Question

我有一个片段，其中我有图像按钮“产品图像”，我正在将图像加载到具有图库意图的图像按钮并使用Glide库加载该图像，以便保留我正在使用onSavedInstanceState的图像（）但问题是，当我将方向更改为横向时，它会保留图像，但是当我再次切换回纵向模式时，它不会保留图像并给我一个空指针执行，如果有一些技术性的东西，我我做错了请指导，因为我对Android开发有点新意。这是我的fragemnt代码。

public class NoteEditFragment extends Fragment {

ImageButton productImage;
private static final int REQUEST_OPEN_RESULT_CODE = 0;
private Uri mImageUri;
EditText productName;
EditText productPrice;
EditText productDescription;
AlertDialog confirmDialogObject;
Uri myuri;




public NoteEditFragment() {
    // Required empty public constructor
}



@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment


    View FragmentLayout = inflater.inflate(R.layout.fragment_note_edit, container, false);
    productImage = (ImageButton) FragmentLayout.findViewById(R.id.editNoteButton);

    if(savedInstanceState != null){
           myuri = Uri.parse(savedInstanceState.getString("imageuri"));

        Glide.with(this)
                .load(myuri)
                .into(productImage);
    }

    productName = (EditText) FragmentLayout.findViewById(R.id.EditNoteTitle);

    Intent intent = getActivity().getIntent();

            });

    productImage.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent1 = new Intent(Intent.ACTION_OPEN_DOCUMENT);
            intent1.addCategory(Intent.CATEGORY_OPENABLE);
            intent1.setType("image/*");
            startActivityForResult(intent1, REQUEST_OPEN_RESULT_CODE);
        }
    });

    return FragmentLayout;
}
@Override
public void onSaveInstanceState(Bundle outState) {

    if(mImageUri != null){
        outState.putString("imageuri",mImageUri.toString());}
    super.onSaveInstanceState(outState);
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent resultData) {
    if(requestCode == REQUEST_OPEN_RESULT_CODE && resultCode == Activity.RESULT_OK ) {
        if(resultData != null) {
            mImageUri = resultData.getData();

            Glide.with(this)
                    .load(mImageUri)
                    .into(productImage);
        }
    }
}

这是我得到的错误

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.ibrahim_01.notebookapp, PID: 4102
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ibrahim_01.notebookapp/com.example.ibrahim_01.notebookapp.NoteDetailActivity}: java.lang.NullPointerException: uriString
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                      at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4077)
                      at android.app.ActivityThread.-wrap15(ActivityThread.java)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1350)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5417)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                   Caused by: java.lang.NullPointerException: uriString
                      at android.net.Uri$StringUri.<init>(Uri.java:475)
                      at android.net.Uri$StringUri.<init>(Uri.java)
                      at android.net.Uri.parse(Uri.java:437)
                      at com.example.ibrahim_01.notebookapp.NoteEditFragment$override.onCreateView(NoteEditFragment.java:66)
                      at com.example.ibrahim_01.notebookapp.NoteEditFragment$override.access$dispatch(NoteEditFragment.java)
                      at com.example.ibrahim_01.notebookapp.NoteEditFragment.onCreateView(NoteEditFragment.java:0)
                      at android.app.Fragment.performCreateView(Fragment.java:2220)
                      at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:973)
                      at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1148)
                      at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1130)
                      at android.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1953)
                      at android.app.FragmentController.dispatchActivityCreated(FragmentController.java:152)
                      at android.app.Activity.performCreateCommon(Activity.java:6232)
                      at android.app.Activity.performCreate(Activity.java:6239)
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                      at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4077) 
                      at android.app.ActivityThread.-wrap15(ActivityThread.java) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1350) 
                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                      at android.os.Looper.loop(Looper.java:148) 
                      at android.app.ActivityThread.main(ActivityThread.java:5417) 
                      at java.lang.reflect.Method.invoke(Native Method) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

第一次旋转时，会设置字段（imageUri）。 onSaveInstanceState()会将此字段保留在包中旋转。

现在在横向中，您将从onCreate()中的包中读取并获取您存储的值。但请注意，imageUri将为空，因为您将其存储到myUri。

第二次轮换时，onSaveInstanceState()将不会保留imageUri，因为它为空。但现在在肖像中，它会尝试读取它（bundle不为null），返回null（因为键“imageuri”没有值），并且你在Uri.parse中获得了空指针。

您可以通过删除字段myUri并将onCreate()中的字符串值分配给imageUri来解决。我想 - 我正在手机上看这个！

Answer 2

覆盖方法 onCreate 并添加setRetainInstance（true），如下所示：

@Override
public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setRetainInstance(true);
}

如何在方向变化时保留片段中的图像

2 个答案: