开源控件PullToRefreshGridView的使用(三)

该开源项目地址：https://github.com/chrisbanes/Android-PullToRefresh

3.往上滑动隐藏头部，往下滑动显示头部

先看效果图：

   

这里要说明一下的是：

a、头部的隐藏与显示是一个动画效果。

b、头部的隐藏与显示对PullToRefreshGridView的布局不会产生任何影响，主要是往上隐藏的时候PullToRefreshGridView不会突然往上移

    往下显示的时候PullToRefreshGridView不会突然往下移，不会有这些不连贯或者卡顿的感觉。

c、是否隐藏与显示是对比滑动过程中两次firstVisiblePosition的大小，也就是判断是上滑还是下滑。

核心代码：

a、布局部分：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/gray"
    android:orientation="vertical" >
    <!--PullToRefreshGridView-->
    <include layout="@layout/pull_gridview_refresh" />
    <!--头部-->
    <include layout="@layout/pull_gridview_refresh_head" />

</RelativeLayout>

注意上面提到的头部不是mPullToRefreshGridView的头部。

mPullToRefreshGridView必须设置一个头部，怎么设置头部，请参考开源控件PullToRefreshGridView的使用(二)，mPullToRefreshGridView的头部的高度必须与布局里面的头部高度一致，可以在布局

中设定，也可以通过代码动态设定。

b、mPullToRefreshGridView设置滑动监听

mPullToRefreshGridView.setOnScrollListener(new OnScrollListener()
        {
            @Override
            public void onScrollStateChanged(AbsListView view , int scrollState)
            {
                // TODO Auto-generated method stub
                if (OnScrollListener.SCROLL_STATE_IDLE == scrollState)
                {
                    if (mAdapter.type == Type.LINE_ONE)
                    {
                        firstVisiblePosition = view.getFirstVisiblePosition() + 1;
                    }
                    else
                    {
                        firstVisiblePosition = view.getFirstVisiblePosition() + 2;
                    }
                }
            }

            @Override
            public void onScroll(AbsListView view , int firstVisibleItem , int visibleItemCount , int totalItemCount)
            {
                // TODO Auto-generated method stub
                if (ll_animation == null || toUp == null)
                {
                    return;
                }
                int temp;
                if (mAdapter.type == Type.LINE_ONE)
                {
                    temp = view.getFirstVisiblePosition() + 1;
                }
                else
                {
                    temp = view.getFirstVisiblePosition() + 2;
                }
                if (mAdapter.type == Type.LINE_ONE)
                {
                    if (temp == 1 && !ll_animation.isShown() && !isDownStarted)
                    {
                        ll_animation.startAnimation(toDown);
                    }
                }
                else
                {
                    if (temp == 2 && !ll_animation.isShown() && !isDownStarted)
                    {
                        ll_animation.startAnimation(toDown);
                    }
                }
                if ((temp > firstVisiblePosition) && firstVisibleItem != 0)//向上滑
                {
                    if (!isUpStarted && ll_animation.isShown())
                    {
                        ll_animation.startAnimation(toUp);
                    }
                    //                    ll_animation.setVisibility(View.GONE);
                }
                else if (temp < firstVisiblePosition)
                {
                    if (!isDownStarted && !ll_animation.isShown())
                    {
                        ll_animation.startAnimation(toDown);
                    }
                    //                    ll_animation.setVisibility(View.VISIBLE);
                }
                //                firstVisiblePosition = temp;
            }
        });

c、动画部分

<?xml version="1.0" encoding="utf-8"?>
<translate xmlns:android="http://schemas.android.com/apk/res/android"
    android:duration="500"
    android:fromYDelta="0%p"
    android:toYDelta="-100%p" />

<?xml version="1.0" encoding="utf-8"?>
<translate xmlns:android="http://schemas.android.com/apk/res/android"
    android:duration="500"
    android:fromYDelta="-100%p"
    android:toYDelta="0%p" />

    private void initAnimation()
    {
        // TODO Auto-generated method stub
        toUp = AnimationUtils.loadAnimation(mActivity, R.anim.searchresult_toup_animation);
        toDown = AnimationUtils.loadAnimation(mActivity, R.anim.searchresult_todown_animation);
        toUp.setAnimationListener(new AnimationListener()
        {
            @Override
            public void onAnimationStart(Animation animation)
            {
                // TODO Auto-generated method stub
                isUpStarted = true;
            }

            @Override
            public void onAnimationRepeat(Animation animation)
            {
                // TODO Auto-generated method stub
            }

            @Override
            public void onAnimationEnd(Animation animation)
            {
                // TODO Auto-generated method stub
                ll_animation.setVisibility(View.GONE);
                isUpStarted = false;
            }
        });
        toDown.setAnimationListener(new AnimationListener()
        {
            @Override
            public void onAnimationStart(Animation animation)
            {
                // TODO Auto-generated method stub
                isDownStarted = true;
            }

            @Override
            public void onAnimationRepeat(Animation animation)
            {
                // TODO Auto-generated method stub
            }

            @Override
            public void onAnimationEnd(Animation animation)
            {
                // TODO Auto-generated method stub
                ll_animation.setVisibility(View.VISIBLE);
                isDownStarted = false;
            }
        });
    }

ps：里面有些变量需参考前一章节