使用FragmentTabHost的onCreateView中的空指針異常

Question

我正在使用包含三個選項卡的FragmentTabHost。我得到一個空指針異常在第一個選項卡，我試圖添加一個webViewClient的onCreateView ..我是新來的android和我無法弄清楚代碼有什麼問題...

我曾經在我的主佈局文件中有一個側邊欄/漢堡包抽屜，但只要我從我的activity_lest_see_main xml文件中移除它..我開始在Tab1Activity中得到一個NullPointerException ..請幫助..我真的停留在這個問題上。 只要我在lest_see_main.xml文件中添加側邊欄/漢堡包抽屜，代碼就會開始運行而不會出現任何錯誤，並且該應用可以正常工作。

我一直收到NullPointerException在mwebView.setWebViewClient(new HelloWebViewClient)在Tab1Activity。

這是我在logcat中獲得與沿的NullPointerException在頂部 -

07-28 18:24:52.735: E/AndroidRuntime(6834): FATAL EXCEPTION: main 
07-28 18:24:52.735: E/AndroidRuntime(6834): java.lang.NullPointerException 
07-28 18:24:52.735: E/AndroidRuntime(6834):  at com.example.itslive.Tab1Activity.onCreateView(Tab1Activity.java:168) 
07-28 18:24:52.735: E/AndroidRuntime(6834):  at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786) 
07-28 14:17:31.274: E/AndroidRuntime(29029): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947) 
07-28 14:17:31.274: E/AndroidRuntime(29029): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126) 
07-28 14:17:31.274: E/AndroidRuntime(29029): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739) 
07-28 14:17:31.274: E/AndroidRuntime(29029): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489) 

這是延伸片段活動

activity_lest_see_main.xml

主要活動我的xml文件

<RelativeLayout 
xmlns:android="http://schemas.android.com/apk/res/android" 
android:id="@+id/rev" 
android:layout_width="match_parent" 
android:layout_height = "match_parent" 
android:layout_gravity="start"> 

<RelativeLayout 
android:id="@+id/mainContent" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
> 
<android.support.v4.app.FragmentTabHost 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:id="@android:id/tabhost"> 

    <LinearLayout 
    android:id="@+id/LinearLayout01" 
    android:orientation="vertical" 
    android:layout_height="fill_parent" 
    android:layout_width="fill_parent"> 

    <TabWidget 
    android:id="@android:id/tabs" 
    android:layout_height="wrap_content" 
    android:layout_width="fill_parent"> 
    </TabWidget> 

    <FrameLayout 
    android:id="@android:id/tabcontent" 
    android:layout_height="fill_parent" 
    android:layout_width="fill_parent"> 
    </FrameLayout> 

    </LinearLayout> 

    </android.support.v4.app.FragmentTabHost> 

    <Button 
    android:id="@+id/exit" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:background="@android:color/transparent" 
    android:layout_gravity="bottom" 
    android:layout_alignParentBottom="true" 
    android:text = "@string/exit_button" 
    android:textColor="@color/blue" 
    android:textSize="20sp" 
    android:layout_centerHorizontal="true"/> 

    </RelativeLayout> 


    </RelativeLayout> 

這是我的MainActivity java文件擴展Fragmentactivity

LetsSeeMainActivity.java

public class LestSeeMainActivity extends FragmentActivity { 
private FragmentTabHost tabHost; 
int flag = 0; 
int n; 
private static final String TAG = "LetsSeeMainActivity"; 
private AudioManager maudioManager; 
Fragment mContent; 


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


    setContentView(R.layout.activity_lest_see_main); 


     maudioManager = (AudioManager) getSystemService(AUDIO_SERVICE); 

    final Button exitb = (Button)findViewById(R.id.exit); 

    exitb.setOnClickListener(new View.OnClickListener() { 

     @Override 
     public void onClick(View v) { 
      // TODO Auto-generated method stub 
      maudioManager.playSoundEffect(AudioManager.FX_KEY_CLICK); 
      finish(); 
     } 
    }); 


    tabHost = (FragmentTabHost) findViewById(android.R.id.tabhost); 
    tabHost.setup(this, getSupportFragmentManager(), android.R.id.tabcontent); 

    tabHost.addTab(
       tabHost.newTabSpec("tab1").setIndicator("Tab1", null), 
       Tab1Activity.class, null); 
     tabHost.addTab(
       tabHost.newTabSpec("tab2").setIndicator("Tab2", null), 
       Tab2Activity.class, null); 
     tabHost.addTab(
       tabHost.newTabSpec("tab3").setIndicator("Tab3", null), 
       Tab3Activity.class, null); 
} 

}

這是我的第一個片段活動的java文件的onCreateView

Tab1Activity.java

public void onCreate(Bundle savedInstanceState) { 

    super.onCreate(savedInstanceState); 
} 

public View onCreateView(LayoutInflater inflater, ViewGroup container, 
     Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    if(v==null) 
    { 
    v = inflater.inflate(R.layout.activity_tab1, container, false); 
    mwebView = (WebView) v.findViewById(R.id.wb1); 
    mwebView.setWebViewClient(new HelloWebViewClient()); 
    registerForContextMenu(mwebView); 

    } 

這是我activity_tab1.xml文件 -

<android.support.v4.widget.SwipeRefreshLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/swipe_refresh_layout" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 

<WebView android:id="@+id/wb1" 
android:layout_width="match_parent" 
android:layout_height="wrap_content" /> 

<ProgressBar 
android:id="@+id/progressBar1" 
style="?android:attr/progressBarStyleHorizontal" 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:maxHeight="5dp" 
android:minHeight="5dp" 
android:visibility="invisible" 
/> 

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

Answer 1

嘗試把

mwebView = (WebView) v.findViewById(R.id.wb1); 
mwebView.setWebViewClient(new HelloWebViewClient()); 
registerForContextMenu(mwebView); 

在onViewCreated（..）。