java - 无法从 Activity 到 fragment 获取 bundle 值

Question

请帮忙，我刚刚学习了 android，我正在尝试使用 bundle 将数据从我的主 Activity 发送到 fragment 。这是 MainActivity 的代码

@Override
    public boolean onQueryTextChange(String newText) {

    if (newText.length()>0){
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        Bundle bundle = new Bundle();
        bundle.putString("query", newText);
        SearchMovieFragment searchMovieFragment = new SearchMovieFragment();
        searchMovieFragment.setArguments(bundle);
        transaction.replace(R.id.frame_container, searchMovieFragment);
        transaction.commit();
     }

这是我的 fragment 中的代码

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    String query = getArguments().getString("query");
    MoviesViewModel moviesViewModel = ViewModelProviders.of(this).get(MoviesViewModel.class);
    moviesViewModel.setSearchedMovie(query);
    moviesViewModel.getMovie().observe(this, getListMovies);

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

此行发生错误String query = getArguments().getString("query");错误是

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference

我该如何解决这个问题？

这是我的主要 Activity

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setStatusBarGradiant(this);
    setContentView(R.layout.activity_main);

    SectionsPagerAdapter sectionsPagerAdapter = new SectionsPagerAdapter(this, getSupportFragmentManager());
    ViewPager viewPager = findViewById(R.id.view_pager);
    viewPager.setAdapter(sectionsPagerAdapter);
    TabLayout tabs = findViewById(R.id.tabs);
    tabs.setupWithViewPager(viewPager);

    ActionBar actionBar = getSupportActionBar();
    if(actionBar != null){
        actionBar.setBackgroundDrawable(getResources().getDrawable(R.drawable.color_primary_gradient));
    }

    getSupportActionBar().setElevation(0);
}

protected void setStatusBarGradiant(Activity activity) {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        Window window = activity.getWindow();
        Drawable background = activity.getResources().getDrawable(R.drawable.color_primary_gradient);
        window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
        window.setStatusBarColor(activity.getResources().getColor(android.R.color.transparent));
        window.setBackgroundDrawable(background);
    }
}

private void loadFragment(Fragment fragment) {
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.frame_container, fragment);
    transaction.commit();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main_menu, menu);

    if(menu instanceof MenuBuilder){
        MenuBuilder m = (MenuBuilder) menu;
        m.setOptionalIconsVisible(true);
    }

    final SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);

    if (searchManager != null) {
        final SearchView searchView = (SearchView) (menu.findItem(R.id.search)).getActionView();
        searchView.setSearchableInfo(searchManager.getSearchableInfo(getComponentName()));

        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {

            @Override
            public boolean onQueryTextSubmit(String query) {
                searchView.clearFocus();
                return true;
            }

            @Override
            public boolean onQueryTextChange(String newText) {

                if (newText.length()>0){
                    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
                    Bundle bundle = new Bundle();
                    bundle.putString("query", newText);
                    SearchMovieFragment searchMovieFragment = new SearchMovieFragment();
                    searchMovieFragment.setArguments(bundle);
                    getSupportFragmentManager().beginTransaction().replace(R.id.frame_container,searchMovieFragment).commit(); 
                }
                else {
                    loadFragment(new SearchMovieFragment());
                }
                return true;
            }
        });
    }
    return true;
}

}

和我的 SearchMovieFragment

public class SearchMovieFragment extends Fragment {
private RecyclerView rvMovies;
private ArrayList<Movie> list = new ArrayList<>();
private CardViewMovieAdapter adapter;
private ProgressBar progressBar;
private String query;

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

private Observer<ArrayList<Movie>> getListMovies = new Observer<ArrayList<Movie>>() {
    @Override
    public void onChanged(ArrayList<Movie> movies) {
        if (movies != null) {
            adapter.setData(movies);
        }
        else {
            Toast.makeText(getContext(), R.string.no_result, Toast.LENGTH_LONG).show();
        }
        showLoading(false);
    }
};

private static final String ARG_PARAM1 = "query";
public static SearchMovieFragment newInstance(String param1) {
    SearchMovieFragment fragment = new SearchMovieFragment();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    fragment.setArguments(args);
    return fragment;
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    query = getArguments().getString("query");
    return inflater.inflate(R.layout.fragment_movies, container, false);
}


public void onViewCreated(View view, Bundle savedInstanceState) {
    rvMovies = view.findViewById(R.id.rv_movies);
    rvMovies.setHasFixedSize(true);
    progressBar = view.findViewById(R.id.progressBar);

    MoviesViewModel moviesViewModel = ViewModelProviders.of(this).get(MoviesViewModel.class);
    moviesViewModel.setSearchedMovie(query);
    moviesViewModel.getMovie().observe(this, getListMovies);

    showLoading(true);
    showRecyclerCardView();
}

private void showRecyclerCardView() {
    rvMovies.setLayoutManager(new LinearLayoutManager(this.getContext()));
    adapter = new CardViewMovieAdapter(list);
    rvMovies.setAdapter(adapter);
}

}

Answer 1

你能尝试删除这个吗？

private static final String ARG_PARAM1 = "query";
public static SearchMovieFragment newInstance(String param1) {
    SearchMovieFragment fragment = new SearchMovieFragment();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    fragment.setArguments(args);
    return fragment;
}

希望它能与您合作