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像 Google 地图一样的 BottomSheetBehavior

Created: November-22, 2018

Version >= 2.1.x

此示例取决于支持库 23.4.0。+。

BottomSheetBehavior 的特点是：

  1. 两个带有动画的工具栏，可响应底部的纸张移动。
  2. 当 FAB 靠近模态工具栏（当你向上滑动时出现的那个）时隐藏的 FAB。
  3. 底部背后的背景图像与某种视差效果。
  4. 工具栏中的标题（TextView）在底部工作表到达时显示。
  5. 通知 satus 栏可以将其背景变为透明或全彩。
  6. 具有锚状态的自定义底部表单行为。

现在让我们逐一检查它们：

工具栏
当你在谷歌地图中打开该视图时，你可以看到一个工具栏，你可以在其中搜索，这是我唯一一个与谷歌地图完全不同的工具栏，因为我想更加通用。无论如何，ToolBar 在 AppBarLayout 中，当你开始拖动 BottomSheet 时它被隐藏，当 BottomSheet 到达 COLLAPSED 状态时它再次出现。
要实现它，你需要：

  • 创建一个 Behavior 并从 AppBarLayout.ScrollingViewBehavior 扩展它
  • 覆盖 layoutDependsOn 和 onDependentViewChanged 方法。这样做你将听取 bottomSheet 的动作。
  • 创建一些方法来隐藏和取消隐藏带有动画的 AppBarLayout / ToolBar。

这是我为第一个工具栏或 ActionBar 做的方式：

@Override
public boolean layoutDependsOn(CoordinatorLayout parent, View child, View dependency) {
    return dependency instanceof NestedScrollView;
}

@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child,
                                      View dependency) {

    if (mChild == null) {
        initValues(child, dependency);
        return false;
    }

    float dVerticalScroll = dependency.getY() - mPreviousY;
    mPreviousY = dependency.getY();

    //going up
    if (dVerticalScroll <= 0 && !hidden) {
        dismissAppBar(child);
        return true;
    }

    return false;
}

private void initValues(final View child, View dependency) {

    mChild = child;
    mInitialY = child.getY();

    BottomSheetBehaviorGoogleMapsLike bottomSheetBehavior = BottomSheetBehaviorGoogleMapsLike.from(dependency);
    bottomSheetBehavior.addBottomSheetCallback(new BottomSheetBehaviorGoogleMapsLike.BottomSheetCallback() {
        @Override
        public void onStateChanged(@NonNull View bottomSheet, @BottomSheetBehaviorGoogleMapsLike.State int newState) {
            if (newState == BottomSheetBehaviorGoogleMapsLike.STATE_COLLAPSED ||
                    newState == BottomSheetBehaviorGoogleMapsLike.STATE_HIDDEN)
                showAppBar(child);
        }

        @Override
        public void onSlide(@NonNull View bottomSheet, float slideOffset) {

        }
    });
}

private void dismissAppBar(View child){
    hidden = true;
    AppBarLayout appBarLayout = (AppBarLayout)child;
    mToolbarAnimation = appBarLayout.animate().setDuration(mContext.getResources().getInteger(android.R.integer.config_shortAnimTime));
    mToolbarAnimation.y(-(mChild.getHeight()+25)).start();
}

private void showAppBar(View child) {
    hidden = false;
    AppBarLayout appBarLayout = (AppBarLayout)child;
    mToolbarAnimation = appBarLayout.animate().setDuration(mContext.getResources().getInteger(android.R.integer.config_mediumAnimTime));
    mToolbarAnimation.y(mInitialY).start();
}

如果需要，这是完整的文件

第二个工具栏或模态工具栏：
你必须覆盖相同的方法，但在这个方法中你必须处理更多行为：

  • 用动画显示/隐藏工具栏
  • 更改状态栏颜色/背景
  • 在 ToolBar 中显示/隐藏 BottomSheet 标题
  • 关闭 bottomSheet 或将其发送到折叠状态

这个的代码有点广泛，所以我会让链接

FAB

这也是一种自定义行为，但是从 FloatingActionButton.Behavior 延伸出来。在 onDependentViewChanged 中，你必须看到它到达 offSet 或你要隐藏它的位置。在我的情况下，当它靠近第二个工具栏时我想要隐藏它，所以我深入研究 FAB 父（CoordinatorLayout）寻找包含 ToolBar 的 AppBarLayout，然后我使用像 OffSet 这样的 ToolBar 位置：

@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, FloatingActionButton child, View dependency) {

    if (offset == 0)
        setOffsetValue(parent);

    if (dependency.getY() <=0)
        return false;

    if (child.getY() <= (offset + child.getHeight()) && child.getVisibility() == View.VISIBLE)
        child.hide();
    else if (child.getY() > offset && child.getVisibility() != View.VISIBLE)
        child.show();

    return false;
}

完成自定义 FAB 行为链接

具有视差效果的 BottomSheet 背后的图像 ：
与其他图像一样，它是一种自定义行为，这一项中唯一复杂的东西是保持图像锚定到 BottomSheet 的小算法，并避免图像崩溃，如默认视差效果：

@Override
public boolean onDependentViewChanged(CoordinatorLayout parent, View child,
                                      View dependency) {

    if (mYmultiplier == 0) {
        initValues(child, dependency);
        return true;
    }

    float dVerticalScroll = dependency.getY() - mPreviousY;
    mPreviousY = dependency.getY();

    //going up
    if (dVerticalScroll <= 0 && child.getY() <= 0) {
        child.setY(0);
        return true;
    }

    //going down
    if (dVerticalScroll >= 0 && dependency.getY() <= mImageHeight)
        return false;

    child.setY( (int)(child.getY() + (dVerticalScroll * mYmultiplier) ) );

    return true;
}

具有视差效果的背景图像的完整文件

现在结束： 自定义 BottomSheet 行为
要实现 3 个步骤，首先你需要了解默认 BottomSheetBehavior 有 5 个状态：STATE_DRAGGING, STATE_SETTLING, STATE_EXPANDED, STATE_COLLAPSED, STATE_HIDDEN 和 Google Maps 行为，你需要在折叠和展开之间添加中间状态：STATE_ANCHOR_POINT。
我试图扩展默认的 bottomSheetBehavior 没有成功，所以我只是复制粘贴所有代码并修改我需要的东西。
要实现我正在谈论的内容，请按照以下步骤操作：

  1. 创建一个 Java 类并从 CoordinatorLayout.Behavior<V> 扩展它

  2. 将默认 BottomSheetBehavior 文件中的粘贴代码复制到新文件中。

  3. 使用以下代码修改方法 clampViewPositionVertical：

    @Override
public int clampViewPositionVertical(View child, int top, int dy) {
    return constrain(top, mMinOffset, mHideable ? mParentHeight : mMaxOffset);
}
int constrain(int amount, int low, int high) {
    return amount < low ? low : (amount > high ? high : amount);
}

  4. 添加新状态

    public static final int STATE_ANCHOR_POINT = X;

  5. 修改下一个方法：onLayoutChild，onStopNestedScroll，BottomSheetBehavior<V> from(V view) 和 setState（可选）

public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirection) {
    // First let the parent lay it out
    if (mState != STATE_DRAGGING && mState != STATE_SETTLING) {
        if (ViewCompat.getFitsSystemWindows(parent) &&
                !ViewCompat.getFitsSystemWindows(child)) {
            ViewCompat.setFitsSystemWindows(child, true);
        }
        parent.onLayoutChild(child, layoutDirection);
    }
    // Offset the bottom sheet
    mParentHeight = parent.getHeight();
    mMinOffset = Math.max(0, mParentHeight - child.getHeight());
    mMaxOffset = Math.max(mParentHeight - mPeekHeight, mMinOffset);

    //if (mState == STATE_EXPANDED) {
    //    ViewCompat.offsetTopAndBottom(child, mMinOffset);
    //} else if (mHideable && mState == STATE_HIDDEN...
    if (mState == STATE_ANCHOR_POINT) {
        ViewCompat.offsetTopAndBottom(child, mAnchorPoint);
    } else if (mState == STATE_EXPANDED) {
        ViewCompat.offsetTopAndBottom(child, mMinOffset);
    } else if (mHideable && mState == STATE_HIDDEN) {
        ViewCompat.offsetTopAndBottom(child, mParentHeight);
    } else if (mState == STATE_COLLAPSED) {
        ViewCompat.offsetTopAndBottom(child, mMaxOffset);
    }
    if (mViewDragHelper == null) {
        mViewDragHelper = ViewDragHelper.create(parent, mDragCallback);
    }
    mViewRef = new WeakReference<>(child);
    mNestedScrollingChildRef = new WeakReference<>(findScrollingChild(child));
    return true;
}

public void onStopNestedScroll(CoordinatorLayout coordinatorLayout, V child, View target) {
    if (child.getTop() == mMinOffset) {
        setStateInternal(STATE_EXPANDED);
        return;
    }
    if (target != mNestedScrollingChildRef.get() || !mNestedScrolled) {
        return;
    }
    int top;
    int targetState;
    if (mLastNestedScrollDy > 0) {
        //top = mMinOffset;
        //targetState = STATE_EXPANDED;
        int currentTop = child.getTop();
        if (currentTop > mAnchorPoint) {
            top = mAnchorPoint;
            targetState = STATE_ANCHOR_POINT;
        }
        else {
            top = mMinOffset;
            targetState = STATE_EXPANDED;
        }
    } else if (mHideable && shouldHide(child, getYVelocity())) {
        top = mParentHeight;
        targetState = STATE_HIDDEN;
    } else if (mLastNestedScrollDy == 0) {
        int currentTop = child.getTop();
        if (Math.abs(currentTop - mMinOffset) < Math.abs(currentTop - mMaxOffset)) {
            top = mMinOffset;
            targetState = STATE_EXPANDED;
        } else {
            top = mMaxOffset;
            targetState = STATE_COLLAPSED;
        }
    } else {
        //top = mMaxOffset;
        //targetState = STATE_COLLAPSED;
        int currentTop = child.getTop();
        if (currentTop > mAnchorPoint) {
            top = mMaxOffset;
            targetState = STATE_COLLAPSED;
        }
        else {
            top = mAnchorPoint;
            targetState = STATE_ANCHOR_POINT;
        }
    }
    if (mViewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) {
        setStateInternal(STATE_SETTLING);
        ViewCompat.postOnAnimation(child, new SettleRunnable(child, targetState));
    } else {
        setStateInternal(targetState);
    }
    mNestedScrolled = false;
}

public final void setState(@State int state) {
    if (state == mState) {
        return;
    }
    if (mViewRef == null) {
        // The view is not laid out yet; modify mState and let onLayoutChild handle it later
        /**
         * New behavior (added: state == STATE_ANCHOR_POINT ||)
         */
        if (state == STATE_COLLAPSED || state == STATE_EXPANDED ||
                state == STATE_ANCHOR_POINT ||
                (mHideable && state == STATE_HIDDEN)) {
            mState = state;
        }
        return;
    }
    V child = mViewRef.get();
    if (child == null) {
        return;
    }
    int top;
    if (state == STATE_COLLAPSED) {
        top = mMaxOffset;
    } else if (state == STATE_ANCHOR_POINT) {
        top = mAnchorPoint;
    } else if (state == STATE_EXPANDED) {
        top = mMinOffset;
    } else if (mHideable && state == STATE_HIDDEN) {
        top = mParentHeight;
    } else {
        throw new IllegalArgumentException("Illegal state argument: " + state);
    }
    setStateInternal(STATE_SETTLING);
    if (mViewDragHelper.smoothSlideViewTo(child, child.getLeft(), top)) {
        ViewCompat.postOnAnimation(child, new SettleRunnable(child, state));
    }
}

public static <V extends View> BottomSheetBehaviorGoogleMapsLike<V> from(V view) {
    ViewGroup.LayoutParams params = view.getLayoutParams();
    if (!(params instanceof CoordinatorLayout.LayoutParams)) {
        throw new IllegalArgumentException("The view is not a child of CoordinatorLayout");
    }
    CoordinatorLayout.Behavior behavior = ((CoordinatorLayout.LayoutParams) params)
            .getBehavior();
    if (!(behavior instanceof BottomSheetBehaviorGoogleMapsLike)) {
        throw new IllegalArgumentException(
                "The view is not associated with BottomSheetBehaviorGoogleMapsLike");
    }
    return (BottomSheetBehaviorGoogleMapsLike<V>) behavior;
}

链接到整个项目 ，你可以在其中查看所有自定义行为

这就是它的样子：
[ CustomBottomSheetBehavior ]