片段,保存onSaveInstanceState上的大型数据列表(如何防止TransactionTooLargeException)

Question

在我的应用程序中,我在ViewPager中有Fragment.片段包含RecyclerView,其中包含基于用户选择从web api获取的数据列表.

在我的片段中,onSaveInstanceState我将列表数据保存到Bunde,以保持配置更改等数据.

public void onSaveInstanceState(Bundle savedState) {
    super.onSaveInstanceState(savedState);
    savedState.putParcelableArrayList(LIST_STORAGE_KEY, new ArrayList<>(mItemAdapter.getModels()));
}

现在我已经开始看到TransactionTooLargeException我的应用程序错误报告.

在某些情况下,似乎我放入Bundle的列表太大(因为它是相当复杂的对象的集合).

我该如何处理这个案子？如何存储(和恢复)我的Fragment状态.

setRetainInstance(true)在ViewPager中的Fragments 上使用是否可以？

Answer 1

为了保留大块数据,谷歌建议使用保留实例的Fragment.想法是创建没有视图的空片段和所有必需的字段,否则这些字段将被保存在Bundle中.添加setRetainInstance(true) ; 到Fragment的onCreate方法.而不是将数据保存在Activity的onDestroy上的Fragment中并将它们加载到onCreate上.以下是活动的示例:

public class MyActivity extends Activity {

private DataFragment dataFragment;

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

    // find the retained fragment on activity restarts
    FragmentManager fm = getFragmentManager();
    dataFragment = (DataFragment) fm.findFragmentByTag("data");

    // create the fragment and data the first time
    if (dataFragment == null) {
        // add the fragment
        dataFragment = new DataFragment();
        fm.beginTransaction().add(dataFragment, "data").commit();
        // load the data from the web
        dataFragment.setData(loadMyData());
    }

    // the data is available in dataFragment.getData()
    ...
}

@Override
public void onDestroy() {
    super.onDestroy();
    // store the data in the fragment
    dataFragment.setData(collectMyLoadedData());
}
}

片段的例子:

public class DataFragment extends Fragment {

// data object we want to retain
private MyDataObject data;

// this method is only called once for this fragment
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // retain this fragment
    setRetainInstance(true);
}

public void setData(MyDataObject data) {
    this.data = data;
}

public MyDataObject getData() {
    return data;
}
}