Interface Painter<T>
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- All Known Implementing Classes:
- AbstractRegionPainter
public interface Painter<T>A painting delegate. The Painter interface defines exactly one method,
paint. It is used in situations where the developer can change the painting routine of a component without having to resort to subclassing the component. It is also generically useful when doing any form of painting delegation.Painters are simply encapsulations of Java2D code and make it fairly trivial to reuse existingPainters or to combine them together. Implementations of this interface are also trivial to write, such that if you can't find aPainterthat does what you need, you can write one with minimal effort. Writing aPainterrequires knowledge of Java2D.A
Paintermay be created with a type parameter. This type will be expected in thepaintmethod. For example, you may wish to write aPainterthat only works with subclasses ofComponent. In that case, when thePainteris declared, you may declare that it requires aComponent, allowing the paint method to be type safe. Ex:Painter<Component> p = new Painter<Component>() { public void paint(Graphics2D g, Component c, int width, int height) { g.setColor(c.getBackground()); //and so forth } }This interface makes no guarantees of threadsafety.
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method and Description voidpaint(Graphics2D g, T object, int width, int height)Renders to the givenGraphics2Dobject.
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Method Detail
paint
void paint(Graphics2D g, T object, int width, int height)
Renders to the given
Graphics2Dobject. Implementations of this method may modify state on theGraphics2D, and are not required to restore that state upon completion. In most cases, it is recommended that the caller pass in a scratch graphics object. TheGraphics2Dmust never be null.State on the graphics object may be honored by the
paintmethod, but may not be. For instance, setting the antialiasing rendering hint on the graphics may or may not be respected by thePainterimplementation.The supplied object parameter acts as an optional configuration argument. For example, it could be of type
Component. APainterthat expected it could then read state from thatComponentand use the state for painting. For example, an implementation may read the backgroundColor and use that.Generally, to enhance reusability, most standard
Painters ignore this parameter. They can thus be reused in any context. Theobjectmay be null. Implementations must not throw a NullPointerException if the object parameter is null.Finally, the
widthandheightarguments specify the width and height that thePaintershould paint into. More specifically, the specified width and height instruct the painter that it should paint fully within this width and height. Any specified clip on thegparam will further constrain the region.For example, suppose I have a
Painterimplementation that draws a gradient. The gradient goes from white to black. It "stretches" to fill the painted region. Thus, if I use thisPainterto paint a 500 x 500 region, the far left would be black, the far right would be white, and a smooth gradient would be painted between. I could then, without modification, reuse thePainterto paint a region that is 20x20 in size. This region would also be black on the left, white on the right, and a smooth gradient painted between.- Parameters:
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g- The Graphics2D to render to. This must not be null. -
object- an optional configuration parameter. This may be null. -
width- width of the area to paint. -
height- height of the area to paint.
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