Question

error image 这是错误信息

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.hkmedical.hkmedical/com.hkmedical.hkmedical.pdf.DocumentActivity}: java.lang.IllegalStateException: Fragment com.hkmedical.hkmedical.pdf.DocumentActivity.PlaceholderFragment must be a public static class to be  properly recreated from instance state.
                                                                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2444)
                                                                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2504)
                                                                         at android.app.ActivityThread.access$900(ActivityThread.java:165)
                                                                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1368)
                                                                         at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                         at android.os.Looper.loop(Looper.java:150)
                                                                         at android.app.ActivityThread.main(ActivityThread.java:5546)
                                                                         at java.lang.reflect.Method.invoke(Native Method)
                                                                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:682)
                                                                      Caused by: java.lang.IllegalStateException: Fragment com.hkmedical.hkmedical.pdf.DocumentActivity.PlaceholderFragment must be a public static class to be  properly recreated from instance state.
                                                                         at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:384)
                                                                         at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:369)
                                                                         at com.hkmedical.hkmedical.pdf.DocumentActivity.onCreate(DocumentActivity.java:55)
                                                                         at android.app.Activity.performCreate(Activity.java:6367)
                                                                         at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1110)
                                                                         at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2397)
                                                                         at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2504) 
                                                                         at android.app.ActivityThread.access$900(ActivityThread.java:165) 
                                                                         at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1368) 
                                                                         at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                         at android.os.Looper.loop(Looper.java:150) 
                                                                         at android.app.ActivityThread.main(ActivityThread.java:5546) 
                                                                         at java.lang.reflect.Method.invoke(Native Method) 
                                                                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792) 
                                                                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:682) 


in  the activity, when onCreate, the runtime exception appeared.
 fragment = new PlaceholderFragment(this);
    if (savedInstanceState == null) {
        this.getSupportFragmentManager().beginTransaction()
                .add(R.id.container, fragment).commit();
    }

这里是内部片段

 @SuppressLint("ValidFragment")
public class PlaceholderFragment extends Fragment {
    private Context mContext;

    public PlaceholderFragment(Context context) {
        mContext = context;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = new View(mContext);
        rootView.setBackgroundColor(Color.GRAY);
        mDoc = new SPDocument();
        long lResult = mDoc.open(mFilePath);
        if (lResult == 0) {
            drawView();
        }
        return rootView;
    }

    public void drawView() {
        mReaderView = new SPReaderViews(mContext, mDoc);
        mView = mReaderView.showDocument();
        LayoutParams params = new LayoutParams(LayoutParams.MATCH_PARENT,
                LayoutParams.MATCH_PARENT);
        getActivity().addContentView(mReaderView, params);
        mView.goToPage(0);}

这是我的傻瓜：

 compileSdkVersion 25
buildToolsVersion '25.0.0'

我想知道如何让它运作良好，我想知道如何让它运作良好，我想知道如何让它运作良好。但是代码在我的其他项目中效果很好。

Answer 1

问题是片段应该有一个空构造函数。如果您的应用程序将被Android系统杀死并再次打开它，Android将尝试恢复活动和片段的最后状态。在这种情况下，它将使用默认构造函数，因此传递给构造函数的所有内容都将丢失。如果需要将数据传递给片段，则应使用fragment.setArguments()。如果您需要获取片段中的上下文，可以使用getActivity()或getContext()

片段必须是要从实例状态正确重新创建的公共静态类

1 个答案: