java - 单击按钮时将 fragment 添加到寻呼机适配器

Question

我有一个带有 1 个 fragment 的选项卡式 Activity ，该 fragment 有一个按钮，我希望当我单击该按钮时它会创建一个新 fragment ，并且我可以在两个 fragment 之间滑动

这是主要 Activity

public class ActivityBeamRec extends AppCompatActivity {

    private SectionsPagerAdapter mSectionsPagerAdapter;

    public static CustomViewPager mViewPager;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_activity_beam_rec);

        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        // Set up the ViewPager with the sections adapter.
        mViewPager = (CustomViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);
        mViewPager.setPagingEnabled(false);

            }

    public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int position) {
                       switch (position){
                case 0 : return PlaceholderFragment.newInstance(position + 1);
         //       case 1 : return the new fragment ;
            }
            return null;
        }

        @Override
        public int getCount() {

            return 1 ; 
        }

            }
}

这是我的 fragment 。

public  class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    public PlaceholderFragment() {
    }

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        final View rootView = inflater.inflate(R.layout.fragment_activity_beam_rec, container, false);

        final EditText etxb;
     etxb = (EditText)rootView.findViewById(R.id.editText);
     final Button buDesign = (Button)rootView.findViewById(R.id.buDesign);

        buDesign.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
    double b;          
    b = Double.valueOf(etxb.getText().toString());

\\here i want the button to create the second fragment and pass the variable d to it
 ActivityBeamRec.mViewPager.setPagingEnabled(true); // this is to enable the siwpe between the fragments
ActivityBeamRec.mViewPager.setCurrentItem(2); // ths is to set the new fragment as the current view

            }
        });
        return rootView;
    }



}

按下按钮后，第二个 fragment 应该在创建 View 阶段进行，如果有办法做到这一点，请告诉我将每个代码放在哪里。

Answer 1

ActivityBeamRec:

public class ActivityBeamRec extends AppCompatActivity {

    private SectionsPagerAdapter mSectionsPagerAdapter;

    private ViewPager mViewPager;

    private TabLayout tabLayout;

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());

        // Set up the ViewPager with the sections adapter.
        mViewPager = (ViewPager) findViewById(R.id.container);
        mViewPager.setAdapter(mSectionsPagerAdapter);

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


    @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);
    }


    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {
        // This list holds the fragments for the pages displayed by view pager.
        private List < Fragment > fragments = new ArrayList < Fragment > ();

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
            // Add the first fragment:
            fragments.add(PlaceholderFragment.newInstance(1));
        }

        private void addFragment(Fragment fragment) {
            fragments.add(fragment);

            // Notify view pager that the contents of the adapter has changed and that it needs to update
            // its pages:
            notifyDataSetChanged();

            // Since content of view pager has changed, re-wire tab layout:
            tabLayout.setupWithViewPager(mViewPager);

            // Set the current page in the view pager to the last added fragment:
            mViewPager.setCurrentItem(fragments.size() - 1);
        }

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

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

        @Override
        public CharSequence getPageTitle(int position) {
            // Set the tab title as the number of the current section:
            return "SECTION " + (position + 1);
        }
    }

    /**
     * Adds a new fragment (page) to the view pager.
     * This method can either be public or package-private (without any modifier) depending on the package
     * of 'PlaceholderFragment'. Since you're new to Java please refer the link to access modifiers below.
     *
     * @param fragment the fragment to be added to the view pager
     **/
    public void addFragment(Fragment fragment) {
        mSectionsPagerAdapter.addFragment(fragment);
    }

    /**
     * Returns the number of the next section (page) to be added.
     *
     * @return the next section number
     */
    public int getNextSectionNumber() {
        return mSectionsPagerAdapter.getCount() + 1;
    }

}

占位符 fragment :

public class PlaceholderFragment extends Fragment {

    /**
     * The fragment argument representing the section number for this
     * fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    public PlaceholderFragment() {}

    /**
     * Returns a new instance of this fragment for the given section
     * number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        final View rootView = inflater.inflate(R.layout.fragment_activity_beam_rec, container, false);

        final EditText etxb;
        etxb = (EditText) rootView.findViewById(R.id.editText);
        final Button buDesign = (Button) rootView.findViewById(R.id.buDesign);

        buDesign.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                double b;
                b = Double.valueOf(etxb.getText().toString());

                //here i want the button to create the second fragment and pass the variable d to it
                int nextSectionNumber = ((ActivityBeamRec) getActivity()).getNextSectionNumber();
                ((ActivityBeamRec) getActivity()).addFragment(PlaceholderFragment.newInstance(nextSectionNumber));
            }
        });
        return rootView;
    }
}

当单击 fragment 中的按钮时，会依次发生以下操作:

通过传递要添加的 fragment 实例来调用父 Activity 的
1. addFragment() 方法。此公共(public)方法用于访问父 Activity 的私有(private)成员mSectionsPagerAdapter。如果将 mSectionsPagerAdapter 设为公共(public)或包私有(private)，我们就可以取消此方法。
2. SectionsPagerAdapter 将传入的 fragment 添加到其 fragment 列表中，然后通知 View 分页器其数据集已更改。
3. TabLayout 刷新以适应新的 fragment (页面)。
4. 最后，使用 setCurrentItem() 方法使 View 分页器滚动到添加的 fragment 。

引用:

• Java Access Control Modifiers
• List Data Structure in Java