Tabhost nullpointerexception when tabhost isn't the only thing in the layout_问答_开发者

I've noticed that there are numerous issues with using tabhost, but none of them really fit my issue. I am trying to create a view with an action bar on top, then a row of tabs under the bar. Here's my activity layout.

<?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"
    style="@style/Dashboard">

    <com.ftni.common.ui.ActionBar
        android:id="@+id/actionbar"
        style="@style/ActionBar"/>

    <TabHost android:id="@android:id/tabhost"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">
        <LinearLayout
            android:orientation="vertical"
            android:layout_wi开发者_运维技巧dth="fill_parent"
            android:layout_height="fill_parent"
            android:padding="5dp">
            <TabWidget
                android:id="@android:id/tabs"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content" />
            <FrameLayout
                android:id="@android:id/tabcontent"
                android:layout_width="fill_parent"
                android:layout_height="fill_parent"
                android:padding="5dp" />
        </LinearLayout>
    </TabHost>
</LinearLayout>

Next, we have my activity declared as such

public class DashboardActivity extends TabActivity {

and I am building my tabs like this.

private void buildTabs()
{
    Resources res = getResources(); // Resource object to get Drawables
    TabHost tabHost = (TabHost)findViewById(android.R.id.tabhost);  // The activity TabHost
    TabHost.TabSpec spec;  // Resusable TabSpec for each tab
    Intent intent;  // Reusable Intent for each tab

    // Create an Intent to launch an Activity for the tab (to be reused)
    intent = new Intent().setClass(this, StatementsActivity.class);

    // Initialize a TabSpec for each tab and add it to the TabHost
    spec = tabHost.newTabSpec("statements").setIndicator("Statements",
                      res.getDrawable(R.drawable.ic_tab_active))
                  .setContent(intent);
    tabHost.addTab(spec);

    // Do the same for the other tabs
    intent = new Intent().setClass(this, PaymentsActivity.class);
    spec = tabHost.newTabSpec("payments").setIndicator("Payments",
                      res.getDrawable(R.drawable.ic_tab_active))
                  .setContent(intent);
    tabHost.addTab(spec);

    tabHost.setCurrentTab(0);
}

when I tried using getTabHost(); it was always returning a null. So, I switched to TabHost tabHost = (TabHost)findViewById(android.R.id.tabhost); which does not return a null tabhost, but tabHost.addTab(spec); still causes a null pointer exception.

And here is the stacktrace

04-26 19:50:12.494: ERROR/AndroidRuntime(7367): FATAL EXCEPTION: main
04-26 19:50:12.494: ERROR/AndroidRuntime(7367): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ftni.consumer/com.ftni.consumer.ui.DashboardActivity}: java.lang.NullPointerException
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1622)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1638)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:928)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.os.Looper.loop(Looper.java:123)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.app.ActivityThread.main(ActivityThread.java:3647)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at java.lang.reflect.Method.invokeNative(Native Method)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at java.lang.reflect.Method.invoke(Method.java:507)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at dalvik.system.NativeStart.main(Native Method)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367): Caused by: java.lang.NullPointerException
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.widget.TabHost.addTab(TabHost.java:212)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at com.ftni.consumer.ui.DashboardActivity.buildTabs(DashboardActivity.java:75)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at com.ftni.consumer.ui.DashboardActivity.onCreate(DashboardActivity.java:29)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1586)
04-26 19:50:12.494: ERROR/AndroidRuntime(7367):     ... 11 more

Line 75 is the first tabHost.addTab(spec);

Also, all my activities are declared in my manifest.

<activity android:name=".ui.DashboardActivity"></activity>
<activity android:name=".ui.StatementsActivity"></activity>
<activity android:name=".ui.PaymentsActivity"></activity>

EDIT:

Just to prove it isn't an issue, I removed the actionbar, put the layout to exactly what is in the tutorial, and I still get a null returned from getTabHost();

EDIT 2: full class code for clarity

public class DashboardActivity extends TabActivity {
    private ProfileModel profile;

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

        profile = Controller.getProfile();

        setContentView(R.layout.dashboard);

        buildTabs();

        new LoadDashboardTask().execute();
    }

    @Override
    public void onContentChanged()
    {
        ActionBar actionBar = (ActionBar)findViewById(R.id.actionbar);
        if (actionBar != null)
        {
            actionBar.setOnTitleClickListener(new OnClickListener() {
                public void onClick(View v) {
                    //do nothing for now.  User is already "home"
                }
            });

            if(profile.Accounts.length == 1)
                actionBar.setTitle(profile.Accounts[0].Name);
            else
                actionBar.setTitle(profile.Name);

        }
    }

    private void buildTabs()
    {
        Resources res = getResources(); // Resource object to get Drawables
        TabHost tabHost = getTabHost();// The activity TabHost

        if(tabHost != null)
        {
            // Initialize a TabSpec for each tab and add it to the TabHost
            TabSpec statementSpec = tabHost.newTabSpec("statements").setIndicator("Statements",
                              res.getDrawable(R.drawable.ic_tabs_statements))
                          .setContent(new Intent().setClass(DashboardActivity.this, StatementsActivity.class));
            tabHost.addTab(statementSpec);

            TabSpec paymentSpec = tabHost.newTabSpec("payments").setIndicator("Payments",
                              res.getDrawable(R.drawable.ic_tabs_payments))
                          .setContent(new Intent().setClass(DashboardActivity.this, PaymentsActivity.class));
            tabHost.addTab(paymentSpec);

            tabHost.setCurrentTab(0);
        }
    }

    private class LoadDashboardTask extends AsyncTask<Void, Void, Void> {
        @Override
        protected void onPreExecute()
        {
            ActionBar actionBar = (ActionBar)findViewById(R.id.actionbar);
            actionBar.setProgressBarVisibility(View.VISIBLE);
        }

        @Override
        protected Void doInBackground(Void... params) 
        {
            return null;
        }

        @Override
        protected void onPostExecute(Void result)
        {
            ActionBar actionBar = (ActionBar)findViewById(R.id.actionbar);
            actionBar.setProgressBarVisibility(View.GONE);
        }
    }
}

The documentation states that you should "Call setup() before adding tabs if loading TabHost using findViewById().", which is what you're doing. See here . However, since you're using a TabActivity, why are you not calling getTabHost() instead of getting the view manually?