Programação para Dispositivos Móveis I

   Toast toast = Toast.makeText(context, text, duration);
   toast.show();

    Toast.makeText(context, text, duration).show();

...
AlertDialog dialog = new AlertDialog.Builder(getActivity()).create();
    dialog.setTitle("Alerta");
    dialog.setMessage("Olá turma!");
    dialog.setButton(DialogInterface.BUTTON_POSITIVE, "Ok", new DialogInterface.OnClickListener(){
        @Override
        public void onClick(DialogInterface dialog, int which) {
        }
    });
    dialog.setButton(DialogInterface.BUTTON_NEGATIVE, "Cancelar", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
        }
    });
    dialog.setButton(DialogInterface.BUTTON_NEUTRAL, "Neutro", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
        }
    });
    dialog.show();

<ListView
        android:id="@+id/lsvAlunos"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        ...
    </ListView>

...
public class ListaSimplesActivity extends AppCompatActivity implements AdapterView.OnItemClickListener {

    ListView listView;

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

        listView = findViewById(R.id.lsvAlunos);

        List<String> alunos = new ArrayList();
        alunos.add("Aluno 1");
        alunos.add("Aluno 2");
        alunos.add("Aluno 3");

        ArrayAdapter adapter = new ArrayAdapter(this,
                android.R.layout.simple_list_item_1, alunos);
        listView.setAdapter(adapter);

    }
}

...
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
    //identifica o objeto da lista pelo "position" na ação do click
    String nome = (String) parent.getAdapter().getItem(position);
    Toast.makeText(this, nome, Toast.LENGTH_SHORT).show();
}

...
listView.setOnItemClickListener(this);

public class Aluno{

    private String nome;
    private double nota1;
    private double nota2;

    //gets e sets
}

...
<TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="19dp"
        android:layout_marginStart="8dp"
        android:layout_marginEnd="8dp"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginEnd="8dp"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginEnd="8dp"
        android:text="TextView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />
...

...
public class AlunoAdapter extends BaseAdapter {

    LayoutInflater inflater;
    List<Aluno> alunos;

    //construtor
    public AlunoAdapter(Context context, List<Aluno> alunos) {
        this.inflater = LayoutInflater.from(context);
        this.alunos = alunos;
    }

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

    @Override
    public Object getItem(int position) {
        return alunos.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        //identifica o item(objeto aluno) da lista através do "position"
        Aluno aluno = alunos.get(position);
        //infla o layout "itens_lista_customizada_aluno" para referênciar/receber o item
        convertView = inflater.inflate(R.layout.item_lista_simples_adapter,null);
        //aponta qual dado o componente do layout vai receber
        ((TextView)convertView.findViewById(R.id.textView)).setText(aluno.getNome());
        ((TextView)convertView.findViewById(R.id.textView2)).setText(String.valueOf(aluno.getNota1()));
        ((TextView)convertView.findViewById(R.id.textView3)).setText(String.valueOf(aluno.getNota2()));

        return convertView;
    }
}

public class aula211020 extends AppCompatActivity {

    ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_aula211020);

        //faz referência ao ListView do layout "activity_lista_customizada"
        listView = findViewById(R.id.lsvAlunos);
        //define uma lista de alunos
        List<Aluno> alunos = new ArrayList<>();
        //cria e inicializa os dados dos alunos
        Aluno a1 = new Aluno("Aluno 1",9.5,6.8);
        Aluno a2 = new Aluno("Aluno 2",8.5,6.8);
        Aluno a3 = new Aluno("Aluno 3",7.5,8.8);
        Aluno a4 = new Aluno("Aluno 4",6.5,7.8);

        //add alunos na lista
        alunos.add(a1);
        alunos.add(a2);
        alunos.add(a3);
        alunos.add(a4);

        AlunoAdapter alunoAdapter = new AlunoAdapter(this,alunos);
        listView.setAdapter(alunoAdapter);
    }
}

dependencies {
    implementation 'androidx.cardview:cardview:1.0.0'
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <!-- A CardView that contains a TextView -->
    <androidx.cardview.widget.CardView
        android:id="@+id/card_view"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        card_view:cardCornerRadius="4dp">

        //itens do card

    </androidx.cardview.widget.CardView>

</LinearLayout>

dependencies {
    implementation 'androidx.recyclerview:recyclerview:1.1.0'
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">


    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/myRecyclerView"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scrollbars="vertical"/>

</LinearLayout>

public class MyActivity extends Activity {

    private RecyclerView recyclerView;
    private RecyclerView.Adapter mAdapter;
    private RecyclerView.LayoutManager layoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_activity);
        recyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        recyclerView.setHasFixedSize(true);

        // use a linear layout manager
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        // specify an adapter (see also next example)
        mAdapter = new MyAdapter(myDataset);
        recyclerView.setAdapter(mAdapter);
    }
    // ...
}

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    private List<String> mDataset;

    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter(List<String> myDataset) {
        this.mDataset = myDataset;
    }

    // Provide a reference to the views for each data item
    // Complex data items may need more than one view per item, and
    // you provide access to all the views for a data item in a view holder
    public static class MyViewHolder extends RecyclerView.ViewHolder {

        // each data item is just a string in this case
        public TextView textView;

        public MyViewHolder(View itemView) {
            super(itemView);
            textView = itemView.findViewById(R.id.textView1);
        }
    }

    // Create new views (invoked by the layout manager)
    @Override
    public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent,
                                                    int viewType) {
        // create a new view
        View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.itens_layout_card, parent, false);

        MyViewHolder vh = new MyViewHolder(view);
        return vh;
    }

    // Replace the contents of a view (invoked by the layout manager)
    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        // - get element from your dataset at this position
        // - replace the contents of the view with that element
        holder.textView.setText(mDataset.get(position));

    }

    // Return the size of your dataset (invoked by the layout manager)
    @Override
    public int getItemCount() {
        return mDataset.size();
    }
}