操作栏.selectTab（）和.setSelectedNavigationItem（）不工作 [英] Action Bar .selectTab() and .setSelectedNavigationItem() not working

问题描述

我有多个选项卡，每个链接到一个片段的动作条。我的问题是，当我使用任何 bar.selectTab（标签）或 bar.setSelectedNavigationItem（INT），这是行不通的。具体而言，当标签得到减小到微调的动作条就会出现此问题。

I have an ActionBar with multiple tabs, each linked to a fragment. The problem I have is that when I use either bar.selectTab(Tab) or bar.setSelectedNavigationItem(int), it doesn't work. Specifically, this problem occurs when the tabs get reduced down to a Spinner in the ActionBar.

推荐答案

有一个已知的bug 的动作条，特别是与上面提到的方法，特别在动作条的标签都降到了微调

There is a known bug with the ActionBar, specifically with the methods mentioned above and specifically when the ActionBar's tabs are reduced to a Spinner.

下面是我的解决方法。它使用反射来钻入的ActionBar如果翼片已经降低到一个微调。在你的Activity类，创建一个方法，像这样：

Here's my workaround. It uses reflection to drill into the ActionBar if the tabs have been reduced to a Spinner. In your Activity class, create a method like so:

/**
 * A documented and yet to be fixed bug exists in Android whereby
 * if you attempt to set the selected tab of an action bar when the
 * bar's tabs have been collapsed into a Spinner due to screen
 * real-estate, the spinner item representing the tab may not get
 * selected. This bug fix uses reflection to drill into the ActionBar
 * and manually select the correct Spinner item 
 */
private void select_tab(ActionBar b, int pos) {
    try {
        //do the normal tab selection in case all tabs are visible
        b.setSelectedNavigationItem(pos);

        //now use reflection to select the correct Spinner if
        // the bar's tabs have been reduced to a Spinner

        View action_bar_view = findViewById(getResources().getIdentifier("action_bar", "id", "android"));
        Class<?> action_bar_class = action_bar_view.getClass();
        Field tab_scroll_view_prop = action_bar_class.getDeclaredField("mTabScrollView");
        tab_scroll_view_prop.setAccessible(true);
        //get the value of mTabScrollView in our action bar
        Object tab_scroll_view = tab_scroll_view_prop.get(action_bar_view);
        if (tab_scroll_view == null) return;
        Field spinner_prop = tab_scroll_view.getClass().getDeclaredField("mTabSpinner");
        spinner_prop.setAccessible(true);
        //get the value of mTabSpinner in our scroll view
        Object tab_spinner = spinner_prop.get(tab_scroll_view);
        if (tab_spinner == null) return;
        Method set_selection_method = tab_spinner.getClass().getSuperclass().getDeclaredMethod("setSelection", Integer.TYPE, Boolean.TYPE);
        set_selection_method.invoke(tab_spinner, pos, true);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

本示例用法可能是：

Example usage of this might be:

private void delete_fragment_and_tab(String fragment_tag) {

    //remove the fragment
    FragmentTransaction ft = getFragmentManager().beginTransaction();
    ft.remove(getFragmentManager().findFragmentByTag(fragment_tag));

    //now remove the tab from the ActionBar
    //and select the previous tab
    ActionBar b = getActionBar();
    Tab tab = b.getSelectedTab();
    bar.removeTab(tab);
    select_tab(bar, bar.getNavigationItemCount() -1); 
}

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