动态更新ViewPager ?

我无法更新ViewPager中的内容。

FragmentPagerAdapter类中instantiateItem()和getItem()方法的正确用法是什么?

我只使用getItem()来实例化并返回我的片段:

@Override
public Fragment getItem(int position) {
    return new MyFragment(context, paramters);
}

这很有效。但我不能改变内容。

所以我发现这个:ViewPager PagerAdapter没有更新视图

我的方法是对instantiateItem()方法中的任何实例化视图使用setTag()方法

现在我想实现instantiateItem()来实现这一点。但我不知道我必须返回什么(类型是对象)和什么与getItem(int位置)的关系?

我读了参考资料:

public abstract Fragment getItem (int position) Return the Fragment associated with a specified position. public Object instantiateItem (ViewGroup container, int position) Create the page for the given position. The adapter is responsible for adding the view to the container given here, although it only must ensure this is done by the time it returns from finishUpdate(ViewGroup). Parameters container The containing View in which the page will be shown. position The page position to be instantiated. Returns Returns an Object representing the new page. This does not need to be a View, but can be some other container of the page.

但我还是不明白

这是我的代码。我用的是v4支持包。

查看页面测试

public class ViewPagerTest extends FragmentActivity {
    private ViewPager pager;
    private MyFragmentAdapter adapter; 

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.pager1);

        pager = (ViewPager)findViewById(R.id.slider);

        String[] data = {"page1", "page2", "page3", "page4", "page5", "page6"};

        adapter = new MyFragmentAdapter(getSupportFragmentManager(), 6, this, data);
        pager.setAdapter(adapter);

        ((Button)findViewById(R.id.button)).setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                reload();
            }
        });
    }

    private void reload() {
        String[] data = {"changed1", "changed2", "changed3", "changed4", "changed5", "changed6"};
        //adapter = new MyFragmentAdapter(getSupportFragmentManager(), 6, this, data);
        adapter.setData(data);
        adapter.notifyDataSetChanged();
        pager.invalidate();

        //pager.setCurrentItem(0);
    }
}

我的片段适配器

class MyFragmentAdapter extends FragmentPagerAdapter {
    private int slideCount;
    private Context context;
    private String[] data;

    public MyFragmentAdapter(FragmentManager fm, int slideCount, Context context, String[] data) {
        super(fm);
        this.slideCount = slideCount;
        this.context = context;
        this.data = data;
    }

    @Override
    public Fragment getItem(int position) {
        return new MyFragment(data[position], context);
    }

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

    public void setData(String[] data) {
        this.data = data;
    }

    @Override
    public int getItemPosition(Object object) {
        return POSITION_NONE;
    }
}

我的片段

public final class MyFragment extends Fragment {
    private String text;

    public MyFragment(String text, Context context) {
        this.text = text;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.slide, null);
        ((TextView)view.findViewById(R.id.text)).setText(text);

        return view;
    }
}

这里还有一个人也有类似的问题，没有答案 http://www.mail-archive.com/android-developers@googlegroups.com/msg200477.html

当前回答

我使用EventBus库更新片段内容在ViewPager。逻辑很简单，就像EventBus文档一样怎么做。不需要控制FragmentPagerAdapter实例。代码在这里:

1:定义事件

定义需要更新的消息。

public class UpdateCountEvent {
    public final int count;

    public UpdateCountEvent(int count) {
        this.count = count;
    }
}

2.准备用户

在需要更新的片段中编写以下代码。

@Override
public void onStart() {
    super.onStart();
    EventBus.getDefault().register(this);
}

@Override
public void onStop() {
    EventBus.getDefault().unregister(this);  
    super.onStop();
}

public void onEvent(UpdateCountEvent event) {//get update message
    Toast.makeText(getActivity(), event.count, Toast.LENGTH_SHORT).show();
}

3.发布事件

在需要更新参数的其他活动或其他片段中编写以下代码

//input update message
EventBus.getDefault().post(new UpdateCountEvent(count));

2015-02-13 09:38:40

其他回答

由于某种原因，没有一个答案对我有用，所以我不得不重写restoreState方法，而不调用我的fragmentStatePagerAdapter中的super。代码:

private class MyAdapter extends FragmentStatePagerAdapter {

    // [Rest of implementation]

    @Override
    public void restoreState(Parcelable state, ClassLoader loader) {}

}

2015-08-18 15:41:47

我尝试了很多不同的方法，但没有一个能真正解决我的问题。下面是我如何用你们提供的混合解决方案来解决这个问题。谢谢每一个人。

class PagerAdapter extends FragmentPagerAdapter {

    public boolean flag_refresh=false;

    public PagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int page) {
        FragmentsMain f;
        f=new FragmentsMain();
        f.page=page;
        return f;
    }

    @Override
    public int getCount() {
        return 4;
    }

    @Override
    public int getItemPosition(Object item) {
        int page= ((FragmentsMain)item).page;

        if (page == 0 && flag_refresh) {
            flag_refresh=false;
            return POSITION_NONE;
        } else {
            return super.getItemPosition(item);
        }
    }

    @Override
    public void destroyItem(View container, int position, Object object) {

        ((ViewPager) container).removeView((View) object);
    }
}

我只想在onResume()后刷新页面0。

 adapter=new PagerAdapter(getSupportFragmentManager());
 pager.setAdapter(adapter);

@Override
protected void onResume() {
    super.onResume();

    if (adapter!=null) {
        adapter.flag_refresh=true;
        adapter.notifyDataSetChanged();
    }
}

在我的FragmentsMain中，有一个公共整数“page”，它可以告诉我这是否是我想要刷新的页面。

public class FragmentsMain extends Fragment {

private Cursor cursor;
private static Context context;
public int page=-1;

2015-06-17 01:38:18

I have lived same problem and I have searched too much times. Any answer given in stackoverflow or via google was not solution for my problem. My problem was easy. I have a list, I show this list with viewpager. When I add a new element to head of the list and I refresh the viewpager nothings changed. My final solution was very easy anybody can use. When a new element added to list and want to refresh the list. Firstly set viewpager adapter to null then recreate the adapter and set i to it to viewpager.

myVPager.setAdapter(null);
myFragmentAdapter = new MyFragmentAdapter(getSupportFragmentManager(),newList);
myVPager.setAdapter(myFragmentAdapter);

确保您的适配器必须扩展FragmentStatePagerAdapter

2017-08-07 09:10:10

我知道我要迟到了。我已经通过调用TabLayout#setupWithViewPager(myViewPager)解决了这个问题;在FragmentPagerAdapter#notifyDataSetChanged()之后;

2015-11-12 03:35:41