使用RecyclerView.Adapter或CursorAdapter的DbFlow

DbFlow 是一个用于 Android 的 ORM（对象关系映射）库，它简化了数据库操作。DbFlow 提供了对 RecyclerView.Adapter 和 CursorAdapter 的支持，使得在 RecyclerView 中显示数据库数据变得更加容易。

使用 RecyclerView.Adapter

1. 添加依赖 在你的 build.gradle 文件中添加 DbFlow 和 RecyclerView 的依赖： dependencies { implementation 'com.raizlabs.android:DBFlow-core:5.0.0-alpha1' implementation 'com.raizlabs.android:DBFlow:5.0.0-alpha1' implementation 'androidx.recyclerview:recyclerview:1.2.1' }
2. 创建数据模型 使用 DbFlow 注解创建一个数据模型类： import com.raizlabs.android.dbflow.annotation.Column; import com.raizlabs.android.dbflow.annotation.PrimaryKey; import com.raizlabs.android.dbflow.annotation.Table; import com.raizlabs.android.dbflow.structure.BaseModel; @Table(database = AppDatabase.class) public class User extends BaseModel { @PrimaryKey(autoincrement = true) long id; @Column String name; @Column int age; }
3. 创建 RecyclerView.Adapter 创建一个继承自 RecyclerView.Adapter 的适配器类，并使用 DbFlow 提供的 FlowQueryList 来获取数据： import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.TextView; import androidx.annotation.NonNull; import androidx.recyclerview.widget.RecyclerView; import com.raizlabs.android.dbflow.sql.language.SQLite; import com.raizlabs.android.dbflow.list.FlowQueryList; import java.util.List; public class UserAdapter extends RecyclerView.Adapter<UserAdapter.UserViewHolder> { private FlowQueryList<User> userList; public UserAdapter() { userList = SQLite.select().from(User.class).queryList(); } @NonNull @Override public UserViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) { View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_user, parent, false); return new UserViewHolder(view); } @Override public void onBindViewHolder(@NonNull UserViewHolder holder, int position) { User user = userList.get(position); holder.nameTextView.setText(user.name); holder.ageTextView.setText(String.valueOf(user.age)); } @Override public int getItemCount() { return userList.size(); } static class UserViewHolder extends RecyclerView.ViewHolder { TextView nameTextView; TextView ageTextView; UserViewHolder(View itemView) { super(itemView); nameTextView = itemView.findViewById(R.id.nameTextView); ageTextView = itemView.findViewById(R.id.ageTextView); } } }
4. 在 Activity 或 Fragment 中设置 RecyclerView import android.os.Bundle; import androidx.appcompat.app.AppCompatActivity; import androidx.recyclerview.widget.LinearLayoutManager; import androidx.recyclerview.widget.RecyclerView; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); RecyclerView recyclerView = findViewById(R.id.recyclerView); recyclerView.setLayoutManager(new LinearLayoutManager(this)); recyclerView.setAdapter(new UserAdapter()); } }

使用 CursorAdapter

DbFlow 也支持使用 CursorAdapter，但需要注意的是，DbFlow 的 CursorAdapter 实现可能与传统的 CursorAdapter 有所不同。

1. 创建 CursorAdapter import android.content.Context; import android.database.Cursor; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.CursorAdapter; import android.widget.TextView; public class UserCursorAdapter extends CursorAdapter { public UserCursorAdapter(Context context, Cursor c, int flags) { super(context, c, flags); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { return LayoutInflater.from(context).inflate(R.layout.item_user, parent, false); } @Override public void bindView(View view, Context context, Cursor cursor) { TextView nameTextView = view.findViewById(R.id.nameTextView); TextView ageTextView = view.findViewById(R.id.ageTextView); String name = cursor.getString(cursor.getColumnIndexOrThrow("name")); int age = cursor.getInt(cursor.getColumnIndexOrThrow("age")); nameTextView.setText(name); ageTextView.setText(String.valueOf(age)); } }
2. 在 Activity 或 Fragment 中设置 CursorAdapter

import android.database.Cursor; import android.os.Bundle; import androidx.appcompat.app.AppCompatActivity; import androidx.recyclerview.widget.LinearLayoutManager; import androidx.recyclerview.widget.RecyclerView; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Cursor cursor = SQLite.select().from(User.class).query(); UserCursorAdapter adapter = new UserCursorAdapter(this, cursor, 0); RecyclerView recyclerView = findViewById(R.id.recyclerView); recyclerView.setLayoutManager(new LinearLayoutManager(this)); recyclerView.setAdapter(adapter); } }