如何从android中的选项卡活动启动fragement活动？

Question

当用户打开应用程序有作为

public class MainCategory extends TabActivity { 
TabHost tabs; 
static TabHost mTabHost; 

ImageView ivSettings; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    requestWindowFeature(Window.FEATURE_NO_TITLE); 

    setContentView(R.layout.maincategory); 

mTabHost = getTabHost(); 


    mTabHost.addTab(mTabHost 
      .newTabSpec("three") 
      .setIndicator("one", 
        getResources().getDrawable(R.drawable.ic_launcher)) 
      .setContent(new Intent(this, SettingsActivity.class))); 


    mTabHost.addTab(mTabHost 
      .newTabSpec("three") 
      .setIndicator("three", 
        getResources().getDrawable(R.drawable.ic_launcher)) 
      .setContent(new Intent(this, MainActivity.class))); 

    mTabHost.setCurrentTab(0);} 

当用户点击第三个标签图标，它启动片段活动

public class MainActivity extends FragmentActivity implements 
    ActionBar.TabListener { 

private ViewPager viewPager; 
private TabsPagerAdapter mAdapter; 
private ActionBar actionBar; 
// Tab titles 
private String[] tabs = { "Top Rated", "Games", "Movies" }; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    // Initilization 
    viewPager = (ViewPager) findViewById(R.id.pager); 
    actionBar = getActionBar(); 
    mAdapter = new TabsPagerAdapter(getSupportFragmentManager()); 

    viewPager.setAdapter(mAdapter); 
    actionBar.setHomeButtonEnabled(false); 
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);   

    // Adding Tabs 
    for (String tab_name : tabs) { 
     actionBar.addTab(actionBar.newTab().setText(tab_name) 
       .setTabListener(this)); 
    } 

    /** 
    * on swiping the viewpager make respective tab selected 
    * */ 
    viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() { 

     @Override 
     public void onPageSelected(int position) { 
      // on changing the page 
      // make respected tab selected 
      actionBar.setSelectedNavigationItem(position); 
     } 

     @Override 
     public void onPageScrolled(int arg0, float arg1, int arg2) { 
     } 

     @Override 
     public void onPageScrollStateChanged(int arg0) { 
     } 
    }); 
} 

@Override 
public void onTabReselected(Tab tab, FragmentTransaction ft) { 
} 

@Override 
public void onTabSelected(Tab tab, FragmentTransaction ft) { 
    // on tab selected 
    // show respected fragment view 
    viewPager.setCurrentItem(tab.getPosition()); 
} 

@Override 
public void onTabUnselected(Tab tab, FragmentTransaction ft) { 
} 

标签看法，但它崩溃我app.This是我的登录猫输出

10-28 06:17:33.036: E/AndroidRuntime(775): FATAL EXCEPTION: main 
10-28 06:17:33.036: E/AndroidRuntime(775): java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.tabsswipe/info.androidhive.tabsswipe.MainActivity}: java.lang.NullPointerException 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.app.ActivityThread.startActivityNow(ActivityThread.java:2054) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:135) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:347) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:749) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.widget.TabHost.setCurrentTab(TabHost.java:413) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:154) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:546) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.view.View.performClick(View.java:4240) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.view.View$PerformClick.run(View.java:17721) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.os.Handler.handleCallback(Handler.java:730) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.os.Handler.dispatchMessage(Handler.java:92) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.os.Looper.loop(Looper.java:137) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.app.ActivityThread.main(ActivityThread.java:5103) 
10-28 06:17:33.036: E/AndroidRuntime(775): at java.lang.reflect.Method.invokeNative(Native Method) 
10-28 06:17:33.036: E/AndroidRuntime(775): at java.lang.reflect.Method.invoke(Method.java:525) 
10-28 06:17:33.036: E/AndroidRuntime(775): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
10-28 06:17:33.036: E/AndroidRuntime(775): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
10-28 06:17:33.036: E/AndroidRuntime(775): at dalvik.system.NativeStart.main(Native Method) 
10-28 06:17:33.036: E/AndroidRuntime(775): **Caused by: java.lang.NullPointerException 
10-28 06:17:33.036: E/AndroidRuntime(775): at info.androidhive.tabsswipe.MainActivity.onCreate(MainActivity.java:31)** 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.app.Activity.performCreate(Activity.java:5133) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
10-28 06:17:33.036: E/AndroidRuntime(775): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175) 
10-28 06:17:33.036: E/AndroidRuntime(775): ... 18 more 

我想下面的输出（无论使用标签活动和操作栏）

Answer 1

您的活动是在Manifest.xml中声明的吗？