多次调用 CreateView 上的片段，以便每次都创建新的片段实例

Question

我正在尝试在视图寻呼机的页面更改中添加片段。 但是每次当我滚动视图寻呼机时，都会创建新的片段时刻。

public void initializeViewPager(int currentPage, String selectedCardNumber) {
currentPosition = currentPage;
FragmentPagerAdapter journeyViewPagerAdapter =
new ViewPagerAdapter(getSupportFragmentManager());

ViewPager.OnPageChangeListener onPageChangeListener = new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
//Default Implementation
}
@Override
public void onPageSelected(int position) {
currentPosition = position;
addFragments(position, selectedCardNumber);
handleScrollState();
}
@Override
public void onPageScrollStateChanged(int state) {
//Default Implementation
}
};
viewPager.addOnPageChangeListener(onPageChangeListener);
initCarousalAdapter();
}

addFragments(( 方法

private void addFragments(int position, final String selectedCardNumber) {
FragmentTransaction fragTransaction = getSupportFragmentManager().beginTransaction();
Bundle bundle = new Bundle();
bundle.putInt(ApplicationConstants.SELECTED__TYPE, position);
bundle.putString(DataConstants.SELECTED__NUMBER, selectedCardNumber);
switch (position) {
case 1:
OffersFragmentOne fragment = OffersFragmentOne.getInstance();
fragment.setArguments(bundle);
fragTransaction.replace(R.id.btmt_fragment_container, fragment);
break;
case 2:
OffersFragmentTwo mtFragment = OffersFragmentTwo.getInstance();
mtFragment.setArguments(bundle);
fragTransaction.replace(R.id.btmt_fragment_container, mtFragment);
break;
case 3:
OffersFragmentThree poFragment = OffersFragmentThree.getInstance();
poFragment.setArguments(bundle);
fragTransaction.replace(R.id.btmt_fragment_container, poFragment);
break;
default:
//Default Implementation
}
fragTransaction.commit();
}

getInstance(( 方法

private static OffersFragmentOne offersFragmentOne;
public static OffersFragmentOne getInstance() {
if (OffersFragmentOne == null) {
offersFragmentOne = new OffersFragmentOne();
}
return offersFragmentOne;
}

查看寻呼适配器.java

public class ViewPagerAdapter extends FragmentPagerAdapter {
private final int[] carousalImages = {R.drawable.ic_po_carousal_banner, 
R.drawable.ic_bt_carousal_banner,
R.drawable.ic_mt_carousal_banner, R.drawable.ic_po_carousal_banner, 
R.drawable.ic_bt_carousal_banner};
public ViewPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
@Override
public Fragment getItem(int position) {
CarousalFragment frag = new CarousalFragment();
CarousalFragmentPresenter.createAndAttach(frag, carousalImages[position]);
return frag;
}
@Override
public int getCount() {
return carousalImages != null ? carousalImages.length : 0;
}
}

Answer 1

你应该用getItem编写你的开关大小写，不需要bundle和片段事务，因为getItem本身会返回选定的Fragment，并将与ViewPager绑定

@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
CarousalFragment();
break;
case 1:
OffersFragmentOne.getInstance();
break;
case 2:
OffersFragmentTwo.getInstance();
break;
case 3:
OffersFragmentThree.getInstance();
break;
default:
//Default Implementation
}
}

OnPageChangeListener只为您提供所选和滚动项目或片段的位置，因此不需要从onPageSelected添加片段

ViewPager.OnPageChangeListener onPageChangeListener = new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
//Default Implementation
}
@Override
public void onPageSelected(int position) {
}
@Override
public void onPageScrollStateChanged(int state) {
//Default Implementation
}
};

Answer 2

如何在视图寻呼机的容器活动中创建片段实例？这样，只有在创建容器时才能创建它们。

编辑：添加示例代码。 例：

public class ContainerActivity extends AppCompatActivity {
private FragmentOne fragmentOne;
private FragmentTwo fragmentTwo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.container_with_view_pager);
fragmentOne = FragmentOne.getInstance();
fragmentTwo = FragmentTwo.getInstance();
ViewPager viewPager = findViewById(R.id.viewpager);
setupViewPager(viewPager);
}
private void setupViewPager(ViewPager viewPager) {
ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());
adapter.addFragment(fragmentOne, "Fragment One");
adapter.addFragment(fragmentTwo, "Fragment Two");
viewPager.setAdapter(adapter);
}
}