如何重绘Java Swing应用程序的所有可见组件？

Question

I have a JFrame which allows user to adjust colors. This colors are set into static fields of class Colors using reflection. Here is the Colors class:

public class Colors {

    public static Color TextBackground = Color.black;
    public static Color TextForeground = Color.white;
}

There are many other components, located in several JFrame's, and they all use fields of Colors class. When I manually cause them to repaint (eg by resizing), they all repaint correctly.

But how can I cause all other components to repaint automatically?

I tried something that seems dirty changing LookAndFeel, but it didn't work:

 UIManager.setLookAndFeel(UIManager.getLookAndFeel());

Update: I need to repaint components in all other JFrame's, that are currently visible.

Answer 1

You'll need to call a method on your JFrame to let it know that its content needs to be repainted when you change colors. I believe the correct method is revalidate() , but repaint() may work as well. For more information on painting in Swing, try looking here:

http://www.oracle.com/technetwork/java/painting-140037.html

Answer 2

Sounds like you don't have a good handle on which components might be out there using your Colors class. In this case I'd give Colors the ability to support PropertyChangeListener s.

class Colors {

  private static Colors instance = new Colors();

  public static Colors getInstance() {
    return instance;
  }

  private Color textBackground = Color.black;

  private PropertyChangeSupport backgroundProp = new PropertyChangeSupport(textBackground);

  public void setBackgroundColor(Color color) {
    this.textBackground = color;
  }

  public void addBackgroundListener(PropertyChangeListener listener) {
    backgroundProp.addPropertyChangeListener(listener);
  }
}

Then whenever a component uses Colors define it as a PropertyChangeListener and let Colors know about it.

class MyTextField extends JTextField implements PropertyChangeListener {

  public MyTextField() {
    super();
    Colors.getInstance().addBackgroundListener(this);
  }

  public void propertyChange(PropertyChangeEvent evt) {
    Color background = (Color)evt.getNewValue();
    setBackground(background);
    repaint();
  }
}

Answer 3

Have a class extend JPanel and override the public void paintComponent function.

when you call frame.repaint(), it will reference code in paintComponent.

Answer 4

This will repaint all owner-less windows

Window[] windows = Frame.getOwnerlessWindows();
for (int i = 0; i < windows.length; i++) {
    windows[i].repaint();
}

Answer 5

This colors are set into static fields of class Colors using reflection.

This is your problem. Rather than a) storing the colors in static variables, b) using reflection to update these values, or c) looping over the array of ownerless windows, use Swing as it's designed. It's a little more code, but it will work cleaner and more efficiently do what you want.

1. Don't use reflection. Create an actual interface for users to update color values, in an instance rather than a static, and tie this into the frame your users will work with to specify the colors they want.

2. Put methods on your ColorManager object that accept ChangeListener objects. At a minimum, simply create at addChangeListener() method, but alternatively you could add more granular control by defining several methods, addBackgroundListener() , addForegroundListener() , etc. These methods should store a list of registered listeners which will be notified when the associated action (the user updates the color) is performed.

3. Make your windows implement the ChangeListener interface, and register them with the ColorManager object. When the stateChanged() method is called your windows can handle it, updating the color and calling repaint() in the same place.

The key advantage here is that now each class is doing exactly what it's supposed to, and has no unexpected side-effects on other classes. The ColorManager is directly (as opposed to via reflection) updated by the user, it notifies exactly the objects that have explicitly asked to be notified (which can still be all windows, if that's what you want), and those objects can do with that information what they need to, whether that's repainting or doing something more complex.