Android-SQLite：構造函數DBHelper未定義

Question

基本上，我試圖顯示一個列表視圖（用QSLite創建）的結果，但在CourseDetails類中提取出產生的列表視圖的元素，有這個問題：

「描述資源路徑位置類型 構造DBHelper（CourseDetails）是未定義CourseDetails.java/MariposaTrainingMobile/src目錄/ COM/mariposatraining /場第31行的Java問題」

我使用這個DBHelper類，但我不知道爲什麼程序向我發送錯誤信息，並且不提供解決方案，我的DBHelper類的代碼是下一個：

public class DBHelper extends SQLiteOpenHelper{ 

private String sql; 
SQLiteDatabase db; 

public DBHelper(Context context, String name, CursorFactory factory, 
     int version) { 
    super(context, name, factory, 1); 
    // TODO Auto-generated constructor stub 
} 

@Override 
public void onCreate(SQLiteDatabase db) 
{ 
    // TODO Auto-generated method stub 
    String sql= " CREATE TABLE courses (" + "_id INTEGER PRIMARY KEY AUTOINCREMENT, " + " title TEXT, " + " instructor TEXT, " + " length TEXT, " + " rating TEXT, " + " topic TEXT, " + " subject TEXT, " + "description TEXT)"; 
    db.execSQL(sql);   
} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 

    db.execSQL("DROP TABLE IF EXISTS courses"); 
    onCreate(db);  
} 


public void insertCourses() 
{ 
    db=getWritableDatabase(); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Enabling Freedom...', 'Instructor: Keith Savell', 'length: 60', 'Rating: 4.82', 'Topic: Creating a Prosthetic Environment ', 'Subject:Learn to evaluate and modify the environment to support our residents with cognitive impairment as they age in place.', 'Description: Residents with dementia and delirium are constantly assessing the environment, looking for clues to help them understand where they are, who others around them are, what they are supposed to be doing and what is expected of them.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Interdisciplinary Care Planning', 'Instructor: Keith Savell', 'length: 60', 'Rating: 4.7', 'Topic: Interdisciplinary Care Planning', 'Subject:Encourage the Interdisciplinary Treatment Team (IDT) to work as a team and view the Care Plan as a resident-centered collaborative effort to enhance the care and quality of resident life.', 'Description: Interdisciplinary Care Planning requires members of the Interdisciplinary Treatment Team (IDT) to view the Care Plan as a resident centered collaborative effort - rather than as a staff centered document. Learn how to utilize the Care Plan to truly function as a team - working together to enhance the care and quality of resident life.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Culture Change: Creating A Climate Of Care...', 'Instructor: Keith Savell', 'length: 60', 'Rating: 5', 'Topic: Culture Change ', 'Subject:Learn to evaluate and modify the environment to support our residents with cognitive impairment as they age in place.', 'Description: Residents with dementia and delirium are constantly assessing the environment, looking for clues to help them understand where they are, who others around them are, what they are supposed to be doing and what is expected of them.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Medical Records Documentation', 'Instructor: Keith Savell', 'length: 60', 'Rating: 5', 'Topic: Medical Records Documentation ', 'Subject:Encourage the Interdisciplinary Treatment Team (IDT) to work as a team and view the Care Plan as a resident-centered collaborative effort to enhance the care and quality of resident life.', 'Description: Interdisciplinary Care Planning requires members of the Interdisciplinary Treatment Team (IDT) to view the Care Plan as a resident centered collaborative effort - rather than as a staff centered document. Learn how to utilize the Care Plan to truly function as a team - working together to enhance the care and quality of resident life.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Census Challenges', 'Instructor: Keith Savell', 'length: 60', 'Rating: 4.45', 'Topic: Creative Solutions to Drive Census ', 'Subject:Learn to evaluate and modify the environment to support our residents with cognitive impairment as they age in place.', 'Description: Residents with dementia and delirium are constantly assessing the environment, looking for clues to help them understand where they are, who others around them are, what they are supposed to be doing and what is expected of them.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Fall Prevention: Reducing Fall Related Injuries', 'Instructor: Keith Savell', 'length: 60', 'Rating: 5', 'Topic: Guidelines for Health Care Providers ', 'Subject:Encourage the Interdisciplinary Treatment Team (IDT) to work as a team and view the Care Plan as a resident-centered collaborative effort to enhance the care and quality of resident life.', 'Description: Interdisciplinary Care Planning requires members of the Interdisciplinary Treatment Team (IDT) to view the Care Plan as a resident centered collaborative effort - rather than as a staff centered document. Learn how to utilize the Care Plan to truly function as a team - working together to enhance the care and quality of resident life.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Meaningful Engagement', 'Instructor: Keith Savell', 'length: 60', 'Rating: 5', 'Topic: Creating The Failure Free Activity Program ', 'Subject:Learn to evaluate and modify the environment to support our residents with cognitive impairment as they age in place.', 'Description: Residents with dementia and delirium are constantly assessing the environment, looking for clues to help them understand where they are, who others around them are, what they are supposed to be doing and what is expected of them.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Dementia and Delirium', 'Instructor: Keith Savell', 'length: 60', 'Rating: 4.69', 'Topic: The Importance of Accurate Diagnosis and Treatment ', 'Subject:Encourage the Interdisciplinary Treatment Team (IDT) to work as a team and view the Care Plan as a resident-centered collaborative effort to enhance the care and quality of resident life.', 'Description: Interdisciplinary Care Planning requires members of the Interdisciplinary Treatment Team (IDT) to view the Care Plan as a resident centered collaborative effort - rather than as a staff centered document. Learn how to utilize the Care Plan to truly function as a team - working together to enhance the care and quality of resident life.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Behavior Management', 'Instructor: Keith Savell', 'length: 60', 'Rating: 5', 'Topic: Using Root Cause ', 'Subject:Learn to evaluate and modify the environment to support our residents with cognitive impairment as they age in place.', 'Description: Residents with dementia and delirium are constantly assessing the environment, looking for clues to help them understand where they are, who others around them are, what they are supposed to be doing and what is expected of them.')"; 
    db.execSQL(sql); 
    sql="INSERT INTO courses(title, instructor, length, rating, topic, subject, description) VALUES ('Communication: Powerful Tools For...', 'Instructor: Keith Savell', 'length: 60', 'Rating: 5', 'Topic: Powerful Tools For Communicating With Residents ', 'Subject:Encourage the Interdisciplinary Treatment Team (IDT) to work as a team and view the Care Plan as a resident-centered collaborative effort to enhance the care and quality of resident life.', 'Description: Interdisciplinary Care Planning requires members of the Interdisciplinary Treatment Team (IDT) to view the Care Plan as a resident centered collaborative effort - rather than as a staff centered document. Learn how to utilize the Care Plan to truly function as a team - working together to enhance the care and quality of resident life.')"; 
    db.execSQL(sql); 
} 

public ArrayList<Courses> getCourses() 
{ 
    db = getWritableDatabase(); 
    sql = "SELECT title, instructor, length, rating, topic, subject, description FROM courses"; 
    Cursor cursor = db.rawQuery(sql, null); 
    ArrayList<Courses> courses = new ArrayList<Courses>(); 

    while (cursor.moveToNext()) 
    { 
     Courses oCourses=new Courses(); 
     oCourses.title=cursor.getString(0); 
     oCourses.instructor=cursor.getString(1); 
     oCourses.length=cursor.getString(2); 
     oCourses.rating=cursor.getString(3); 
     oCourses.topic=cursor.getString(4); 
     oCourses.subject=cursor.getString(5); 
     oCourses.description=cursor.getString(6); 
     courses.add(oCourses);   
    } 

    db.close(); 
    cursor.close(); 
    return courses; 

}} 

和我的表演類CourseDetails元素選擇：

public class CourseDetails extends Activity { 
protected TextView tTitle; 
protected TextView tInstructor; 
protected TextView tLength; 
protected TextView tRating; 
protected TextView tTopic; 
protected TextView tSubject; 
protected TextView tDescription; 

protected int courseId; 


@Override 
protected void onCreate(Bundle savedInstanceState) { 
    // TODO Auto-generated method stub 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.course_details); 

    courseId = getIntent().getIntExtra("COURSE_ID", 0); 
    SQLiteDatabase db = **(new DBHelper(this))**.getWritableDatabase(); 
    Cursor cursor = db.rawQuery("SELECT emp._id, emp.title, emp.instructor, emp.length, emp.rating, emp.topic, emp.subject, emp.description, mgr.title managerTitle, mgr.instructor managerInstructor FROM courses emp LEFT OUTER JOIN courses mgr ON emp.rating = mgr._id WHERE emp._id = ?", 

      new String[]{""+courseId}); 

    if (cursor.getCount() == 1) 
    { 
      cursor.moveToFirst(); 

      tTitle = (TextView) findViewById(R.id.tTitle); 
      tTitle.setText(cursor.getString(cursor.getColumnIndex("title"))); 

      tInstructor = (TextView) findViewById(R.id.tInstructor); 
      tInstructor.setText(cursor.getString(cursor.getColumnIndex("instructor"))); 

      tLength = (TextView) findViewById(R.id.tLength); 
      tLength.setText(cursor.getString(cursor.getColumnIndex("length"))); 

      tRating = (TextView) findViewById(R.id.tRating); 
      tRating.setText(cursor.getString(cursor.getColumnIndex("rating"))); 

      tTopic = (TextView) findViewById(R.id.tTopic); 
      tTopic.setText(cursor.getString(cursor.getColumnIndex("topic"))); 

      tSubject = (TextView) findViewById(R.id.tSubject); 
      tSubject.setText(cursor.getString(cursor.getColumnIndex("subject"))); 

      tDescription = (TextView) findViewById(R.id.tDescription); 
      tDescription.setText(cursor.getString(cursor.getColumnIndex("description"))); 

    } 

}} 

真的會感謝你的幫助

Answer 1

錯誤消息告訴你到底出了什麼問題。你調用構造函數：

(new DBHelper(this)) 

這意味着構造函數簽名應該是這樣的：

public DBHelper(Context context) 

但你已經定義了唯一的構造，這是一個：

public DBHelper(Context context, String name, CursorFactory factory, 
    int version) 

你需要用正確的參數調用構造函數，或者用你想要的任何參數添加一個新的構造函數。

Answer 2

你正在創建DBHelper是這樣的：

new DBHelper(this) 

在哪裏 「這」 是一個CourseDetails對象。

但是，您提供的唯一的構造是

public DBHelper(Context context, String name, CursorFactory factory, int version)