初始化NavigationDrawer时出现NullPointerException

概述我试图在我的应用程序中使用导航抽屉,但我一直遇到NullPointerExceptions,但我不明白为什么.我当前的代码主要基于thisdeveloperlink：publicclassMainActivityextendsActivity{privateString[]mPages;privateDrawerLayoutmDrawerLayout;privateListViewmDrawerLis

我试图在我的应用程序中使用导航抽屉,但我一直遇到NullPointerExceptions,但我不明白为什么.我当前的代码主要基于this developer link：

public class MainActivity extends Activity {private String[] mPages;private DrawerLayout mDrawerLayout;private ListVIEw mDrawerList;private ActionbarDrawerToggle mDrawerToggle;private CharSequence mDrawerTitle;private CharSequence mTitle;@OverrIDeprotected voID onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentVIEw(R.layout.activity_main);    mPages = getResources().getStringArray(R.array.page_Titles);    mDrawerLayout = (DrawerLayout) findVIEwByID(R.ID.drawer_layout);    mDrawerList = (ListVIEw) findVIEwByID(R.ID.left_drawer);    mDrawerList.setAdapter(new ArrayAdapter<String>(this,            R.layout.drawer_List_item, mPages));    mTitle = mDrawerTitle = getTitle();    mDrawerLayout = (DrawerLayout) findVIEwByID(R.ID.drawer_layout);    mDrawerToggle = new ActionbarDrawerToggle(this,     mDrawerLayout,    R.drawable.ic_drawer,     R.string.drawer_open,     R.string.drawer_close     ) {        public voID onDrawerClosed(VIEw vIEw) {            getActionbar().setTitle(mTitle);        }        public voID onDrawerOpened(VIEw drawerVIEw) {            getActionbar().setTitle(mDrawerTitle);        }    };    mDrawerLayout.setDrawerListener(mDrawerToggle);    getActionbar().setdisplayHomeAsUpEnabled(true);    getActionbar().setHomebuttonEnabled(true);}@OverrIDeprotected voID onPostCreate(Bundle savedInstanceState) {    super.onPostCreate(savedInstanceState);    // Sync the toggle state after onRestoreInstanceState has occurred.    mDrawerToggle.syncState();}@OverrIDepublic voID onConfigurationChanged(Configuration newConfig) {    super.onConfigurationChanged(newConfig);    mDrawerToggle.onConfigurationChanged(newConfig);}@OverrIDepublic boolean onoptionsItemSelected(MenuItem item) {    if (mDrawerToggle.onoptionsItemSelected(item)) {        return true;    }    return super.onoptionsItemSelected(item);}@OverrIDepublic boolean onCreateOptionsMenu(Menu menu) {    getMenuInflater().inflate(R.menu.main, menu);    return true;}}

和我的drawer_layout.xml：

<androID.support.v4.Widget.DrawerLayoutxmlns:androID="http://schemas.androID.com/apk/res/androID"androID:ID="@+ID/drawer_layout"androID:layout_wIDth="match_parent"androID:layout_height="match_parent"><!-- The main content vIEw --><FrameLayout    androID:ID="@+ID/content_frame"    androID:layout_wIDth="match_parent"    androID:layout_height="match_parent" /><!-- The navigation drawer --><ListVIEw androID:ID="@+ID/left_drawer"    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="#111"/>

我的堆栈跟踪：

08-12 15:55:54.524: E/AndroIDRuntime(1409): FATAL EXCEPTION: main08-12 15:55:54.524: E/AndroIDRuntime(1409): java.lang.RuntimeException:     Unable to start activity     ComponentInfo{com.test.androID.nav/com.test.androID.nav.MainActivity}:     java.lang.NullPointerException08-12 15:55:54.524: E/AndroIDRuntime(1409):     at     androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:2059)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.app.ActivityThread.access0(ActivityThread.java:130)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.os.Handler.dispatchMessage(Handler.java:99)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.os.Looper.loop(Looper.java:137)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.app.ActivityThread.main(ActivityThread.java:4745)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at java.lang.reflect.Method.invokeNative(Native Method)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at java.lang.reflect.Method.invoke(Method.java:511)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at com.androID.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:553)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at dalvik.system.NativeStart.main(Native Method)08-12 15:55:54.524: E/AndroIDRuntime(1409): Caused by: java.lang.NullPointerException08-12 15:55:54.524: E/AndroIDRuntime(1409):     at com.test.androID.nav.MainActivity.onCreate(MainActivity.java:30)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.app.Activity.performCreate(Activity.java:5008)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)08-12 15:55:54.524: E/AndroIDRuntime(1409):     at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:2023)08-12 15:55:54.524: E/AndroIDRuntime(1409):     ... 11 more

第30行是：mDrawerList.setAdapter(new ArrayAdapter< String>(this,
                R.layout.drawer_List_item,mPages));我确实在res文件夹中将其作为xml文件保存.

现在,在该行之前,我在此行上获得了NullPointerException：mDrawerLayout.setDrawerListener(mDrawerToggle);

任何帮助将非常感激！

解决方法:

我看到NullPointerException的两个潜在原因：

第一个可能是这一行：

mPages = getResources().getStringArray(R.array.page_Titles);

不会将有效数组返回给mPages.我想您的资源文件夹中没有名为“ page_Titles”的字符串数组.

如果您发布的代码绝对正确,则另一原因可能是此行：

setContentVIEw(R.layout.activity_main);

因为根据您的代码,导航抽屉的布局文件是抽屉_布局.xml.所以它应该看起来像这样：

setContentVIEw(R.layout.drawer_layout);

我认为,您的DrawerLayout的资源ID和.xml文件的名称都为“ drawer_layout”,这非常容易引起误解,我强烈建议您进行更改.

此外,我看不出您为什么要拨打此行的原因：

 mDrawerLayout = (DrawerLayout) findVIEwByID(R.ID.drawer_layout);

在您的onCreate()方法中两次.

总结

以上是内存溢出为你收集整理的初始化NavigationDrawer时出现NullPointerException全部内容，希望文章能够帮你解决初始化NavigationDrawer时出现NullPointerException所遇到的程序开发问题。

如果觉得内存溢出网站内容还不错，欢迎将内存溢出网站推荐给程序员好友。