android - ViewPager+Fragment，某个Fragment里面的一条数据发生变化，如何局部刷新这条数据

Question

ViewPager+Fragment，某个Fragment里面的一条数据发生变化，如何局部刷新这条数据

Answer 1

When the item of ViewPager is Fragment, FragmentPagerAdapter is generally used as the Adapter, and this class will be used when adding Fragment To add a tag, see the instantiateItem() method in the source code of FragmentPagerAdapterViewPager的item是Fragment时一般使用FragmentPagerAdapter作为Adapter, 而这个类在添加Fragment的时候会添加tag, 看FragmentPagerAdapter的源码中的instantiateItem()方法

@Override
public Object instantiateItem(ViewGroup container, int position) {
    // 省略
    if (fragment != null) {
        // 省略
    } else {
        // 省略部分代码
        // 下面这句就是添加Fragment的语句, 第三个参数就是指定Fragment的tag, 
        // 你可以利用这个tag获取到对应的Fragment实例, 有了实例就可以随意更新Fragment的视图了
        mCurTransaction.add(container.getId(), fragment,
                makeFragmentName(container.getId(), itemId));
    }
    // 省略
    return fragment;
}

这个tag是通过一个makeFragmentName()的私有方法获取, 不过只要把这个方法直接复制出来就可以了, 这个方法的参数viewId应该是ViewPager的id, itemId是adapter的getItemId() rrreee
This tag is obtained through a private method of makeFragmentName(), but you only need to copy this method directly. The parameter viewId of this method should be the id of ViewPager , itemId is the getItemId() method of the adapter, so you can assemble the tag yourself and get the Fragment.

That’s it.🎜

Answer 2

If you use RecyclerView, you can use Eventbus like this

mAdapter.getItem(event.position).setCommentCount(mAdapter.getItem(event.position).getCommentCount()+1);
mAdapter.notifyItemChanged(event.position);

Answer 3

I have also been thinking about this problem for a while, and after searching for it, I couldn’t find a good solution. The pagerfragmentadapter doesn’t seem to provide an API for getting the corresponding fragment.
I made a list of weak references in the index and added it to the adapter when it initialized the fragment, and then rewritten the adapter's onDestroyItem (probably called this? I can't remember) to remove the corresponding entry in the list here.
Once you get the fragment instance, you can operate it as you like.

Answer 4

1. When the Fragment is in the foreground, you can use LocalBroadcastManager / EventBus / otto / Rx to subscribe to an event (message)

2. When the Fragment switches to the background, cancel the subscription. When the Fragment switches to the foreground again, refresh the page data and resubscribe