FragmentTabHost - 在第一次查看之前,标签不可寻址

Question

我使用的是多选项卡的FragmentTabHost(构造如图所示这里).但是,我无法使用getFragmentByTag(在这种情况下返回null)随机地查找我的选项卡,除非通过至少单击选项卡一次激活已解决的选项卡.

FragmentTabHost似乎延迟了标签的创建,直到我们确实需要它们(也就是用户点击它并想要查看它).
有没有办法强制主机立即创建它们,以便我可以通过getFragmentByTag安全地访问它们？
或者是否可以"自己创建"标签并将它们添加到TabHost？

Answer 1

有没有办法强制主机立即创建它们,以便我可以通过getFragmentByTag安全地访问它们？

不,因为交易是在执行的onAttachedToWindow().我们来看看源代码:

@Override
protected void onAttachedToWindow() {
    super.onAttachedToWindow();
    String currentTab = getCurrentTabTag();
    // Go through all tabs and make sure their fragments match.
    // the correct state.
    FragmentTransaction ft = null;
    for (int i=0; i<mTabs.size(); i++) {
        TabInfo tab = mTabs.get(i);
        tab.fragment = mFragmentManager.findFragmentByTag(tab.tag);
        if (tab.fragment != null && !tab.fragment.isDetached()) {
            if (tab.tag.equals(currentTab)) {
                // The fragment for this tab is already there and
                // active, and it is what we really want to have
                // as the current tab.  Nothing to do.
                mLastTab = tab;
            } else {
                // This fragment was restored in the active state,
                // but is not the current tab.  Deactivate it.
                if (ft == null) {
                    ft = mFragmentManager.beginTransaction();
                }
                ft.detach(tab.fragment);
            }

        }
    }
    // We are now ready to go.  Make sure we are switched to the
    // correct tab.
    mAttached = true;
    ft = doTabChanged(currentTab, ft);
    if (ft != null) {
        ft.commit();
        mFragmentManager.executePendingTransactions();
    }
}
@Override
protected void  onDetachedFromWindow() {
    super.onDetachedFromWindow();
    mAttached = false;
}

如你所见,mFragmentManager.executePendingTransactions();执行于onAttachedToWindow.

或者是否可以"自己创建"标签并将它们添加到TabHost？

是的,您可以使用tabhost,您可以使用以下方法创建选项卡内容.

public TabHost.TabSpec setContent(int viewId)

public TabHost.TabSpec setContent(Intent intent)

public TabHost.TabSpec setContent(TabHost.TabContentFactory contentFactory)