我正在尝试通过单击按钮打开并使用单独的片段填充导航抽屉。抽屉本身只是在activity_main.xml 中声明的空RelativeLayouts。
活动主.xml：
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent">
<!--Main View-->
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="xxx.MainActivity">
</RelativeLayout>
<!--Left drawer-->
<RelativeLayout android:id="@+id/drawer_left"
android:layout_width="290dp"
android:layout_height="match_parent"
android:layout_gravity="start">
</RelativeLayout>
<!--Right drawer-->
<RelativeLayout android:id="@+id/drawer_right"
android:layout_width="290dp"
android:layout_height="match_parent"
android:layout_gravity="end">
</RelativeLayout>
main_view 在 MainActivity 中填充了一个片段，所以它看起来像这样：
MainActivity 类：
public class MainActivity extends AppCompatActivity {
android.app.FragmentManager fragmentManager;
android.app.FragmentTransaction fragmentTransaction;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragmentManager = getFragmentManager();
//Set fragment
Frag1 frag1 = new Frag1();
fragmentTransaction = getFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.fragment_container,frag1).commit();
}
Frag1 类：
public class Frag1 extends Fragment {
ImageButton imageButtonOpenDrawer;
DrawerLayout mDrawerLayout;
RelativeLayout mDrawer_left;
android.app.FragmentManager fragmentManager;
android.app.FragmentTransaction fragmentTransaction;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.frag1, container, false);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
View v = getView();
imageButtonOpenDrawer = (ImageButton) v.findViewById(R.id.imageButtonOpenDrawer);
fragmentManager = getFragmentManager();
mDrawerLayout = (DrawerLayout) v.findViewById(R.id.drawer_layout);
mDrawer_left = (RelativeLayout) v.findViewById(R.id.drawer_left);
imageButtonOpenDrawer.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DrawerFragment drawerFragment = new DrawerFragment();
fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.fragment_container,drawerFragment).commit();
}
});
}
从 MainActivity 类完成时，同样的原理也适用。但是当我尝试从 Fragments 类打开抽屉时，会抛出这个空指针错误：
java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法“void android.support.v4.widget.DrawerLayout.openDrawer(android.view.View)”