Question

有没有让Android设计支持库的折叠动画在滚动时更流畅？当我释放滚动时，它会突然停止。但我想要的是：即使你停止滚动，折叠动画仍将顺利进行。 Android-ObservableScrollView和Scrollable是顺利崩溃的库。

Answer 1

您可以使用新的layout_scrollFlag按钮在AppBarLayout状态内平滑滚动。但我所经历的是，当RecyclerView达到顶峰时，滚动停止。即没有其他滚动，CollapsingToolbarLayout将不会展开。为了使RecyclerView能够平滑地向上滚动并展开CollapsingToolbarLayout，我在recyclerview上使用了ScrollListener。

class Parent: MyProtocol {}
class Child: Parent {}

protocol MyProtocol {
    func printMe()
}

extension MyProtocol {
    func printMe() {
        if let me = self as? Child {
            print("Child")
        } else if let me = self as? Parent {
            print("Parent")
        }
        // Do something with `me` or you gonna get another warning
    }
}

let parent = Parent()
let child = Child()
parent.printMe()
child.printMe()

我使用“scroll | exitUntilCollapsed”作为layout_scrollFlags。

    recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
        int scrollDy = 0;
        @Override
        public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
            scrollDy += dy;
        }

        @Override
        public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
            super.onScrollStateChanged(recyclerView, newState);
            if(scrollDy==0&&(newState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE))
            {
                AppBarLayout appBarLayout = ((AppBarLayout) view.findViewById(R.id.app_bar));

                appBarLayout.setExpanded(true);
            }
        }
    });

Answer 2

这个是相当新的，但最近更新了AppBarLayout以使用名为snap的新layout_scrollFlag处理您正在寻找的内容。

用法：

app:layout_scrollFlags="scroll|snap"

当我这样做时，我会尝试寻找我的来源并更新我的答案。

编辑：当然，它来自android developer blog。

Answer 3

我是通过AppBarLayout完成的。通过覆盖onNestedFling和onNestedPreScroll。

如果ScrollingView的顶级子项接近Adapter中的数据开头，则诀窍是重建fling事件。

来源Flinging with RecyclerView + AppBarLayout

public final class FlingBehavior extends AppBarLayout.Behavior {
private static final int TOP_CHILD_FLING_THRESHOLD = 3;
private boolean isPositive;

public FlingBehavior() {
}

public FlingBehavior(Context context, AttributeSet attrs) {
    super(context, attrs);
}
@Override
public boolean onNestedFling(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, float velocityX, float velocityY, boolean consumed) {
    if (velocityY > 0 && !isPositive || velocityY < 0 && isPositive) {
        velocityY = velocityY * -1;
    }
    if (target instanceof RecyclerView && velocityY < 0) {
        final RecyclerView recyclerView = (RecyclerView) target;
        final View firstChild = recyclerView.getChildAt(0);
        final int childAdapterPosition = recyclerView.getChildAdapterPosition(firstChild);
        consumed = childAdapterPosition > TOP_CHILD_FLING_THRESHOLD;
    }
    return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
}

@Override
public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, AppBarLayout child, View target, int dx, int dy, int[] consumed) {
    super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed);
    isPositive = dy > 0;
  }
}

然后将布局行为设置为FlingBehavior class

<android.support.design.widget.AppBarLayout
app:layout_behavior="package.FlingBehavior"
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="250dip"
android:fitsSystemWindows="true">

Answer 4

添加代码

 app:layout_scrollFlags="scroll|enterAlways"

在AppBarLayout中的视图中。这是我的演示代码将工具栏与Android设计支持库折叠。

  <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark">
        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:layout_scrollFlags="scroll|enterAlways">

            <bubee.inews.Items.ItemMenu
                android:id="@+id/itemMenu"
                android:layout_width="match_parent"
                android:layout_height="wrap_content" />
        </android.support.v7.widget.Toolbar>
    </android.support.design.widget.AppBarLayout>

Answer 5

我也在研究这个问题并提出可能不是非常优化的解决方案，但你可以改进它。一旦我改进它，我肯定会编辑答案，直到看看这个。

public abstract class AppBarStateChangeListener implements AppBarLayout.OnOffsetChangedListener {
private static final String TAG = "app_AppBarStateChange";
public enum State {
    EXPANDED,
    COLLAPSED,
    IDLE
}

private State mCurrentState = State.IDLE;
private int mInitialPosition = 0;
private boolean mWasExpanded;
private boolean isAnimating;
@Override
public final void onOffsetChanged(AppBarLayout appBarLayout, int i) {
    if (i == 0) {
        if (mCurrentState != State.EXPANDED) {
            onStateChanged(appBarLayout, State.EXPANDED);
        }
        mCurrentState = State.EXPANDED;
        mInitialPosition = 0;
        mWasExpanded = true;
        Log.d(TAG, "onOffsetChanged 1");
        isAnimating = false;
        appBarLayout.setEnabled(true);
    } else if (Math.abs(i) >= appBarLayout.getTotalScrollRange()) {
        if (mCurrentState != State.COLLAPSED) {
            onStateChanged(appBarLayout, State.COLLAPSED);
        }
        mCurrentState = State.COLLAPSED;
        mInitialPosition = appBarLayout.getTotalScrollRange();
        mWasExpanded = false;
        Log.d(TAG, "onOffsetChanged 2");
        isAnimating = false;
        appBarLayout.setEnabled(true);
    } else {
        Log.d(TAG, "onOffsetChanged 3");
        int diff = Math.abs(Math.abs(i) - mInitialPosition);
        if(diff >= appBarLayout.getTotalScrollRange()/3 && !isAnimating) {
            Log.d(TAG, "onOffsetChanged 4");
            isAnimating = true;
            appBarLayout.setEnabled(false);
            appBarLayout.setExpanded(!mWasExpanded,true);
        }
        if (mCurrentState != State.IDLE) {
            onStateChanged(appBarLayout, State.IDLE);
        }
        mCurrentState = State.IDLE;
    }
}

public abstract void onStateChanged(AppBarLayout appBarLayout, State state);

public State getCurrentState() {
    return mCurrentState;
}

}

创建此类并调用以下代码

private AppBarStateChangeListener mAppBarStateChangeListener = new AppBarStateChangeListener() {
    @Override
    public void onStateChanged(AppBarLayout appBarLayout, State state) {
        Log.d(TAG, "ToBeDeletedActivity.onStateChanged :: " + state);
        if(state == State.EXPANDED || state == State.IDLE) {
            getSupportActionBar().setTitle("");
        } else {
            getSupportActionBar().setTitle("Hello World");
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
                mAppBarLayout.setElevation(0);
            }
        }
    }


};

mAppBarLayout.addOnOffsetChangedListener(mAppBarStateChangeListener);

请注意，不要设置匿名类OffsetChangedListener，因为它会被保存为弱引用，并且会被GC收集。我发现自己处于困境。

请探索此代码并对其进行改进（任何人）并重新分享。谢谢

Answer 6

尝试添加以下代码：

repositories {
    maven { url 'http://repo1.maven.org/maven2' }
    jcenter { url "http://jcenter.bintray.com/" }
}

使用Android设计支持库

6 个答案: