如何使用接口接收到的字符串

Question

我有一个 Activity 有 2 个碎片。现在实现了将数据从一个片段发送到我的 Activity 的接口，我想在 Textview 中显示我的数据（字符串）。但我怎么能做到这一点？我得到了方法：

@Override
public void sendText(String dataInput) {

}

但是如何访问我的字符串？

主要Activity:

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener, AddDataFragment.OnFragmentInteractionListener {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.scanbutton);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Hier kann man später QR-Codes scannen", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        Fragment fragment;
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        fragment = new ListViewFragment();
        ft.replace(R.id.container, fragment);
        ft.addToBackStack(null);
        ft.commit();
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

     @SuppressWarnings("StatementWithEmptyBody")
     @Override
     public boolean onNavigationItemSelected(MenuItem item) {
         Fragment fragment;
         FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
         fragment = new ListViewFragment();
         int id = item.getItemId();

             if (id == R.id.nav_listview) {
                 fragment= new ListViewFragment();

             } else if (id == R.id.nav_add_data) {
                 fragment= new AddDataFragment();

             } else if (id == R.id.nav_settings) {

             } else if (id == R.id.nav_legal_information) {
                 fragment = new LegalInformationFragment();
             }
         ft.replace(R.id.container, fragment);
         ft.addToBackStack(null);
         ft.commit();

         DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
         drawer.closeDrawer(GravityCompat.START);
         return true;
     }


    @Override
    public void sendText(String dataInput) {
        return;
    }
}

添加数据片段：

public class AddDataFragment extends Fragment {

    Button buttonadd;
    Button buttondelete;

    private EditText inputProduct;
    private EditText inputLabel;
    private EditText inputSerial;
    private EditText inputMac;
    private EditText inputDaaId;
    private EditText inputBill;

    private TextView listElement;

    private OnFragmentInteractionListener mListener;

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnFragmentInteractionListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_add_data, container, false);
        inputProduct = (EditText) view.findViewById(R.id.editText_product);
        inputLabel = (EditText) view.findViewById(R.id.editText_label);
        inputSerial = (EditText) view.findViewById(R.id.editText_serial);
        inputMac = (EditText) view.findViewById(R.id.editText_mac);
        inputDaaId = (EditText) view.findViewById(R.id.editText_daa_id);
        inputBill = (EditText) view.findViewById(R.id.editText_bill);
        buttonadd = (Button) view.findViewById(R.id.button_add_addData);
        buttondelete = (Button) view.findViewById(R.id.button_delete_addData);

        final String Bsp = "BEISPIELEINTRAG 1234214124";

        buttonadd.setEnabled(true);
        buttondelete.setEnabled(true);

        buttonadd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String dataInput = inputProduct.getText().toString() + inputLabel.getText().toString() +
                        inputSerial.getText().toString() + inputMac.getText().toString() +
                        inputDaaId.getText().toString() + inputBill.getText().toString();

                mListener.sendText(dataInput);
            }

        });

        return view;
    }

    public interface OnFragmentInteractionListener {
        void sendText(String dataInput);
    }
}

我只想将我的数据从 AddDataFragment 发送到我的 ListViewFragment。有人说这将是通过接口进行通信的最佳方式...

编辑：我只能在 MainACtivity 的 sendText 方法中使用 AddFragments Data，我说得对吗？问题是如何显示这个字符串。抱歉初学者问题...

Answer 1

android 中的接口用于从 'child' 到 'parent' 的回调。例如你的 activity 创建一个片段并告诉他他是实现 OnFragmentInteractionListener 的委托。然后片段可以通过调用 mListener.sendText(dataInput) 来触发 activity 中的代码。太好了。

但是，因为您想将数据发送到另一个片段（而不是父片段 activity），所以这不是一个好方法。

           Activity
          /       \
Fragment A         Fragment B

从 Activity 到片段 A 并返回很容易。对于 B 也是如此，但是从片段 A 直接通信到 B 并不容易。至少没有接口。

您最好暂时将 dataInput 存储在 sharedpreferences（或其他地方）中，这样您就可以将它们存储在 AddDataFragment 中并轻松地在您的 ListViewFragment 中检索它们。

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