android - 自定义 ScrollingViewBehavior 不加载

Question

我写了一个自定义的ScrollingViewBahavior:

package app.library.util.view;

//***

public class FillParentViewBehavior extends AppBarLayout.ScrollingViewBehavior {

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

        resizeChildAsNeeded(child, dependency);

        return false;
    }
}

接下来，我在资源中声明了一个类路径(类比appcompat声明):

<resources>
    <string name="appbar_fill_parent_view_behavior" translatable="false">app.library.util.view.FillParentViewBehavior</string>
</resources>

并将其设置在我的布局中:

<layout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <android.support.design.widget.CoordinatorLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context="app.library.activity.MainActivity">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/appBar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <!-- Inner views -->

        </android.support.design.widget.AppBarLayout>

        <android.support.v4.view.ViewPager
            android:id="@+id/view_pager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_fill_parent_view_behavior"/>

    </android.support.design.widget.CoordinatorLayout>
</layout>

但是我的应用程序崩溃了，日志输出:

java.lang.RuntimeException: Unable to start activity ComponentInfo{app/app.library.activity.MainActivity}: java.lang.RuntimeException: Could not inflate Behavior subclass app.library.util.view.FillParentViewBehavior

我试图重建一个项目，但它没有帮助我。这很奇怪，因为来自 AppCompat 库的行为完美无缺。
我做错了什么？

Answer 1

因为您正试图从代码创建此类，所以您需要再添加一个构造函数(通常，对于您从代码创建的任何 XML View 都是如此)。

所以，你的类应该是这样的:

public class FillParentViewBehavior extends AppBarLayout.ScrollingViewBehavior {

    public FillParentViewBehavior() {
        super();
    }
    
    public FillParentViewBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

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

        resizeChildAsNeeded(child, dependency);

        return false;
    }
}