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
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;
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;
}
private void acquireVelocityTracker(final MotionEvent event) {
if (null == mVelocityTracker) {
mVelocityTracker = VelocityTracker.obtain();
}
mVelocityTracker.addMovement(event);
}
private void releaseVelocityTracker() {
if (null != mVelocityTracker) {
mVelocityTracker.clear();
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
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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