Question

在我的计划中，我使用tabs实施了fragments。我在Tab2中放置了EditText。我想在Tab2 onCreateView的{{1}}（）内写fragment的所有主要代码，以便每次向Tab2移动时都这样代码被执行。为了测试每次刷到Tab2时是否调用Tab2（），我在onCreateView的{{1}}（）中写了以下语句：

onCreateView

现在，当我运行应用程序并滑动到Tab2时，我看到＆＃39;默认＆＃39;书面。现在，如果我手动更改此文本，然后滑动到Tab1并返回到Tab2-我仍然看到写入相同的文本。这显然意味着当我第二次刷到Tab2时没有再次调用Tab2（）？我该如何解决这个问题？

Tab2.java

text.setText("default");

MainActivity.java

onCreateView

Answer 1

如果您使用ViewPager

ViewPager viewPager;

尝试在setOnPageChangeListener

中使用MainActivity

viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {
             if(mFragmentList.size() > position && mFragmentList.get(position) instanceof Tab2)
             {
                 ((Tab2)mFragmentList.get(position)).changeText("changed text")
             }
 // you can use interface insted 
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });

Tab2

中的

public void changeText(String string){
  text.setText(string);
}

更新 MainActivity.java

public class MainActivity extends AppCompatActivity
{
public static int itemPosition;

private Toolbar toolbar;
private TabLayout tabLayout;
private ViewPager viewPager;
ViewPagerAdapter adapter;
private final List<Fragment> mFragmentLists = new ArrayList<>();

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

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

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setDisplayShowTitleEnabled(false);

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

    tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(viewPager);
    viewPager.setOffscreenPageLimit(0);

     viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {
             if(mFragmentList.size() > position && mFragmentList.get(position) instanceof Tab2)
             {
                 ((Tab2)mFragmentList.get(position)).changeText("changed text")
             }
 // you can use interface insted 
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });

}

private void setupViewPager(ViewPager viewPager)
{
    adapter = new ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new Tab1(), "ONE");
    adapter.addFragment(new Tab2(), "TWO");
    viewPager.setAdapter(adapter);

    mFragmentLists = adapter.getFragements();
}

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 List<Fragment> getFragements()
    {
      return mFragmentList;
    }

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

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

如何确保每次刷到它的选项卡时都会调用片段类的onCreateView（）？

1 个答案: