Android 自定义View实现抽屉效果
说明
- 这个自定义View，没有处理好多点触摸问题 View跟着手指移动，没有采用传统的scrollBy方法，而是通过不停地重新布局子View的方式，来使得子View产生滚动效果menuView.layout(menuLeft, 0, menuLeft + menuWidth, menuHeight); 相应的，由于没有使用scrollBy方法，就没有产生getScrollX值，所以不能通过Scroller的startScroll方法来完成手指离开后的平滑滚动效果，而是使用了Animation动画的applyTransformation方法来完成插值，从而实现动画效果
主要算法是：动画当前值=起始值+（目标值-起始值）*interpolatedTime
其中interpolatedTime是一个0.0f~1.0f的数字，系统自己插值计算好了（默认是线性变化的），当然你可以自己写插值器
/** * 由于上面不能使用scrollBy，那么这里就不能使用Scroller这个类来完成平滑移动了，还好我们有动画 */ class MyAnimation extends Animation { private int viewCurrentLfet; private int viewStartLfet; private int viewTargetLfet; private int viewWidth; private View view; private int cha; public MyAnimation(View view, int viewStartLfet, int viewTargetLfet, int viewWidth) { this.view = view; this.viewStartLfet = viewStartLfet; this.viewTargetLfet = viewTargetLfet; this.viewWidth = viewWidth; cha = viewTargetLfet - viewStartLfet; setDuration(Math.abs(cha)); } @Override protected void applyTransformation(float interpolatedTime, Transformation t) { super.applyTransformation(interpolatedTime, t); viewCurrentLfet = (int) (viewStartLfet + cha * interpolatedTime); view.layout(viewCurrentLfet, 0, viewCurrentLfet + viewWidth, menuHeight); } }
完整代码
package com.sunshine.choutidemo;import android.content.Context;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.VelocityTracker;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.view.animation.Animation;import android.view.animation.AnimationSet;import android.view.animation.Transformation;/** * Created by a on 2016/8/15. */public class ChouTiView extends ViewGroup { private View mainView; private View menuView; private int menuWidth; private int downX; private int lastX; private int moveX; private int deltaX; private int menuLeft; private int mainLeft; private int menuHeight; private int mainWidth; private int mainHeight; private int menuLeftBorder; private int mainLeftBorder; private int menuRightBorder; private int mainRightBorder; private int mMaxVelocity; private VelocityTracker mVelocityTracker; private int mPointerId; private float velocityX; private float velocityY; public ChouTiView(Context context) { super(context); init(); } public ChouTiView(Context context, AttributeSet attrs) { super(context, attrs); init(); } private void init() {// 0.获得此次最大速率 mMaxVelocity = ViewConfiguration.get(getContext()).getMaximumFlingVelocity(); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); mainView.measure(widthMeasureSpec, heightMeasureSpec); menuView.measure(widthMeasureSpec, heightMeasureSpec);// 获得子View的正确宽度（只能获取具体的数字值）,但是不能这样获取高度，因为这里match—parent为-1 menuWidth = menuView.getLayoutParams().width; menuLeft = (int) (-menuWidth * 0.5); menuLeftBorder = (int) (-menuWidth * 0.5); menuRightBorder = 0; mainLeft = 0; mainLeftBorder = 0; mainRightBorder = menuWidth; } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) { menuHeight = b; mainWidth = r; mainHeight = b; mainView.layout(l, t, r, b); menuView.layout(menuLeft, t, menuLeft + menuWidth, b); } @Override protected void onFinishInflate() { super.onFinishInflate(); mainView = getChildAt(1); menuView = getChildAt(0); } @Override public boolean onTouchEvent(MotionEvent event) { final int action = event.getActionMasked(); acquireVelocityTracker(event); //1.向VelocityTracker添加MotionEvent final VelocityTracker verTracker = mVelocityTracker; switch (action) { case MotionEvent.ACTION_DOWN: //2.求第一个触点的id， 此时可能有多个触点，但至少一个 // 获取索引为0的手指id mPointerId = event.getPointerId(0); downX = (int) event.getX(); lastX = downX; break; case MotionEvent.ACTION_MOVE:// 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); moveX = (int) event.getX(pointerIndex); deltaX = moveX - lastX;// 把触摸移动引起的增量，体现在menu和main的左侧left上 menuLeft = (int) (menuLeft + deltaX * 0.43);//让菜单移动的慢一点 mainLeft = mainLeft + deltaX;// 让菜单根据手指增量移动，考虑两侧边界问题（通过不停地layout实现移动效果）// 为何不适用scrollBy，因为scrollBy移动的是外层的大View，现在需求是分别移动这个大view内的两个小View// scrollBy的话，会让菜单和主页面同时移动，不会产生错位效果，// 你会想，那让小view自己scrollBy，这样也是不行的，// 因为让小view，例如menu调用scrollBy的话，会让menu自己的边框在动，// 看上去，是menu内部的文字在移动，但是menu并没有在外层的大View里移动// 说的很拗口，但是真的不能用scrollBy if (menuLeft >= menuRightBorder) { menuLeft = menuRightBorder; } else if (menuLeft <= menuLeftBorder) { menuLeft = menuLeftBorder; } menuView.layout(menuLeft, 0, menuLeft + menuWidth, menuHeight);// 让主页面根据手指增量移动，考虑两侧边界问题 if (mainLeft >= mainRightBorder) { mainLeft = mainRightBorder; } else if (mainLeft <= mainLeftBorder) { mainLeft = mainLeftBorder; } mainView.layout(mainLeft, 0, mainLeft + mainWidth, mainHeight); lastX = moveX; break; case MotionEvent.ACTION_UP: //3.求伪瞬时速度 verTracker.computeCurrentVelocity(1000, mMaxVelocity); velocityX = verTracker.getXVelocity(mPointerId); Log.e("qwe", velocityX + "/" + mMaxVelocity); if (velocityX > 1000) { smoothToMenu(); } else if (velocityX < -2000) { smoothToMain(); } else {// 判断松手的位置，如果大于1/2.5的菜单宽度就打开菜单，否则打开主页面 if (mainLeft > menuWidth / 2.5) { Log.e("qqq", "显示菜单"); smoothToMenu(); } else { Log.e("qqq", "显示主页面"); smoothToMain(); } }// 4.ACTION_UP释放VelocityTracker,交给其他控件使用 releaseVelocityTracker(); break; case MotionEvent.ACTION_CANCEL:// 4.ACTION_UP释放VelocityTracker,交给其他控件使用 releaseVelocityTracker(); case MotionEvent.ACTION_POINTER_UP: // 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 downX = (int) event.getX(reIndex);// y = event.getY(reIndex); releaseVelocityTracker(); } releaseVelocityTracker(); break; } return true; } private void smoothToMain() { MyAnimation menuAnimation = new MyAnimation(menuView, menuLeft, menuLeftBorder, menuWidth); MyAnimation mainAnimation = new MyAnimation(mainView, mainLeft, mainLeftBorder, mainWidth); AnimationSet animationSet = new AnimationSet(true); animationSet.addAnimation(menuAnimation); animationSet.addAnimation(mainAnimation); startAnimation(animationSet); //一定记得更新menu和main的左侧状态，这影响到了，再次手指触摸时候的动画，否则突变 menuLeft = menuLeftBorder; mainLeft = mainLeftBorder; } private void smoothToMenu() { MyAnimation menuAnimation = new MyAnimation(menuView, menuLeft, menuRightBorder, menuWidth); MyAnimation mainAnimation = new MyAnimation(mainView, mainLeft, mainRightBorder, mainWidth); AnimationSet animationSet = new AnimationSet(true); animationSet.addAnimation(menuAnimation); animationSet.addAnimation(mainAnimation); startAnimation(animationSet); //一定记得更新menu和main的左侧状态，这影响到了，再次手指触摸时候的动画，否则突变 menuLeft = menuRightBorder; mainLeft = mainRightBorder; } /** * @param event 向VelocityTracker添加MotionEvent * @see android.view.VelocityTracker#obtain() * @see android.view.VelocityTracker#addMovement(MotionEvent) */ private void acquireVelocityTracker(final MotionEvent event) { if (null == mVelocityTracker) { mVelocityTracker = VelocityTracker.obtain(); } mVelocityTracker.addMovement(event); } /** * 释放VelocityTracker * * @see android.view.VelocityTracker#clear() * @see android.view.VelocityTracker#recycle() */ private void releaseVelocityTracker() { if (null != mVelocityTracker) { mVelocityTracker.clear(); mVelocityTracker.recycle(); mVelocityTracker = null; } } /** * 由于上面不能使用scrollBy，那么这里就不能使用Scroller这个类来完成平滑移动了，还好我们有动画 */ class MyAnimation extends Animation { private int viewCurrentLfet; private int viewStartLfet; private int viewTargetLfet; private int viewWidth; private View view; private int cha; public MyAnimation(View view, int viewStartLfet, int viewTargetLfet, int viewWidth) { this.view = view; this.viewStartLfet = viewStartLfet; this.viewTargetLfet = viewTargetLfet; this.viewWidth = viewWidth; cha = viewTargetLfet - viewStartLfet; setDuration(Math.abs(cha)); } @Override protected void applyTransformation(float interpolatedTime, Transformation t) { super.applyTransformation(interpolatedTime, t); viewCurrentLfet = (int) (viewStartLfet + cha * interpolatedTime); view.layout(viewCurrentLfet, 0, viewCurrentLfet + viewWidth, menuHeight); } }}
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