Repaint method in java swing

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Repaint method in java swing

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Can someone help? Hope this helps! Basically, there are two important differences between The thing you are worried about is In the frame, you can use the First, you will have to create a Heavy weight components like Abstract Window Toolkit Already have an account? Sign in. Your comment on this question: Your name to display optional : Email me at this address if a comment is added after mine: Email me if a comment is added after mine Privacy: Your email address will only be used for sending these notifications.

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repaint method in java swing

Related Questions In Java. How to create text labels in Swing, Java? Create Buttons in Java Swing First, you will have to create a How to change selection listener in JComboBox? Welcome back to the World's most active Tech Community! Please enter a valid emailid. Forgot Password? Subscribe to our Newsletter, and get personalized recommendations. Sign up with Google Signup with Facebook Already have an account? Email me at this address if a comment is added after mine: Email me if a comment is added after mine.

Privacy: Your email address will only be used for sending these notifications.Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available. By now you know that the paintComponent method is where all of your painting code should be placed. It is true that this method will be invoked when it is time to paint, but painting actually begins higher up the class heirarchy, with the paint method defined by java.

This method will be executed by the painting subsystem whenever you component needs to be rendered. Its signature is:. JComponent extends this class and further factors the paint method into three separate methods, which are invoked in the following order:. The API does nothing to prevent your code from overriding paintBorder and paintChildrenbut generally speaking, there is no reason for you to do so. For all practical purposes paintComponent will be the only method that you will ever need to override.

As previously mentioned, most of the standard Swing components have their look and feel implemented by separate UI Delegates. This means that most or all of the painting for the standard Swing components proceeds as follows. This is why our SwingPaintDemo code invokes super.

We could add an additional comment to make this more clear:. If you have understood all of the demo code provided in this lesson, congratulations! You have enough practical knowledge to write efficient painting code in your own applications. If however you want a closer look "under the hood", please refer to the SDN article linked to from the first page of this lesson.

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All rights reserved. Hide TOC. Performing Custom Painting. Its signature is: public void paint Graphics g javax. JComponent extends this class and further factors the paint method into three separate methods, which are invoked in the following order: protected void paintComponent Graphics g protected void paintBorder Graphics g protected void paintChildren Graphics g The API does nothing to prevent your code from overriding paintBorder and paintChildrenbut generally speaking, there is no reason for you to do so.

If the ui property is non-null, paintComponent invokes ui.

[Java] How to make a Swing Paint and Drawing application ?

If the component's opaque property is true, ui. Previous page: Refining the Design Next page: Summary.Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available. Finally, we will add the event-handling code to programatically repaint the component whenever the user clicks or drags the mouse. To keep our custom painting as efficient as possible, we will track the mouse coordinates and repaint only the areas of the screen that have changed.

This is a recommended best practice that will keep your application running as efficiently as possible. Alternatively, to compile and run the example yourself, consult the example index. This change first imports the various mouse classes from the java. The constructor has been updated to register event listeners for mouse presses and drags.

Whenever a MouseEvent received, it is forwarded to the moveSquare method, which updates the square's coordinates and repaints the component in an intelligent manner. Note that by default, any code that is placed within these event handlers will be executed on the Event Dispatch Thread.

But the most important change is the invocation of the repaint method. This method is defined by java. Component and is the mechanism that allows you to programatically repaint the surface of any given component.

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It has a no-arg version which repaints the entire component and a multi-arg version which repaints only the specified area. This area is also known as the clip. Invoking the multi-arg version of repaint takes a little extra effort, but guarantees that your painting code will not waste cycles repainting areas of the screen that have not changed.

Because we are manually setting the clip, our moveSquare method invokes the repaint method not once, but twice. The first invocation tells Swing to repaint the area of the component where the square previously was the inherited behavior uses the UI Delegate to fill that area with the current background color.

The second invocation paints the area of the component where the square currently is. An important point worth noting is that although we have invoked repaint twice in a row in the same event handler, Swing is smart enough to take that information and repaint those sections of the screen all in one single paint operation.

In other words, Swing will not repaint the component twice in a row, even if that is what the code appears to be doing.

repaint method in java swing

All rights reserved. Hide TOC. Performing Custom Painting. SwingUtilities; import javax. JFrame; import javax. JPanel; import javax. BorderFactory; import java. Color; import java. Dimension; import java. Graphics; import java. MouseEvent; import java. MouseListener; import java. MouseAdapter; import java. MouseMotionListener; import java. RED ; g. BLACK ; g.Manage your account and access personalized content. Sign up for an Oracle Account. Access your cloud dashboard, manage orders, and more.

Sign up for a free trial. In a graphical system, a windowing toolkit is usually responsible for providing a framework to make it relatively painless for a graphical user interface GUI to render the right bits to the screen at the right time.

Both the AWT abstract windowing toolkit and Swing provide such a framework. But the APIs that implement it are not well understood by some developers -- a problem that has led to programs not performing as well as they could.

This article explains the AWT and Swing paint mechanisms in detail. Its purpose is to help developers write correct and efficient GUI painting code. While the article covers the general paint mechanism where and when to renderit does not tell how to use Swing's graphics APIs to render a correct output.

To learn how to render nice graphics, visit the Java 2D Web site. This allowed the AWT to rely heavily on the paint subsystem in each native platform. This scheme took care of details such as damage detection, clip calculation, and z-ordering. With the introduction of lightweight components in JDK 1. Consequently, there are subtle differences in how painting works for heavyweight and lightweight components. After JDK 1.

For the most part, the Swing painting mechanism resembles and relies on the AWT's. But it also introduces some differences in the mechanism, as well as new APIs that make it easier for applications to customize how painting works.

In AWT, there are two kinds of painting operations: system-triggered paintingand application-triggered painting. In a system-triggered painting operation, the system requests a component to render its contents, usually for one of the following reasons:.

In an application-triggered painting operation, the component decides it needs to update its contents because its internal state has changed. For example. Regardless of how a paint request is triggered, the AWT uses a "callback" mechanism for painting, and this mechanism is the same for both heavyweight and lightweight components.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I've spent maybe the last two hours browsing and reading up on these methods and the Graphics class, and maybe I'm stupid, haha, but I'm just not understanding them. What are they for?

Difference between Paint() and Repaint() method

I understand that they're supposed redraw or update components on the screen, but I have never understood why this is required I'm new to this. For example, if I'm moving a JLabel around the screen, a call to setLocation moves it just fine. Is that a scenario in which repaint isn't required? In which scenarios is it useful, and why? Apologies if you feel that this is a question that could be solved using the search function, but for whatever reason I'm not getting it.

This method holds instructions to paint this component.

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Actually, in Swing, you should change paintComponent instead of paintas paint calls paintBorderpaintComponent and paintChildren. You shouldn't call this method directly, you should call repaint instead. This method can't be overridden. You should call this method to get a component to repaint itself. If you have done anything to change the look of the component, but not its size like changing color, animating, etc.

The repaint method is used to cause paint to be invoked by the AWT painting thread. It's not necessary to call repaint unless you need to render something specific onto a component. Learn more. Asked 7 years, 10 months ago. Active 2 years, 1 month ago. Viewed k times.As of 1. Any calls to repaint on one of these will call into the appropriate addDirtyRegion method.

String toString Returns a string that displays and identifies this object's properties. You rarely call this constructor. To get the default RepaintManager, use RepaintManager. Note: This method exists for backward binary compatibility with earlier versions of the Swing library. It simply returns the result returned by currentManager Component. See Also: JComponent. See Also: addInvalidComponent javax. If c already has a dirty region, the rectangle x,y,w,h will be unioned with the region that should be redrawn.

Parameters: c - Component to repaint, null results in nothing happening. Parameters: window - Window to repaint, null results in nothing happening. Parameters: applet - Applet to repaint, null results in nothing happening. Return an empty rectangle if the component is not dirty. If computing dirty regions is expensive for your component, use this method and avoid computing dirty region if it return true. See Also: addDirtyRegion javax.

By default there is a double buffer per RepaintManager. The buffer might be smaller than proposedWidth,proposedHeight This happens when the maximum double buffer size as been set for the receiving repaint manager. The image returned will be an instance of VolatileImage, or null if a VolatileImage object could not be instantiated.

This buffer might be smaller than proposedWidth,proposedHeight. This happens when the maximum double buffer size has been set for this repaint manager.

Since: 1. CAUTION: The default value for this property is set for optimal paint performance on the given platform and it is not recommended that programs modify this property directly.

The default value for this property may vary from platform to platform. On platforms where native double buffering is supported in the AWT, the default value will be false to avoid unnecessary buffering in Swing.Documentation of repaint in Component class.

This thread is responsible for accepting input events and calling the paint method. The programmer should leave calling paint to this thread.

repaint method in java swing

Java applets rarely call paint directly. The GUI thread makes these calls.

Painting in AWT and Swing

Every applet or application with a GUI i. There are four situations when the GUI thread calls paint spontaneously. Paint is called to reconstruct the damaged parts of the uncovered window after deiconification in an applet after init has finished when a browser returns to a page which contains an applet, provided the applet is at least partially exposed.

The repaint Method The second case, when paint calls are genereted is when the program calls repaint or update.

The repaint method is the one invoked by a program to do drawing. Their are 4 versions of this method but the one with no arguments is usually used. Drawing via repaint most often takes place in response to user input. It schedules a call to an intermediate method, update. Finally, update calls paint unless you override update. The reason for this complexity is Java's support for concurrent programming. It does this using threads. Using repaint can be tricky for at least three reasons.

The repaint method is asynchronous. All these potential complications are considered in details below.

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However, let's start with a discussion what happens if paint or update are called directly. Using paint and update directly. What is of concern here is what happens if the user, for example, covers all or part of your drawing by another window, and then uncovers your drawing again.

Does it survive? Similarly, what happens if the user resizes the browser window? Not the right way -- RepaintApplet. Java Source When paint is called after initor after the applet has been covered or iconified, it uses the default paint which just paints the background colour, thereby erasing the image. Note, however, the useful method getGraphics used in this example. Putting drawing in the paint methodcalling paint directly -- RepaintApplet1.

Java Source A paint method has been added.


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