设置ViewPager适配器之前，异步调用并将值传递给片段

Question

我的MainActivity类中有一个SlideTabLayout。我在活动中执行异步网络操作，并将获取的结果传递给SlideTabLayout中所需的片段，但是适配器将片段设置为空值，而我的网络操作稍后会获取数据因此，我无法将值传递给片段。如果您可以看到下面的代码.ArrayList的值在初始阶段为0，Activity将null值传递给所有片段。不断更新，这些更新不会传递给片段。

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_meat);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    CatalogueService catalogueService = App42API.buildCatalogueService();
    Intent categoryIntent = getIntent();
    catalogueName = categoryIntent.getStringExtra("CATALOGUE");
    viewPager = (ViewPager) findViewById(R.id.viewpager_meat);

    tabLayout = (TabLayout) findViewById(R.id.tabs_meat);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent intent = new Intent(MeatActivity.this,CartActivity.class);
            startActivity(intent);
        }
    });
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    String chickenCategoryName = "Chicken";
    catalogueService.getItemsByCategory(catalogueName, chickenCategoryName, new App42CallBack() {
        @Override
        public void onSuccess(Object o) {
            Catalogue catalogue = (Catalogue) o;
            for (int i = 0; i < catalogue.getCategoryList().size(); i++) {
                String category = catalogue.getCategoryList().get(i).getName();
                if (category.equals("Chicken")) {
                    chickenList = catalogue.getCategoryList().get(i).getItemList();
                }
            }
            Log.e("Chicken Size 1",String.valueOf(chickenList.size()));
        }

        @Override
        public void onException(Exception e) {

            final String error = e.getMessage();
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(MeatActivity.this,error,Toast.LENGTH_LONG).show();
                }
            });

        }
    });

    String muttonCategoryName = "Mutton";
    catalogueService.getItemsByCategory(catalogueName, muttonCategoryName, new App42CallBack() {
        @Override
        public void onSuccess(Object o) {
            Catalogue catalogue = (Catalogue) o;
            for (int i = 0; i < catalogue.getCategoryList().size(); i++) {
                String category = catalogue.getCategoryList().get(i).getName();
                if (category.equals("Mutton")) {
                    muttonList = catalogue.getCategoryList().get(i).getItemList();
                    break;
                }

            }
        }

        @Override
        public void onException(Exception e) {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(MeatActivity.this,"Unable to fetch data",Toast.LENGTH_SHORT).show();
                }
            });
        }
    });

    String seaFoodName = "Sea Foods";
    catalogueService.getItemsByCategory(catalogueName, seaFoodName, new App42CallBack() {
        @Override
        public void onSuccess(Object o) {
            Catalogue catalogue = (Catalogue) o;
            for (int i = 0; i < catalogue.getCategoryList().size(); i++) {
                String category = catalogue.getCategoryList().get(i).getName();
                if (category.equals("Sea Foods")) {
                    seaFoodList = catalogue.getCategoryList().get(i).getItemList();
                    break;
                }

            }
        }

        @Override
        public void onException(Exception e) {

        }
    });

    setupViewPager(viewPager);
    tabLayout.setupWithViewPager(viewPager);
}
private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new OneFragment(activityId, chickenList), "CHICKEN");
    Log.e("Chicken Size 2",String.valueOf(chickenList.size()));
    adapter.addFragment(new TwoFragment(activityId,muttonList), "MUTTON");
    adapter.addFragment(new ThreeFragment(activityId,seaFoodList), "SEAFOODS");
    viewPager.setAdapter(adapter);
}

Answer 1

实际上，问题是您在进行异步网络调用。 做这样的事情-

将类级别的变量计数器声明为int计数器；

现在，在三个onSuccess（）方法的每一个中，只需执行

counter ++;
setupViewPager();

在您的setupViewPager方法中添加检查

setupViewPager(ViewPager viewPager) {
    if(counter == 3){
        // your code to set the adapter
    }
}