今天看到百度手機助手首頁上的滑動效果非常nice，主要功能歸結為：

1、當手指上劃時，頂部搜尋欄隨手指移動距離而縮小到隱藏，隱藏後內容還是可以繼續移動
2、手指下滑時，當顯示內容達到第一個時，頂部搜尋欄逐漸變大顯示

自己實現用到的知識：

1、android事件傳遞機制：捕獲到手指移動事件後，根據移動的方向與功能欄的高度對功能欄大小進行修改 。由於listview與功能欄高度要同時移動，需要重寫了dispatchTouchEvent方法，直接呼叫this.onTouchEvent(ev);進行所有事件的捕捉分析
2、自定義viewgroup：測量view高度

額外新增的功能：

功能欄高度<=1/2時，會自動隱藏
功能欄高度>1/2時，會自動改變到最大值
程式碼實現在MotionEvent.ACTION_UP

效果展示，錄影工具太卡，將就著看吧：

本來想做成一個通用的工具類，工作比較忙就偷懶了，在ScrollHideLayout類中定義了兩個常量，直接寫死了需要被捕獲滑動事件與改變大小的viewID，使用時可以自己再次封裝，或者直接修改ID，雖然不推薦，但是省事哈！！！

private int scrollViewId = R.id.scrollView; //滑動後變化功能欄的viewid
private int changeViewId = R.id.changeView;// 大小隨之變化的viewid

完整程式碼：
1、自定義的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;

/**
 * 滑動隱藏控制元件
 * 
 *
 */
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);
                // 滑動控制元件
                if (child.getId() == scrollViewId && child instanceof AbsListView) {
                    scrollView = (AbsListView) child;
                    setScrollViewRect();
                }
                if (child.getId() == changeViewId) {
                    changeView = child;
                    changeView.setMinimumHeight(0);

                    changeViewMaxHeight = changeView.getMeasuredHeight();
                }

            }
        } else {
            // 重新計算滾動控制元件的位置
            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() {
        // 獲取滾動控制元件的範圍
        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;

            // 滑動控制元件移動事件
            float distance = ev.getY() - touchPoint.y;

            // 最大高度，不能向下拖動
            if (height >= changeViewMaxHeight && distance > 0) {
                touchPoint.y = ev.getY();
                break;
            }
            // 已經隱藏 不能向上滑動
            if (height <= 0 && distance < 0) {
                touchPoint.y = ev.getY();
                break;
            }

            // listview到達頂部才可以向下拖動
            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:

            // 高度超過一半，自動隱藏
            int[] values = null;
            // 向上滑動,剩餘位置不足一半
            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) {
        // 直接攔截事件
        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

    }
}