Question

使用滑动ViewPager我想创建一个文章列表。在移动过程中，我想动态更改操作栏中的标题。标题存储在字符串列表中，每个列表的标题是当前片段的位置。因此，例如，给出此列表：

List<String> leftItems = new List<String> ();
leftItems.Add ("First title");
leftItems.Add ("Second title");
leftItems.Add ("Third title");

我想在观看片段2（索引1）时显示标题

第二个标题

片段中操作栏的标题我更改了此代码：

((ActionBarActivity)Activity).SupportActionBar.Title = this.leftItems[this.position];

变量'position'，它与方法GetItem（）中的适配器一起提供：

public override Android.Support.V4.App.Fragment GetItem(int position) {
            return new ArticlesFragment (this.articles [this.leftItems [position]], 
                this.leftItems, this.position);
        }

public ArticlesFragment(List<Article> articles, List<String> leftItems, int position) : base() {
            this.articles = articles;
            this.leftItems = leftItems;
            this.position = position;
        }

我遇到了什么问题？好吧，操作栏的标题总是一个比它应该更大的索引。因此对于片段1（索引0），标题是

第二个标题

而不是我想要的

第一个标题

但是，在最后一个片段中，标题不会改变，只会保留前一个片段。

有人可以帮助我吗？

@edit

我添加了适配器和片段的全部内容：

ArticlesFragmentAdapter.cs

public class ArticlesFragmentAdapter : FragmentStatePagerAdapter {
    Dictionary<String, List<Article>> articles;
    List<String> leftItems;

    public ArticlesFragmentAdapter(Android.Support.V4.App.FragmentManager fm, 
        Dictionary<String, List<Article>> articles,
        List<String> leftItems) : base(fm) {
        this.articles = articles;
        this.leftItems = leftItems;
    }

    public override int Count {
        get { return this.leftItems.Count; }
    }

    public override Android.Support.V4.App.Fragment GetItem(int position) {
        return new ArticlesFragment (this.articles [this.leftItems [position]], 
            this.leftItems, position);
    }
}

ArticlesFragment.cs

public class ArticlesFragment : Android.Support.V4.App.Fragment {
    List<Article> articles;
    List<String> leftItems;
    ListView articlesListView;
    int position;
    ArticlesAdapter articlesAdapter;

    public ArticlesFragment(List<Article> articles, List<String> leftItems, int position) : base() {
        this.articles = articles;
        this.leftItems = leftItems;
        this.position = position;
    }

    public override View OnCreateView (LayoutInflater inflater, 
        ViewGroup container, Bundle savedInstanceState)
    {
        var view = inflater.Inflate (Resource.Layout.Articles, container, false);

        this.articlesListView = view.FindViewById<ListView> (Resource.Id.articlesListView);
        ((ActionBarActivity)Activity).SupportActionBar.Title = this.leftItems[this.position - 1];

        this.articlesAdapter = new ArticlesAdapter ((ActionBarActivity)this.Activity, this.articles);

        this.articlesListView.Adapter = this.articlesAdapter;

        return view;
    }
}

Answer 1

您可以使用http://developer.android.com/reference/android/support/v4/view/ViewPager.OnPageChangeListener.html#onPageSelected(int)在页面更改时更新活动中的标题

获取ViewPager片段中的当前索引

1 个答案: