2014-10-31 251 views
2

我在關閉Android中抽屜佈局時遇到問題。每次我調用drawer.closeDrawers()或drawer.closeDrawers(list)時,我都遇到一個空指針異常。Android - 抽屜佈局 - 關閉抽屜導致空指針異常

這是我的MainActivity.java代碼。

// Sliding drawer menu 
private DrawerLayout drawer; 
// Drawer list 
private ListView drawerList; 
... 
... 
... 
// List of menu options 
final String[] menu = new String[]{ 
     "Item 1", 
     "Item 2", 
     "Item 3", 
     "Item 4", 
     "Item 5" 
}; 
// Initialize the drawer menu layout 
drawer = (DrawerLayout) findViewById(R.layout.activity_main); 
// Initialize the drawer list 
drawerList = (ListView) findViewById(R.id.list_slidermenu); 
// Drawer list adapter 
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, menu); 
// Set the adapter for the list 
drawerList.setAdapter(adapter); 
// Set the background selector for each menu item 
drawerList.setSelector(android.R.color.holo_blue_dark); 
// On click listener for the list 
drawerList.setOnItemClickListener(new OnItemClickListener() { 
    // When a menu item is clicked 
    public void onItemClick(AdapterView<?> e, View v, int position, long id) { 
     // Close the drawer 
     drawer.closeDrawers(); // Causes a Null Pointer Exception 
    } 
}); 

這是我的activity_main.xml代碼。

<!-- Left sided swipe in Drawer layout --> 
<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" > 

<!-- Framelayout to display Fragments --> 
<FrameLayout 
    android:id="@+id/frame_container" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" > 

    <!-- Google maps fragment --> 
    <fragment 
     android:id="@+id/google_map" 
     android:name="com.google.android.gms.maps.MapFragment" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" > 
    </fragment> 
</FrameLayout> 

<!-- Listview to display slider menu --> 
<ListView 
    android:id="@+id/list_slidermenu" 
    android:layout_width="240dp" 
    android:layout_height="match_parent" 
    android:layout_gravity="start" 
    android:choiceMode="singleChoice" 
    android:divider="@android:color/transparent" 
    android:dividerHeight="0dp" 
    android:background="#F0F0F0"/> 

</android.support.v4.widget.DrawerLayout> 

這是我的錯誤堆棧跟蹤。

10-30 20:29:21.956: E/AndroidRuntime(1959): FATAL EXCEPTION: main 
10-30 20:29:21.956: E/AndroidRuntime(1959): Process: com.dziz.umbcparkingpal, PID: 1959 
10-30 20:29:21.956: E/AndroidRuntime(1959): java.lang.NullPointerException 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at com.dziz.umbcparkingpal.MainActivity$1.onItemClick(MainActivity.java:108) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at android.widget.AdapterView.performItemClick(AdapterView.java:301) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at android.widget.AbsListView.performItemClick(AbsListView.java:1113) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at android.widget.AbsListView$PerformClick.run(AbsListView.java:2911) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at android.widget.AbsListView$3.run(AbsListView.java:3645) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at android.os.Handler.handleCallback(Handler.java:733) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at android.os.Handler.dispatchMessage(Handler.java:95) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at android.os.Looper.loop(Looper.java:136) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at android.app.ActivityThread.main(ActivityThread.java:5097) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at java.lang.reflect.Method.invokeNative(Native Method) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at java.lang.reflect.Method.invoke(Method.java:515) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601) 
10-30 20:29:21.956: E/AndroidRuntime(1959):  at dalvik.system.NativeStart.main(Native Method) 

誰能告訴我我在做什麼導致這個空指針異常嗎?

回答

1

設置你的抽屜,

drawer= (DrawerLayout) findViewById(R.id.DrawerLayout); 
0

你需要從內就檢索意見之前膨脹的佈局:

LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE) 
View drawer = inflater.inflate(R.layout.activity_main, null); 

那麼你就可以獲取訪問量:

drawerList = (ListView) drawer.findViewById(R.id.list_slidermenu); 
+0

這沒有奏效。 Android試圖誇大視圖時遇到錯誤。另外,你對於我應該用膨脹視圖做的事情不是很具體,它只是掛在那裏沒用。 – 2014-10-31 00:34:37

+0

「視圖」是你的「抽屜」 – habitats 2014-10-31 00:35:24

+0

是的,我試圖使用演員初始化我的DrawerLayout與膨脹的視圖。它沒有幫助,它只在開始時崩潰了程序。 – 2014-10-31 00:36:12

0

我有同樣的問題,並通過調用這個解決它:

DrawerLayout drawerLayout = (DrawerLayout) ((MainActivity) getActivity()).findViewById(R.id.drawer_layout); 
drawerLayout.closeDrawers(); 

內的片段。 MainActivity是放置drawer_layout的地方。

此外,請確保在調用closeDrawers()之前獲取對drawerLayout的引用,因爲在我的情況下,在我的片段的onCreateView()的開頭調用findViewById()時,仍然有NullPointer。

所以你的情況在你的onItemClicked()方法中調用findViewById()。

希望這會有所幫助。

0

我有使用抽屜,它與任何錯誤完美運行。這是我的代碼的一部分。我認爲這可能會對你有所幫助。

HomeActivity.java

public class HomeActivity extends Activity { 
    DrawerLayout mDrawerLayout; 
    ListView mDrawerList; 
    private String[] navMenuTitles; 
    private TypedArray navMenuIcons; 
    private ArrayList<NavDrawerItem> navDrawerItems; 
    private NavDrawerListAdapter adapter; 


    @Override 
     protected void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 
      setContentView(R.layout.activity_main); 
      Log.d("Activity :", getClass().getName().toString()); 

      initDrawer(savedInstanceState); 

    } 

    private void initDrawer(Bundle savedInstanceState) { 
      mTitle = mDrawerTitle = getTitle(); 

      navMenuTitles = getResources().getStringArray(
        R.array.student_nav_drawer_items); 
      navMenuIcons = getResources().obtainTypedArray(
        R.array.student_nav_drawer_icons); 

      mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout); 
      mDrawerList = (ListView) findViewById(R.id.left_drawer); 

      navDrawerItems = new ArrayList<NavDrawerItem>(); 


      mDrawerList.setOnItemClickListener(new DrawerItemClickListener()); 

      adapter = new NavDrawerListAdapter(getApplicationContext(), 
        navDrawerItems); 
      mDrawerList.setAdapter(adapter); 

      getActionBar().setDisplayHomeAsUpEnabled(true); 
      getActionBar().setHomeButtonEnabled(true); 
      getActionBar().setIcon(android.R.color.transparent); 
      getActionBar().setDisplayShowCustomEnabled(true); 
      getActionBar().setCustomView(R.layout.custom_titlebar); 

      tvTitle = (TextView) findViewById(R.id.tv_title); 
      tvTitle.setText(getString(R.string.title_activity_home)); 

      mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, 
        R.drawable.slider_icon, R.string.app_name, R.string.app_name 

      ) { 
       public void onDrawerClosed(View view) { 
        getActionBar().setTitle(mTitle); 
        invalidateOptionsMenu(); 
       } 

       public void onDrawerOpened(View drawerView) { 
        getActionBar().setTitle(mDrawerTitle); 
        invalidateOptionsMenu(); 
       } 
      }; 
      mDrawerLayout.setDrawerListener(mDrawerToggle); 

      if (savedInstanceState == null) { 
       selectItem(0); 

      } 
     } 

private void selectItem(int position) { 

     switch (position) { 
     case 0: 

      break; 
     case 1: 

      break; 
     case 2: 

      break; 

     case 3: 


      break; 
     default: 


      break; 
     } 

     mDrawerLayout.closeDrawer(mDrawerList); 
    } 

activity_main.xml中

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/drawer_layout" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" > 

    <RelativeLayout 
     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/content" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" > 
    </RelativeLayout> 

    <!-- The navigation drawer --> 

    <ListView 
     android:id="@+id/left_drawer" 
     android:layout_width="250dp" 
     android:layout_height="match_parent" 
     android:layout_gravity="start" 
     android:background="#FFFFFF" 
     android:choiceMode="singleChoice" 
     android:divider="#444" 
     android:dividerHeight="1dp" 
     android:minHeight="?android:attr/listPreferredItemHeightSmall" 
     android:textAppearance="?android:attr/textAppearanceListItemSmall" /> 

</android.support.v4.widget.DrawerLayout> 
0

如果(mDrawerLayout.isDrawerOpen(mRecyclerDrawer)){ mDrawerLayout.closeDrawer(列表視圖); } else { mDrawerLayout.openDrawer(listview); }