我已经在我的 Android 应用程序中成功创建了一个数据库。它有一个称为注册号的主键，用户在注册我的应用程序时输入该主键。一切正常，但如果两个用户输入相同的注册号，则不会创建帐户并抛出异常:
android.database.sqlite.SQLiteConstraintException: column registration_number
is not unique (code 19)
这很好。我希望应用程序的行为像这样。但如何通知用户该注册号不可用呢？ 我的代码:
public class DatabaseOperations extends SQLiteOpenHelper {
public static final int database_version=1;
public static final String DATABASE_NAME = "Aliah.db";
public static final String TABLE_NAME = "student_info";
public static final String REGISTRATION_NUMBER = "registration_number";
public static final String USER_NAME = "user_name";
public static final String USER_PASS = "user_pass";
public static final String EMAIL = "email";
public DatabaseOperations(Context context) {
super(context, DATABASE_NAME, null, database_version);
Log.d("Databse operations", "Database created");
}
@Override
public void onCreate(SQLiteDatabase sdb) {
try{
sdb.execSQL("create table "+ TABLE_NAME +" (registration_number VARCHAR PRIMARY KEY, user_name VARCHAR, user_pass VARCHAR, email VARCHAR);");
Log.d("Databse operations", "one row inserted");}catch(SQLException e){};
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
}
public void putInformation(DatabaseOperations dop,String registration_number,String name,String pass,String email){
SQLiteDatabase SQ = dop.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(REGISTRATION_NUMBER,registration_number);
cv.put(USER_NAME, name);
cv.put(USER_PASS,pass);
cv.put(EMAIL,email);
long k = SQ.insert(TABLE_NAME,null,cv);
Log.d("Databse operations", "One row inserted");
}
public Cursor getInformation(DatabaseOperations dop){
SQLiteDatabase SQ = dop.getReadableDatabase();
String[] columns = {REGISTRATION_NUMBER, USER_NAME, USER_PASS, EMAIL};
Cursor CR = SQ.query(TABLE_NAME,columns,null,null,null,null,null);
return CR;
}
}
最佳答案
使用insertOrThrow而不是insert。这样，您可以捕获它可能抛出的 SQLException 并执行您想要的操作(在本例中，通知用户)。
关于java - Android SQLite数据库主键查询，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44035001/