java - 抽屉导航 Activity ，通过 fragment 发送

Question

我创建了一个抽屉导航 Activity 。我想将信息(通过 EditText 和按钮)发送到我的 receive_fragment，其中信息应显示在 TextView 中。当我尝试在 mainActivity 中实现一个接口(interface)并在各自的 fragment 中添加“sendText”和“SetText”方法时，我收到了“null 未定义”的错误消息，因此我必须考虑替代用法，但完全陷入困境。我怎样才能从我的 Communicate 类发送消息以最终进入我的 Recieve_fragment 类？

沟通:

public class communicate_fragment extends Fragment{   

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

        return rootView;
    }    
    }

SEND_FRAGMENT

public class recieve_fragment extends Fragment{    

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_recieve, container, false);
        return rootView;
    }   
}

我尝试在 Main_activity 中添加一个接口(interface)来处理来自 communications_fragment 的请求并将其发送回 receive_fragment，但是我收到“无法实例化”的错误消息

MAIN_ACTIVITY

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener{

    @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.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", 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);

        android.app.FragmentManager fm = getFragmentManager();
        fm.beginTransaction().replace(R.id.content_frame, new mainfragment()).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();
        }
    }

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

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.

        android.app.FragmentManager fm = getFragmentManager();

        int id = item.getItemId();

        if (id == R.id.about_me) {
            fm.beginTransaction().replace(R.id.content_frame, new about_me_fragment()).commit();

        } else if (id == R.id.another_fragment) {
            fm.beginTransaction().replace(R.id.content_frame, new another_fragment()).commit();    

        } else if (id == R.id.send) {
            fm.beginTransaction().replace(R.id.content_frame, new communicate_fragment()).commit();

        }
        else if (id == R.id.recieve) {
            fm.beginTransaction().replace(R.id.content_frame, new recieve_fragment()).commit();
        }

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

Answer 1

首先创建监听器接口(interface):

public interface YourCustomListener {
    void onItemClick(int position, int ID);
}

现在将其添加到您的第一个 fragment 中:

YourCustomListener mListener;

以及您的 fragment onclick 方法:

mListener.onItemClick(position,"YOUR ID");

添加此:

@Override
    public void onAttach(Context con) {
        super.onAttach(con);
        try {
            mListener= (YourCustomListener ) con;
        } catch (ClassCastException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onDetach() {
        mListener=null;
        super.onDetach();
    }

在Activity类中实现接口(interface)。在派生方法中:

@Override
    public void onItemClick(int position,int ID) {
        fragment2 =new SecondFragment();
        Bundle arg= new Bundle();
        arg.putInt("ID",ID);
        arg.putString("title","ANY TITLE");
        fragment2.setArguments(arg);

        if (fragment2 != null) {
            FragmentManager fragmentManager = getSupportFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.setCustomAnimations(R.anim.slide_left_enter,R.anim.slide_left_exit,R.anim.slide_left_enter,R.anim.slide_left_exit);
            fragmentTransaction.replace(R.id.container_body, fragment2,"PROF");
            fragmentTransaction.addToBackStack(null);
            fragmentTransaction.commit();
            getSupportActionBar().setLogo(null);
        }
    }

现在在您的第二个 fragment 上，在创建方法中使用以下内容:

Bundle pb=getArguments();
        h=pb.getInt("ID");
        title=pb.getString("title");

现在您有了 int h 的值和字符串标题。使用此值显示在您的 TextView 中。