Question

我检查了使用Logcat从Activity传递给Fragment的值。但是发生“ java.lang.NullPointerException：println需要消息”错误，并且应用程序关闭。我该如何解决？

我通过这种方式将AString从String传递给Fragment：

Bundle bundle = new Bundle();
bundle.putString("sb", sb.toString());

SlideshowFragment slideshowFragment = new SlideshowFragment();
slideshowFragment.setArguments(bundle);

FragmentTransaction fragmentTransaction =
        getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.nav_host_fragment, slideshowFragment);
fragmentTransaction.commit();

这是SlideshowFragment.java：

public class SlideshowFragment extends Fragment {
    private static final String ARG_PARAM1 = "param1";


    private String mParam1;

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


    public static SlideshowFragment newInstance(String param1) {

        SlideshowFragment fragment = new SlideshowFragment();
        Bundle args = new Bundle();
        args.putString("sb", param1);
        fragment.setArguments(args);
        Log.i("TEST", "instance");

        return fragment;
    }

    // I think I Received values on here:

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString("sb");
            Log.i("TEST", "oncreate");
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        //I could see values on here:
        Log.i("TEST onceateview", mParam1);

        return inflater.inflate(R.layout.fragment_slideshow, container, false);
    }
}

这是Logcat

09-08 18:39:04.102 16245-16245/com.example.nav2 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.nav2, PID: 16245
    java.lang.NullPointerException: println needs a message
        at android.util.Log.println_native(Native Method)
        at android.util.Log.i(Log.java:207)
        at com.example.nav2.ui.slideshow.SlideshowFragment.onCreateView(SlideshowFragment.java:53)
        at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2439)
        at androidx.fragment.app.FragmentManagerImpl.moveToState(FragmentManager.java:1460)
        at androidx.fragment.app.FragmentManagerImpl.addAddedFragments(FragmentManager.java:2646)
        at androidx.fragment.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2416)
        at androidx.fragment.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2372)
        at androidx.fragment.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
        at androidx.fragment.app.FragmentManagerImpl$1.run(FragmentManager.java:733)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:158)
        at android.app.ActivityThread.main(ActivityThread.java:7229)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

Answer 1

SlideshowFragment可以接受字符串，因为参数不是bundle。

SlideshowFragment slideshowFragment = SlideshowFragment.newInstance（sb.toString（））;

如何修复Android上的'println需要消息'错误

1 个答案: