我有Activity
,它得到了TabHost
。 XML文件是:Android無法在第二個標籤上獲取ListView
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TabHost
android:id="@android:id/tabhost"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TabWidget
android:id="@android:id/tabs"
android:layout_width="match_parent"
android:layout_height="70sp"
android:layout_alignParentBottom="true" >
</TabWidget>
<FrameLayout
android:id="@android:id/tabcontent"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="@android:id/tabs" >
<LinearLayout
android:id="@+id/tab1"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
android:id="@+id/listDictionary"
android:layout_width="match_parent"
android:layout_height="match_parent" >
</ListView>
</LinearLayout>
<LinearLayout
android:id="@+id/tab2"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
android:id="@+id/listFavourites"
android:layout_width="match_parent"
android:layout_height="356dp"
android:layout_weight="1" >
</ListView>
</LinearLayout>
<LinearLayout
android:id="@+id/tab3"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ScrollView
android:id="@+id/scrollView1"
android:layout_width="wrap_content"
android:layout_height="match_parent" >
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<ImageView
android:id="@+id/imageView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/wikibilim" />
<TextView
android:id="@+id/textFavourite"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/wiki" />
</LinearLayout>
</ScrollView>
</LinearLayout>
</FrameLayout>
</RelativeLayout>
</TabHost>
在我MainActivity
在開始時onCreate
方法,我寫道:
我使用異步任務輕鬆地上傳數據dictionaryList
。當它試圖獲得favouritesList
似乎有一個NullPointerException
tabHost.setOnTabChangedListener(new OnTabChangeListener() {
@Override
public void onTabChanged(String tabId) {
// TODO Auto-generated method stub
if (tabId.equals("tag2")) {
View view = tabHost.getChildAt(tabHost.getCurrentTab());
favouritesList = (ListView) view.findViewById(R.id.listFavourites);
Toast.makeText(getApplicationContext(), favouritesList.toString(), Toast.LENGTH_LONG).show();
}
}
});
:從那以後,我已經添加監聽器TabHost
。我做錯了什麼 ?
的logcat:
02-19 21:40:52.360: E/AndroidRuntime(25828): FATAL EXCEPTION: main
02-19 21:40:52.360: E/AndroidRuntime(25828): java.lang.NullPointerException
02-19 21:40:52.360: E/AndroidRuntime(25828): at kz.wikibilim.sozdik.MainActivity$1.onTabChanged(MainActivity.java:117)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.widget.TabHost.invokeOnTabChangeListener(TabHost.java:402)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.widget.TabHost.setCurrentTab(TabHost.java:387)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:150)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:560)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.view.View.performClick(View.java:4223)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.view.View$PerformClick.run(View.java:17275)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.os.Handler.handleCallback(Handler.java:615)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.os.Handler.dispatchMessage(Handler.java:92)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.os.Looper.loop(Looper.java:137)
02-19 21:40:52.360: E/AndroidRuntime(25828): at android.app.ActivityThread.main(ActivityThread.java:4898)
02-19 21:40:52.360: E/AndroidRuntime(25828): at java.lang.reflect.Method.invokeNative(Native Method)
02-19 21:40:52.360: E/AndroidRuntime(25828): at java.lang.reflect.Method.invoke(Method.java:511)
02-19 21:40:52.360: E/AndroidRuntime(25828): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1008)
02-19 21:40:52.360: E/AndroidRuntime(25828): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:775)
02-19 21:40:52.360: E/AndroidRuntime(25828): at dalvik.system.NativeStart.main(Native Method)
我發現如何得到這個listFavourites
和設置好的適配器。當我開始申請時,它開始順利,沒有錯誤。然而,當我點擊第二個選項卡,在此ListView
位於,再次給了我NullPointerException
空指針異常什麼行,請發佈logcat – user2450263
favouritesList.toString是爲? – user2450263
檢查是否找到此ListView –