Android:getSupportActionBar() 在 ActionBarSherlock 库中总是返回 null

Question

我正在尝试使用 ActionBarSherlock库为我的 Android 应用程序中的选项卡提供向后兼容的 ActionBar 支持，因此我下载了最新版本，构建了演示并运行了它。

如果您转到操作栏，然后选择标签导航，它每次都会崩溃。这是堆栈跟踪:

09-03 02:34:47.940: ERROR/AndroidRuntime(3078): FATAL EXCEPTION: main  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.actionbarsherlock.sample.demos/com.actionbarsherlock.sample.demos.app.ActionBarTabNavigation}: java.lang.NullPointerException  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1748)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1764)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.access$1500(ActivityThread.java:122)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1002)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.os.Handler.dispatchMessage(Handler.java:99)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.os.Looper.loop(Looper.java:132)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.main(ActivityThread.java:4025)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at java.lang.reflect.Method.invokeNative(Native Method)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at java.lang.reflect.Method.invoke(Method.java:491)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at dalvik.system.NativeStart.main(Native Method)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): Caused by: java.lang.NullPointerException  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at com.actionbarsherlock.sample.demos.app.ActionBarTabNavigation.onCreate(ActionBarTabNavigation.java:19)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1048)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1712)  
09-03 02:34:47.940: ERROR/AndroidRuntime(3078): ... 11 more  

在解决此问题之前，我无法继续使用我的应用程序。我写了一堆代码，在我的应用程序中设置了操作栏，并尝试运行它，但由于 getSupportActionBar() 上的 null 返回值，它崩溃并出现 NPE。打电话。

相关代码其实在库的demo中:

public class ActionBarTabNavigation extends FragmentActivity implements ActionBar.TabListener {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        getSupportFragmentManager()
            .beginTransaction()
            .add(android.R.id.content, FragmentStackSupport.CountingFragment.newInstance(0))
            .commit();

        getSupportActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        for (int i = 0; i < 3; i++) {
            ActionBar.Tab tab = getSupportActionBar().newTab();
            tab.setText("Tab " + i);
            tab.setTabListener(this);
            getSupportActionBar().addTab(tab);
        }
    }

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

    @Override
    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        getSupportFragmentManager()
            .beginTransaction()
            .replace(android.R.id.content, FragmentStackSupport.CountingFragment.newInstance(tab.getPosition()))
            .commit();
    }

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

Answer 1

您应该将 Sherlock 主题添加到您的应用程序中

<application android:icon="@drawable/icon" android:label="@string/app_name"
        android:debuggable="false" android:theme="@style/Theme.Sherlock">