如何保存为列表视图片段的状态 [英] How to save state of Fragment having listview

问题描述

这是一种情况。我想从片段A-导航> B->℃。

Here is a situation. I want to navigate from Fragment A-> B-> C.

输入B片段有列表视图。在项目点击我打开详细视图C语言程序段。 Ofcourse我用替换法，并添加addtoBackStack（空），而选自B transactiong到C，这样就回到preSS它返回到B。

In B Fragment there is listview. On item click I open the detail view C Fragment. Ofcourse I used replace method and added addtoBackStack(null) while transactiong from B to C so that on Back press it returned to B.

一切顺利。但是，当我返回到B从C，该视图被刷新，因此Web服务被再次调用。我不想这样做。我想保留对B片段状态列表视图。

All goes well. But when I return to B from C, the view is being refreshed and hence the webservice is being called again. I don't want to do this. I want to retain the B Fragment state with listview.

我得到了保留实例的一些职位，但它并没有帮助那么多。

I got some post of Retain Instance, but it didn't help that much.

任何帮助是非常AP preciated。

Any help is much appreciated.

感谢。

推荐答案

由于这里解释你可以使用的onSaveInstanceState（），以将数据保存在捆绑和检索的onRestoreInstanceState（）方法的数据。

As explained here you can use onSaveInstanceState() to save data in the Bundle and retrieve that data in the onRestoreInstanceState() method.

通常setRetainState（真）被提及的方式保持在片段中的UI状态，但对于你，因为你正在使用的backstack这是行不通的。

Often setRetainState(true) is mentioned as way to keep the ui state in fragment, but it does not work for you because you are using the backstack.

因此​​，对于你的好方法可能是保存的onSaveInstanceState（中的scrollPosition），并恢复它在onRestoreInstanceState（）是这样的：

So a good way for you could be to save the scrollposition in onSaveInstanceState() and restore it in onRestoreInstanceState() like this:

public class MyListFragment extends ListFragment {

@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);

     int index = this.getListView().getFirstVisiblePosition();
     View v = this.getListView().getChildAt(0);
     int top = (v == null) ? 0 : v.getTop();

     outState.putInt("index", index);
     outState.putInt("top", top);
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    [...]
    if (savedInstanceState != null) {
        // Restore last state for checked position.
        index = savedInstanceState.getInt("index", -1);
        top = savedInstanceState.getInt("top", 0);
    }
    if(index!=-1){
     this.getListView().setSelectionFromTop(index, top);
  }

}

更进一步，你可以在这里找到更详细的similiar例如。

Further more you can find a more detailed similiar example here.

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