Android开发之ListView的head消失页面导航栏的渐变出现和隐藏

<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:ptr="http://schemas.android.com/apk/res-auto"
tools:context=".fragment.home.HomeStoreFragment"
>
<com.handmark.pulltorefresh.library.PullToRefreshListView
android:id="@+id/lv_home_store_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
ptr:ptrDrawable="@drawable/default_ptr_flip"
ptr:ptrAnimationStyle="flip"
/>
<!--top 搜索栏-->
<LinearLayout
android:id="@+id/ll_top_search"
android:layout_width="match_parent"
android:layout_height="60dp"
android:background="@color/zuti"
android:visibility="invisible"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="15dp"
android:layout_marginRight="15dp"
android:layout_marginTop="8dp"
android:layout_marginBottom="8dp"
android:background="@drawable/shape_edit_cornor"
android:gravity="center"
>
<ImageView
android:id="@+id/iv_search_icon"
android:layout_width="30dp"
android:layout_height="30dp"
android:src="@drawable/icon_navbar_search"
android:layout_marginRight="5dp"
/>
<EditText
android:id="@+id/et_store_search"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:hint="输入商家或商品名"
android:textColorHint="@color/shenhui"
android:background="@null"
/>
</LinearLayout>
</LinearLayout>
</RelativeLayout>

private boolean isFlingScroll;
private View headView;
private PullToRefreshListView lvHomeStore;
initView(){
lvHomeStore = (PullToRefreshListView) view.findViewById(R.id.lv_home_store_list);
lvHomeStore.setMode(PullToRefreshBase.Mode.BOTH);
ListView listView = lvHomeStore.getRefreshableView();
headView = initHeadView();
AbsListView.LayoutParams layoutParams = new AbsListView.LayoutParams(AbsListView.LayoutParams.MATCH_PARENT, AbsListView.LayoutParams.WRAP_CONTENT);//这句要加上去
headView.setLayoutParams(layoutParams);
listView.addHeaderView(headView);
lvHomeStore.setAdapter(adapter);
lvHomeStore.setOnScrollListener(this);
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (scrollState == SCROLL_STATE_FLING) {//手指离开手机界面，Listview还在滑动
isFlingScroll = true;
} else if (scrollState == SCROLL_STATE_TOUCH_SCROLL) {//手指在界面上滚动的情况
isFlingScroll = false;
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
showSearchBarShow();
}
private void showSearchBarShow() {
int headBottomToParentTop = headView.getHeight() + headView.getTop();
Log.d("homeStore", "headView.getHeight(): " + headView.getHeight());
Log.d("homeStore", "headView.getTop(): " + headView.getTop());
Log.d("homeStore", "headBottomToParentTop: " + headBottomToParentTop);
if (!isFlingScroll) {//手指在界面滑动的情况
int height = layoutSearch.getHeight();
Log.d("homeStore", "height: " + height);
if (headBottomToParentTop > height) {
layoutSearch.setVisibility(View.INVISIBLE);
} else if (headBottomToParentTop <= height) {//缓慢滑动，这部分代码工作正常，快速滑动，里面的数据就跟不上节奏了。
float alpha = (height - headBottomToParentTop) * 1f / height;
Log.d("homeStore", "alpha: " + alpha);
layoutSearch.setAlpha(alpha);
layoutSearch.setVisibility(View.VISIBLE);
}
if (!headView.isShown()){//解决快速滑动，上部分代码不能正常工作的问题。
layoutSearch.setAlpha(1);
layoutSearch.setVisibility(View.VISIBLE);
}
} else {//手指离开，listview还在滑动，一般情况是列表快速滑动，这种情况直接设置导航栏的可见性
if (!headView.isShown()) {
if (!layoutSearch.isShown()){
layoutSearch.setVisibility(View.VISIBLE);
layoutSearch.setAlpha(1);
}
} else {
if (layoutSearch.isShown()){
layoutSearch.setVisibility(View.INVISIBLE);
}
}
}
}