無法解析Android Studio中的getWritableDatabase（）方法

Question

我在Android中首次使用SQLite。我想添加新的危機可以在後​​臺完成。但是當我調用引用來寫入數據庫時​​，我遇到一個錯誤。我嘗試使用asyncTasck方法在數據庫中添加新的危機。不工作的代碼在方法void addCrisi（Crisi crisi）。下面是它：

// 1. get reference to writable DB 
SQLiteDatabase db = this.getWritableDatabase(); 

的完整代碼：

public class DatabaseHandler extends SQLiteOpenHelper { 
// All Static variables 
// Database Version 
private static final int DATABASE_VERSION = 1; 

// Database Name 
private static final String DATABASE_NAME = "crisisManager"; 

// Crisis table name 
private static final String TABLE_CRISIS = "crisis"; 
//Singleton 
private static DatabaseHandler instance; 
public static DatabaseHandler getInstance(Context context) { 
    if (instance == null) { 
     instance = new DatabaseHandler(context.getApplicationContext()); 
    } 
    return instance; 
} 

// Crisis Table Columns names 
private static final String KEY_ID = "id"; 
private static final String KEY_START_DATE = "start_date"; 
private static final String KEY_END_DATE = "end_date"; 
private static final String KEY_LATITUDE = "latitude"; 
private static final String KEY_LONGITUDE = "longitude"; 

public DatabaseHandler(Context context) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
} 

// Creating Tables 
public void onCreate(SQLiteDatabase db) { 
    String CREATE_CRISIS_TABLE = "CREATE TABLE " + TABLE_CRISIS + "(" 
      + KEY_ID + " INTEGER PRIMARY KEY," 
      + KEY_START_DATE + " TEXT," 
      + KEY_END_DATE + " TEXT," 
      + KEY_LATITUDE + " DOUBLE," 
      + KEY_LONGITUDE + " DOUBLE" + ")"; 
    db.execSQL(CREATE_CRISIS_TABLE); 
} 

// Upgrading database 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    // Drop older table if existed 
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_CRISIS); 
    // Create tables again 
    onCreate(db); 
} 

/** 
* All CRUD(Create, Read, Update, Delete) Operations 
*/ 
// Adding new crisi 
void addCrisi(Crisi crisi) { 
    Log.d("Add Crisi", crisi.toString()); 
    //SQLiteDatabase db = this.getWritableDatabase(); 

    ContentValues values = new ContentValues(); 
    values.put(KEY_START_DATE, crisi.getStartDate()); // Start Date 
    values.put(KEY_END_DATE, crisi.getEndDate()); // End Date 
    values.put(KEY_LATITUDE, crisi.getLatitude()); // Latitude 
    values.put(KEY_LONGITUDE, crisi.getLongitude()); // Longitude 

    // Inserting Row Async Inserting 
    //AsyncTask is anonymous class 
    new AsyncTask<ContentValues, Void, Void>() { 
     @Override 
     protected Void doInBackground(ContentValues... params) { 

      // 1. get reference to writable DB 
      SQLiteDatabase db = this.getWritableDatabase(); 

      // 3. insert 
      db.insert(TABLE_CRISIS, null, params[0]); 

      // 4. close 
      db.close(); 
      return null; 
     } 
    }.execute(values); 
    //db.insert(TABLE_CRISIS, null, values); 
    //db.close(); // Closing database connection 
} 
// Getting All Crisis 
public List<Crisi> getAllCrisis() { 
    List<Crisi> crisiList = new ArrayList<Crisi>(); 
    // Select All Query 
    String selectQuery = "SELECT * FROM " + TABLE_CRISIS; 

    SQLiteDatabase db = this.getWritableDatabase(); 
    Cursor cursor = db.rawQuery(selectQuery, null); 

    // looping through all rows and adding to list 
    if (cursor.moveToFirst()) { 
     do { 
      Crisi crisi = new Crisi(); 
      crisi.setId(Integer.parseInt(cursor.getString(0))); 
      //crisi.setName(cursor.getString(1)); 
      //crisi.setPhoneNumber(cursor.getString(2)); 
      crisi.setStartDate(cursor.getString(1)); 
      crisi.setEndDate(cursor.getString(2)); 
      crisi.setLatitude(Double.parseDouble(cursor.getString(3))); 
      crisi.setLongitude(Double.parseDouble(cursor.getString(4))); 
      // Adding crisi to list 
      crisiList.add(crisi); 
     } while (cursor.moveToNext()); 
    } 

    // return crisi list 
    return crisiList; 
} 

// Updating single crisi 
public int updateCrisi(Crisi crisi) { 
    SQLiteDatabase db = this.getWritableDatabase(); 

    ContentValues values = new ContentValues(); 
    values.put(KEY_START_DATE, crisi.getStartDate()); 
    values.put(KEY_END_DATE, crisi.getEndDate()); 
    values.put(KEY_LATITUDE, crisi.getLatitude()); // Latitude 
    values.put(KEY_LONGITUDE, crisi.getLongitude()); // Longitude 
    values.put(KEY_LOCALITY, crisi.getLatitude()); // Locality 
    values.put(KEY_COUNTRY, crisi.getLongitude()); // Country 

    // updating row 
    return db.update(TABLE_CRISIS, values, KEY_ID + " = ?", 
      new String[] { String.valueOf(crisi.getId()) }); 
} 

// Deleting single crisi 
public void deleteCrisi(Crisi crisi) { 
    SQLiteDatabase db = this.getWritableDatabase(); 
    db.delete(TABLE_CRISIS, KEY_ID + " = ?", 
      new String[] { String.valueOf(crisi.getId()) }); 
    db.close(); 
} 

// Getting crisis Count 
public int getCrisisCount() { 
    String countQuery = "SELECT * FROM " + TABLE_CRISIS; 
    SQLiteDatabase db = this.getReadableDatabase(); 
    Cursor cursor = db.rawQuery(countQuery, null); 
    cursor.close(); 

    // return count 
    return cursor.getCount(); 
} 
} 

是否有人可以幫忙嗎？謝謝！ Ps：我很抱歉我的英文不好。

Answer 1

this指的是內部的Asynctask而不是DatabaseHandler。使用DatabaseHandler.this（NameOuter.this一般）來指內部類的外部類