屏幕旋转后2片段，保存值丢失

时间：2013-11-17 18:54:35

标签： android android-fragments rotation savestate

基于来自示例API的FragmentLayout示例，我遇到了片段问题 如下所述：http://developer.android.com/guide/components/fragments.html#Example

除非我想在Bundle of DetailsFragment中保存/恢复值，否则一切正常 处理屏幕旋转。

为了说明这一点，我修改了FragmentLayout示例的DetailsFragment 附加一个随机值 （在TextView底部模拟对片段的操作） 并且此值保存在onSaveInstanceState中并在onCreateView中检索。

现在问题是：

  1. 以纵向模式开始并选择列表中的项目 DetailsFragment显示为 新的意图在底部有一个随机值。
  2. 以横向模式旋转设备 该列表位于左侧，包含所选项目 突出显示（我移动了getListView（）的调用.setItemChecked（mCurCheckPosition，true） 在TitlesFragment的onStart方法中因为它不起作用 当在showDetail方法中制作时）在右侧， 显示DetailsFragment 文本对应于所选项目但值 不是那个得救的人 但是新的 如log（见下文）所示，在旋转之后创建DetailsFragment并且随机值为 正确恢复但TitleFragment创建了另一个实例，因为 findFragmentById返回null，DetailsFragment创建一个新的随机值 所以有 两个片段，一个可见，具有错误的随机值，另一个在某处，不可见， 我需要的价值！

    如何解决此问题以显示正确的片段，当然不创建新片段？

    如果我们继续旋转设备：
  3. 以纵向模式向后旋转，然后再次选择与第1点相同的项目
  4. 以横向模式再次旋转 现在findFragmentById返回一个片段并作为 getShownIndex获取与索引相同的值，没有DetailsFragment的新实例，显示第2点显示的randon值。

    5. 这是带注释的日志

    ********************************************************
* 1. Start in portrait mode - select item 6 (Othello)  *
* new DetailsFragment created with new rand value 4769 *
* this value is saved in onSaveInstanceState           *
********************************************************

D/TitlesFragment(21894): Entering onCreateView
D/TitlesFragment(21894): Entering onActivityCreated
D/TitlesFragment(21894): onActivityCreated - portrait mode
D/TitlesFragment(21894): Entering onStart
D/TitlesFragment(21894): Entering showDetails - index: 6
D/TitlesFragment(21894): showDetails - Single Pane - start new activity
D/TitlesFragment(21894): showDetails - position: 6 - title: Othello

D/DetailsActivity(21894): Entering onCreate
D/DetailsActivity(21894): onCreate - portrait mode
D/DetailsActivity(21894): onCreate - new DetailsFragment: DetailsFragment{41980540}

D/DetailsFragment(21894): Entering onCreateView - this: DetailsFragment{41980540 #0 id=0x1020002}
D/DetailsFragment(21894): onCreateView - new mRandValue: 4769

D/TitlesFragment(21894): Entering onSaveInstanceState - save position: 6

D/DetailsFragment(21894): Entering onSaveInstanceState - this: DetailsFragment{41980540 #0 id=0x1020002}
D/DetailsFragment(21894): onSaveInstanceState - save value: 4769


*********************************************************
* 2. Rotate in landscape mode                           *
* DetailsFragment created with rand value 4769 restored *
* Another DetailsFragment created for entry 6 (Othello) *
* with new rand value 5572                              *
*********************************************************

D/DetailsActivity(21894): Entering onCreate
D/DetailsActivity(21894): onCreate - landscape mode - finish

D/DetailsFragment(21894): Entering onCreateView - this: DetailsFragment{4199d458 #0 id=0x1020002}
D/DetailsFragment(21894): onCreateView - restored randValue: 4769

D/FragmentLayout (Activity)(21894): Entering onCreate

D/TitlesFragment(21894): Entering onCreateView
D/TitlesFragment(21894): Entering onActivityCreated
D/TitlesFragment(21894): onActivityCreated - landscape mode
D/TitlesFragment(21894): onActivityCreated - dual pane, calling show details - position: 6
D/TitlesFragment(21894): Entering showDetails - index: 6
D/TitlesFragment(21894): showDetails - DetailsFragment found by id: null
D/TitlesFragment(21894): showDetails - calling DetailsFragment newInstance for index: 6

D/DetailsFragment(21894): Entering newInstance - index: 6
D/DetailsFragment(21894): newInstance: DetailsFragment{419e16a8}
D/DetailsFragment(21894): Entering onCreateView - this: DetailsFragment{419e16a8 #1 id=0x7f060004}
D/DetailsFragment(21894): onCreateView - new mRandValue: 5572

D/TitlesFragment(21894): Entering onStart
D/TitlesFragment(21894): Entering onSaveInstanceState - save position: 6

D/DetailsFragment(21894): Entering onSaveInstanceState - this: DetailsFragment{419e16a8 #1 id=0x7f060004}
D/DetailsFragment(21894): onSaveInstanceState - save value: 5572


*********************************************************
* 3. Rotate back in portrait mode                       *
* DetailsFragment created with rand value 5572 restored *
* Select again item 6 (Othello)                         *
* New DetailsFragment created with new rand value 5685  *
* Both DetailsFragment save each its rand value         *
*********************************************************

D/FragmentLayout (Activity)(21894): Entering onCreate

D/TitlesFragment(21894): Entering onCreateView
D/TitlesFragment(21894): Entering onActivityCreated
D/TitlesFragment(21894): onActivityCreated - portrait mode

D/DetailsFragment(21894): Entering onCreateView - this: DetailsFragment{419e6248 #1 id=0x7f060004}
D/DetailsFragment(21894): onCreateView - restored randValue: 5572

D/TitlesFragment(21894): Entering onStart
D/TitlesFragment(21894): Entering showDetails - index: 6
D/TitlesFragment(21894): showDetails - Single Pane - start new activity
D/TitlesFragment(21894): showDetails - position: 6 - title: Othello

D/DetailsActivity(21894): Entering onCreate
D/DetailsActivity(21894): onCreate - portrait mode
D/DetailsActivity(21894): onCreate - new DetailsFragment: DetailsFragment{419bcf98}

D/DetailsFragment(21894): Entering onCreateView - this: DetailsFragment{419bcf98 #0 id=0x1020002}
D/DetailsFragment(21894): onCreateView - new mRandValue: 5685

D/TitlesFragment(21894): Entering onSaveInstanceState - save position: 6

D/DetailsFragment(21894): Entering onSaveInstanceState - this: DetailsFragment{419e6248 #1 id=0x7f060004}
D/DetailsFragment(21894): onSaveInstanceState - save value: 5572
D/DetailsFragment(21894): Entering onSaveInstanceState - this: DetailsFragment{419bcf98 #0 id=0x1020002}
D/DetailsFragment(21894): onSaveInstanceState - save value: 5685


******************************************************************
* 4. Rotate again in landscape mode                              *
* DetailsFragment created with rand value 5685 restored          *
* DetailsFragment found by id with same index 6, no new instance *
* the found fragment is created with rand value 5572 restored,   *
* this is the rand value visible in point 2.                     *
******************************************************************

D/DetailsActivity(21894): Entering onCreate
D/DetailsActivity(21894): onCreate - landscape mode - finish

D/DetailsFragment(21894): Entering onCreateView - this: DetailsFragment{419c2fc0 #0 id=0x1020002}
D/DetailsFragment(21894): onCreateView - restored randValue: 5685

D/FragmentLayout (Activity)(21894): Entering onCreate

D/TitlesFragment(21894): Entering onCreateView
D/TitlesFragment(21894): Entering onActivityCreated
D/TitlesFragment(21894): onActivityCreated - landscape mode
D/TitlesFragment(21894): onActivityCreated - dual pane, calling show details - position: 6
D/TitlesFragment(21894): Entering showDetails - index: 6
D/TitlesFragment(21894): showDetails - DetailsFragment found by id: DetailsFragment{41a07e08 #1 id=0x7f060004}
D/TitlesFragment(21894): showDetails - details.getShownIndex: 6

D/DetailsFragment(21894): Entering onCreateView - this: DetailsFragment{41a07e08 #1 id=0x7f060004}
D/DetailsFragment(21894): onCreateView - restored randValue: 5572

D/TitlesFragment(21894): Entering onStart

    我做了一些修改的代码的一部分

    在TitlesFragment中

    ：

    public class TitlesFragment extends ListFragment
{
    private final String TAG = "TitlesFragment";

    ...
    @Override
    public void onStart()
    {
        Log.d(TAG, "Entering onStart");
        super.onStart();
        if (mDualPane) {
            // call here because doesn't work when called in showDetails
            getListView().setItemChecked(mCurCheckPosition, true);
        }
    }

    ...
    void showDetails(int index) {
        Log.d(TAG, "Entering showDetails - index: " + index);
        mCurCheckPosition = index;

        if (mDualPane) {
            // We can display everything in-place with fragments, so update
            // the list to highlight the selected item and show the data.
            // This doesn't work here, moved in onStart
            //getListView().setItemChecked(index, true);

            // Check what fragment is currently shown, replace if needed.
            DetailsFragment details = (DetailsFragment)
                    getFragmentManager().findFragmentById(R.id.details);
            Log.d(TAG, "showDetails - DetailsFragment found by id: " + details);
            if (details != null) {
                Log.d(TAG, "showDetails - details.getShownIndex: " + details.getShownIndex());
            }

            if (details == null || details.getShownIndex() != index) {
                Log.d(TAG, "showDetails - calling DetailsFragment newInstance for index: " + index);

                // Make new fragment to show this selection.
                details = DetailsFragment.newInstance(index);

                // Execute a transaction, replacing any existing fragment
                // with this one inside the frame.
                FragmentTransaction ft = getFragmentManager().beginTransaction();
                //if (index == 0) {
                    ft.replace(R.id.details, details);
                //} else {
                    // following crash!!
                    //ft.replace(R.id.a_item, details);
                //}
                ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
                ft.commit();
            }

        } else {
            Log.d(TAG, "showDetails - Single Pane - start new activity");
            Log.d(TAG, "showDetails - position: " + index + " - title: " + getListAdapter().getItem(index));

            // Otherwise we need to launch a new activity to display
            // the dialog fragment with selected text.
            Intent intent = new Intent();
            intent.setClass(getActivity(), DetailsActivity.class);
            intent.putExtra("index", index);
            startActivity(intent);
        }
    }    
}

    并在DetailsFragment中：

    public class DetailsFragment extends Fragment
{
    private final String TAG = "DetailsFragment";

    private int mRandValue = 9999;

    ...
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState)
    {
        Log.d(TAG, "Entering onCreateView - this: " + this.toString());

        if (savedInstanceState != null) {
            mRandValue = savedInstanceState.getInt("randValue", 8888);
            Log.d(TAG, "onCreateView - restored randValue: " + mRandValue);
        }

        if (container == null) {
            // We have different layouts, and in one of them this
            // fragment's containing frame doesn't exist.  The fragment
            // may still be created from its saved state, but there is
            // no reason to try to create its view hierarchy because it
            // won't be displayed.  Note this is not needed -- we could
            // just run the code below, where we would create and return
            // the view hierarchy; it would just never be used.
            return null;
        }

        ScrollView scroller = new ScrollView(getActivity());
        TextView text = new TextView(getActivity());
        int padding = (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP,
                4, getActivity().getResources().getDisplayMetrics());
        text.setPadding(padding, padding, padding, padding);
        scroller.addView(text);
        final int idx = getShownIndex();
        text.setText(Shakespeare.TITLES[idx] + "\n\n" + Shakespeare.DIALOGUE[idx]);
        //text.setText(Shakespeare.DIALOGUE[getShownIndex()]);

        // create a new random value to simultate an action in the fragment
        if (mRandValue > 7000) {
            mRandValue = (int)(System.currentTimeMillis() % 7000);
            Log.d(TAG, "onCreateView - new mRandValue: " + mRandValue);
        }
        text.append("\n\nRand Value = " + mRandValue);

        return scroller;
    }

    @Override
    public void onSaveInstanceState(Bundle _outState)
    {
        Log.d(TAG, "Entering onSaveInstanceState - this: " + this.toString());
        Log.d(TAG, "onSaveInstanceState - save value: " + mRandValue);
        super.onSaveInstanceState(_outState);
        _outState.putInt("randValue", mRandValue);
    }
}

    我的问题

    我需要更改以正确处理旋转？
    'rand value'是我想要保留的DetailsFragment！

2 个答案:

答案 0 :(得分：0)

旋转重新创建您的活动您必须覆盖onsaved实例并保存其中所需的值....... 然后在onResume（）方法中，您可以获取这些值

答案 1 :(得分：0)

也许最好在putInt之后调用super.onSaveInstanceState：

@Override
public void onSaveInstanceState(Bundle _outState)
{
    Log.d(TAG, "Entering onSaveInstanceState - this: " + this.toString());
    Log.d(TAG, "onSaveInstanceState - save value: " + mRandValue);

    **_outState.putInt("randValue", mRandValue);**
    super.onSaveInstanceState(_outState);

}
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