Android Studio 中使用 SQLite 数据库开发完整指南 (Java 版本)

最新推荐文章于 2025-05-28 14:19:51 发布

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最新推荐文章于 2025-05-28 14:19:51 发布

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分类专栏：包罗万象文章标签： android studio sqlite 数据库开发 kotlin android 开发语言 ide

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本文将详细介绍在 Android Studio 中使用 Java 语言开发 SQLite 数据库应用的完整方案，包括每一个步骤、每一个文件和每一段代码。

1. 项目准备

1.1 创建新项目

打开 Android Studio
选择 “Start a new Android Studio project”
选择 “Empty Activity” 模板
设置项目名称（例如 “SQLiteDemoJava”）
选择语言（选择 Java）
设置最低 API 级别（建议 API 21 或更高）
点击 “Finish” 完成项目创建

1.2 添加必要依赖

确保 build.gradle (Module: app) 中包含以下依赖：

dependencies {
    implementation 'androidx.appcompat:appcompat:1.4.1'
    implementation 'com.google.android.material:material:1.5.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
    
    // Room 数据库（SQLite 的抽象层）
    implementation "androidx.room:room-runtime:2.4.2"
    annotationProcessor "androidx.room:room-compiler:2.4.2"
    
    // ViewModel 和 LiveData
    implementation "androidx.lifecycle:lifecycle-viewmodel:2.4.1"
    implementation "androidx.lifecycle:lifecycle-livedata:2.4.1"
    
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

点击 “Sync Now” 同步项目。

2. 数据库设计

假设我们要创建一个简单的笔记应用，包含以下数据表：

notes 表：
- id: 主键，自增
- title: 笔记标题
- content: 笔记内容
- created_at: 创建时间
- updated_at: 更新时间

3. 实现数据库

3.1 创建实体类 (Entity)

在 com.yourpackage.model 包下创建 Note.java 文件：

import androidx.room.Entity;
import androidx.room.PrimaryKey;
import androidx.room.TypeConverters;
import java.util.Date;

@Entity(tableName = "notes")
public class Note {
    @PrimaryKey(autoGenerate = true)
    private long id;
    
    private String title;
    private String content;
    
    @TypeConverters(DateConverter.class)
    private Date created_at;
    
    @TypeConverters(DateConverter.class)
    private Date updated_at;
    
    public Note(String title, String content) {
        this.title = title;
        this.content = content;
        this.created_at = new Date();
        this.updated_at = new Date();
    }

    // Getters and Setters
    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public Date getCreated_at() {
        return created_at;
    }

    public void setCreated_at(Date created_at) {
        this.created_at = created_at;
    }

    public Date getUpdated_at() {
        return updated_at;
    }

    public void setUpdated_at(Date updated_at) {
        this.updated_at = updated_at;
    }
}

3.2 创建日期转换器

由于 Room 不能直接存储 Date 对象，我们需要创建一个转换器：

在 com.yourpackage.database 包下创建 DateConverter.java：

import androidx.room.TypeConverter;
import java.util.Date;

public class DateConverter {
    @TypeConverter
    public static Date toDate(Long timestamp) {
        return timestamp == null ? null : new Date(timestamp);
    }

    @TypeConverter
    public static Long toTimestamp(Date date) {
        return date == null ? null : date.getTime();
    }
}

3.3 创建数据访问对象 (DAO)

在 com.yourpackage.dao 包下创建 NoteDao.java 文件：

import androidx.lifecycle.LiveData;
import androidx.room.Dao;
import androidx.room.Delete;
import androidx.room.Insert;
import androidx.room.OnConflictStrategy;
import androidx.room.Query;
import androidx.room.Update;
import com.yourpackage.model.Note;
import java.util.List;

@Dao
public interface NoteDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void insertNote(Note note);
    
    @Update
    void updateNote(Note note);
    
    @Delete
    void deleteNote(Note note);
    
    @Query("SELECT * FROM notes ORDER BY updated_at DESC")
    LiveData<List<Note>> getAllNotes();
    
    @Query("SELECT * FROM notes WHERE id = :noteId")
    Note getNoteById(long noteId);
    
    @Query("SELECT * FROM notes WHERE title LIKE :query OR content LIKE :query ORDER BY updated_at DESC")
    LiveData<List<Note>> searchNotes(String query);
    
    @Query("DELETE FROM notes")
    void deleteAllNotes();
}

3.4 创建数据库类

在 com.yourpackage.database 包下创建 AppDatabase.java 文件：

import android.content.Context;
import androidx.room.Database;
import androidx.room.Room;
import androidx.room.RoomDatabase;
import androidx.room.TypeConverters;
import com.yourpackage.dao.NoteDao;
import com.yourpackage.model.Note;

@Database(entities = {Note.class}, version = 1, exportSchema = false)
@TypeConverters(DateConverter.class)
public abstract class AppDatabase extends RoomDatabase {
    public abstract NoteDao noteDao();
    
    private static volatile AppDatabase INSTANCE;
    
    public static AppDatabase getDatabase(final Context context) {
        if (INSTANCE == null) {
            synchronized (AppDatabase.class) {
                if (INSTANCE == null) {
                    INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                                    AppDatabase.class, "notes_database")
                            .fallbackToDestructiveMigration()
                            .build();
                }
            }
        }
        return INSTANCE;
    }
}

4. 创建 Repository

在 com.yourpackage.repository 包下创建 NoteRepository.java 文件：

import android.app.Application;
import androidx.lifecycle.LiveData;
import com.yourpackage.dao.NoteDao;
import com.yourpackage.database.AppDatabase;
import com.yourpackage.model.Note;
import java.util.List;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class NoteRepository {
    private NoteDao noteDao;
    private LiveData<List<Note>> allNotes;
    private ExecutorService executorService;
    
    public NoteRepository(Application application) {
        AppDatabase database = AppDatabase.getDatabase(application);
        noteDao = database.noteDao();
        allNotes = noteDao.getAllNotes();
        executorService = Executors.newSingleThreadExecutor();
    }
    
    public LiveData<List<Note>> getAllNotes() {
        return allNotes;
    }
    
    public void insert(Note note) {
        executorService.execute(() -> noteDao.insertNote(note));
    }
    
    public void update(Note note) {
        executorService.execute(() -> {
            note.setUpdated_at(new Date());
            noteDao.updateNote(note);
        });
    }
    
    public void delete(Note note) {
        executorService.execute(() -> noteDao.deleteNote(note));
    }
    
    public Note getNoteById(long id) {
        return noteDao.getNoteById(id);
    }
    
    public LiveData<List<Note>> searchNotes(String query) {
        return noteDao.searchNotes("%" + query + "%");
    }
    
    public void deleteAllNotes() {
        executorService.execute(() -> noteDao.deleteAllNotes());
    }
}

5. 创建 ViewModel

在 com.yourpackage.viewmodel 包下创建 NoteViewModel.java 文件：

import android.app.Application;
import androidx.lifecycle.AndroidViewModel;
import androidx.lifecycle.LiveData;
import com.yourpackage.model.Note;
import com.yourpackage.repository.NoteRepository;
import java.util.List;

public class NoteViewModel extends AndroidViewModel {
    private NoteRepository repository;
    private LiveData<List<Note>> allNotes;
    
    public NoteViewModel(Application application) {
        super(application);
        repository = new NoteRepository(application);
        allNotes = repository.getAllNotes();
    }
    
    public void insert(Note note) {
        repository.insert(note);
    }
    
    public void update(Note note) {
        repository.update(note);
    }
    
    public void delete(Note note) {
        repository.delete(note);
    }
    
    public void deleteAllNotes() {
        repository.deleteAllNotes();
    }
    
    public LiveData<List<Note>> getAllNotes() {
        return allNotes;
    }
    
    public Note getNoteById(long id) {
        return repository.getNoteById(id);
    }
    
    public LiveData<List<Note>> searchNotes(String query) {
        return repository.searchNotes(query);
    }
}

6. 实现 UI 层

6.1 创建笔记列表 Activity

创建 NotesListActivity.java 和对应的布局文件 activity_notes_list.xml

activity_notes_list.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 
    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"
    tools:context=".ui.NotesListActivity">

    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/Theme.SQLiteDemoJava.AppBarOverlay">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/Theme.SQLiteDemoJava.PopupOverlay"
            app:title="@string/app_name" />

        <com.google.android.material.textfield.TextInputLayout
            android:id="@+id/search_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox">

            <com.google.android.material.textfield.TextInputEditText
                android:id="@+id/search_input"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="@string/search_hint"
                android:imeOptions="actionSearch"
                android:inputType="text" />
        </com.google.android.material.textfield.TextInputLayout>
    </com.google.android.material.appbar.AppBarLayout>

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/notes_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:clipToPadding="false"
        android:paddingBottom="72dp"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab_add_note"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="16dp"
        android:contentDescription="@string/add_note"
        android:src="@drawable/ic_add"
        app:backgroundTint="@color/purple_500"
        app:tint="@android:color/white" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

NotesListActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.ViewModelProvider;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.inputmethod.EditorInfo;
import android.widget.EditText;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import com.yourpackage.R;
import com.yourpackage.adapter.NotesAdapter;
import com.yourpackage.model.Note;
import com.yourpackage.viewmodel.NoteViewModel;
import java.util.Objects;

public class NotesListActivity extends AppCompatActivity {
    private NoteViewModel noteViewModel;
    private NotesAdapter adapter;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_notes_list);
        
        // 设置Toolbar
        setSupportActionBar(findViewById(R.id.toolbar));
        Objects.requireNonNull(getSupportActionBar()).setTitle("Notes");
        
        // 初始化ViewModel
        noteViewModel = new ViewModelProvider(this).get(NoteViewModel.class);
        
        // 设置RecyclerView
        RecyclerView recyclerView = findViewById(R.id.notes_recycler_view);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setHasFixedSize(true);
        
        adapter = new NotesAdapter();
        recyclerView.setAdapter(adapter);
        
        // 观察笔记列表变化
        noteViewModel.getAllNotes().observe(this, notes -> {
            adapter.setNotes(notes);
        });
        
        // 设置添加笔记按钮
        FloatingActionButton fabAddNote = findViewById(R.id.fab_add_note);
        fabAddNote.setOnClickListener(view -> {
            Intent intent = new Intent(NotesListActivity.this, NoteDetailActivity.class);
            startActivity(intent);
        });
        
        // 设置搜索功能
        EditText searchInput = findViewById(R.id.search_input);
        searchInput.setOnEditorActionListener((v, actionId, event) -> {
            if (actionId == EditorInfo.IME_ACTION_SEARCH) {
                String query = searchInput.getText().toString().trim();
                if (!query.isEmpty()) {
                    noteViewModel.searchNotes(query).observe(this, notes -> {
                        adapter.setNotes(notes);
                    });
                } else {
                    noteViewModel.getAllNotes().observe(this, notes -> {
                        adapter.setNotes(notes);
                    });
                }
                return true;
            }
            return false;
        });
    }
    
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }
    
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == R.id.action_delete_all) {
            noteViewModel.deleteAllNotes();
            Snackbar.make(findViewById(android.R.id.content), "All notes deleted", Snackbar.LENGTH_SHORT).show();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

6.2 创建笔记详情 Activity

创建 NoteDetailActivity.java 和对应的布局文件 activity_note_detail.xml

activity_note_detail.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout 
    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"
    tools:context=".ui.NoteDetailActivity">

    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/Theme.SQLiteDemoJava.AppBarOverlay">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/Theme.SQLiteDemoJava.PopupOverlay" />
    </com.google.android.material.appbar.AppBarLayout>

    <androidx.core.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:padding="16dp">

            <com.google.android.material.textfield.TextInputLayout
                android:id="@+id/title_layout"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox">

                <com.google.android.material.textfield.TextInputEditText
                    android:id="@+id/title_input"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:hint="@string/title_hint"
                    android:inputType="textCapSentences|textAutoCorrect"
                    android:maxLines="1" />
            </com.google.android.material.textfield.TextInputLayout>

            <com.google.android.material.textfield.TextInputLayout
                android:id="@+id/content_layout"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="16dp"
                style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox">

                <com.google.android.material.textfield.TextInputEditText
                    android:id="@+id/content_input"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:hint="@string/content_hint"
                    android:inputType="textMultiLine|textCapSentences|textAutoCorrect"
                    android:minLines="5"
                    android:gravity="top" />
            </com.google.android.material.textfield.TextInputLayout>
        </LinearLayout>
    </androidx.core.widget.NestedScrollView>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab_save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="16dp"
        android:contentDescription="@string/save_note"
        android:src="@drawable/ic_save"
        app:backgroundTint="@color/purple_500"
        app:tint="@android:color/white" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

NoteDetailActivity.java

import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.ViewModelProvider;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.MenuItem;
import android.widget.EditText;
import com.google.android.material.snackbar.Snackbar;
import com.google.android.material.textfield.TextInputLayout;
import com.yourpackage.R;
import com.yourpackage.model.Note;
import com.yourpackage.viewmodel.NoteViewModel;
import java.util.Date;

public class NoteDetailActivity extends AppCompatActivity {
    public static final String EXTRA_NOTE_ID = "extra_note_id";
    
    private NoteViewModel noteViewModel;
    private EditText titleInput, contentInput;
    private TextInputLayout titleLayout, contentLayout;
    private long noteId = -1;
    private boolean isNewNote = true;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_note_detail);
        
        // 设置Toolbar
        setSupportActionBar(findViewById(R.id.toolbar));
        Objects.requireNonNull(getSupportActionBar()).setDisplayHomeAsUpEnabled(true);
        
        // 初始化ViewModel
        noteViewModel = new ViewModelProvider(this).get(NoteViewModel.class);
        
        // 初始化视图
        titleInput = findViewById(R.id.title_input);
        contentInput = findViewById(R.id.content_input);
        titleLayout = findViewById(R.id.title_layout);
        contentLayout = findViewById(R.id.content_layout);
        
        // 检查是否是编辑现有笔记
        if (getIntent().hasExtra(EXTRA_NOTE_ID)) {
            noteId = getIntent().getLongExtra(EXTRA_NOTE_ID, -1);
            isNewNote = false;
            loadNote();
        }
        
        // 设置保存按钮
        findViewById(R.id.fab_save).setOnClickListener(view -> saveNote());
        
        // 设置输入验证
        setupTextWatchers();
    }
    
    private void loadNote() {
        Note note = noteViewModel.getNoteById(noteId);
        if (note != null) {
            titleInput.setText(note.getTitle());
            contentInput.setText(note.getContent());
        }
    }
    
    private void setupTextWatchers() {
        titleInput.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
            
            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {}
            
            @Override
            public void afterTextChanged(Editable s) {
                validateInputs();
            }
        });
        
        contentInput.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
            
            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {}
            
            @Override
            public void afterTextChanged(Editable s) {
                validateInputs();
            }
        });
    }
    
    private boolean validateInputs() {
        boolean titleValid = !titleInput.getText().toString().trim().isEmpty();
        boolean contentValid = !contentInput.getText().toString().trim().isEmpty();
        
        titleLayout.setError(titleValid ? null : getString(R.string.title_required));
        contentLayout.setError(contentValid ? null : getString(R.string.content_required));
        
        return titleValid && contentValid;
    }
    
    private void saveNote() {
        if (!validateInputs()) return;
        
        String title = titleInput.getText().toString().trim();
        String content = contentInput.getText().toString().trim();
        
        if (isNewNote) {
            Note note = new Note(title, content);
            noteViewModel.insert(note);
            Snackbar.make(findViewById(android.R.id.content), "Note saved", Snackbar.LENGTH_SHORT).show();
        } else {
            Note existingNote = noteViewModel.getNoteById(noteId);
            if (existingNote != null) {
                existingNote.setTitle(title);
                existingNote.setContent(content);
                existingNote.setUpdated_at(new Date());
                noteViewModel.update(existingNote);
                Snackbar.make(findViewById(android.R.id.content), "Note updated", Snackbar.LENGTH_SHORT).show();
            }
        }
        finish();
    }
    
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == android.R.id.home) {
            onBackPressed();
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

6.3 创建 RecyclerView Adapter

在 com.yourpackage.adapter 包下创建 NotesAdapter.java 文件：

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.google.android.material.card.MaterialCardView;
import com.yourpackage.R;
import com.yourpackage.model.Note;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public class NotesAdapter extends RecyclerView.Adapter<NotesAdapter.NoteViewHolder> {
    private List<Note> notes = new ArrayList<>();
    private OnItemClickListener listener;
    
    @NonNull
    @Override
    public NoteViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.item_note, parent, false);
        return new NoteViewHolder(itemView);
    }
    
    @Override
    public void onBindViewHolder(@NonNull NoteViewHolder holder, int position) {
        Note currentNote = notes.get(position);
        holder.title.setText(currentNote.getTitle());
        holder.content.setText(currentNote.getContent());
        
        SimpleDateFormat dateFormat = new SimpleDateFormat("MMM dd, yyyy - hh:mm a", Locale.getDefault());
        holder.date.setText(dateFormat.format(currentNote.getUpdated_at()));
        
        holder.cardView.setOnClickListener(v -> {
            if (listener != null && position != RecyclerView.NO_POSITION) {
                listener.onItemClick(notes.get(position));
            }
        });
    }
    
    @Override
    public int getItemCount() {
        return notes.size();
    }
    
    public void setNotes(List<Note> notes) {
        this.notes = notes;
        notifyDataSetChanged();
    }
    
    public Note getNoteAt(int position) {
        return notes.get(position);
    }
    
    class NoteViewHolder extends RecyclerView.ViewHolder {
        private TextView title, content, date;
        private MaterialCardView cardView;
        
        public NoteViewHolder(@NonNull View itemView) {
            super(itemView);
            title = itemView.findViewById(R.id.note_title);
            content = itemView.findViewById(R.id.note_content);
            date = itemView.findViewById(R.id.note_date);
            cardView = (MaterialCardView) itemView;
        }
    }
    
    public interface OnItemClickListener {
        void onItemClick(Note note);
    }
    
    public void setOnItemClickListener(OnItemClickListener listener) {
        this.listener = listener;
    }
}

创建对应的列表项布局文件 item_note.xml：

<?xml version="1.0" encoding="utf-8"?>
<com.google.android.material.card.MaterialCardView 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="8dp"
    app:cardCornerRadius="8dp"
    app:cardElevation="4dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="16dp">

        <TextView
            android:id="@+id/note_title"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textAppearance="@style/TextAppearance.AppCompat.Headline"
            android:textColor="@android:color/black" />

        <TextView
            android:id="@+id/note_content"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:ellipsize="end"
            android:maxLines="2"
            android:textAppearance="@style/TextAppearance.AppCompat.Body1"
            android:textColor="@android:color/darker_gray" />

        <TextView
            android:id="@+id/note_date"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:textAppearance="@style/TextAppearance.AppCompat.Caption"
            android:textColor="@android:color/darker_gray" />
    </LinearLayout>
</com.google.android.material.card.MaterialCardView>

7. 添加菜单资源

在 res/menu 目录下创建 menu_main.xml 文件：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    
    <item
        android:id="@+id/action_delete_all"
        android:icon="@drawable/ic_delete"
        android:title="@string/delete_all"
        app:showAsAction="never" />
</menu>

8. 添加字符串资源

在 res/values/strings.xml 文件中添加以下字符串：

<resources>
    <string name="app_name">SQLite Notes (Java)</string>
    <string name="title_hint">Title</string>
    <string name="content_hint">Content</string>
    <string name="search_hint">Search notes...</string>
    <string name="add_note">Add new note</string>
    <string name="save_note">Save note</string>
    <string name="delete_all">Delete all notes</string>
    <string name="title_required">Title is required</string>
    <string name="content_required">Content is required</string>
</resources>

9. 添加图标资源

确保在 res/drawable 目录下有以下矢量图标：

ic_add.xml (添加按钮图标)
ic_save.xml (保存按钮图标)
ic_delete.xml (删除按钮图标)

10. 更新 AndroidManifest.xml

确保 AndroidManifest.xml 包含两个 Activity：

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/Theme.SQLiteDemoJava">
    
    <activity
        android:name=".ui.NoteDetailActivity"
        android:parentActivityName=".ui.NotesListActivity" />
    
    <activity
        android:name=".ui.NotesListActivity"
        android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

11. 运行和测试应用

现在，您可以运行应用程序并测试以下功能：

添加新笔记
查看笔记列表
编辑现有笔记
删除笔记
搜索笔记
删除所有笔记

12. 数据库调试技巧

12.1 查看数据库内容

在 Android Studio 中打开 “Device File Explorer” (View -> Tool Windows -> Device File Explorer)
导航到 /data/data/com.yourpackage/databases/
找到 notes_database 文件
右键点击并选择 “Save As” 将其保存到本地
使用 SQLite 浏览器工具（如 DB Browser for SQLite）打开该文件查看内容

12.2 使用 Stetho 进行调试

添加 Stetho 依赖到 build.gradle:

implementation 'com.facebook.stetho:stetho:1.6.0'

创建一个自定义 Application 类：

import android.app.Application;
import com.facebook.stetho.Stetho;

public class NotesApplication extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        Stetho.initializeWithDefaults(this);
    }
}

更新 AndroidManifest.xml 中的 application 标签：

<application
    android:name=".NotesApplication"
    ...>
    ...
</application>

运行应用后，在 Chrome 浏览器中访问 chrome://inspect 可以查看和调试数据库。

13. 数据库迁移

当您需要更改数据库结构时（例如添加新表或修改现有表），需要进行数据库迁移。

13.1 修改实体类

例如，我们要为 Note 添加一个 is_pinned 字段：

@Entity(tableName = "notes")
public class Note {
    // 现有字段...
    private boolean isPinned;
    
    // Getter 和 Setter
    public boolean isPinned() {
        return isPinned;
    }
    
    public void setPinned(boolean pinned) {
        isPinned = pinned;
    }
}

13.2 更新数据库版本

修改 AppDatabase.java:

@Database(entities = {Note.class}, version = 2, exportSchema = false)
@TypeConverters(DateConverter.class)
public abstract class AppDatabase extends RoomDatabase {
    // ...
}

13.3 添加迁移策略

static final Migration MIGRATION_1_2 = new Migration(1, 2) {
    @Override
    public void migrate(SupportSQLiteDatabase database) {
        database.execSQL("ALTER TABLE notes ADD COLUMN is_pinned INTEGER NOT NULL DEFAULT 0");
    }
};

// 在 databaseBuilder 中添加迁移
INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                AppDatabase.class, "notes_database")
        .addMigrations(MIGRATION_1_2)
        .build();

14. 性能优化建议

使用事务：对于批量操作，使用事务可以显著提高性能：

@Dao
public interface NoteDao {
    @Transaction
    default void insertAll(List<Note> notes) {
        for (Note note : notes) {
            insertNote(note);
        }
    }
}

索引优化：为常用查询字段添加索引：

@Entity(tableName = "notes", indices = {@Index(value = {"title"}, unique = false)})
public class Note {
    // ...
}

避免在主线程操作数据库：始终确保数据库操作在后台线程执行。

15. 总结

本指南详细介绍了在 Android Studio 中使用 Java 语言开发 SQLite 数据库应用的完整流程，包括：

设置项目和依赖
设计数据库结构
实现 Room 数据库组件（Entity, DAO, Database）
创建 Repository 层
实现 ViewModel
构建用户界面
添加数据库迁移支持
性能优化建议

通过遵循这些步骤，您可以构建一个功能完善、结构清晰的 Android 应用，充分利用 SQLite 数据库的强大功能。