如何对嵌套类使用行为？

Question

我正在执行在 AppToolBar 隐藏时隐藏视图的行为。如果我将具有行为的 Cardview 放在定义 CoordinatorLayout 的相同 xml 中，则此方法有效。但是，我需要这种行为在层次结构中更深层次，当我在 Fragments 中使用它时，它不再起作用。

public  class BottomBehaviour extends CoordinatorLayout.Behavior<CardView> {
  int totalHeigh;
  float dencity;
  int statusBarHeigh;
  public BottomBehaviour() {
  }

  public BottomBehaviour(Context context, AttributeSet attrs) {
    super(context, attrs);
    dencity=context.getResources().getDisplayMetrics().density;
    int height = context.getResources().getDisplayMetrics().heightPixels;
    statusBarHeigh = getStatusBarHeight(context);
   totalHeigh=height;
    //totalHeigh = (int) (context.getResources().getDisplayMetrics().heightPixels - (56 * dencity));
    Log.e("mcheck", "BottomBehaviour:  ");
  }

  public int getStatusBarHeight(Context context) {
    int result = 0;
    int resourceId = context.getResources().getIdentifier("status_bar_height", "dimen", "android");
    if (resourceId > 0) {
      result = context.getResources().getDimensionPixelSize(resourceId);
    }
    return result;
  }
  @Override
  public boolean layoutDependsOn(CoordinatorLayout parent, CardView child, View dependency) {

    return dependency instanceof AppBarLayout;
  }

  @Override
  public boolean onDependentViewChanged(CoordinatorLayout parent, CardView child, View dependency) {
    int top = (int)(totalHeigh-child.getHeight()-(dependency.getY()));
   child.setTranslationY(top);

    Log.e("mcheck", "onDependentViewChanged:  "+(dependency.getY()-statusBarHeigh)+" height "+dependency.getHeight()/dencity);
    return super.onDependentViewChanged(parent, child, dependency);
  }
}

一些片段xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:card_view="http://schemas.android.com/apk/res-auto"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  xmlns:app="http://schemas.android.com/tools"
  android:orientation="vertical">

  <android.support.v7.widget.RecyclerView
    android:id="@+id/list"
    android:layout_width="match_parent"
    android:layout_height="0dip"

    android:layout_weight="1" />

  <android.support.v7.widget.CardView
    android:layout_width="match_parent"
    android:layout_height="56dip"
    app:layout_behavior="ua.miui.forum.widget.BottomBehaviour"
    card_view:cardCornerRadius="0dip"
    card_view:cardElevation="8dip">

    <LinearLayout
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:orientation="horizontal">

    </LinearLayout>

  </android.support.v7.widget.CardView>
</LinearLayout>

Answer 1

CoordinatorLayout.Behavior 仅在目标视图（即包含 app:layout_behavior="ua.miui.forum.widget.BottomBehaviour" 的视图是 CoordinatorLayout 的直接后代时才有效。否则它不会收到嵌套的滚动事件。

如果您的 LinearLayout 是 CoordinatorLayout 的直接子代，请向其添加行为，然后您可能应该调整您以查找（例如视图 ID）您的CardView并作用于嵌套滚动。

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