我找到了一个用片段实现tab的代码。我试图将listview放在片段中，但应用程序崩溃时出现以下错误。你能不能看看代码并指导我。谢谢。
01-18 11:44:49.130: E/AndroidRuntime(1908): FATAL EXCEPTION: main
01-18 11:44:49.130: E/AndroidRuntime(1908): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.abe/com.example.abe.TabsFragmentActivity}: java.lang.NullPointerException
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.app.ActivityThread.access$600(ActivityThread.java:130)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.os.Handler.dispatchMessage(Handler.java:99)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.os.Looper.loop(Looper.java:137)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.app.ActivityThread.main(ActivityThread.java:4745)
01-18 11:44:49.130: E/AndroidRuntime(1908): at java.lang.reflect.Method.invokeNative(Native Method)
01-18 11:44:49.130: E/AndroidRuntime(1908): at java.lang.reflect.Method.invoke(Method.java:511)
01-18 11:44:49.130: E/AndroidRuntime(1908): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-18 11:44:49.130: E/AndroidRuntime(1908): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-18 11:44:49.130: E/AndroidRuntime(1908): at dalvik.system.NativeStart.main(Native Method)
01-18 11:44:49.130: E/AndroidRuntime(1908): Caused by: java.lang.NullPointerException
01-18 11:44:49.130: E/AndroidRuntime(1908): at com.example.abe.Tab1Fragment.onCreateView(Tab1Fragment.java:44)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1460)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:911)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1070)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1861)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:547)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1163)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.app.Activity.performStart(Activity.java:5018)
01-18 11:44:49.130: E/AndroidRuntime(1908): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2032)
01-18 11:44:49.130: E/AndroidRuntime(1908): ... 11 more
TABFRAGMENTACTIVITY类：
import java.util.HashMap;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.view.View;
import android.widget.TabHost;
import android.widget.TabHost.TabContentFactory;
public class TabsFragmentActivity extends FragmentActivity implements TabHost.OnTabChangeListener {
private TabHost mTabHost;
private HashMap<String, TabInfo> mapTabInfo = new HashMap<String, TabsFragmentActivity.TabInfo>();
private TabInfo mLastTab = null;
private class TabInfo {
private String tag;
private Class<?> clss;
private Bundle args;
private Fragment fragment;
TabInfo(String tag, Class<?> clazz, Bundle args) {
this.tag = tag;
this.clss = clazz;
this.args = args;
}
}
class TabFactory implements TabContentFactory {
private final Context mContext;
public TabFactory(Context context)
{
mContext = context;
}
public View createTabContent(String tag)
{
View v = new View(mContext);
v.setMinimumWidth(0);
v.setMinimumHeight(0);
return v;
}
}
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tabs_layout);
initialiseTabHost(savedInstanceState);
if (savedInstanceState != null) {
mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab")); //set the tab as per the saved state
}
}
protected void onSaveInstanceState(Bundle outState) {
outState.putString("tab", mTabHost.getCurrentTabTag()); //save the tab selected
super.onSaveInstanceState(outState);
}
private void initialiseTabHost(Bundle args) {
mTabHost = (TabHost)findViewById(android.R.id.tabhost);
mTabHost.setup();
TabInfo tabInfo = null;
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab1").setIndicator("Tab 1"), ( tabInfo = new TabInfo("Tab1", Tab1Fragment.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab2").setIndicator("Tab 2"), ( tabInfo = new TabInfo("Tab2", Tab2Fragment.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
TabsFragmentActivity.addTab(this, this.mTabHost, this.mTabHost.newTabSpec("Tab3").setIndicator("Tab 3"), ( tabInfo = new TabInfo("Tab3", Tab3Fragment.class, args)));
this.mapTabInfo.put(tabInfo.tag, tabInfo);
this.onTabChanged("Tab1");
mTabHost.setOnTabChangedListener(this);
}
private static void addTab(TabsFragmentActivity activity, TabHost tabHost, TabHost.TabSpec tabSpec, TabInfo tabInfo) {
tabSpec.setContent(activity.new TabFactory(activity));
String tag = tabSpec.getTag();
tabInfo.fragment = activity.getSupportFragmentManager().findFragmentByTag(tag);
if (tabInfo.fragment != null && !tabInfo.fragment.isDetached()) {
FragmentTransaction ft = activity.getSupportFragmentManager().beginTransaction();
ft.detach(tabInfo.fragment);
ft.commit();
activity.getSupportFragmentManager().executePendingTransactions();
}
tabHost.addTab(tabSpec);
}
public void onTabChanged(String tag) {
TabInfo newTab = this.mapTabInfo.get(tag);
if (mLastTab != newTab) {
FragmentTransaction ft = this.getSupportFragmentManager().beginTransaction();
if (mLastTab != null) {
if (mLastTab.fragment != null) {
ft.detach(mLastTab.fragment);
}
}
if (newTab != null) {
if (newTab.fragment == null) {
newTab.fragment = Fragment.instantiate(this,
newTab.clss.getName(), newTab.args);
ft.add(R.id.realtabcontent, newTab.fragment, newTab.tag);
} else {
ft.attach(newTab.fragment);
}
}
mLastTab = newTab;
ft.commit();
this.getSupportFragmentManager().executePendingTransactions();
}
}
}
TABFRAGMENT类 - 这是我试图放置listview的地方：
import android.annotation.TargetApi;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.ListFragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;
public class Tab1Fragment extends ListFragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ListView lv = (ListView)getView().findViewById(R.id.listView1);
String android_array1[] = new String[50];
for(int i=0;i<50;i++)
{
android_array1[i]="ab"+i;
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity().getBaseContext(), android.R.layout.simple_list_item_1, android_array1);
lv.setAdapter(adapter);
return (LinearLayout)inflater.inflate(R.layout.tab_frag1_layout, container, false);
}
}
这是tabfragment类的xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#FF0000"
>
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1" >
</ListView>
</LinearLayout>
答案 0 :(得分：1)
注意：
如果您在 Tab1Fragment 中扩展 ListFragment 然后无需使用
ListView lv = (ListView) root.findViewById(R.id.listView1);
只需删除它。
最后，您的onCreateView(..)方法看起来像这样：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
String android_array1[] = new String[50];
for(int i=0;i<50;i++)
{
android_array1[i]="ab"+i;
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity().getBaseContext(), android.R.layout.simple_list_item_1, android_array1);
setListAdapter(adapter);
return super.onCreateView(inflater, container, savedInstanceState);
}
更多信息请参阅此链接
http://wptrafficanalyzer.in/blog/creating-navigation-tabs-using-tabhost-and-fragments-in-android/