Question

我从MyListFragment中的args获取null，无法弄清楚原因。

基本上我要做的是从地图获取位置并将旧片段替换为具有更新位置的新片段，

MyListFragmnet是NavigationDrawerActivity

中的“默认”片段

// MyListFragment.java

public static MyListFragment newInstance() {
    Bundle args = new Bundle();
    return newInstance(args);
}

public static MyListFragment newInstance(Bundle args) {
    MyListFragment fragment = new MyListFragment();
    fragment.setArguments(args);
    return fragment;
}

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

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    this.setHasOptionsMenu(true);

    Bundle args = getArguments();
    searchQuery = args.getString(SEARCH_QUERY_ARG, ""); //NULL ERROR!!
    final MyLocation checkLocation = (MyLocation) args.getSerializable(LOCATION_ARG);

    if (!searchQuery.isEmpty()) {
        activity.setTitle("\""+searchQuery+"\"");
    }
    setLocation(checkLocation);

............

private void setLocation(final MyLocation checkLocation) {
        if (checkLocation != null) {
            // If no location is set and there is a check
            location = new Location("");
            location.setLatitude(checkLocation.latitude);
            location.setLongitude(checkLocation.longitude);
        } else {
            // If no location was provided, get the current one
            location = LocationHelper.getInstance().getLocation(context);
        }
    }

// NavigationDrawerActivity.java

public class NavigationDrawerActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {

    private DrawerLayout drawerLayout;
    private ActionBarDrawerToggle toggle;
    private NavigationView navLayout;

    //Location
    private MyLocation checkLocation;
    private boolean active;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_drawer_navigation);
        setupReferences();

        Toolbar toolbar = (Toolbar)findViewById(R.id.toolbar);
        toolbar.setTitleTextColor(Color.WHITE);
        setSupportActionBar(toolbar);
        ActionBar actionBar = getSupportActionBar();
        try {
            assert actionBar != null;
            actionBar.setDisplayHomeAsUpEnabled(true);
            actionBar.setHomeButtonEnabled(true);
            actionBar.setSubtitle(getString(R.string.subtitle));
            actionBar.setDisplayShowTitleEnabled(true);
        } catch (Exception ignored) {
        }

        drawerLayout = (DrawerLayout)findViewById(R.id.drawerLayout);

        toggle = new ActionBarDrawerToggle(this,
                drawerLayout,
                toolbar,
                R.string.navigation_drawer_open,
                R.string.navigation_drawer_close);
        drawerLayout.setDrawerListener(toggle);
        toggle.syncState();

        navLayout= (NavigationView)findViewById(R.id.navLayout);
        navLayout.setNavigationItemSelectedListener(this);

        active = false;
        checkLocation = (MyLocation) getIntent().getSerializableExtra(MyListFragment.LOCATION_ARG);
        handleIntent(getIntent());

        FragmentTransaction tx = getSupportFragmentManager().beginTransaction();
        tx.replace(R.id.frameLayout, new MyListFragment());
        tx.commit();

    }
    @Override
    public  boolean onNavigationItemSelected(MenuItem menuItem){
        switch (menuItem.getItemId()){
            case R.id.navigation_item_1:
                break;
            case R.id.navigation_item_2:
                break;
            case R.id.navigation_item_3:
                break;

        }
        return false;
    }

    @Override
    protected void onNewIntent(Intent intent) {
        if (active) {
            // Only handles the Intent again if the Activity was already active
            handleIntent(intent);
        }
    }
    @Override
    public void startActivity(Intent intent) {
        super.startActivity(intent);

        if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
            intent.putExtra(MyListFragment.LOCATION_ARG, checkLocation);
        }

        active = true;
    }
    private void handleIntent(Intent intent) {
        Bundle args = new Bundle();

        if (Intent.ACTION_SEARCH.equals(intent.getAction())) {
            String searchQuery = intent.getStringExtra(SearchManager.QUERY);
            args.putString(MyListFragment.SEARCH_QUERY_ARG, searchQuery);
            args.putSerializable(MyListFragment.LOCATION_ARG, checkLocation);
        } else if (MyListFragment.ACTION_CHECK.equals(intent.getAction())) {
            checkLocation = (MyLocation) intent.getSerializableExtra(LocationActivity.EXTRA_LOCATION);
            args.putSerializable(MyListFragment.LOCATION_ARG, checkLocation);
        }

        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.frameLayout, MyListFragment.newInstance(args)).commit();
    }

}

请帮忙！感谢。

Answer 1

您没有使用MyListFragment.newInstance()，只是致电new MyListFragment()

这一行

  tx.replace(R.id.frameLayout, new MyListFragment());

应该是

 tx.replace(R.id.frameLayout, MyListFragment.newInstance());

Answer 2

下面：

...
tx.replace(R.id.frameLayout, new MyListFragment());
...

在创建MyListFragment Fragment的对象时不传递任何包。

通过调用newInstance(Bundle args)静态方法来获取Fragment对象。

 Bundle bundle = new Bundle();
 bundle.putString(SEARCH_QUERY_ARG, "data_here"); 
 ...
 tx.replace(R.id.frameLayout, new MyListFragment.newInstance(bundle));
 ...

Android片段getArguments返回null

2 个答案: