带导航的 Android Studio ViewPager

Question

我有这种情况：

Fragment1 使用viewPager，然后当点击viewPager 的子片段内的某个组件时，它会打开Fragment2，它也使用viewPager。

到目前为止一切顺利。但是，单击后退按钮时，不会返回Fragment1，而是返回我的主要活动。该应用使用单一 Activity 和 Android 导航。

我已经尝试过使用viewPager2，它发生了同样的事情。

如果有人可以帮助我，谢谢。

public class Fragment1 extends AbstractNavFragment {

    private Fragment1 binder;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        binder = Fragment1Binding.inflate(inflater, container, false);
        return binder.getRoot();
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        binder.viewPager.setAdapter(new PageAdapterInternal(getChildFragmentManager()));
        binder.viewPager.setOffscreenPageLimit(2);
        binder.tabLayout.getTab().setupWithViewPager(binder.viewPager);
    }

    public void navigateToFragment2() {
        navigate(R.id.action_Fragment1_to_Fragment2);
    }

    private class PageAdapterInternal extends FragmentStatePagerAdapter {

        public PageAdapterInternal(@NonNull FragmentManager fm) {
            super(fm, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT);
        }

        @NonNull
        @Override
        public Fragment getItem(int position) {
            switch (position) {
                case 0:
                    return new IrcSupplyPositionsFragment(IrcSupplyPositionsFragment.FragmentType.PENDING);
                case 1:
                    return new IrcSupplyPositionsFragment(IrcSupplyPositionsFragment.FragmentType.COMPLETED);
                default:
                    throw new IllegalStateException("Unexpected value: " + position);
            }
        }

        @Nullable
        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return translate("rotativeInventory.supply.pendingPositions");
                case 1:
                    return translate("rotativeInventory.supply.positionsCompleted");
                default:
                    return "";
            }
        }

        @Override
        public int getCount() {
            return 2;
        }
    }
}

public class Fragment2 extends AbstractNavFragment {

    private Fragment2 binder;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        binder = Fragment2Binding.inflate(inflater, container, false);
        return binder.getRoot();
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        binder.viewPager.setAdapter(new RotativeInventorySupplyUDFragment.PageAdapterInternal(getChildFragmentManager()));
        binder.viewPager.setOffscreenPageLimit(2);
        binder.tabLayout.getTab().setupWithViewPager(binder.viewPager);
    }

    @Override
    protected void doOnViewCreate() {}

    private class PageAdapterInternal extends FragmentStatePagerAdapter {

        public PageAdapterInternal(@NonNull FragmentManager fm) {
            super(fm);
        }

        @NonNull
        @Override
        public Fragment getItem(int position) {
            switch (position) {
                case 0:
                    return new IrcSupplyUDFragment(IrcSupplyUDFragment.FragmentType.PENDING);
                case 1:
                    return new IrcSupplyUDFragment(IrcSupplyUDFragment.FragmentType.COMPLETED);
                default:
                    throw new IllegalStateException("Unexpected value: " + position);
            }
        }

        @Nullable
        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return translate("rotativeInventory.supply.pendingPositions");
                case 1:
                    return translate("rotativeInventory.supply.positionsCompleted");
                default:
                    return "";
            }
        }

        @Override
        public int getCount() {
            return 2;
        }
    }
}

Answer 1

您必须覆盖 Activity 的 onBackPressed 方法，以控制所有这些内容或将您的片段注册为 OnBackPressedDispatcher 并且当用户单击设备的后退按钮时，做出决定，例如 ==> @ 987654323@