java - 使用外键填充 SQLite 数据库表

Question

我目前正在尝试使用 Android studio 填充我的 SQLite 数据库。到目前为止，我可以填充图书表，但不确定为什么我无法填充章节表。如果我去查看我的章节表，我不会得到任何输出。

据我所知，这是由于该表中使用的外键造成的。

在我的 onCreate 方法中，我是否对外键做了错误的操作？

下面是我的代码。

助手类

public class DatabaseHelper extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "formularyApp.db";
public static final int DB_VERSION = 1;
public DatabaseHelper(Context context) {
    super(context, DATABASE_NAME, null, DB_VERSION);
}

//when called creates query
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
    String sqlBook = "CREATE TABLE book(id INTEGER PRIMARY KEY AUTOINCREMENT, bookName VARCHAR, bookAuthor VARCHAR);";
    String sqlChapter = "CREATE TABLE chapter(id INTEGER PRIMARY KEY AUTOINCREMENT, chapterName VARCHAR, book_id INTEGER, FOREIGN KEY(book_id) REFERENCES book(id))";


    sqLiteDatabase.execSQL(sqlBook);
    sqLiteDatabase.execSQL(sqlChapter);


}


public boolean addChapter(String chapterName, Integer book_id){
    SQLiteDatabase db = getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("chapterName", chapterName);
    contentValues.put("bookID", book_id);
    db.insert("chapter", null, contentValues);
    db.close();
    return true;
}

public boolean addBook(String bookName, String bookAuthor){
    SQLiteDatabase db = getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("bookName", bookName);
    contentValues.put("bookAuthor", bookAuthor);
    db.insert("book", null, contentValues);
    db.close();
    return true;
}



@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
    String sqlBook = "DROP TABLE IF EXISTS book";
    String sqlChapter = "DROP TABLE IF EXISTS chapter";
    sqLiteDatabase.execSQL(sqlBook);
    sqLiteDatabase.execSQL(sqlChapter);
    onCreate(sqLiteDatabase);

}
}

主要 Activity

public class MainActivity extends AppCompatActivity {

ViewPager viewPager;
DatabaseHelper db;

/** Called when the activity is created. */
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    db = new DatabaseHelper(this);
    db.addBook("Tester Book 5", "Test author");
    db.addChapter("The basics", 5);
    Toast.makeText(this, "updated", Toast.LENGTH_SHORT).show();

    viewPager = findViewById(R.id.viewPager);
    IntroAdapter adapter = new IntroAdapter(getSupportFragmentManager());
    viewPager.setAdapter(adapter);

}

Answer 1

在您的 addChapter 方法中，您有一个拼写错误:

contentValues.put("bookID", book_id);

应该是

contentValues.put("book_id", book_id);

您使用了错误的列名称