首先，本文代码部分参考了conglida博主写的自定义scrollview 实现标题栏渐变：
http://download.csdn.net/download/conglida/9183723
此资源只使用自定义scrollview 实现标题栏渐变和上拉下拉刷新。如果需要listview，等其他控件，需实现onScrollListener，在onscroll中嵌入渐变代码。
再次感谢conglida博主的无私奉献！
由于Recyclerview已经推出很长时间了，不得不说这个控件确实好，可以替代scrollview、listview、gridview，功能很强大，目前我已经用这个新控件实现了标题栏渐变的效果。
本代码使用了三方开源组件：
HeaderAndFooterRecyclerView是支持addHeaderView、 addFooterView、分页加载的RecyclerView解决方案，滑动底部自动加载更多。
项目地址：https://github.com/cundong/HeaderAndFooterRecyclerView
开始正题。
布局文件：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/app_bg"
android:orientation="vertical"
>
<include
android:id="@+id/load_view"
layout="@layout/pull_to_load_footer"
android:visibility="gone" />
<android.support.v4.widget.SwipeRefreshLayout
android:id="@+id/swipe_container"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</android.support.v4.widget.SwipeRefreshLayout>
<RelativeLayout
android:id="@+id/index_title_bar"
android:layout_alignParentTop="true"
style="@style/title_bar_style_home_v19"
android:fitsSystemWindows="true"
android:gravity="center"
android:paddingTop="@dimen/title_bar_padding_top"
>
<TextView
android:id="@+id/current_city_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_centerVertical="true"
android:layout_marginLeft="10dp"
android:drawableTop="@drawable/ic_location"
android:drawablePadding="2dp"
android:text="北京"
android:textColor="#fff"
android:textSize="10sp" />
<TextView
android:id="@+id/tv_title"
android:layout_centerVertical="true"
android:layout_width="match_parent"
android:layout_height="33dp"
android:gravity="center_vertical"
android:layout_weight="10"
android:background="@drawable/shape_edit_corners_bg"
android:hint="请输入商品名称"
android:imeOptions="actionSearch"
android:singleLine="true"
android:textColor="@color/black_text"
android:textColorHint="#ffb6b6b6"
android:textSize="14sp"
android:maxLength="10"
android:paddingLeft="5dp"
android:paddingRight="3dp"
android:drawableLeft="@drawable/ic_search"
android:drawableRight="@drawable/bg_btn_voice"
android:layout_toLeftOf="@+id/image_right"
android:layout_toRightOf="@+id/current_city_text"
android:layout_marginLeft="10dp"
android:layout_marginRight="10dp"/>
<TextView
android:id="@+id/image_right"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:layout_marginRight="10dp"
android:drawableTop="@drawable/ic_category"
android:drawablePadding="2dp"
android:text="分类"
android:textColor="#fff"
android:textSize="10sp" />
</RelativeLayout>
</RelativeLayout>
部分代码：
CommonHeader headerView;
private void initView(View view) {
mSwipeRefreshLayout = (SwipeRefreshLayout)view.findViewById(R.id.swipe_container);
mSwipeRefreshLayout.setProgressViewOffset(false, 0, Util.dip2px(getActivity(), 92));
//设置刷新时动画的颜色，可以设置4个
mSwipeRefreshLayout.setColorSchemeResources(android.R.color.holo_blue_light, android.R.color.holo_red_light, android.R.color.holo_orange_light, android.R.color.holo_green_light);
mSwipeRefreshLayout.setOnRefreshListener(this);
mSwipeRefreshLayout.setRefreshing(true);
mRecyclerView = (RecyclerView) view.findViewById(R.id.recycler_view);
mGridAdapter = new HotsGridAdapter(getActivity(),mHandler);
mHeaderAndFooterRecyclerViewAdapter = new HeaderAndFooterRecyclerViewAdapter(mGridAdapter);
mRecyclerView.setAdapter(mHeaderAndFooterRecyclerViewAdapter);
layoutManager = new GridLayoutManager(getActivity(), 2);
layoutManager.setSpanSizeLookup(new HeaderSpanSizeLookup((HeaderAndFooterRecyclerViewAdapter) mRecyclerView.getAdapter(), layoutManager.getSpanCount()));
layoutManager.setOrientation(GridLayoutManager.VERTICAL);
layoutManager.setSmoothScrollbarEnabled(true);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(layoutManager);
headerView = new CommonHeader(getActivity(),R.layout.layout_home_header);
RecyclerViewUtils.setHeaderView(mRecyclerView, headerView);
mTitlebar = (RelativeLayout) view.findViewById(R.id.index_title_bar);
mTitlebar.setVisibility(View.VISIBLE);
mTitlebar.getBackground().setAlpha(0);
keyTextView = (TextView) mTitlebar.findViewById(R.id.tv_title);
mCurCityText = (TextView) mTitlebar.findViewById(R.id.current_city_text);
categorizeTextView = (TextView) view.findViewById(R.id.image_right);
slideShowView = (SlideShowView) headerView.findViewById(R.id.slideshowView);
moreSpecialProduct = headerView.findViewById(R.id.special_more);
mCurCityText.setOnClickListener(this);
keyTextView.setOnClickListener(this);
moreSpecialProduct.setOnClickListener(this);
categorizeTextView.setOnClickListener(this);
slideShowView = (SlideShowView) headerView.findViewById(R.id.slideshowView);
cart_btn = getActivity().findViewById(R.id.shop_cart_btn);
animation_viewGroup = createAnimLayout();
imageLoader = ImageLoader.getInstance();
mRecyclerView.addOnScrollListener(mOnScrollListener);
}
关键代码：
headerView = new CommonHeader(getActivity(),R.layout.layout_home_header);
RecyclerViewUtils.setHeaderView(mRecyclerView, headerView);
为RecyclerView添加headerview，headview包括了所有的其他view，如下图所示，所看到的view都包含在headerView里面，不包括titlebar哦。
滑动监听事件：
boolean pauseOnScroll = false, pauseOnFling=true;
private RecyclerOnScrollListener mOnScrollListener = new RecyclerOnScrollListener() {
@Override
public void onScrolled(int dx, int dy) {
super.onScrolled(dx, dy);
if (slideShowView.getHeight() > 0) {
//define it for scroll height
int lHeight = slideShowView.getHeight();
if(dy < 0){
mTitlebar.getBackground().setAlpha(0);
}else {
if (dy < lHeight) {
int progress = (int) (new Float(dy) / new Float(lHeight) * 200);//255
mTitlebar.getBackground().setAlpha(progress);
} else {
mTitlebar.getBackground().setAlpha(255 - 55);
}
}
}
}
@Override
public void onBottom() {
super.onBottom();
Log.d(TAG, "onBottom");
LoadingFooter.State state = RecyclerViewStateUtils.getFooterViewState(mRecyclerView);
if(state == LoadingFooter.State.Loading) {
Log.d(TAG, "the state is Loading, just wait..");
return;
}
if (mCurPageIndex < totalPage) {
// loading more
RecyclerViewStateUtils.setFooterViewState(getActivity(), mRecyclerView, REQUEST_COUNT, LoadingFooter.State.Loading, null);
mHandler.sendEmptyMessage(GET_LIST_DATA);
Log.d(TAG, "onBottom loading");
} else {
//the end
RecyclerViewStateUtils.setFooterViewState(getActivity(), mRecyclerView, REQUEST_COUNT, LoadingFooter.State.TheEnd, null);
}
}
@Override
public void onScrollStateChanged(int newState) {
//根据newState状态做处理
if (imageLoader != null) {
switch (newState) {
case 0:
imageLoader.resume();
break;
case 1:
if (pauseOnScroll) {
imageLoader.pause();
} else {
imageLoader.resume();
}
break;
case 2:
if (pauseOnFling) {
imageLoader.pause();
} else {
imageLoader.resume();
}
break;
}
}
}
};
代码中涉及到的封装控件下载：http://download.csdn.net/detail/jdsjlzx/9391838，没有demo，请大家自行实现效果。
具体原理请参考
conglida博主写的自定义scrollview 实现标题栏渐变：
http://download.csdn.net/download/conglida/9183723
