Question

如果与MySQL的连接是JLabel或null，我的!null必须更改颜色和文字。并且我试图了解如何使其动态化，因此，当连接丢失时，JLabel会将颜色和文字更改为红色＆＃34;未连接＆＃34; 。< / p>

例如：

1.Connect.java

public class Connect {
    String driver = "com.mysql.jdbc.Driver";
    String url = "jdbc:mysql://localhost/";
    String dbName = "db_name";
    String username = "user_name";
    String password = "password";
    Connection conn = null;

public Connection check(){
    try {
        Class.forName(driver).newInstance();
        conn = DriverManager.getConnection(url + dbName, username, password);
        conn.close();
        } catch (Exception e) {
            e.printStackTrace();
            }
    return conn;
    }
}
/////////////////////////////////

2。 Panel.java

public class Panel extends JPanel{
    public Panel(){
        //....lots of components and settings
        JLabel label = new JLabel(); //the component we need...
        }
    Loop loop = new Loop(label);
    }
/////////////////////////////////

3。 Loop.java

public class Loop{
    Connect connect = new Connect();
    JLabel label;
    int x = 0;
    public Loop(JLabel j){
        label = j;
    }
    ////////////////////////////////
    while(x < 1){ //this is what i'm trying to do 
    if(connect.check() != null){
        label.setText("Connected");
        label.setForeground(Color.GREEN);
        }else{
            label.setText("Not Connected");
            label.setForeground(Color.RED);
        }
    }
    ////////////////////////////////
}

4。主

public static void main(String[] args){
    Panel panel = new Panel();
}

Answer 1

您可以实施观察者模式。

Connect.java

asInstanceOf

Loop.java

public class Connect extends Observable {

    Connection conn;

    public Connect(Observer o) {
        addObserver(o);
    }

    public void getConnection() {
        // TODO getConnection
        hasChanged();
        notifyObservers();
    }

    public void closeConnection() {
        // TODO closeConnection
        hasChanged();
        notifyObservers();
    }
}

有用的链接：

（java）循环检查连接

1 个答案: