随机片段使用 setText 更新

Question

我有一个包含一个活动和三个片段的 Android 项目。所有片段上都有相同的视图项。它基于 TabbedActivity 示例项目。这会创建同一个片段视图的多个实例。

所有的编辑框都有相同的 id： android:id="@+id/editText2"

片段上有相同的按钮和相同的编辑框，按下按钮会启动一个网络活动，尝试更新同一片段上的编辑框。

    final EditText resultBox = (EditText) findViewById(R.id.editText2);

    System.out.println("reponse: " + decodedStr);
    try 
    {
        runOnUiThread(new Runnable() 
        {
    
        @Override
        public void run() {
            resultBox.setText(decodedStr);
        }
         });
    }

但只有一个片段被更新，有时甚至不是活动片段。当我执行 findViewById(R.id.editText2);

时，这里到底发生了什么

编辑：添加了更多代码，结果 getText 函数也获取了错误的数据：

public class MainActivity extends AppCompatActivity {

    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
     * may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */
    private SectionsPagerAdapter mSectionsPagerAdapter;

    /**
     * The {@link ViewPager} that will host the section contents.
     */
    private ViewPager mViewPager;

    @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);
    }



    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        private static final String ARG_PAGE_TITLE = "page_title";

        public PlaceholderFragment() {
        }

        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static PlaceholderFragment newInstance(String pageTitle) {
            PlaceholderFragment fragment = new PlaceholderFragment();
            Bundle args = new Bundle();
            args.putString(ARG_PAGE_TITLE, pageTitle);
            fragment.setArguments(args);
            return fragment;
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            TextView textView = (TextView) rootView.findViewById(R.id.section_label);
            textView.setText(getString(R.string.section_format, getArguments().getString(ARG_PAGE_TITLE)));
            return rootView;
        }
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            // Return a PlaceholderFragment (defined as a static inner class below).

            String pageTitle;
            switch (position)
            {
                case 0:
                    pageTitle = "1";
                    break;
                case 1:
                    pageTitle = "2";
                    break;
                case 2:
                    pageTitle = "3";
                    break;
                default:
                    pageTitle = "4";
                    break;
            }
            return PlaceholderFragment.newInstance(pageTitle);
        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "SECTION 1";
                case 1:
                    return "SECTION 2";
                case 2:
                    return "SECTION 3";
            }
            return null;
        }
    }

    /** Called when the user touches the button */
    public void randomFunc(View view) {
        try {

            // Get the current Fragment in View using the ViewPager's currentItem
            PlaceholderFragment fragment = (PlaceholderFragment) mSectionsPagerAdapter.getItem(mViewPager.getCurrentItem());
            // Get the current Fragment's View
            View fragview = fragment.getView(); // Same view that onCreateView returns
            System.out.println("fragView " + fragview); // NULL

            EditText et = (EditText) fragview.findViewById(R.id.editText); // CRASH!!

...
        }
        catch (Exception e)
        {
            System.out.println("func failed" + e.toString());
        }
    }

}

在xml中：

android:onClick="randomFunc"

Answer 1

我假设您使用 ViewPager，以便更新正确的片段：

// Get the current Fragment in View using the ViewPager's currentItem
PlaceholderFragment fragment = (PlaceholderFragment) mSectionsPagerAdapter.getItem(mViewPager.getCurrentItem());
// Get the current Fragment's View
View view = fragment.getView();
// Find the view your looking for, and update its text
final EditText resultBox = (EditText) view.findViewById(R.id.editText2);
try {
    runOnUiThread(new Runnable() {

    @Override
    public void run() {
        resultBox.setText(decodedStr);
    }
     });
}