Question

我的主要活动有3个标签，每个标签加载一个不同的片段。我试图将数据从片段1传递到片段3，但它不起作用

可以加载所有3个片段，但问题是当我启动应用程序时只加载了1＆amp; 2。因此当我运行应用程序并且我想从片段1到3传递一个字符串时它不起作用，因为它还不存在。我怎么能改变这个？

我使用Eventbus（https://github.com/greenrobot/EventBus）进行片段之间的通信。

公共类MainActivity扩展了AppCompatActivity {

    private Toolbar mToolbar;
    private TabLayout mTabLayout;
    private ViewPager mPager;
    private MyPagerAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mAdapter = new MyPagerAdapter(getSupportFragmentManager());
        mToolbar = (Toolbar) findViewById(R.id.app_bar);
        setSupportActionBar(mToolbar);
        mTabLayout = (TabLayout) findViewById(R.id.tab_layout);

        mPager = (ViewPager) findViewById(R.id.pager);
        mPager.setAdapter(mAdapter);

        mTabLayout.setTabsFromPagerAdapter(mAdapter);

        mTabLayout.setupWithViewPager(mPager);
        mPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(mTabLayout));
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public static class MyFragment extends Fragment {
        public static final java.lang.String ARG_PAGE = "arg_page";

        public MyFragment() {
        }

        public static MyFragment newInstance(int pageNumber) {
            MyFragment myFragment = new MyFragment();
            Bundle arguments = new Bundle();
            arguments.putInt(ARG_PAGE, pageNumber + 1);
            myFragment.setArguments(arguments);
            return myFragment;
        }
    }



class MyPagerAdapter extends FragmentStatePagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        Fragment fragment = MainActivity.MyFragment.newInstance(position); //FRAGMENT fragment;
        switch (position) {
            case 0:
                fragment = new Fragment1();
                break;
            case 1:
                fragment = new Fragment2();
                break;
            case 2:
                fragment = new Fragment3();
                break;
            default:
                break;
        }
        return fragment;
    }


    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) { //set tab names

        switch (position) {
            case 0:
                return "Thread";
            case 1:
                return "AsyncTask";
            case 2:
                return "TODO";
        }
        return null;
    }}}

Answer 1

您希望适配器加载的最小页数以这种方式设置

Viewpager.setOffscreenPageLimit(3);

在viewpager中的片段之间传递字符串无法正常工作

1 个答案: