FragmentPagerAdapter始终加载下一个片段，而不是当前片段 [英] FragmentPagerAdapter always load the next fragment instead the current

问题描述

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main_dictionary);

    getWindow().setSoftInputMode(
            WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);

    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    viewPager = (ViewPager) findViewById(R.id.viewpager);
    setupViewPager(viewPager);

    tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(viewPager);

    tabLayout.setTabGravity(TabLayout.GRAVITY_FILL);
    setupNavMenu();
}

private void setupViewPager(ViewPager viewPager) {
    adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new A(), "A");
    adapter.addFragment(new B(), "B");
    adapter.addFragment(new C(), "C");
    adapter.addFragment(new D(), "D");
    viewPager.setAdapter(adapter);
}

class ViewPagerAdapter extends FragmentPagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);
    }
}

问题是:当我开始活动时，我得到第一个片段的视图(A)，但是下一个片段(B)加载而没有该视图，所以当我滑动到下一个视图(B)时，我得到了已经加载的视图在前面的片段上，所以现在是加载片段C ...

The problem is: When I starts the activity, i get the first fragment's view(A), BUT the next fragment(B) loads without the view, so when I slide to the next view(B), i get the view that i'v been loaded at the previous fragment, so now It's load fragment C...

问题在于片段B的内容取决于片段A中的输入(保存的数据是共享首选项)，因此我总是在片段B上获得默认值，因为它已加载到片段A中.

the problem is that fragment B's content depends on the input in fragment A (data saved is sharedpreferences) so I allways get the default value at fragment B because it was loaded in fragment A.

当我进入片段D时，该错误的工作方式相同，因此当我向左滑动到片段C时，它将显示片段C并同时加载片段B.

The bug works the same way when I'm in the fragment D, so when I'll slide left to fragment C, it will show fragment C AND loads fragment B also.

推荐答案

它不是bug，它不是viewpager的默认功能.对于第n页，第n-1页和第(n + 1)页会自动与第n页一起加载.我认为没有任何直接的方法可以实现您想要的.

its not a bug its the default functionality of a viewpager. for each nth page (n-1)th and (n+1)th page loads automatically with the nth page. I don't think there is any straight forward way to achieve what you want.

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