1

当我按照本教程创建单独的项目以在 Android 中创建带有操作栏的选项卡布局时，它工作正常。

但是，当我尝试通过单击按钮从主要活动加载选项卡式活动时，应用程序会崩溃。我在 Main 活动的 Tabbed 活动中调用 onCreate，如下所示：

Button ListBtn = (Button) findViewById(R.id.main_btn);
ListBtn.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        startActivity(new Intent(Main.this, Tabbed.class));
    }
});

日志猫

05-02 16:43:39.879: D/gralloc_goldfish(4337): Emulator without GPU emulation detected.
05-02 16:43:39.909: I/dalvikvm(4337): threadid=3: reacting to signal 3
05-02 16:43:39.929: I/dalvikvm(4337): Wrote stack traces to '/data/anr/traces.txt'
05-02 16:43:42.309: D/AndroidRuntime(4337): Shutting down VM
05-02 16:43:42.309: W/dalvikvm(4337): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
05-02 16:43:42.339: E/AndroidRuntime(4337): FATAL EXCEPTION: main
05-02 16:43:42.339: E/AndroidRuntime(4337): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.T/com.
AppName.Tabbed}: 
java.lang.NullPointerException
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.os.Handler.dispatchMessage(Handler.java:99)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.os.Looper.loop(Looper.java:137)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.app.ActivityThread.main(ActivityThread.java:4424)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at java.lang.reflect.Method.invokeNative(Native Method)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at java.lang.reflect.Method.invoke(Method.java:511)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at dalvik.system.NativeStart.main(Native Method)
05-02 16:43:42.339: E/AndroidRuntime(4337): Caused by: java.lang.NullPointerException
05-02 16:43:42.339: E/AndroidRuntime(4337):     at packageName.Tabbed.onCreate(Tabbed.java:17)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.app.Activity.performCreate(Activity.java:4465)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
05-02 16:43:42.339: E/AndroidRuntime(4337):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
05-02 16:43:42.339: E/AndroidRuntime(4337):     ... 11 more
05-02 16:43:42.979: I/dalvikvm(4337): threadid=3: reacting to signal 3
05-02 16:43:43.009: I/dalvikvm(4337): Wrote stack traces to '/data/anr/traces.txt'
05-02 16:43:43.319: I/dalvikvm(4337): threadid=3: reacting to signal 3
05-02 16:43:43.349: I/dalvikvm(4337): Wrote stack traces to '/data/anr/traces.txt'

Oncreate 方法

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

        ActionBar actionBar = getActionBar();

        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        String label1 = getResources().getString(R.string.label1);
        Tab tab = actionBar.newTab();
        tab.setText(label1);
        TabListener<Tab1Fragment> tl = new TabListener<Tab1Fragment>(this,
                label1, Tab1Fragment.class);
        tab.setTabListener(tl);
        actionBar.addTab(tab);

        String label2 = getResources().getString(R.string.label2);
        tab = actionBar.newTab();
        tab.setText(label2);
        TabListener<Tab2Fragment> tl2 = new TabListener<Tab2Fragment>(this,
                label2, Tab2Fragment.class);
        tab.setTabListener(tl2);
        actionBar.addTab(tab);

    }
4

1 回答 1

1

似乎getActionBar()返回null。尝试编辑您的 AndroidManifest.xml，使其具有<uses-sdk android:minSdkVersion="11" />. 除非您使用ActionBarSherlock，否则操作栏将无法在较旧的 SDK 上运行。

在调用之前添加以下行getActionBar()：

getWindow().requestFeature(Window.FEATURE_ACTION_BAR);

于 2013-05-02T13:56:22.747 回答