Question

我需要将MainActivity中的值传递给我的标签Fragments，以便我可以相应地使用该值。任何帮助将不胜感激。提前谢谢。

主要活动：

    //Value from Login Activity. The value I need to pass    
    Intent intent = getIntent();
    String username = intent.getStringExtra("username");

    //Menu on my Drawer
    mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
    @Override
    public boolean onNavigationItemSelected(MenuItem menuItem) {
    mDrawerLayout.closeDrawers();

    if (menuItem.getItemId() == R.id.nav_request) {
        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.containerView,new RequestFragment()).commit();
    }

    if (menuItem.getItemId() == R.id.nav_requisitions) {
        FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
        xfragmentTransaction.replace(R.id.containerView,new RequisitionsFragment()).commit();
    }
    return false;
}

});

3个标签属于RequisitionsFragment()。这是我需要传递用户名值的地方。

这是我的RequisitionsFragment()：

    public class RequisitionsFragment extends Fragment {

    public static TabLayout tabLayout;
    public static ViewPager viewPager;
    public static int int_items = 3 ;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View x =  inflater.inflate(R.layout.tab_layout,null);
        tabLayout = (TabLayout) x.findViewById(R.id.tabs);
        viewPager = (ViewPager) x.findViewById(R.id.viewpager);
        viewPager.setAdapter(new MyAdapter(getChildFragmentManager()));
        tabLayout.post(new Runnable() {
            @Override
            public void run() {
                tabLayout.setupWithViewPager(viewPager);
            }
        });
        return x;
    }


    class MyAdapter extends FragmentPagerAdapter {
        public MyAdapter(FragmentManager fm) {
            super(fm);
        }
        @Override
        public Fragment getItem(int position)
        {
            switch (position){
                case 0 : return new PendingFragment();
                case 1 : return new ApprovedFragment();
                case 2 : return new CompletedFragment();
            }
            return null;
        }

        @Override
        public int getCount() {
            return int_items;
        }

        @Override
        public CharSequence getPageTitle(int position) {

            switch (position){
                case 0 :
                    return "Pending";
                case 1 :
                    return "Approved";
                case 2 :
                    return "Completed";
            }
            return null;
        }
    }
}

这是我需要使用值PendingFragment()的部分：

public class PendingFragment extends Fragment {
.....
......    
private void sendRequest(){

            StringRequest stringRequest = new StringRequest(Request.Method.POST, JSON_URL,
                    new Response.Listener<String>()
                    {
                        @Override
                        public void onResponse(String response) {
                            showJSON(response);
                        }
                    },
                    new Response.ErrorListener()
                    {
                        @Override
                        public void onErrorResponse(VolleyError error) {
                            Toast.makeText(PendingFragment.this.getActivity(),error.getMessage(),Toast.LENGTH_LONG).show();
                        }
                    }
            ) {
                @Override
                protected Map<String, String> getParams()
                {
                    Map<String, String> params = new HashMap<>();
                    params.put("username", username);
                    return params;
                }
            };
            RequestQueue queue = Volley.newRequestQueue(PendingFragment.this.getActivity());
            queue.add(stringRequest);
        }

Answer 1

您通过调用RequisitionsFragment来实例化new RequisitionsFragment()。而不是这样做，使用newInstance()方法模式。像这样：

在RequisitionsFragment中，声明此方法：

public static RequisitionsFragment newInstance(String username) {
    RequisitionsFragment fragment = new RequisitionsFragment();
    Bundle args = new Bundle();
    args.putString("USERNAME", username);
    fragment.setArguments(args);
    return fragment;
}

在您的MainActivity中，请调用此方法：

 fragmentTransaction.replace(R.id.containerView, RequestFragment.newInstance(username)).commit();

此后，当您需要访问片段内的参数时，请调用

String username = getArguments().getString("USERNAME");

应该这样做。如果这有帮助，请告诉我。

修改

对RequisitionsFragment：
进行这些更改
public class RequisitionsFragment extends Fragment { public static TabLayout tabLayout; public static ViewPager viewPager; public static int int_items = 3 ; String username; public RequisitionsFragment() { // Required empty public constructor } public static RequisitionsFragment newInstance(String username) { RequisitionsFragment fragment = new RequisitionsFragment(); Bundle args = new Bundle(); args.putString("USERNAME", username); fragment.setArguments(args); return fragment; } @Nullable @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View x = inflater.inflate(R.layout.tab_layout,null); tabLayout = (TabLayout) x.findViewById(R.id.tabs); viewPager = (ViewPager) x.findViewById(R.id.viewpager); viewPager.setAdapter(new MyAdapter(getChildFragmentManager())); tabLayout.post(new Runnable() { @Override public void run() { tabLayout.setupWithViewPager(viewPager); } }); username = getArguments().getString("USERNAME"); return x; } class MyAdapter extends FragmentPagerAdapter { public MyAdapter(FragmentManager fm) { super(fm); } @Override public Fragment getItem(int position) { switch (position){ case 0 : return PendingFragment.newInstance(username); case 1 : return new ApprovedFragment(); case 2 : return new CompletedFragment(); } return null; } @Override public int getCount() { return int_items; } @Override public CharSequence getPageTitle(int position) { switch (position){ case 0 : return "Pending"; case 1 : return "Approved"; case 2 : return "Completed"; } return null; } } }

然后在newInstance()内写一个PendingFragment方法：

public class PendingFragment extends Fragment { String username; public PendingFragment(){ //Required empty constructor } public static PendingFragment newInstance(String username) { PendingFragment fragment = new PendingFragment(); Bundle args = new Bundle(); args.putString("USERNAME", username); fragment.setArguments(args); return fragment; } .....//Initialize username inside onCreateView like this: //username = getArguments().getString("USERNAME"); ...... private void sendRequest(){ StringRequest stringRequest = new StringRequest(Request.Method.POST, JSON_URL, new Response.Listener<String>() { @Override public void onResponse(String response) { showJSON(response); } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { Toast.makeText(PendingFragment.this.getActivity(),error.getMessage(),Toast.LENGTH_LONG).show(); } } ) { @Override protected Map<String, String> getParams() { Map<String, String> params = new HashMap<>(); params.put("username", username); return params; } }; RequestQueue queue = Volley.newRequestQueue(PendingFragment.this.getActivity()); queue.add(stringRequest); }

如果有帮助，请告诉我。

Answer 2

在PagerAdapter（）中尝试这样做

 Bundle bundle=new Bundle();
 bundle.putString(.....);
 new PendingFragment().setArgument(bundle);

同样，您可以在Activity

中调用setArgument（）函数

Answer 3

有更好，更强大的方法在类之间发送数据。 Event Bus支持您无法使用构造函数类或接口进行的某些交互。对于动态数据通信，这个第三方库是完美且易于使用的

将值从主活动传递到选项卡片段

3 个答案: