Room Database trong Android – hướng dẫn sử dụng chi tiết

dependencies {
...
    implementation 'android.arch.persistence.room:runtime:' + rootProject.archRoomVersion;
...
}

<?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:gravity="center_horizontal"
    android:orientation="vertical">

    <EditText
        android:id="@+id/etName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="10dp"
        android:ems="10"

        android:hint="Employ Name"
        android:inputType="textPersonName|textCapWords"
        android:singleLine="true"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        tools:layout_editor_absoluteY="7dp" />

    <EditText
        android:id="@+id/etDesignation"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:ems="10"
        android:hint="Designation"
        android:inputType="textPersonName|textCapWords"
        android:singleLine="true"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        tools:layout_editor_absoluteY="75dp" />

    <Button
        android:background="@android:color/holo_blue_bright"
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="Save"
        app:layout_constraintTop_toBottomOf="@+id/editText2" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="16dp">

    <TextView
        android:text="data"
        android:id="@+id/txt_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />
    </ScrollView>

</LinearLayout>

@Entity
public class Employee {
    @PrimaryKey(autoGenerate = true)
    public long employId;
    @ColumnInfo(name = "employ_name")
    public String name;
    public String designation;
}

@Dao
public interface EmployDao {
    @Insert(onConflict = REPLACE)
    void insertEmploy(Employee employee);

    @Insert(onConflict = IGNORE)
    void insertOrReplaceEmploy(Employee... employees);

    @Update(onConflict = REPLACE)
    void updateEmploy(Employee employee);

    @Query("DELETE FROM Employee")
    void deleteAll();

    @Query("SELECT * FROM Employee")
    public List<Employee> findAllEmploySync();
}

@Database(entities = {Employee.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
    private static AppDatabase INSTANCE;
    public abstract EmployDao employDao();
    public static AppDatabase getInMemoryDatabase(Context context) {
        if (INSTANCE == null) {
            INSTANCE = 
Room.inMemoryDatabaseBuilder(context.getApplicationContext(), AppDatabase.class)
                           // To simplify the codelab, allow queries on the main thread.
                           // Don't do this on a real app! See PersistenceBasicSample for an example.
                           .allowMainThreadQueries()
                           .build();
        }
         return INSTANCE;
    }
    public static void destroyInstance() {
        INSTANCE = null;
    }
}

//Hàm xử lý click
Employee employee = new Employee();
employee.name = name;
employee.designation = designation;
mDb.employDao().insertEmploy(employee);
Toast.makeText(this, "Saved successfully", Toast.LENGTH_SHORT).show();
etName.setText("");
etDesignation.setText("");
etName.requestFocus();
populateEmployList();