android - DrawaerLayout.onDrawerOpened 从未被调用

Question

我想更改 DrawerLayout 中的 TextView 。所以我用我自己的类扩展它。问题是当我调试这段代码时，永远不会调用 onDrawerOpened，特别是在打开抽屉时。

    import android.support.v4.widget.DrawerLayout;

    public class MyDrawerLayout extends DrawerLayout implements DrawerLayout.DrawerListener {
    //Context context;

    public MyDrawerLayout(Context c) {
        this(c, null);
    }

    public MyDrawerLayout(Context c, AttributeSet attrs) {
        this(c, attrs, 0);
    }

    public MyDrawerLayout (Context c, AttributeSet attrs, int defStyle) {
        super (c, attrs, defStyle);
        setDrawerListener(this);
    }

    public void onDrawerOpened(View drawerView) {

        LinearLayout root = (LinearLayout)(drawerView.findViewById(R.id.root));
        TextView t = (TextView) (root.findViewById(R.id.textView));
        t.setText(((MainActivity) MainActivity.main_activity).globalScenarioName);
        Snackbar.make(((MainActivity)MainActivity.main_activity).container, "NAVVIEW Open", Snackbar.LENGTH_LONG)
                .setAction("Action", null).show();
    }

    public void  onDrawerSlide (View drawerView, float slide) {

    }

    public void onDrawerClosed (View drawerView) {

    }

    public  void onDrawerStateChanged (int newState) {}
}

activity_main.xml 布局看起来很标准:

<net.mycom.myproject.widget.MyDrawerLayout 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:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer" />

</net.mycom.myproject.widget.MyDrawerLayout>

Answer 1

在你的构造函数中，你应该调用 setDrawerListener(this)，将你的类注册为监听器，因为它正在实现 DrawerLayout.DrawerListener

public MyDrawerLayout(Context c) {
    this(c, null);
}

public MyDrawerLayout(Context c, AttributeSet attrs) {
    this(c, attrs, 0);
}

public MyDrawerLayout (Context c, AttributeSet attrs, int defStyle) {
    super (c, attrs, defStyle);
    setDrawerListener(this);
}

您不必保留对上下文的引用。 View 具有方法 getContext()