自定义侧滑栏

为了学习Scroller类，自己写了个自定义侧滑的demo，但是效果还是有点问题，主要是会滑出边界的问题。原来都是直接用别人的开源的项目来做效果，现在想自己也弄得玩。虽然达不到很好的效果。

package com.example.learnscroller;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.widget.LinearLayout;import android.widget.Scroller;public class MyScrollView extends LinearLayout {private static final String TAG = "MyScrollerView";private View mPerLayout;//主界面viewprivate View mSliderLayout;//侧边栏viewprivate int screenWidth; //屏幕宽度private int screenHeight;//屏幕高度private float scale = 0.5f;//侧边栏占比例private Scroller scroller;private int startX;//记录开始X位置public static final int SNAP_VELOCITY  = 200;//默认开始滑动像素点private VelocityTracker velocityTracker;private int mMaxVelocity;private int verlocity;private boolean isOpen = false;public MyScrollView(Context context) {this(context, null);}public MyScrollView(Context context, AttributeSet attrs) {super(context, attrs);initView(context);}@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {super.onLayout(changed,l,t,r, b);mSliderLayout.layout((int) -(screenWidth*scale+100), 0, 0, screenHeight);mPerLayout.layout(0, 0, screenWidth, screenHeight);}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);screenWidth = MeasureSpec.getSize(widthMeasureSpec);screenHeight = MeasureSpec.getSize(heightMeasureSpec);}@Overridepublic boolean onTouchEvent(MotionEvent event) {int currentX = 0;addVelocityTracker(event);switch (event.getAction()) {case MotionEvent.ACTION_DOWN:startX = (int) event.getX();break;case MotionEvent.ACTION_MOVE:verlocity = getScrollXVelocity();currentX = (int) event.getX();Log.i(TAG, "getScrollX():"+getScrollX());if(Math.abs(verlocity)> SNAP_VELOCITY){if(getScrollX()>0||-getScrollX()>scale * screenWidth){return true;}scrollBy(-(currentX - startX), 0);}startX = currentX;break;case MotionEvent.ACTION_UP:verlocity = getScrollXVelocity();currentX = (int) event.getX();if(isOpen){if(-verlocity > 500 ||-getScrollX() <= scale * screenWidth/3 ){toLeftMove();}else{toRightMove();}}else{if(verlocity > 500 ||-getScrollX()>= 2 * scale * screenWidth/3){toRightMove();}else{toLeftMove();}}startX  = 0;removeVelocityTracker();break;}return true;}private void toLeftMove(){scroller.startScroll(getScrollX(), 0, -getScrollX(), 0);postInvalidate();isOpen = false;}private void toRightMove() {scroller.startScroll(getScrollX(), 0, -getScrollX()-(int)(screenWidth*scale), 0);postInvalidate();isOpen = true;}@Overridepublic void computeScroll() {super.computeScroll();if(scroller.computeScrollOffset()){scrollTo(scroller.getCurrX(), scroller.getCurrY());postInvalidate();}}public void setPerLayout(View perLayout) {mPerLayout = perLayout;addView(mPerLayout);}public void setSliderLayout(View sliderLayout) {mSliderLayout = sliderLayout;addView(mSliderLayout);}public void setScale(float scale) {this.scale = scale;}private void initView(Context context){scroller = new Scroller(context);ViewConfiguration.get(context);mMaxVelocity = ViewConfiguration.getMaximumFlingVelocity();}private void addVelocityTracker(MotionEvent event){if(velocityTracker == null){velocityTracker = VelocityTracker.obtain();}velocityTracker.addMovement(event);}private void removeVelocityTracker(){velocityTracker.recycle();}private int getScrollXVelocity(){velocityTracker.computeCurrentVelocity(1000,mMaxVelocity);  int velocity = (int) velocityTracker.getXVelocity();  return velocity;}}