在Android中做片段的正确方法是什么？

Question

I'm relatively new to Android Studio and I'm doing an app, one of it's interface's function is to show the data of various user's and I saw various tutorials on how to list data using FirebaseRecyclerAdapter but they are not working. And now I'm trying to do fragments which I don't know how to do yet.

I'd like to know if this code is properly set up to do a fragment.

My MainActivity.java

public class MainActivity extends AppCompatActivity {

    private RelativeLayout pills_layout, appoint_layout, add_pills_layout, add_appoints_layout, account_layout, add_button;
    private TextView AccountName0, AccountAge0;
    private RecyclerView recyclerView;
    private LinearLayoutManager linearLayoutManager;
    private FirebaseRecyclerAdapter adapter;
    private View view;

    private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
            = new BottomNavigationView.OnNavigationItemSelectedListener() {

        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            switch (item.getItemId()) {
                case R.id.navigation_home:
                    Home();
                    return true;
                case R.id.navigation_pills:
                    Pills();
                    return true;
                case R.id.navigation_appointment:
                    Appointment();
                    return true;
                case R.id.navigation_account:
                    Account();
                    return true;
            }
            return false;
        }
    };

    public MainActivity() {
    }

    private void Account(){
        RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) add_button.getLayoutParams();
        params.addRule(RelativeLayout.BELOW, R.id.account);

        pills_layout.setVisibility(View.GONE);
        appoint_layout.setVisibility(View.GONE);
        add_pills_layout.setVisibility(View.GONE);
        add_appoints_layout.setVisibility(View.GONE);
        //account_layout.setVisibility(View.VISIBLE);

        add_button.setVisibility(View.VISIBLE);

        /*Button accountChangePass = findViewById(R.id.AccountChangePass);

        accountChangePass.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Intent ChangePW = new Intent(MainActivity.this, ChangePW.class);
                startActivity(ChangePW);
            }
        });*/
    }


    private void Appointment() {
        RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) add_button.getLayoutParams();
        params.addRule(RelativeLayout.BELOW, R.id.add_appoints);

        pills_layout.setVisibility(View.GONE);
        appoint_layout.setVisibility(View.GONE);
        add_pills_layout.setVisibility(View.GONE);
        add_appoints_layout.setVisibility(View.VISIBLE);
        //account_layout.setVisibility(View.GONE);

        add_button.setVisibility(View.VISIBLE);
    }

    private void Pills() {
        RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) add_button.getLayoutParams();
        params.addRule(RelativeLayout.BELOW, R.id.add_pills);

        pills_layout.setVisibility(View.GONE);
        appoint_layout.setVisibility(View.GONE);
        add_pills_layout.setVisibility(View.VISIBLE);
        add_appoints_layout.setVisibility(View.GONE);
        //account_layout.setVisibility(View.GONE);

        add_button.setVisibility(View.VISIBLE);
    }

    private void Home() {
        pills_layout.setVisibility(View.VISIBLE);
        appoint_layout.setVisibility(View.VISIBLE);
        add_pills_layout.setVisibility(View.GONE);
        add_appoints_layout.setVisibility(View.GONE);
        //account_layout.setVisibility(View.GONE);

        add_button.setVisibility(View.GONE);
    }

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

        FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
        if (user == null) {
            Intent VerifyLogin = new Intent(MainActivity.this, Launcher.class);
            VerifyLogin.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
            startActivity(VerifyLogin);
        }

        pills_layout = findViewById(R.id.pills_layout);
        appoint_layout = findViewById(R.id.appoint_layout);
        add_pills_layout = findViewById(R.id.add_pills);
        add_appoints_layout = findViewById(R.id.add_appoints);
        //account_layout = findViewById(R.id.accountlist);

        AccountName0 = findViewById(R.id.AccountName0);
        AccountAge0 = findViewById(R.id.AccountAge0);

        add_button = findViewById(R.id.add);

        pills_layout.setVisibility(View.VISIBLE);
        appoint_layout.setVisibility(View.VISIBLE);
        add_pills_layout.setVisibility(View.GONE);
        add_appoints_layout.setVisibility(View.GONE);
        //account_layout.setVisibility(View.GONE);
        add_button.setVisibility(View.GONE);

        recyclerView = findViewById(R.id.accountlist);

        linearLayoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(linearLayoutManager);
        recyclerView.setHasFixedSize(true);

        BottomNavigationView navigation = findViewById(R.id.navigation);
        navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
    }

    public class ViewHolder extends RecyclerView.ViewHolder {
        public RelativeLayout root;
        public TextView txtTitle;
        public TextView txtDesc;

        public ViewHolder(View itemView) {
            super(itemView);
            root = itemView.findViewById(R.id.account);
            txtTitle = itemView.findViewById(R.id.AccountName0);
            txtDesc = itemView.findViewById(R.id.AccountAge0);
        }

        public void setTxtTitle(String string) {
            txtTitle.setText(string);
        }


        public void setTxtDesc(String string) {
            txtDesc.setText(string);
        }
    }

    @Override
    protected void onStart() {
        super.onStart();
        Query query = FirebaseDatabase.getInstance()
                .getReference()
                .child("Users");

        FirebaseRecyclerOptions<Account> options =
                new FirebaseRecyclerOptions.Builder<Account>()
                        .setQuery(query, new SnapshotParser<Account>() {
                            @NonNull
                            @Override
                            public Account parseSnapshot(@NonNull DataSnapshot snapshot) {
                                return new Account(snapshot.child("name").getValue().toString(),
                                        snapshot.child("idade").getValue().toString());
                            }
                        })
                        .build();

        adapter = new FirebaseRecyclerAdapter<Account, ViewHolder>(options) {
            @Override
            public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                view = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.account, parent, false);

                return new ViewHolder(view);
            }


            @Override
            protected void onBindViewHolder(ViewHolder holder, final int position, Account model) {
                holder.setTxtTitle(model.getName());
                holder.setTxtDesc(model.getIdade());

                holder.root.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Toast.makeText(MainActivity.this, String.valueOf(position), Toast.LENGTH_SHORT).show();
                    }
                });
            }

        };
        recyclerView.setAdapter(adapter);
        adapter.startListening();
    }

    @Override
    protected void onStop() {
        super.onStop();
        Query query = FirebaseDatabase.getInstance()
                .getReference()
                .child("Users");

        FirebaseRecyclerOptions<Account> options =
                new FirebaseRecyclerOptions.Builder<Account>()
                        .setQuery(query, new SnapshotParser<Account>() {
                            @NonNull
                            @Override
                            public Account parseSnapshot(@NonNull DataSnapshot snapshot) {
                                return new Account(snapshot.child("name").getValue().toString(),
                                        snapshot.child("idade").getValue().toString());
                            }
                        })
                        .build();

        adapter = new FirebaseRecyclerAdapter<Account, ViewHolder>(options) {
            @Override
            public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                view = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.account, parent, false);

                return new ViewHolder(view);
            }


            @Override
            protected void onBindViewHolder(ViewHolder holder, final int position, Account model) {
                holder.setTxtTitle(model.getName());
                holder.setTxtDesc(model.getIdade());

                holder.root.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View view) {
                        Toast.makeText(MainActivity.this, String.valueOf(position), Toast.LENGTH_SHORT).show();
                    }
                });
            }

        };
        recyclerView.setAdapter(adapter);
        adapter.stopListening();
    }
};

My Account.java

public class Account {
    private String name, idade;

    public Account() {

    }

    public Account(String name, String idade) {
        this.name = name;
        this.idade = idade;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getIdade() {
        return idade;
    }

    public void setIdade(String idade) {
        this.idade = idade;
    }
}

My account.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/account">

        <RelativeLayout
            android:id="@+id/AccountUser"
            android:layout_width="match_parent"
            android:layout_height="163dp"
            android:layout_marginStart="15dp"
            android:layout_marginLeft="15dp"
            android:layout_marginTop="15dp"
            android:layout_marginEnd="15dp"
            android:layout_marginRight="15dp"
            android:layout_marginBottom="15dp"
            android:background="@drawable/edit_bg"
            android:padding="15dp">

            <RelativeLayout
                android:id="@+id/AccountImage"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content">

                <ImageView
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:src="@drawable/ic_user"/>

            </RelativeLayout>

            <RelativeLayout
                android:id="@+id/AccountInfos"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_toRightOf="@id/AccountImage"
                android:layout_toEndOf="@id/AccountImage"
                android:layout_marginStart="15dp"
                android:layout_marginLeft="15dp">

                <TextView
                    android:id="@+id/AccountName0"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:paddingTop="5dp"
                    android:paddingBottom="5dp"
                    android:text="Nome1"
                    android:textColor="@color/colorWhite"
                    android:textSize="20sp"
                    android:textStyle="bold" />

                <TextView
                    android:id="@+id/AccountAge0"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_below="@+id/AccountName0"
                    android:paddingTop="5dp"
                    android:paddingBottom="5dp"
                    android:text="Idade1"
                    android:textColor="@color/colorWhite"
                    android:textSize="20sp"
                    android:textStyle="bold" />

                <Button
                    android:id="@+id/AccountChangePass"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_below="@+id/AccountAge0"
                    android:text="Mudar Palavra-Passe"
                    android:textColor="@color/colorWhite"
                    android:textSize="18sp"
                    android:textStyle="bold"
                    android:textAllCaps="false"
                    android:padding="10dp"
                    android:layout_marginTop="10dp"
                    android:background="@drawable/custom_button"/>
            </RelativeLayout>

        </RelativeLayout>
    </RelativeLayout>

</RelativeLayout>

Answer 1

the best way to do that in my opinion is using Fragments.

Create 3 fragments:

Just check the checkBox that says " Create layout XML? "

Create a java class and add this code after create 3 fragments:

public class /* class name 1 */ extends FragmentPagerAdapter {

public /* class name 1 */ (FragmentManager fm) {

    super(fm);
}

@Override
public Fragment getItem(int position) {

    switch (position){
        case 0:
            Fragment1 fragment1= new Fragment1 ();
            return fragment1;
        case 1:
            Fragment2 fragment2 = new Fragment2();
            return fragment2 ;
        case 2:
            Fragment3 fragment3 = new Fragment3 ();
            return fragment3 ;

        default:
            return null;
    }
}


@Override
public int getCount() {

    return 3;

}

public CharSequence getPageTitle(int position){

    switch (position){
        case 0:
            return "/* set a name to fragment1*/";
        case 1:
            return "/* set a name to fragment2*/";
        case 2:
            return "/* set a name to fragment3*/";
        default:
            return null;
    }

}

}

Now in your mainActivity.java add this code:

public class MainActivity extends AppCompatActivity {

private ViewPager mViewPager;

private /* class name 1 */ mSectionsPagerAdapter;

private TabLayout mTabLayout;

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

    mViewPager = findViewById(R.id.main_tabPager);

    mSectionsPagerAdapter = new /* class name 1 */(getSupportFragmentManager());

    mViewPager.setAdapter(mSectionsPagerAdapter);

    mTabLayout = findViewById(R.id.main_tabs);
    mTabLayout.setupWithViewPager(mViewPager);

}

}

Now in your mainactivity.xml add this:

 <android.support.v4.view.ViewPager
    android:id="@+id/main_tabPager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_alignParentStart="true"
    android:layout_alignParentTop="true"
    android:visibility="visible"
    tools:ignore="UnknownId"></android.support.v4.view.ViewPager>
<android.support.design.widget.TabLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/colorAccent"
    android:id="@+id/main_tabs">
</android.support.design.widget.TabLayout>

The final result will look like this:

Answer 2

I suppose pills_layout, appoint_layout, .. are your fragment layouts. Maintaining them by changing their VISIBILITY property is not a good idea.

You have to use the supportFragmentManager instead. Create a loadFragment method like this

    public final boolean loadFragment(@NotNull Fragment fragment) {
    this.getSupportFragmentManager().beginTransaction()
      .replace(<<id of your fragment container layout>>, fragment, "fragment").commit();
    return true;
}

And change your onNavigationItemSelected method to this:

@Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.navigation_home:
                return loadFragment(new HomeFragment());
            case R.id.navigation_pills:
                return loadFragment(new PillsFragment());
            case R.id.navigation_appointment:
                return loadFragment(new AppointmentFragment());
            case R.id.navigation_account:
                return loadFragment(new AccountFragment());
        }
        return false;
    }
};

Now make a seperate class for each fragment and inflate the layout of the right fragment. here is an example of how your HomeFragment-class has to look like this:

public final class HomeFragment extends Fragment {

@Override
public View onCreate(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
    return inflater.inflate(R.layout.<<your homefragment layout name>>, null);
}

}

I hope it's enough to help you out. I'm sorry if there are little mistakes in syntax, I'm used to code Android in Kotlin. But you will get the idea behind it.