android - "java.lang.IllegalStateException: Can' 使用 ViewPager#setCurrentItem() 时 t 更改 fragment 标签”错误

Question

我正在尝试使用 ViewPager + FragmentPagerAdapter 切换 fragment 。 我目前使用的是最新的 Android 支持包 v4

我的应用程序中有 5 个选项卡。当我选择第 4 个选项卡时，应用程序突然退出并显示“无法更改 fragment 标签 ~~”。

我没有尝试替换包含在布局 xml 文件中的 Fragment，所以我无法找出原因。

错误发生的代码如下:

@Override
public void onTabSelected(ActionBar.Tab tab,
        FragmentTransaction fragmentTransaction) {
    // When the given tab is selected, switch to the corresponding page in
    // the ViewPager.
    mViewPager.setCurrentItem(tab.getPosition());
}

下面是我正在使用的 FragmentPagerAdapter 的 fragment

@Override
    public Fragment getItem(int i) {
        if (fragment_list.get(i) == null) {
            fragment_list.add(i, getFragment(i));
        }

        return fragment_list.get(i);
    }

    private Fragment getFragment(int index) {
        switch (index) {
        case TOP:
            return UseCaseListWithOptionFragment.newInstance(
                    URLHelper.USE_CASES_TOP_URL, R.array.comment);
        case FEED:
            int user_id = UserHelper.getCurrentUser(MainActivity.this).id;
            return UseCaseListFragment.newInstance(
                    URLHelper.getMyFeedsURL(user_id), true);
        case RECENT:
            return UseCaseListFragment.newInstance(
                    URLHelper.USE_CASES_RECENT_URL, true);
        case CATEOGORY:
            return UseCaseGroupListFragment.newInstance(
                    URLHelper.USE_CASE_GROUPS_URL, R.array.use_case);
        case MY:
            return UserProfileFragment.newInstance(UserHelper
                    .getCurrentUser(MainActivity.this));
        default:
            throw new IllegalStateException("Tab index out of bound.");
        }
    }

    @Override
    public int getCount() {
        return TAB_COUNT;
    }

下面是我遇到的错误日志:

08-04 17:51:55.983: E/AndroidRuntime(1112): FATAL EXCEPTION: main
08-04 17:51:55.983: E/AndroidRuntime(1112): java.lang.IllegalStateException: Can't change tag of fragment UseCaseGroupListFragment{4055f558 id=0x7f050034 android:switcher:2131034164:3}: was android:switcher:2131034164:3 now android:switcher:2131034164:4
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:356)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:347)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:99)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:692)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.support.v4.view.ViewPager.populate(ViewPager.java:875)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:469)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:441)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:422)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at org.everyuse.android.activity.MainActivity.onTabSelected(MainActivity.java:176)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at com.actionbarsherlock.internal.app.ActionBarImpl.selectTab(ActionBarImpl.java:526)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at com.actionbarsherlock.internal.app.ActionBarImpl$TabImpl.select(ActionBarImpl.java:907)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at com.actionbarsherlock.internal.widget.ScrollingTabContainerView$TabClickListener.onClick(ScrollingTabContainerView.java:503)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.view.View.performClick(View.java:2485)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.view.View$PerformClick.run(View.java:9080)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.os.Handler.handleCallback(Handler.java:587)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.os.Handler.dispatchMessage(Handler.java:92)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.os.Looper.loop(Looper.java:123)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at android.app.ActivityThread.main(ActivityThread.java:3683)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at java.lang.reflect.Method.invokeNative(Native Method)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at java.lang.reflect.Method.invoke(Method.java:507)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
08-04 17:51:55.983: E/AndroidRuntime(1112):     at dalvik.system.NativeStart.main(Native Method)

提前致谢...

Answer 1

我在错误地实现 getCount 方法时遇到了同样的异常。您是否检查过返回的尺寸是否正确？

@Override
public int getCount() {
    return 5;
}