今天看到百度手机助手首页上的滑动效果非常nice，主要功能归结为：

1、当手指上划时，顶部搜索栏随手指移动距离而缩小到隐藏，隐藏后内容还是可以继续移动

2、手指下滑时，当显示内容达到第一个时，顶部搜索栏逐渐变大显示

自己实现用到的知识：

1、android事件传递机制：捕获到手指移动事件后，根据移动的方向与功能栏的高度对功能栏大小进行修改 。由于listview与功能栏高度要同时移动，需要重写了dispatchTouchEvent方法，直接调用this.onTouchEvent(ev);进行所有事件的捕捉分析

2、自定义viewgroup：测量view高度

额外添加的功能：

功能栏高度<=1/2时，会自动隐藏

功能栏高度>1/2时，会自动改变到最大值

代码实现在MotionEvent.ACTION_UP

效果展示，录像工具太卡，将就着看吧：

本来想做成一个通用的工具类，工作比较忙就偷懒了，在ScrollHideLayout类中定义了两个常量，直接写死了需要被捕获滑动事件与改变大小的viewID，使用时可以自己再次封装，或者直接修改ID，虽然不推荐，但是省事哈！！！

private int scrollViewId = R.id.scrollView; //滑动后变化功能栏的viewid

private int changeViewId = R.id.changeView;// 大小随之变化的viewid

完整代码：

1、自定义的viewgroup

package com.example.materialtest.widget;

import android.animation.ObjectAnimator;

import android.animation.ValueAnimator;

import android.animation.ValueAnimator.AnimatorUpdateListener;

import android.content.Context;

import android.graphics.PointF;

import android.graphics.RectF;

import android.support.v4.view.ViewCompat;

import android.util.AttributeSet;

import android.util.Log;

import android.view.MotionEvent;

import android.view.View;

import android.widget.AbsListView;

import android.widget.AbsListView.OnScrollListener;

import android.widget.LinearLayout;

import com.example.materialtest.R;

/**

* 滑动隐藏控件

*

*

*/

public class ScrollHideLayout extends LinearLayout implements OnScrollListener {

private static final String TAG = ScrollHideLayout.class.getSimpleName();

private int scrollViewId = R.id.scrollView;

private int changeViewId = R.id.changeView;

private int changeViewMaxHeight;

private PointF touchPoint = new PointF();

private View changeView;

private AbsListView scrollView;

private RectF scrollViewRect = new RectF();

public ScrollHideLayout(Context context, AttributeSet attrs) {

this(context, attrs, 0);

}

public ScrollHideLayout(Context context) {

this(context, null);

}

public ScrollHideLayout(Context context, AttributeSet attrs, int defStyleAttr) {

super(context, attrs, defStyleAttr);

}

@Override

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

super.onMeasure(widthMeasureSpec, heightMeasureSpec);

int len = getChildCount();

if (null == changeView || null == scrollView) {

for (int i = 0; i < len; i++) {

View child = getChildAt(i);

// 滑动控件

if (child.getId() == scrollViewId && child instanceof AbsListView) {

scrollView = (AbsListView) child;

setScrollViewRect();

}

if (child.getId() == changeViewId) {

changeView = child;

changeView.setMinimumHeight(0);

changeViewMaxHeight = changeView.getMeasuredHeight();

}

}

} else {

// 重新计算滚动控件的位置

setScrollViewRect();

}

Log.i(TAG, "find scrollview and changeView :" + scrollViewId + "," + changeViewId);

Log.i(TAG, "scrollview rect:" + changeView.getLayoutParams().getClass().getCanonicalName());

if (null == changeView || null == scrollView) {

throw new IllegalArgumentException("could not foud changeView or scrollView");

}

}

private void setScrollViewRect() {

// 获取滚动控件的范围

float left = ViewCompat.getX(scrollView);

float top = ViewCompat.getY(scrollView);

float right = left + scrollView.getMeasuredWidth();

float bottom = top + scrollView.getMeasuredHeight();

scrollViewRect.left = left;

scrollViewRect.top = top;

scrollViewRect.right = right;

scrollViewRect.bottom = bottom;

}

@Override

public boolean onTouchEvent(MotionEvent ev) {

if (!isScrollViewTouch(ev)) {

return false;

}

final android.view.ViewGroup.LayoutParams params = changeView.getLayoutParams();

switch (ev.getAction()) {

case MotionEvent.ACTION_DOWN:

touchPoint.x = ev.getX();

touchPoint.y = ev.getY();

break;

case MotionEvent.ACTION_MOVE:

int height = params.height;

// 滑动控件移动事件

float distance = ev.getY() - touchPoint.y;

// 最大高度，不能向下拖动

if (height >= changeViewMaxHeight && distance > 0) {

touchPoint.y = ev.getY();

break;

}

// 已经隐藏 不能向上滑动

if (height <= 0 && distance < 0) {

touchPoint.y = ev.getY();

break;

}

// listview到达顶部才可以向下拖动

if (distance > 0 && scrollView.getFirstVisiblePosition() != 0) {

touchPoint.y = ev.getY();

break;

}

height = Math.round(height + distance);

if (height > changeViewMaxHeight) {

height = changeViewMaxHeight;

}

if (height <= 0 && distance < 0) {

height = 0;

// TODO onhide

}

params.height = height;

changeView.requestLayout();

touchPoint.x = ev.getX();

touchPoint.y = ev.getY();

break;

case MotionEvent.ACTION_CANCEL:

case MotionEvent.ACTION_UP:

// 高度超过一半，自动隐藏

int[] values = null;

// 向上滑动,剩余位置不足一半

if (params.height <= changeViewMaxHeight / 2) {

values = new int[] { params.height, 0 };

} else {

values = new int[] { params.height, changeViewMaxHeight };

}

if (null != values) {

ValueAnimator anim = ObjectAnimator.ofInt(changeView, "translationY", values);

anim.addUpdateListener(new AnimatorUpdateListener() {

@Override

public void onAnimationUpdate(ValueAnimator animation) {

int value = (int) animation.getAnimatedValue();

params.height = value;

changeView.requestLayout();

}

});

anim.setDuration(250);

anim.setTarget(changeView);

anim.start();

}

break;

}

return true;

}

@Override

public boolean dispatchTouchEvent(MotionEvent ev) {

// 直接拦截事件

this.onTouchEvent(ev);

return super.dispatchTouchEvent(ev);

}

private boolean isScrollViewTouch(MotionEvent ev) {

float x = ev.getX();

float y = ev.getY();

return (x >= scrollViewRect.left && x <= scrollViewRect.right) && (y >= scrollViewRect.top && y <= scrollViewRect.bottom);

}

/**

* @return Whether it is possible for the child view of this layout to

* scroll up. Override this if the child view is a custom view.

*/

public boolean canChildScrollUp() {

if (android.os.Build.VERSION.SDK_INT < 14) {

if (scrollView instanceof AbsListView) {

final AbsListView absListView = (AbsListView) scrollView;

return absListView.getChildCount() > 0

&& (absListView.getFirstVisiblePosition() > 0 || absListView.getChildAt(0).getTop() < absListView.getPaddingTop());

} else {

return ViewCompat.canScrollVertically(scrollView, -1) || scrollView.getScrollY() > 0;

}

} else {

return ViewCompat.canScrollVertically(scrollView, -1);

}

}

@Override

public void onScrollStateChanged(AbsListView view, int scrollState) {

// TODO Auto-generated method stub

}

@Override

public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

// TODO Auto-generated method stub

}

}

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