單擊按鈕將片段添加到尋呼機適配器

Question

我有一個帶1個片段的選項卡式活動，該片段有一個按鈕，我想當我單擊按鈕時創建一個新片段，我可以在兩個片段之間滑動

這是主要活動

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 ; 
        }

            }
}

這是我的片段。

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;
    }



}

按下按鈕后，第二個片段應該進入創建視圖階段，如果可以的話，請告訴我將每個代碼放在哪里。

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;
    }

}

占位符片段：

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;
    }
}

單擊片段中的按鈕時，將依次發生以下情況：

1. 通過傳遞要添加的片段實例來調用父活動的addFragment()方法。 此公共方法用於訪問父活動的私有成員mSectionsPagerAdapter 。 如果將mSectionsPagerAdapter公共或程序包私有，則可以取消此方法。
2. SectionsPagerAdapter將傳入的片段添加到其片段列表中，然后通知視圖分頁器其數據集已更改。
3. TabLayout刷新以適應新的片段（頁面）。
4. 最后，使用setCurrentItem()方法使視圖分頁器滾動到添加的片段。

參考：

• Java訪問控制修飾符
• 用Java列出數據結構

Answer 2

在您的SectionsPagerAdapter中

private ArrayList<Fragment> fragments = new ArrayList<>();

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

@Override
public Fragment getItem(int position) {
  if(position<fragments.size())
      return fragments.get(position);
  throw new NullPointerException("No Fragment with this position found.");
}
public void addFragment(Fragment newFragment){
  fragments.add(newFragment);
}

在MainActivity中，使用mViewPager.setAdapter(mSectionsPagerAdapter);設置適配器之前mViewPager.setAdapter(mSectionsPagerAdapter); 添加您的第一個片段（在您的情況下為PlaceHolder ）。 （或在SectionPagerAdapter的構造函數中執行此操作）。

然后在您的OnClickListener調用SectionPagerAdapter的addFragment方法。

編輯：在MainActivity中：

mSectionsPagerAdapter.addFragment(PlaceholderFragment.newInstance(0));
mSectionsPagerAdapter.setAdapter(mSectionsPagerAdapter);