Android可滾動Tabs：Scrollable

Android可滾動Tabs：Scrollable。

This library encapsulates scrolling logic when implementing scrolling tabs (hot topic nowadays in Android development). It saves us from unpleasant routine akaaddHeader,addFooterfor every scrolling content which appears in tabs and synchronising it with our real headers. It also works good for a single scrolling widget, for e.g. RecyclerView which has it's own issues with headers (at least parallaxing them). Also check out theScrollableDialogin sample application it mimics new Android Lollipop Intent chooser behavior.

compile 'ru.noties:scrollable:x.x.x'

Howto

Simply wrap your views inru.noties.scrollable.ScrollableLayout. The final xml might be looking something like that (don't copy, it's not valid):

<ru.noties.scrollable.ScrollableLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/scrollable_layout"
    app:scrollable_maxScroll="@dimen/header_height"> --!(1)

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="@dimen/header_height" --!(2)
            android:background="@color/header_background" 
            android:textColor="@color/white"
            android:textSize="30sp"
            android:text="Header"
            android:id="@+id/header"
            android:gravity="center"/>

        <ru.noties.scrollable.sample.TabsLayout
            android:layout_width="match_parent"
            android:layout_height="@dimen/tabs_height" --!(3)
            android:background="@color/tabs_background"
            android:id="@+id/tabs" />

    </LinearLayout>

    <android.support.v4.view.ViewPager
        android:layout_width="match_parent"
        android:layout_height="match_parent" --!(4)
        android:layout_marginTop="@dimen/tabs_height" --!(5)
        android:id="@+id/view_pager" />

</ru.noties.scrollable.ScrollableLayout>

The most imprortant things here are:

1. app:scrollable_maxScroll="@dimen/header_height"- it's the value of header height aka the max scroll distance for a ScrollableLayout
2. It's what will be a header
3. It you wish to create sticky behavior to a certain View, you should indicate it's heigth here & in step 5
4. Out main content should havematch_parentas it's layout_height attribute
5. Crucial for a sticky behavior

Then we should init out logic in code (copied from sample application):

final View header = findViewById(R.id.header);
final TabsLayout tabs = findView(this, R.id.tabs);

mScrollableLayout = findView(this, R.id.scrollable_layout);
mScrollableLayout.setDraggableView(tabs);
final ViewPager viewPager = findView(this, R.id.view_pager);
final ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager(), getResources(), getFragments());
viewPager.setAdapter(adapter);

tabs.setViewPager(viewPager);

// Note this bit, it's very important
mScrollableLayout.setCanScrollVerticallyDelegate(new CanScrollVerticallyDelegate() {
    @Override
    public boolean canScrollVertically(int direction) {
        return adapter.canScrollVertically(viewPager.getCurrentItem(), direction);
    }
});

mScrollableLayout.setOnScrollChangedListener(new OnScrollChangedListener() {
  @Override
  public void onScrollChanged(int y, int oldY, int maxY) {

    // Sticky behavior
    final float tabsTranslationY;
    if (y < maxY) {
        tabsTranslationY = .0F;
    } else {
        tabsTranslationY = y - maxY;
    }

    tabs.setTranslationY(tabsTranslationY);

    header.setTranslationY(y / 2);
  }
});

In order to start rolling we should pass to our ScrollableLayout aru.noties.scrollable.CanScrollVerticallyDelegate. For e.g. PagerAdapter implements it what way:

boolean canScrollVertically(int position, int direction) {  return getItem(position).canScrollVertically(direction);
}

And fragments implements it that way:

@Override public boolean canScrollVertically(int direction) {  return mView != null && mView.canScrollVertically(direction);
}

Additionally you could provide a ScrollableLayout with aru.noties.scrollable.OnScrollChangedListenerand implement where your own logic. It's the place to implement parallax and all other possible stuff.

Hope this will help.

項目主頁：http://www.baiduhome.net/lib/view/home/1428548390135