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我在Android Studio实现菜单抽屉时遇到了错误。

androidandroid-fragmentsandroid-studio
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我正在Android Studio中实现菜单抽屉。

我使用了包含抽屉设置的DrawerFragment。我还使用了包含在抽屉中显示列表视图的DrawerAdapter。

这是我的MainActivity.java文件。

public class MainActivity extends AppCompatActivity{

    private DrawerFragment drawerFragment;
    private Toolbar toolbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        toolbar = (Toolbar) findViewById(R.id.toolbar);

        drawerFragment = (DrawerFragment) getFragmentManager().findFragmentById(R.id.navigation_drawer);
        drawerFragment.setUp(R.id.navigation_drawer,toolbar,(DrawerLayout) findViewById(R.id.drawer_layout),MainActivity.this);
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.mithilamin.menudrawer.MainActivity">

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.Toolbar
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:id="@+id/toolbar"
        android:layout_gravity="center_horizontal"
        android:background="@drawable/vehicle_toolbar"
        android:layout_alignParentTop="true">

    </android.support.v7.widget.Toolbar>

    <TextView
        android:id="@+id/vehicle_toolbar_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="hello_world"
        android:layout_gravity="right|center_vertical"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:textColor="@android:color/background_dark"
        android:textSize="24sp"
        android:alpha="0.7"
        android:paddingLeft="20dp"
        android:paddingRight="30dp"
        android:paddingTop="10dp"
        android:paddingBottom="10dp" />
</FrameLayout>

<fragment android:id="@+id/navigation_drawer"
    android:layout_width="@dimen/drawer_width" android:layout_height="match_parent"
    android:layout_gravity="start"
    class = "com.example.mithilamin.menudrawer.drawer.DrawerFragment" />

错误


（注：此处为错误提示）
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.mithilamin.menudrawer, PID: 16507
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mithilamin.menudrawer/com.example.mithilamin.menudrawer.MainActivity}: android.view.InflateException: Binary XML file line #40: Binary XML file line #40: Error inflating class fragment
 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: android.view.InflateException: Binary XML file line #40: Binary XML file line #40: Error inflating class fragment
 at android.view.LayoutInflater.inflate(LayoutInflater.java:539)
at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:256)
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109)
at com.example.mithilamin.menudrawer.MainActivity.onCreate(MainActivity.java:21)
at android.app.Activity.performCreate(Activity.java:6237)
 at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
 at android.os.Handler.dispatchMessage(Handler.java:102) 
 at android.os.Looper.loop(Looper.java:148) 
 at android.app.ActivityThread.main(ActivityThread.java:5417) 
 at java.lang.reflect.Method.invoke(Native Method) 
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
 Caused by: android.view.InflateException: Binary XML file line #40: Error inflating class fragment
 at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:782)
 at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:835)
 at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798)
 at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
 at android.view.LayoutInflater.inflate(LayoutInflater.java:423) 
 at android.view.LayoutInflater.inflate(LayoutInflater.java:374) 
 at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:256) 
at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109) 
at com.example.mithilamin.menudrawer.MainActivity.onCreate(MainActivity.java:21) 
at android.app.Activity.performCreate(Activity.java:6237) 
 at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) 
 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) 
 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
 at android.app.ActivityThread.-wrap11(ActivityThread.java) 
 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
 at android.os.Handler.dispatchMessage(Handler.java:102) 
 at android.os.Looper.loop(Looper.java:148) 
 at android.app.ActivityThread.main(ActivityThread.java:5417) 
 at java.lang.reflect.Method.invoke(Native Method) 
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String)' on a null object reference
                                                       at com.example.mithilamin.menudrawer.drawer.DrawerFragment.onCreate(DrawerFragment.java:46)
                                                       at android.app.Fragment.performCreate(Fragment.java:2198)
                                                       at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:942)
                                                       at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
                                                       at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1228)
                                                       at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2201)
                                                       at android.app.FragmentController.onCreateView(FragmentController.java:98)
                                                       at android.app.Activity.onCreateView(Activity.java:5546)
                                                       at android.support.v4.app.BaseFragmentActivityHoneycomb.onCreateView(BaseFragmentActivityHoneycomb.java:34)
                                                       at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:79)
                                                       at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:754)
                                                       at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:704) 
                                                       at android.view.LayoutInflater.rInflate(LayoutInflater.java:835) 
                                                       at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:798) 
                                                       at android.view.LayoutInflater.inflate(LayoutInflater.java:515) 
                                                       at android.view.LayoutInflater.inflate(LayoutInflater.java:423) 
                                                       at android.view.LayoutInflater.inflate(LayoutInflater.java:374) 
                                                       at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:256) 
                                                       at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:109) 
                                                       at com.example.mithilamin.menudrawer.MainActivity.onCreate(MainActivity.java:21) 
                                                       at android.app.Activity.performCreate(Activity.java:6237) 
                                                       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) 
                                                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) 
                                                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                                                       at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                                                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                                                       at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                       at android.os.Looper.loop(Looper.java:148) 
                                                       at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                       at java.lang.reflect.Method.invoke(Native Method) 
                                                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

DrawerFragment.java

public class DrawerFragment extends Fragment {

private static final String STATE_SELECTED_POSITION = "selected_navigation_drawer_position";

private Activity drawerCallingActivity;

private ListView mainList, settingsList;
private View fragmentContainerView;

private int currentSelectPosition = 0;

private ActionBarDrawerToggle drawerToggle;
protected List<DrawerData> drawerDataList = new ArrayList<>();
protected List<DrawerData> drawerSettingList = new ArrayList<>();
private DrawerLayout drawerLayout;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if(savedInstanceState==null)
        currentSelectPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);

    drawerDataList.add(new DrawerData(getString(R.string.drawer_item_1),R.drawable.vehicle_drawer_icon,0));
    drawerDataList.add(new DrawerData(getString(R.string.drawer_item_2), R.drawable.expense_drawer_icon, 0));

    drawerSettingList.add(new DrawerData(getString(R.string.drawer_settings_item_2), R.drawable.logout_drawer_icon, 0));
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    setHasOptionsMenu(true);
}

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.drawerbar,container,false);

    mainList = (ListView) view.findViewById(R.id.drawer_list);
    settingsList = (ListView) view.findViewById(R.id.drawer_settings);

    mainList.setAdapter(new DrawerAdapter(drawerDataList, getActivity()));
    settingsList.setAdapter(new DrawerAdapter(drawerSettingList, getActivity()));

    mainList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            selectItem(position);
        }
    });
    settingsList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            selectSettingItem(position);
        }
    });
    TextView userName = (TextView) view.findViewById(R.id.drawer_text_username);

    mainList.setItemChecked(currentSelectPosition, true);
    return view;
}

public void setUp(int fragmentId, Toolbar toolbar, DrawerLayout drawerLayout, Activity activity) {
    fragmentContainerView = getActivity().findViewById(fragmentId);
    this.drawerLayout = drawerLayout;
    this.drawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
    this.drawerCallingActivity = activity;

    drawerToggle = new ActionBarDrawerToggle(getActivity(),this.drawerLayout,toolbar,R.string.open_drawer,R.string.close_drawer){
        @Override
        public void onDrawerClosed(View drawerView) {
            super.onDrawerClosed(drawerView);
            if(!isAdded())
                return;
            getActivity().invalidateOptionsMenu();
        }

        @Override
        public void onDrawerOpened(View drawerView) {
            super.onDrawerOpened(drawerView);
            if(!isAdded())
                return;;
            getActivity().invalidateOptionsMenu();
        }
    };

    drawerLayout.post(new Runnable() {
        @Override
        public void run() {
            drawerToggle.syncState();
        }
    });
    drawerLayout.setDrawerListener(drawerToggle);
}

private void selectItem(int position) {
    currentSelectPosition = position;

    if (mainList != null) {
        mainList.setItemChecked(position, true);
    }

    if (drawerLayout != null) {
        drawerLayout.closeDrawer(fragmentContainerView);
    }

    switch (position){
        case 0:
            Toast.makeText(getActivity(),getString(R.string.drawer_item_1),Toast.LENGTH_SHORT).show();
            break;

        case 1:
            Toast.makeText(getActivity(),getString(R.string.drawer_item_2),Toast.LENGTH_SHORT).show();
    }
}

private void selectSettingItem(int position) {
    if (settingsList != null)
        settingsList.setItemChecked(position, true);

    if (drawerLayout != null)
        drawerLayout.closeDrawer(fragmentContainerView);

    switch (position) {
        case 0:
            Toast.makeText(getActivity(), getString(R.string.drawer_settings_item_2), Toast.LENGTH_SHORT).show();
            break;
    }
}

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt(STATE_SELECTED_POSITION, currentSelectPosition);
}

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    drawerToggle.onConfigurationChanged(newConfig);
}

}

1个回答
1
问题出在onCreate方法中。
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if(savedInstanceState!=null)
        currentSelectPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);

    drawerDataList.add(new DrawerData(getString(R.string.drawer_item_1),R.drawable.vehicle_drawer_icon,0));
    drawerDataList.add(new DrawerData(getString(R.string.drawer_item_2), R.drawable.expense_drawer_icon, 0));

    drawerSettingList.add(new DrawerData(getString(R.string.drawer_settings_item_2), R.drawable.logout_drawer_icon, 0));
}
请在此处发布您的抽屉片段代码，它出现了NullPointerException异常。 - Eric B.
谢谢你的帮助，但是还是有同样的问题。它显示InflateException。 - Mithil Amin
MainActivity.java 有任何问题吗？@ Eric B. - Mithil Amin
问题在 DrawerFragment 中，正如此日志所述 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.os.Bundle.getInt(java.lang.String)' on a null object reference at com.example.mithilamin.menudrawer.drawer.DrawerFragment.onCreate(DrawerFragment.java:46)。 - Eric B.
这里我放置了DrawerFragment.java类。 - Mithil Amin
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