Android 如何从FragmentPagerAdapter返回多个片段

如果将

TabLayout

与

FragmentPagerAdapter

一起使用，则重写的函数getItem（int位置）只返回一个片段。在大屏幕的情况下，我想有2个碎片要返回。 我怎么做？应该将这两个片段包装成一个片段并使用它，还是有更好的解决方案

FragmentPagerAdapter:

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0: //Ingredients
                return IngredientsFragment.newInstance(mRecipe);
            case 1: // Details
            {
                // TODO Here instead of DetailFragment I want to return
                // two fragments called DetailFragment and StepFragment.
                return DetailFragment.newInstance(mRecipe);
            }
            default:
                throw new RuntimeException(this.toString() + " Wrong fragment!");
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        // Initializing, etc.

        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = findViewById(R.id.tabs);
        mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
    }

public class DetailStepWideScreenFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_detail_step_wide_screen, container, false);

        // I added the fragments here. StepFragment can be replaced using
        // replaceStepFragment function.
        DetailFragment detailFragment = DetailFragment.newInstance(mRecipe);
        StepFragment stepFragment = StepFragment.newInstance(mRecipe, mStepId);
        FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
        transaction.add(R.id.fl_detail_fragment_wide_screen, detailFragment);
        transaction.add(R.id.fl_step_fragment_wide_screen, stepFragment);
        transaction.commit();

        return view;
    }

    public void replaceStepFragment(String stepId) {
        mStepId = stepId;
        FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
        StepFragment stepFragment = StepFragment.newInstance(mRecipe, mStepId);
        transaction.replace(R.id.fl_step_fragment_wide_screen, stepFragment);
        transaction.commit();
    }
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    private DetailStepWideScreenFragment currentFragment;

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
        currentFragment = null;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0: //Ingredients
                return IngredientsFragment.newInstance(mRecipe);
            case 1: // Details
            {
                // Show base on screen size.
                if (mIsLargeScreen) {
                    DetailStepWideScreenFragment detailStepWideScreenFragment = DetailStepWideScreenFragment.newInstance(mRecipe, "0");
                    currentFragment = detailStepWideScreenFragment;
                    return detailStepWideScreenFragment;
                } else {
                    return DetailFragment.newInstance(mRecipe);
                }
            }
            default:
                throw new RuntimeException(this.toString() + " Wrong fragment!");
        }
    }

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

    public DetailStepWideScreenFragment getCurrentFragment() {
        return currentFragment;
    }

}

然后在我的活动onCreate:

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0: //Ingredients
                return IngredientsFragment.newInstance(mRecipe);
            case 1: // Details
            {
                // TODO Here instead of DetailFragment I want to return
                // two fragments called DetailFragment and StepFragment.
                return DetailFragment.newInstance(mRecipe);
            }
            default:
                throw new RuntimeException(this.toString() + " Wrong fragment!");
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        // Initializing, etc.

        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = findViewById(R.id.tabs);
        mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
    }

public class DetailStepWideScreenFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_detail_step_wide_screen, container, false);

        // I added the fragments here. StepFragment can be replaced using
        // replaceStepFragment function.
        DetailFragment detailFragment = DetailFragment.newInstance(mRecipe);
        StepFragment stepFragment = StepFragment.newInstance(mRecipe, mStepId);
        FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
        transaction.add(R.id.fl_detail_fragment_wide_screen, detailFragment);
        transaction.add(R.id.fl_step_fragment_wide_screen, stepFragment);
        transaction.commit();

        return view;
    }

    public void replaceStepFragment(String stepId) {
        mStepId = stepId;
        FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
        StepFragment stepFragment = StepFragment.newInstance(mRecipe, mStepId);
        transaction.replace(R.id.fl_step_fragment_wide_screen, stepFragment);
        transaction.commit();
    }
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    private DetailStepWideScreenFragment currentFragment;

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
        currentFragment = null;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0: //Ingredients
                return IngredientsFragment.newInstance(mRecipe);
            case 1: // Details
            {
                // Show base on screen size.
                if (mIsLargeScreen) {
                    DetailStepWideScreenFragment detailStepWideScreenFragment = DetailStepWideScreenFragment.newInstance(mRecipe, "0");
                    currentFragment = detailStepWideScreenFragment;
                    return detailStepWideScreenFragment;
                } else {
                    return DetailFragment.newInstance(mRecipe);
                }
            }
            default:
                throw new RuntimeException(this.toString() + " Wrong fragment!");
        }
    }

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

    public DetailStepWideScreenFragment getCurrentFragment() {
        return currentFragment;
    }

}

---

我看你这里没有多少回旋余地

这两个选项是唯一的：

返回一个片段和两个嵌套片段（包装片段）

您将返回两个片段，每个片段都锚定到自己的选项卡上 若您希望两个片段出现在ViewPager的单一页面上，那个么您别无选择，只能将它们包装起来。

---

否则，滑动将在这两个片段之间进行，这与它们完全不同的情况相同，即不相关。

好的，我成功地解决了这个问题，使用了一个

片段

作为子片段，由另外两个片段组成。 在这种情况下，不要忘记使用

getChildFragmentManager（）

填充

FragmentManager

对象才能正常工作。 有关更多信息，请查看我的BakingApp项目

detailStepWideCreenFragment.java

片段包装器：

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0: //Ingredients
                return IngredientsFragment.newInstance(mRecipe);
            case 1: // Details
            {
                // TODO Here instead of DetailFragment I want to return
                // two fragments called DetailFragment and StepFragment.
                return DetailFragment.newInstance(mRecipe);
            }
            default:
                throw new RuntimeException(this.toString() + " Wrong fragment!");
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        // Initializing, etc.

        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = findViewById(R.id.tabs);
        mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
    }

public class DetailStepWideScreenFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_detail_step_wide_screen, container, false);

        // I added the fragments here. StepFragment can be replaced using
        // replaceStepFragment function.
        DetailFragment detailFragment = DetailFragment.newInstance(mRecipe);
        StepFragment stepFragment = StepFragment.newInstance(mRecipe, mStepId);
        FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
        transaction.add(R.id.fl_detail_fragment_wide_screen, detailFragment);
        transaction.add(R.id.fl_step_fragment_wide_screen, stepFragment);
        transaction.commit();

        return view;
    }

    public void replaceStepFragment(String stepId) {
        mStepId = stepId;
        FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
        StepFragment stepFragment = StepFragment.newInstance(mRecipe, mStepId);
        transaction.replace(R.id.fl_step_fragment_wide_screen, stepFragment);
        transaction.commit();
    }
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    private DetailStepWideScreenFragment currentFragment;

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
        currentFragment = null;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0: //Ingredients
                return IngredientsFragment.newInstance(mRecipe);
            case 1: // Details
            {
                // Show base on screen size.
                if (mIsLargeScreen) {
                    DetailStepWideScreenFragment detailStepWideScreenFragment = DetailStepWideScreenFragment.newInstance(mRecipe, "0");
                    currentFragment = detailStepWideScreenFragment;
                    return detailStepWideScreenFragment;
                } else {
                    return DetailFragment.newInstance(mRecipe);
                }
            }
            default:
                throw new RuntimeException(this.toString() + " Wrong fragment!");
        }
    }

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

    public DetailStepWideScreenFragment getCurrentFragment() {
        return currentFragment;
    }

}

PagerAdapter:

public class SectionsPagerAdapter extends FragmentPagerAdapter {

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0: //Ingredients
                return IngredientsFragment.newInstance(mRecipe);
            case 1: // Details
            {
                // TODO Here instead of DetailFragment I want to return
                // two fragments called DetailFragment and StepFragment.
                return DetailFragment.newInstance(mRecipe);
            }
            default:
                throw new RuntimeException(this.toString() + " Wrong fragment!");
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        // Initializing, etc.

        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = findViewById(R.id.tabs);
        mViewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        tabLayout.addOnTabSelectedListener(new TabLayout.ViewPagerOnTabSelectedListener(mViewPager));
    }

public class DetailStepWideScreenFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_detail_step_wide_screen, container, false);

        // I added the fragments here. StepFragment can be replaced using
        // replaceStepFragment function.
        DetailFragment detailFragment = DetailFragment.newInstance(mRecipe);
        StepFragment stepFragment = StepFragment.newInstance(mRecipe, mStepId);
        FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
        transaction.add(R.id.fl_detail_fragment_wide_screen, detailFragment);
        transaction.add(R.id.fl_step_fragment_wide_screen, stepFragment);
        transaction.commit();

        return view;
    }

    public void replaceStepFragment(String stepId) {
        mStepId = stepId;
        FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
        StepFragment stepFragment = StepFragment.newInstance(mRecipe, mStepId);
        transaction.replace(R.id.fl_step_fragment_wide_screen, stepFragment);
        transaction.commit();
    }
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {
    private DetailStepWideScreenFragment currentFragment;

    public SectionsPagerAdapter(FragmentManager fm) {
        super(fm);
        currentFragment = null;
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
            case 0: //Ingredients
                return IngredientsFragment.newInstance(mRecipe);
            case 1: // Details
            {
                // Show base on screen size.
                if (mIsLargeScreen) {
                    DetailStepWideScreenFragment detailStepWideScreenFragment = DetailStepWideScreenFragment.newInstance(mRecipe, "0");
                    currentFragment = detailStepWideScreenFragment;
                    return detailStepWideScreenFragment;
                } else {
                    return DetailFragment.newInstance(mRecipe);
                }
            }
            default:
                throw new RuntimeException(this.toString() + " Wrong fragment!");
        }
    }

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

    public DetailStepWideScreenFragment getCurrentFragment() {
        return currentFragment;
    }

}

---

我认为返回一个包裹其他两个的片段是明智的解决方案