在哪里还原ViewPager内部的片段状态 [英] Where to restore fragment state that is inside ViewPager
问题描述
短版:
我有一个带有ViewPager的活动. ViewPager内部有三个片段.我通过实现Parcelable将数据存储在片段内部,并将其存储在包中.
I have an Activity that has a ViewPager. The ViewPager has three fragments inside it. I am storing the data inside the fragments by implementing Parcelable and storing it inside the bundle.
现在的问题是我应该在哪里恢复数据.我很困惑,因为(据我所知)每次旋转屏幕时ViewPager都会创建片段的新实例. (创建一个新的活动->新的ViewPager->新的片段).如果我错了,请纠正我.
Now the question is where do I restore the data. I am confused because (from what I know) the ViewPager is creating a new instance of the fragment each time I rotate the screen. (A new activity is created -> new ViewPager -> new Fragment). Please do correct me if I am wrong.
长版:
MainActivity中的我的ViewPager
My ViewPager inside MainActivity
ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
viewPager.setAdapter(new ForecastFragmentPageAdapter(getSupportFragmentManager(),
ForecastActivity.this));
viewPager.setOffscreenPageLimit(2);
我的FragmentPagerAdapter
My FragmentPagerAdapter
@Override
public Fragment getItem(int position) {
if (position == 0) {
return new NowForecastFragment();
} else if (position == 1) {
return new HourlyForecastFragment();
} else {
return new DailyForecastFragment();
}
}
在我的一个片段中保存状态
Saving state in one of my fragments
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// save data source
if (nowDataList != null) {
outState.putParcelableArrayList("savedNowDataList", nowDataList);
}
}
提前谢谢!
更新:
根据发布到类似问题的其他解决方案,我还在片段的onCreateView中添加了 setRetainInstance(true); .这就是我保存和恢复状态的方式:
According to other solutions posted to similar problems, I also added setRetainInstance(true); in the onCreateView of my fragment. And this is how I am saving and restoring state:
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// save data source
if (nowDataList != null) {
Log.v("---------------->","saved!");
outState.putParcelableArrayList("savedNowDataList", nowDataList);
}
}
并在onCreateView中还原
and restoring in onCreateView
if(savedInstanceState!=null) {
Log.v("---------------->","restored!");
nowDataList = savedInstanceState.getParcelableArrayList("savedNowDataList");
nowForecastAdapter.notifyDataSetChanged();
}
我看到两个日志都被触发了.为什么不能还原数据?
I see both the logs being triggered. Why is the data not being restored?
推荐答案
所以我找到了问题所在.只需在此处发布答案即可.因此,当旋转屏幕时,尽管我正在更新数据源,但尚未将列表视图与更新的适配器重新连接.所以我就这样做了,而且行得通.
So I found where the problem was. Just posting the answer here. So when the screen is rotated, although I am updating the data source, I have not reattached the listview with the updated adapter. So I just did that and it works.
if(savedInstanceState!=null) {
Log.v("---------------->","restored!");
nowDataList = savedInstanceState.getParcelableArrayList("savedNowDataList");
nowForecastAdapter = new NowForecastAdapter(this, nowDataList);
lvNowList.setAdapter(nowForecastAdapter);
nowForecastAdapter.notifyDataSetChanged();
}
只要有人犯了同样的错误并且想知道出了什么问题,就发布答案.
Just posted the answer if anyone made the same mistake and was wondering what went wrong.
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