Android自定义viewgroup快速滑动（4）

上一篇文章自定义viewgroup（3）地址：//www.jb51.net/article/100618.htm

代码：

package com.example.libingyuan.horizontallistview.ScrollViewGroup;
import android.content.Context;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.Scroller;

public class ScrollViewGroup extends ViewGroup {
  //滚动计算辅助类
  private Scroller mScroller;
  //手指落点的X坐标
  private float mLastMotionX = 0;
  //屏幕宽度
  private int screenWidth;
  //手指加速度辅助类
  private VelocityTracker mVelocityTracker;
  //每秒移动的最小dp
  private int mMinimumVelocity;
  //每秒移动的最大dp
  private int mMaximumVelocity;
  
  public ScrollViewGroup(Context context) {
    this(context, null);
  }
  
  public ScrollViewGroup(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }
  
  public ScrollViewGroup(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init(context);
  }
  
  private void init(Context context) {
    //初始化辅助类
    mScroller = new Scroller(context);
    //获取屏幕宽度
    WindowManager manager = (WindowManager) context
        .getSystemService(Context.WINDOW_SERVICE);
    DisplayMetrics outMetrics = new DisplayMetrics();
    manager.getDefaultDisplay().getMetrics(outMetrics);
    screenWidth = outMetrics.widthPixels;
    //获取最小和最大的移动距离
    final ViewConfiguration configuration = ViewConfiguration.get(context);
    mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
    mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
  }
  
  @Override
  public void computeScroll() {
    //判断滚动时候停止
    if (mScroller.computeScrollOffset()) {
      //滚动到指定的位置
      scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
      //这句话必须写，否则不能实时刷新
      postInvalidate();
    }
  }
  
  @Override
  public boolean onTouchEvent(MotionEvent event) {
    // TODO Auto-generated method stub
    int action = event.getAction();
    //获取现在手指所在的位置的x坐标
    float x = event.getX();
    //判断触发的时间
    switch (action) {
      //按下事件
      case MotionEvent.ACTION_DOWN:
        //初始化或服用加速度测试器
        initOrResetVelocityTracker();
        //测试器添加按下事件
        mVelocityTracker.addMovement(event);
        //如果停止滚动则取消动画（即手指按下就停止滚动）
        if (!mScroller.isFinished()) {
          mScroller.abortAnimation();
        }
        //获取现在的x坐标
        mLastMotionX = event.getX();
        break;
      //移动事件
      case MotionEvent.ACTION_MOVE:
        //测试器添加移动事件
        if (mVelocityTracker != null) {
          mVelocityTracker.addMovement(event);
        }
        //计算移动的偏移量
        float delt = mLastMotionX - x;
        //重置手指位置
        mLastMotionX = x;
        //滚动
        scrollBy((int) delt, 0);
        break;
      //手指抬起事件
      case MotionEvent.ACTION_UP:
        //测试器添加抬起事件
        mVelocityTracker.addMovement(event);
        //添加加速度的测试时间，这里是测量1000毫秒内的加速度
        mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
        //获取x方向加速度
        float pxsec = mVelocityTracker.getXVelocity();
        //得到最后一个子View
        View lastChild = getChildAt(getChildCount() - 1);
        //获取滑动的最大滑动距离（最后一个Child的右边框的坐标减去屏幕的宽度）
        int finalyChild = (int) (lastChild.getX() + lastChild.getWidth() - screenWidth);
        //如果x的加速度大于系统设定的最小移动距离，就可以惯性滑动
        if (Math.abs(pxsec) > mMinimumVelocity)
          mScroller.fling(getScrollX(), 0, (int) -pxsec, 0, 0, finalyChild, 0, 0);
        //如果滑动的距离小于第一个控件的最左边（0）则回弹至（0,0）点
        if (getScrollX() < 0) {
          scrollTo(0, 0);
        }
        //如果滑动的距离大于最大可滑动距离则滑动到最后一个子View
        if (getScrollX() >= finalyChild)
          scrollTo(finalyChild, 0);
        //刷新界面
        invalidate();
        //清空测试器
        recycleVelocityTracker();
        break;
      default:
        break;
    }
    return true;
  }
  
  private void initOrResetVelocityTracker() {
    if (mVelocityTracker == null) {
      mVelocityTracker = VelocityTracker.obtain();
    } else {
      mVelocityTracker.clear();
    }
  }
  
  private void recycleVelocityTracker() {
    if (mVelocityTracker != null) {
      mVelocityTracker.recycle();
      mVelocityTracker = null;
    }
  }
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    //重新设置宽高
    this.setMeasuredDimension(measureWidth(widthMeasureSpec, heightMeasureSpec), measureHeight(widthMeasureSpec, heightMeasureSpec));
  }
   
  private int measureWidth(int widthMeasureSpec, int heightMeasureSpec) {
    // 宽度
    int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
    int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
    //父控件的宽（wrap_content）
    int width = 0;
    int childCount = getChildCount();
    //重新测量子view的宽度，以及最大高度
    for (int i = 0; i < childCount; i++) {
      View child = getChildAt(i);
      measureChild(child, widthMeasureSpec, heightMeasureSpec);
      MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
      int childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
      width += childWidth;
    }
    return modeWidth == MeasureSpec.EXACTLY ? sizeWidth : width;
  }
  
  private int measureHeight(int widthMeasureSpec, int heightMeasureSpec) {
    //高度
    int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
    int modeHeight = MeasureSpec.getMode(heightMeasureSpec);
    //父控件的高（wrap_content）
    int height = 0;
    int childCount = getChildCount();
    //重新测量子view的宽度，以及最大高度
    for (int i = 0; i < childCount; i++) {
      View child = getChildAt(i);
      measureChild(child, widthMeasureSpec, heightMeasureSpec);
      MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
      int childHeight = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
      height += childHeight;
    }
    height = height / childCount;
    return modeHeight == MeasureSpec.EXACTLY ? sizeHeight : height;
  }
  
  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    int childLeft = 0;//子View左边的间距
    int childWidth;//子View的宽度
    int height = getHeight();//屏幕的宽度
    int childCount = getChildCount();//子View的数量
    for (int i = 0; i < childCount; i++) {
      View child = getChildAt(i);
      MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
      childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
      child.layout(childLeft, 0, childLeft + childWidth, height);
      childLeft += childWidth;
    }
  }
  @Override
  public LayoutParams generateLayoutParams(AttributeSet attrs) {
    return new MarginLayoutParams(getContext(), attrs);
  }
}

您可能感兴趣的文章:Android继承ViewGroup实现Scroll滑动效果的方法示例Android中实现可滑动的Tab的3种方式Android中实现监听ScrollView滑动事件android中使用Activity实现监听手指上下左右滑动android 通过向viewpage中添加listview来完成滑动效果(类似于qq滑动界面)Android中实现水平滑动（横向滑动）ListView示例解析Android中实现滑动翻页之ViewFlipper的使用详解android开发教程之实现滑动关闭fragment示例Android利用ViewPager实现滑动广告板实例源码Android自定义ViewGroup实现弹性滑动效果