Swing/AWT/SWT :: Repaint Method Is Automatically Erasing Old Circle?
Feb 19, 2014
This code is shown to eliminate "smearing":
public void paintComponent (Graphics g) {
g.setColor(Color.white);
g.fillRect(0,0,this.getWidth(), this.getHeight());
g.setColor(Color.green);
g.fillOval(x, y, 40, 40);
}
I had done all the previous code (in my own style) and found that the background rectangle was either being redrawn on its own, or there was something else removing the old circles from the screen. I then typed in the code from the previous page exactly as it was, to see if I had some change in syntax that would cause this, and it did the same thing.
Here's my code:
import javax.swing.*;
import java.awt.*;
public class SimpleAnimation {
int x, y;
private static final int HEIGHT = 600;
private static final int WIDTH = 600;
[Code] .....
Is this because I'm using JRE7? I can't find any documentation that indicates the repaint() method has changed since Java 5.
I have two classes. One constructs my a rectangle using Graphics2D (the class is called Rectangles). The second takes a user input for the triangle, which I am passing back to the first class. I am trying to trigger a repaint of class one from the action listener I have on a button in the second class. how to trigger this event?
I have the following code where I call panel repaint method from the action listener of the calc button but it causes stack over flow but when I modify it to call paint component method and removing the super term, the program executes. here is the code
I'm trying to make a simple program that will feature some graphics. It will have a JCombobox that the user selects to draw various shapes. I can't get the repaint function to work however.
Java/Swing dialog box appears on the user's screenIt allows the user to enter 2 values into labelled text fields (fname/sname)They select a "Click Me" push button which I hope will write the data into the table. But the table does not get refreshed.
If I minimise the dialog box and then open it again, the data still does not appear.
The code I originally built using eclipse/WindowBuilder. I've cut it back and tried to isolate the issue. But I still cannot figure it out.
I've added some diagnostic log messages to ensure that I am seeing the various events I think I need to see and have put code in the action callbacks etc.
I would like to be able to draw things onto the panel (via paintComponent), but I'd like it to draw 'on top' of what's already there. The default seems to be that it resets every time I call repaint.
I have been baffled by the functioning of repaint() - and the SwingPaintDemo3 with the moving square seems mysterious - you call repaint(x,y,w,h) twice and the first time it clears the clip area and the 2nd time it paints the red box. The code in paintComponent tells it to paint the box both times, yet somehow it ignores the initial box and only paints the 2nd one.
I've been writing code to bounce some balls in a box to try and understand the behavior. I set up an array of ball objects, loop through them, move them adjusting for collisions with walls and each other, then repaint(). I call repaint x2 for each ball, just like in the example. In my paintComponenet code, if I try to just paint the current ball only one ball will move, even if I send a different ball object each time. The only way to get all the balls to show up is to put a loop in paintComponenet that goes through all 100 balls every time I call it. I was worried that to move 100 balls I was painting 100x100 times.
So I put some System.out.println commands in my ball move loop, inside my object ball draw commands, and inside the paint component.
So even though I called repaint() 200 times (twice for each ball), repaint was actually only called once, drew all the balls at once, and then went back. And I just noticed it appears to have waited until I exited the calculateMoveBall loop to go into paintComponent! The spooky things is how does it know to do that? Does the Java machine 'see' that it is inside of a loop, and perhaps also sees the loop inside of paintComponent, and somehow correctly guesses that it doesn't have to do it 200 times, but can wait and do it once? If I attempt to do the same thing in code, take the loop out of paintComponent() and call repaint() with the current ball, expecting the machine to do exactly what I tell it, it refuses and does it's own thing, waiting to call paintComponent on the 100th ball, drawing only the last ball (so I guess the loop inside paintComponent is not in the logic).
So a call to repaint() is a request for a higher being to decide if it has the time or energy to repaint the clip. If not, it ignores the call, or stacks them up for later (maybe I should try a million and see if it has room for that!) - well so far up to 4000 it behaves the same. This is useful if you are happy with "this is how it works so use it that way". However I really don't like having some kind of hidden logic that I have to trust to work the right way. If I don't want it to wait until later I'm not sure what to do. And I don't trust the machine to do whatever whenever. How do you debug that???
Questions: Is there documentation to know what repaint() will do or how it decides when to call paintComponent? The Swing tutorial gives the example but not the why. "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" "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." (What the code appears to be doing - now we have to guess what it is doing)
Is there a way to force repaint() to call paintComponent on a clip rectangle (not just on the whole thing?) I would think invalidate() would force repainting of the whole componenet.
Perhaps this is when you draw to a bitmap in memory and paint the whole thing on the screen...
What's that diameter? Create a new method for the circle class called diameter. Add this method to the circle class described on page 15-1. It should return a double that is the diameter of the circle. No parameters are passed to this method.
In a tester class, test the performance of your new diameter method as follows:
(Your project should have two classes, Tester and Circle.)
here is what i have so far:
public class Circle { public Circle (double r) { radius = r; } public double area() { double a = Math.PI * radius * radius;
public class Circle { private double PI = 3.14159; private double radius; public Circle() { radius = 0.0;
[Code] ....
This is the error i am receiving:
Circle.java:78: error: method getRadius in class Circle cannot be applied to given types; System.out.println("A circle with a radius of " + circle.getRadius() + " will have an area of " + circle.getArea() + " , a diameter of " + circle.getDiameter() + " and a circumference of " + circle.getCircumference()); ^ required: double found: no arguments reason: actual and formal argument lists differ in length 1 error
I'm new to programming and I have an assignment due in java class. Here is the error code:
TestCircle.java:10: error: method setradius in class Circle cannot be applied to given types; circle1 = inputCircle.setradius(); ^ required: double found: no arguments reason: actual and formal argument lists differ in length
And here is my code:
import java.util.Scanner; public class TestCircle { public static void main(String[] args) { double circle1; double circle2; double circle3; Circle inputCircle = new Circle();
I want to have JTextField automatically highlighting the current values for overwriting when the box is selected. Is there a way to do this? It seems like something that might occur in an action listener.
i want to draw a circle inside a circle in java. so far i'm using this piece of code
private Ellipse2D.Float drawEllipse(int x1, int y1, int x2, int y2) { int x = Math.min(x1, x2); int y = Math.min(y1, y2); int width = Math.abs(x1 - x2); int height = Math.abs(y1 - y2); return new Ellipse2D.Float(x, y, width, height); }
I'm working on Java-GUI implementation in Ubuntu. Used font-type in the application throughout is "Arial". At earlier stage of application it was the same font-type("Arial"). As the implementation grew the font-type has been changed automatically to another font type. It seems Serif-font type.
Now I could not able to figure out the problem; why it is so.
Note- I used HTML code also for setting font style of Dialog box messages and buttons. This is the only point which I figured out. Can it is ?
So Ive got to make a turtle on an image draw a semicircle that starts at the top of a circle and goes down and to the left, changing colors halfway through. I've got everything down, I can draw the turtles and make them do straight lines. My problem is more math related. I need to use the equation of a circle, give it points, and figure out how to write that code in java.
We use the equation for a circle: (x - a)^2 + (y - b)^2 = r^2
How would I go about erasing the first buffered image before displaying the second one and eventually a third and fourth so that it appears the image is moving across the screen?
It has to be from another class because the other class controls the fps timer, and I want it to repaint() the panel every tick. However, I cannot seem to find a way to do this because repaint() is not static, and therefor can not be called in any way from another class.
Why is paintComponent not being called by repaint();? Also, paintComponent is called twice when the program starts, that works, repaint is the thing that doesn't work.
I am trying to repaint a window from another class. the class Window handles an interface that displays pictures of movies. Via a JMenuBar you can add a new movie and its picture but in order for it to show in the Window i need to repaint certain aspects in the Window class GUI;
The window class constructor:
public Window() { addComponents(); configurFrame(); addMenu(); }
The functions i want to repaint:
public void repaintWindow() { this.getContentPane().validate(); this.getContentPane().repaint(); }
From my other class where i add a movie to an ArrayList i have made a "private Window myWindow;" there i call the function repaintWindow via mywindow.repaintWindow(); But this gives me an NullPointerException related to the repaintWindow function.
So as of right now, I'm trying to swap my bar arrays and repaint it. For now, I'm using the index 5 and swapping it with index 23. When I click the shuffle button, It swaps, but the highest bar still remains the same.
Here's my code.
import java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.event.ChangeEvent; import javax.swing.event.ChangeListener; public class AssortedAssortmentsOfSorts extends JFrame
I am teaching myself AWT/Swing ... It concerns an application that creates dynamic graphics using the Graphics class. I understand that the code that creates graphics should be put in a "paintComponent" method of a (descendant of a) JPanel class. And that when you want to change something on this panel outside "paintComponent", you have to call the "repaint" method, that somehow causes "paintComponent" to be invoked.
However, I don't fully understand the explanation of the example at [URL]... . It concerns an application that moves a red square when a mouse button is clicked. The code can be found at the link, but I also repeat it below.
This code indeed works. However, I don't understand why. The explanation at the Oracle site is the following.
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.
However, what I don't understand: when repaint is first invoked, squareX and squareY still have their old values. If the invocation of repaint simply causes an invocation of paintComponent, then paintComponent should draw a red square at (squareX, squareY). Just like the second invocation of repaint causes paintComponent to draw a red suare at the new values of (squareX, squareY). Instead, the first invocation results in the red square being wiped out by the background color.
So apparently, the first invocation of repaint does not simply cause an invocation of paintComponent. What does it do?
I have a problem using JFreeChart with JavaFX. I wrote a small program here . At first the graph likes this:
I use fullScreen function to display the JFreeChart Line Chart Demo 2. Here I use SwingNode, ChartPanel to embedded JFreeChart into JavaFX Panel.(Detail part will be included in code later)
Then I press ESC to exit fullScreen. Then it looks like this:
So far, it's as expected. Then I use mouse drag to enlarge the window. Here comes the problem, as the following picture.
Can you see that, seems like appear another graph. And I must click on the window, then everything will become good. I wish the graph shows well even when I drag the window to enlarge, is there something I missed? And here is my code:
I'm writing a JavaFX desktop app, and would like to make it automatically run after installation, but I'm not sure where to look to make this happen (or even if it's possible?). I have successfully created a .dmg installer using E(fx)clipse & Ant. Are there options I'm overlooking which I can use in the build.xml? or am I looking in the wrong place entirely?
