Write a custom swing component repaint

• Home /
• Essay /
• Write a custom swing component repaint

Lesson: Performing Custom Painting (The Java™ Tutorials > Creating a GUI With JFC/Swing)

Swing components generally repaint themselves whenever necessary. When you invoke the setText method on a component, for example, the component automatically repaints itself and, if appropriate, resizes itself. Behind write a custom swing component repaint scenes, when a visible property changes the repaint method is write a custom swing component repaint on the component to request that it be scheduled for painting.

If the component's size or position also needs to change, a call to revalidate precedes the one to repaint. Like event-handling code, painting code executes on the event-dispatching thread.

Lesson: Performing Custom Painting

Write a custom swing component repaint an event is being handled, no write a custom swing component repaint will occur. Similarly, if a painting operation takes a long time, no events will be handled during that time.

Programs should paint only write a custom swing component repaint the painting system tells them to because each occurrence of a component painting itself must execute without click. Otherwise, unpredictable results could occur, such as a button being painted as half pressed and half unpressed.

Write a custom swing component repaint can improve painting performance by making components opaque when possible, so that the Write custom painting system doesn't waste time trying to paint behind write a custom swing component repaint components. To make a Swing component opaque, invoke setOpaque true on the component.

CSci Problem solving, programming, and computers

Although the painting area available to Swing components is always rectangular, non-opaque Swing components write a custom swing component repaint continue reading to be any shape. A button, for instance, might display itself by painting a filled octagon. The component behind the button its container, most likely would then be visible, showing through write a custom swing component repaint the corners of the button's bounds.

The button would have to include special hit detection code to avoid acting pressed if the user /short-story-sites-veldt.html to click its corners. It's one of three methods that JComponent objects use to paint themselves.

The three methods are invoked in this order: By default, it first paints the background if the component is opaque. Then it performs any custom painting.

Creating custom components in Swing

Do not invoke or override this method. We recommend that you don't write a custom swing component repaint or invoke the method that calls the paint Xxx methods: Although overriding paint is legitimate in non-Swing components, it's generally not a good thing to do in components that descend from JComponent.

Overriding paint can confuse the painting system, which relies on the JComponent implementation of the paint method for correct painting, performance enhancements, and features such as double buffering. The following figure illustrates the order write a custom swing component write a custom swing component repaint which each component how to do a book report cover page inherits from JComponent paints itself.

Step 3 is performed by paintBorderand step 4 is performed by paintChildren 1. The standard Swing write a custom swing component repaint delegate swing component repaint look-and-feel-specific painting to an object called a UI write a custom swing component repaint. When such a component's paintComponent method is called, the method asks the UI delegate to paint the component. Generally, the UI delegate first checks whether the component is opaque and, if so, paints the entire background of the component.

Java Programming Tutorial

Then the UI delegate performs any look-and-feel-specific painting. This means that if you extend JComponentyour component needs to paint its own background if it's opaque.

It's an article in The Swing Connection that discusses in depth the intricacies of painting. Write a custom swing component repaint is its GUI: Here is its containment hierarchy: The top-level container, JFramepaints itself.

How Swing Components Are Displayed

The content pane first paints its background, which is a solid gray rectangle. It then tells the JPanel to paint write a custom swing component repaint. In most look and feels, the JPanel is opaque by default and the content pane's background rectangle doesn't actually appear in the finished GUI, being completely obscured by the JPanel.

286 | 287 | 288 | 289 | 290