWidth) { int offset = scrollHight - desireHeight; View view = new View(getContext()); view.setBackgroundResource(R.color.top_layout_color); LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, offset); addView(view, getChildCount() - 1, lp); desireWidth = scrollHight; } setMeasuredDimension(resolveSize(desireWidth, widthMeasureSpec), resolveSize(desireHeight, heightMeasureSpec)); scrollYButtom = desireHeight - getMeasuredHeight() - top_hight; nScrollYButtom = desireHeight - getMeasuredHeight(); //如果上啦拖出一半的高度，就代表将要执行上啦 pullDownMin = nScrollYButtom - top_hight / 2; if(isFirst){ scrollTo(0, top_hight); isFirst=false; } } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { final int parentLeft = getPaddingLeft(); final int parentRight = r - l - getPaddingRight(); final int parentTop = getPaddingTop(); final int parentBottom = b - t - getPaddingBottom(); if (BuildConfig.DEBUG) Log.d("onlayout", "parentleft: " + parentLeft + " parenttop: " + parentTop + " parentright: " + parentRight + " parentbottom: " + parentBottom); int left = parentLeft; int top = parentTop; int count = getChildCount(); for (int i = 0; i < count; ++i) { View v = getChildAt(i); if (v.getVisibility() != View.GONE) { LayoutParams lp = (LayoutParams) v.getLayoutParams(); final int childWidth = v.getMeasuredWidth(); final int childHeight = v.getMeasuredHeight(); final int gravity = lp.gravity; final int horizontalGravity = gravity & Gravity.HORIZONTAL_GRAVITY_MASK; final int verticalGravity = gravity & Gravity.VERTICAL_GRAVITY_MASK; // layout vertical, and only consider horizontal gravity left = parentLeft; top += lp.topMargin; switch (horizontalGravity) { case Gravity.LEFT: break; case Gravity.CENTER_HORIZONTAL: left = parentLeft + (parentRight - parentLeft - childWidth) / 2 + lp.leftMargin - lp.rightMargin; break; case Gravity.RIGHT: left = parentRight - childWidth - lp.rightMargin; break; } v.layout(left, top, left + childWidth, top + childHeight); top += childHeight + lp.bottomMargin; } } } @Override protected android.view.ViewGroup.LayoutParams generateDefaultLayoutParams() { return new LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT); } @Override public android.view.ViewGroup.LayoutParams generateLayoutParams( AttributeSet attrs) { return new LayoutParams(getContext(), attrs); } @Override protected android.view.ViewGroup.LayoutParams generateLayoutParams( android.view.ViewGroup.LayoutParams p) { return new LayoutParams(p); } public static class LayoutParams extends MarginLayoutParams { public int gravity = -1; public LayoutParams(Context c, AttributeSet attrs) { super(c, attrs); TypedArray ta = c.obtainStyledAttributes(attrs, R.styleable.SlideGroup); gravity = ta.getInt(R.styleable.SlideGroup_layout_gravity, -1); ta.recycle(); } public LayoutParams(int width, int height) { this(width, height, -1); } public LayoutParams(int width, int height, int gravity) { super(width, height); this.gravity = gravity; } public LayoutParams(android.view.ViewGroup.LayoutParams source) { super(source); } public LayoutParams(MarginLayoutParams source) { super(source); } } /** * onInterceptTouchEvent()用来询问是否要拦截处理。 onTouchEvent()是用来进行处理。 * <p/> * 例如：parentLayout----childLayout----childView 事件的分发流程： * parentLayout::onInterceptTouchEvent()---false?---> * childLayout::onInterceptTouchEvent()---false?---> * childView::onTouchEvent()---false?---> * childLayout::onTouchEvent()---false?---> parentLayout::onTouchEvent() * <p/> * <p/> * <p/> * 如果onInterceptTouchEvent()返回false，且分发的子View的onTouchEvent()中返回true， * 那么onInterceptTouchEvent()将收到所有的后续事件。 * <p/> * 如果onInterceptTouchEvent()返回true，原本的target将收到ACTION_CANCEL，该事件 * 将会发送给我们自己的onTouchEvent()。 */ @Override public boolean onInterceptTouchEvent(MotionEvent ev) { final int action = ev.getActionMasked(); if (BuildConfig.DEBUG) Log.d("onInterceptTouchEvent", "action: " + action); if (action == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { // 该事件可能不是我们的 return false; } boolean isIntercept = false; switch (action) { case MotionEvent.ACTION_DOWN: // 如果动画还未结束，则将此事件交给onTouchEvet()处理， // 否则，先分发给子View isIntercept = !mScroller.isFinished(); // 如果此时不拦截ACTION_DOWN时间，应该记录下触摸地址及手指id，当我们决定拦截ACTION_MOVE的event时， // 将会需要这些初始信息（因为我们的onTouchEvent将可能接收不到ACTION_DOWN事件） mPointerId = ev.getPointerId(0);// if (!isIntercept) { downX = x = ev.getX(); downY = y = ev.getY();// } break; case MotionEvent.ACTION_MOVE: int pointerIndex = ev.findPointerIndex(mPointerId); if (BuildConfig.DEBUG) Log.d("onInterceptTouchEvent", "pointerIndex: " + pointerIndex + ", pointerId: " + mPointerId); float mx = ev.getX(pointerIndex); float my = ev.getY(pointerIndex); if (BuildConfig.DEBUG) Log.d("onInterceptTouchEvent", "action_move [touchSlop: " + mTouchSlop + ", deltaX: " + (x - mx) + ", deltaY: " + (y - my) + "]"); // 根据方向进行拦截，（其实这样，如果我们的方向是水平的，里面有一个ScrollView，那么我们是支持嵌套的） if (Math.abs(y - my) >= mTouchSlop) { isIntercept = true; } //如果不拦截的话，我们不会更新位置，这样可以通过累积小的移动距离来判断是否达到可以认为是Move的阈值。 //这里当产生拦截的话，会更新位置（这样相当于损失了mTouchSlop的移动距离，如果不更新，可能会有一点点跳的感觉） if (isIntercept) { x = mx; y = my; } break; case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: // 这是触摸的最后一个事件，无论如何都不会拦截 if (velocityTracker != null) { velocityTracker.recycle(); velocityTracker = null; } break; case MotionEvent.ACTION_POINTER_UP: solvePointerUp(ev); break; } return isIntercept; } private void solvePointerUp(MotionEvent event) { // 获取离开屏幕的手指的索引 int pointerIndexLeave = event.getActionIndex(); int pointerIdLeave = event.getPointerId(pointerIndexLeave); if (mPointerId == pointerIdLeave) { // 离开屏幕的正是目前的有效手指，此处需要重新调整，并且需要重置VelocityTracker int reIndex = pointerIndexLeave == 0 ? 1 : 0; mPointerId = event.getPointerId(reIndex); // 调整触摸位置，防止出现跳动 x = event.getX(reIndex); y = event.getY(reIndex); if (velocityTracker != null) velocityTracker.clear(); } } @Override public boolean onTouchEvent(MotionEvent event) { final int action = event.getActionMasked(); if (velocityTracker == null) { velocityTracker = VelocityTracker.obtain(); } velocityTracker.addMovement(event); switch (action) { case MotionEvent.ACTION_DOWN: // 获取索引为0的手指id isMove = false; mPointerId = event.getPointerId(0); x = event.getX(); y = event.getY(); if (!mScroller.isFinished()) mScroller.abortAnimation(); break; case MotionEvent.ACTION_MOVE: isMove = true; // 获取当前手指id所对应的索引，虽然在ACTION_DOWN的时候，我们默认选取索引为0 // 的手指，但当有第二个手指触摸，并且先前有效的手指up之后，我们会调整有效手指 // 屏幕上可能有多个手指，我们需要保证使用的是同一个手指的移动轨迹， // 因此此处不能使用event.getActionIndex()来获得索引 final int pointerIndex = event.findPointerIndex(mPointerId); float mx = event.getX(pointerIndex); float my = event.getY(pointerIndex); moveBy((int) (x - mx), (int) (y - my)); x = mx; y = my; break; case MotionEvent.ACTION_UP: isMove = false; velocityTracker.computeCurrentVelocity(1000, maxFlingVelocity); float velocityX = velocityTracker.getXVelocity(mPointerId); float velocityY = velocityTracker.getYVelocity(mPointerId); completeMove(-velocityX, -velocityY); if (velocityTracker != null) { velocityTracker.recycle(); velocityTracker = null; } break; case MotionEvent.ACTION_POINTER_UP: // 获取离开屏幕的手指的索引 isMove = false; int pointerIndexLeave = event.getActionIndex(); int pointerIdLeave = event.getPointerId(pointerIndexLeave); if (mPointerId == pointerIdLeave) { // 离开屏幕的正是目前的有效手指，此处需要重新调整，并且需要重置VelocityTracker int reIndex = pointerIndexLeave == 0 ? 1 : 0; mPointerId = event.getPointerId(reIndex); // 调整触摸位置，防止出现跳动 x = event.getX(reIndex); y = event.getY(reIndex); if (velocityTracker != null) velocityTracker.clear(); } break; case MotionEvent.ACTION_CANCEL: isMove = false; break; } return true; } private Boolean isPull = false; //此处的moveBy是根据水平或是垂直排放的方向，//来选择是水平移动还是垂直移动 public void moveBy(int deltaX, int deltaY) { if (BuildConfig.DEBUG) Log.d("moveBy", "deltaX: " + deltaX + " deltaY: " + deltaY); if (Math.abs(deltaY) >= Math.abs(deltaX)) { int mScrollY = getScrollY(); if (mScrollY <= 0) { scrollTo(0, 0); } else if (mScrollY >= getNScrollYButtom()) { scrollTo(0, getNScrollYButtom()); } else { scrollBy(0, deltaY); } if (isEnablePullDown && deltaY > 0 && mScrollY >= pullDownMin) { isPull = true; Log.d("onlayout", "isPull: true"); } } } private void completeMove(float velocityX, float velocityY) { int mScrollY = getScrollY(); int maxY = getScrollYButtom(); int minY = getScrollYTop(); if (mScrollY >= maxY) {//如果滚动，超过了 下边界，就回弹到下边界 if (isPull) {//滚动到最底部 mScroller.startScroll(0, mScrollY, 0, getNScrollYButtom() - mScrollY, 300); invalidate(); //显示雷达 fooder_layout.showFooderRadar(); if (pullDownListem != null) { pullDownListem.onPullDown(); } Log.d("onlayout", "isPull: true 滚动到最底部，显示出雷达"); } else { mScroller.startScroll(0, mScrollY, 0, maxY - mScrollY); invalidate(); Log.d("onlayout", "isPull: true"); } } else if (mScrollY <= minY) {//如果滚动，超过了上边界，就回弹到上边界 // 超出了上边界，弹回 mScroller.startScroll(0, mScrollY, 0, minY - mScrollY); invalidate(); } else if (Math.abs(velocityY) >= minFlingVelocity && maxY > 0) {//大于1页的时候// mScroller.fling(0, mScrollY, 0, (int) (velocityY * 1.2f), 0, 0, minY, maxY); mScroller.fling(0, mScrollY, 0, (int) (velocityY * 2f), 0, 0, getNScrollYTop(), getNScrollYButtom()); invalidate(); } } public void ifNeedScrollBack() { int mScrollY = getScrollY(); int maxY = getScrollYButtom(); int minY = getScrollYTop(); if (mScrollY > maxY) { // 超出了下边界，弹回 mScroller.startScroll(0, mScrollY, 0, maxY - mScrollY); invalidate(); } else if (mScrollY < minY) { // 超出了上边界，弹回 mScroller.startScroll(0, mScrollY, 0, minY - mScrollY); invalidate(); } } @Override protected void onScrollChanged(int l, int t, int oldl, int oldt) { super.onScrollChanged(l, t, oldl, oldt); } @Override public void computeScroll() { if (mScroller.computeScrollOffset()) { scrollTo(0, mScroller.getCurrY()); postInvalidate(); } else { Log.d("onlayout", "computeScroll,isMove:"+isMove+",isPull:"+isPull); if (!isMove && !isPull) { ifNeedScrollBack(); } } } public void onPullSuccess() { soomToBack(); } public void soomToBack() { int mScrollY = getScrollY(); int maxY = getScrollYButtom(); Log.d("onlayout", "soomToBack: (maxY - mScrollY)="+(maxY - mScrollY)+"，maxY="+maxY+",mScrollY="+mScrollY); // 超出了下边界，弹回 mScroller.startScroll(0, mScrollY, 0, maxY - mScrollY, 300); invalidate(); postDelayed(new Runnable() { @Override public void run() { fooder_layout.showFooderPull(); isPull = false; } }, 310); } private PullDownListem pullDownListem; public void setPullDownListem(PullDownListem pullDownListem) { this.pullDownListem = pullDownListem; } public interface PullDownListem { public void onPullDown(); }}
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