如何從非活動接收信息到活動類

Question

我必須在我的android項目中上課，第一類是Main Activity，它是extend Activity，另一個類是MSSQLConnect，它是一個簡單的類，用於從數據庫獲取數據並返回它作爲數組列表

我用這個方法調用MSSQLConnect類，但它不工作：

MainActivity類別

public class MainActivity extends Activity { 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 


MSSQLConnect cdb = new MSSQLConnect("id", "mytable", "", ""); 
Toast.makeText(this, cdb.getdata("getApplicationContext()"), Toast.LENGTH_SHORT).show(); }} 

MSSQLConnect類：

public class MSSQLConnect extends ContextWrapper { 


private final String table; 
private final String columns; 
private final String whereColumn; 
private final String equalsEntry; 


public MSSQLConnect (Context context, String columns, String table, String whereColumn, String equalsEntry) { 
    super(context); 
    this.table = table; 
    this.columns = columns; 
    this.whereColumn = whereColumn; 
    this.equalsEntry = equalsEntry; 

} 

static String JDBC_DRIVER = "net.sourceforge.jtds.jdbc.Driver"; 
static String DB_URL ="jdbc:jtds:sqlserver://xxx.xxx.x.x:xxx;DatabaseName=xxxx"; 

// Database credentials 
static String USER = "xxxxx"; 
static String PASS = "xxxxx"; 

public ArrayList<ArrayList<String>> ourQuerryMethod() { 
    Connection conn = null; 
    Statement stmt = null; 

    String data[][] = null; 
    ArrayList<ArrayList<String>> setData = new ArrayList<ArrayList<String>>(); 
    try { 
     Class.forName(getJDBC_DRIVER()); 
     conn = DriverManager.getConnection(getDB_URL(), getUSER(), getPASS()); 
     stmt = conn.createStatement(); 
     String sql; 
     if(whereColumn.equals("") && equalsEntry.equals("")) 
     { 
      sql = "SELECT " + (columns) + " FROM " + (table); 
     } 
     else 
      sql = "SELECT " + (columns) + " FROM " + (table) + " WHERE "+ (whereColumn) +" = "+ (equalsEntry) +""; 

     ResultSet rs; 
     rs = stmt.executeQuery(sql); 

      int nc = 1; 
      ArrayList<String> columns = new ArrayList<String>(); 
      int rowCount =0; 
      while(rs.next()) // loop rows 
      { 

       rowCount++; 
       if(rowCount == 1) 
       { 
        while(true){ //loop columns 
         try { 
          columns.add(rs.getString(nc)); 
         } catch (Exception e) { 
          // TODO: handle exception 

          break; 
         } 
         nc++; 
        } 
       } 

       int rrowrr = 0; 
       for(int i=1;i<nc;i++) 
       { 
        rrowrr++; 
        if(rrowrr == 1) 
        { 
         setData.add(new ArrayList<String>()); 
        } 
        setData.get(rs.getRow()-1).add(rs.getString(i)); 
       } 

      } 
     rs.close(); 
    }catch (SQLException se) { 
     // Handle errors for JDBC 
     se.printStackTrace(); 
     Log.d("DBError1", se.getMessage()); 
    } catch (Exception e) { 
     // Handle errors for Class.forName 
     e.printStackTrace(); 
     Log.d("DBError2", e.getMessage()); 

    } finally { 
     // finally block used to close resources 
     try { 
      if (stmt != null) 
       conn.close(); 
     } catch (SQLException se) { 
      Log.d("DBError3", se.getMessage()); 

     } 
     try { 
      if (conn != null) 
       conn.close(); 
     } catch (SQLException se) { 
      se.printStackTrace(); 
      Log.d("DBError4", se.getMessage()); 

     } // end finally try 
    } // end try 
    return setData; 
} // end main 

public static String getJDBC_DRIVER() { 
    return JDBC_DRIVER; 
} 
public static void setJDBC_DRIVER(String aJDBC_DRIVER) { 
    JDBC_DRIVER = aJDBC_DRIVER; 
} 

public static String getDB_URL() { 
    return DB_URL; 
} 


public static void setDB_URL(String aDB_URL) { 
    DB_URL = aDB_URL; 
} 


public static String getUSER() { 
    return USER; 
} 

public static void setUSER(String aUSER) { 
    USER = aUSER; 
} 
public static String getPASS() { 
    return PASS; 
} 

public static void setPASS(String aPASS) { 
    PASS = aPASS; 
}} 

Answer 1

使用此

public class MainActivity extends Activity { 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
MSSQLConnect connect=new MSSQLConnect(); 
ArrayList<String> list = new ArrayList<String>(); 
list=connect.ourQuerryMethod(); 

ConnectDB cdb = new ConnectDB("id", "mytable", "", ""); 
Toast.makeText(this, cdb.getdata("getApplicationContext()"), Toast.LENGTH_SHORT).show(); }} 

Answer 2

JDBC爲Android ???你瘋了嗎？我建議你使用php頁面進行sql查詢並使用asynctask在json中解析它，但是如果你喜歡JDBC，我會問你幾個問題，爲什麼MSSQLConnect類會重命名爲ConnectDB？和MSSQLConnect生成器有5個參數，但你有4個參數創建對象？