Class Icon

java.lang.Object
   |
   +----java.awt.Component
           |
           +----java.awt.Canvas
                   |
                   +----ImageLabel
                           |
                           +----Icon

public class Icon

extends ImageLabel

By default, with FlowLayout the Icon takes its minimum size (just enclosing the image). The default with BorderLayout is to expand to fill the region in width (North/South), height (East/West) or both (Center). This is the same behavior as the builtin Label class and of ImageLabel, upon which Icon is built. If you perform an explicit resize or reshape call before adding the ImageLabel to the Container, this size will override the defaults.

This can be used in two ways. In the first, the Component itself watches the mouse events, and allows the user to drag it around. This has one major advantage:

• It doesn't require any changes in the code for the Container. Thus, Icons can be placed in arbitrary Containers (including builtin ones such as Panels, Applets, and Frames).

• If you move the mouse too quickly, especially for small Icons, you can lose the cursor. Given that there is no cursorLocation or warpCursor methods, there is no way to get it back.
• If you drag over the top of another Icon, the one on top gets the mouse events. Unfortunately, controlling who is on top is not portable.

• You cannot lose track of the mouse as long as the cursor stays inside the Container. So you can drag very small Icons while moving the mouse quickly.
• You can drag over the top of other Icons reliably.

• Since it requires changes in the Container's code, it cannot be used for builtin classes or classes for which source is not available. The user would have to write custom Container subclasses in such a case.
• Maintenance is more difficult since code is required in multiple classes.
• You still cannot drag over the top of arbitrary Components. If the Component is looking for a mouse drag event and is on top, it will get the event and may never pass it on to the Container. So care must be taken when using Icons with other custom Components that make use of mouseDrag.

If the Container does not already have a custom handleEvent method, insert the following:

   public boolean handleEvent(Event event) {
     if (Icon.handleIconEvent(event, this))
       return(true);
     else
       return(super.handleEvent(event));
   }
 

   public boolean handleEvent(Event event) {
     if (Icon.handleIconEvent(event, this))
       return(true);
     Original handleEvent code here
   }
 

The original of the Icon source code is at http://www.apl.jhu.edu/~hall/java/ImageLabel/Icon.java, the documentation is at .../Icon.html, and a small example program can be found at .../IconTest.html.

No warranty of any kind is provided. Permission is granted to use and/or modify for any purpose.

7/96 Marty Hall:

• Java Resource Page.
• Email.
• Home Page.

Version:

1.0 (August 1996)

See Also:

ImageButton

dragCursor

The cursor to get when dragging.

draggable

Can the image be dragged with the mouse? Default = true.

highlightable

Should the image be highlighted when you click/drag? Default = true.

highlightColor

The Color to use for the highlight rectangle.

highlightThickness

How thick should the highlighting rectangle be? Default = 3.

Icon()

Create an Icon with the default image.

Icon(Image)

Create an Icon using the image specified.

Icon(String)

Create an Icon using the image at URL specified by the string.

Icon(URL)

Create an Icon using the image at URL specified.

componentUnder(int, int, Container)

Finds the Component (if any) that is under the specified (x,y) location.

handleEvent(Event)

If the Container was always going to handle the mouse events, it could simply look up the event type and call a helper method directly.

handleIconEvent(Event, Container)

Called from the handleEvent method of the Container if the Container is to handle the mouse events.

mouseDown(Event, int, int)

Changes the cursor from the current to dragCursor, and optionally draws a highlighting rectangle around image.

mouseDrag(Event, int, int)

If it is draggable, moves the Component to be recentered at the specified (x,y).

mouseUp(Event, int, int)

Changes the cursor from dragCursor to whatever it was at mouseDown.

paint(Graphics)

Calls the parent class' paint to draw the image, then draws a highlighting rectangle if highlightable is set.

  public boolean highlightable

Should the image be highlighted when you click/drag? Default = true.

  public int highlightThickness

How thick should the highlighting rectangle be? Default = 3. Ignored if highlightable is false.

  public Color highlightColor

The Color to use for the highlight rectangle. Default is Color.blue. Ignored if highlightable is false.

  public boolean draggable

Can the image be dragged with the mouse? Default = true. (If it will always be false, use an ImageLabel instead).

  public int dragCursor

The cursor to get when dragging. Default is Frame.MOVE_CURSOR

  public Icon()

Create an Icon with the default image.

See Also:

defaultImageString

  public Icon(String imageURLString)

Create an Icon using the image at URL specified by the string.

Parameters:

imageURLString - A String specifying the URL of the image.

  public Icon(URL imageURL)

Create an Icon using the image at URL specified.

Parameters:

imageURL - The URL of the image.

  public Icon(Image image)

Create an Icon using the image specified. You would only want to call it directly if you already have an image (e.g. created via createImage).

Parameters:

image - The image.

  public boolean handleEvent(Event event)

If the Container was always going to handle the mouse events, it could simply look up the event type and call a helper method directly. This, however, allows event handling either locally (if ignoreEvents is false) or in the Container. You cannot override this arbitrarily in subclasses.

Overrides:

handleEvent in class Component

  public static boolean handleIconEvent(Event event,
                                        Container container)

Called from the handleEvent method of the Container if the Container is to handle the mouse events. See the introduction to this class.

  public boolean mouseDown(Event e,
                           int x,
                           int y)

Changes the cursor from the current to dragCursor, and optionally draws a highlighting rectangle around image.

Returns:

true if it is draggable, false otherwise.

Overrides:

mouseDown in class Component

See Also:

dragCursor, highlightable, draggable

  public boolean mouseUp(Event e,
                         int x,
                         int y)

Changes the cursor from dragCursor to whatever it was at mouseDown. Erases the highlighting rectangle if necessary.

Returns:

true if it is draggable, false otherwise.

Overrides:

mouseUp in class Component

See Also:

dragCursor, highlightable, draggable

  public boolean mouseDrag(Event e,
                           int x,
                           int y)

If it is draggable, moves the Component to be recentered at the specified (x,y).

Overrides:

mouseDrag in class Component

See Also:

draggable

  public void paint(Graphics g)

Calls the parent class' paint to draw the image, then draws a highlighting rectangle if highlightable is set.

Overrides:

paint in class ImageLabel

See Also:

highlightable

  public static Component componentUnder(int x,
                                         int y,
                                         Container container)

Finds the Component (if any) that is under the specified (x,y) location. In the Container's coordinate system. Put here because Netscape has a bug in which it doesn't process inside() and locate() tests correctly. They work properly with appletviewer and for applications.

See Also:

locate