jpanel | 易学教程

JPanel not listening to key event when there is a child component with JButton on it

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问题 I'm working on a map editor for my college project. And I had a problem that the map panel is not listening key event while it should. This happens when I add a ToolBarPane (which extends JPanel) with JComponent such as JButton, JComboBox that implements ActionListener on it AND the map panel (which extends the JPanel) together on to the Frame (I used BorderLayout). I have System.out.println statement to test if the key press is received, and it's not printing, if I remove the ToolBar, the

Visual Artifacts appearing on JPanel

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问题 I am trying to create a program with 2 JPanel using BorderLayout . The center panel is for random drawing of rectangle while the south panel is for the buttons. I am getting a weird image of the button on the top left corner of the JFrame whenever I hover the mouse cursor over the North or South button. I did some research and found out that this could be the reason for having a transparent background. I tried using super.paintComponent(g) for the panel but the rest of the rectangles drawn

JPanel not keeping color alpha when changing background

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问题 Ever so slowly the jpanel's background color will become more opaque than it previously was. Notable I am using the setBackground method of the jpanel. Here are a few links to code you might want to look at. Custom GUI Button The Gui it's in -- Look at line 158. 回答1: Two things popout Swing doesn't support alpha based colors, either a Swing component is opaque or transparent. You have to fake it, by making the component transparent and then override paintComponent and use a AlphaCompositeto

How can I switch between jpanels?

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问题 I'm still very new to java programming, so please help me to correct any mistakes I might have overlooked or give tips on how to improve this program. Okay, so a lot of problems have been solved, and now I have a CardLayout, but I still have questions about how I should make my pipes show inside it. When I tried to add in my refresh rate timer and my speed timer, I have problems about how I need to declare and initialize boolean variables. Also, when I compile and run this game, I get files

Specifying the location of Canvas in Swing

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问题 I'm learning Swing GUI design. One thing I haven't quite sorted out is how to add an add a Canvas to a specific location in a container. More specifically: I create a Canvas class that uses Paint method. Object of this class is added to a Panel. What I do not quite understand, is how and where it is added to a Panel. In Tkinter Canvas is a widget that contains only an image, but in Swing there is no similar widget (probably not the best word) added to the Frame that contains only Canvas

Why gif animation doesn't animate when using it in paintComponent()?

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问题 I'm using paintComponent() to paint a gif animated image at the backgound of JPanel . It shows up the gif but doesn't animate. I use java 1.5 and i know that i can use label with icon. Does any body know why and how to fix it? private static class CirclePanel extends JPanel { ImageIcon imageIcon = new ImageIcon(BarcodeModel.class.getResource("verify.gif")); Point point = f.getLocation(); protected void paintComponent(Graphics g) { Graphics gc = g.create(); Graphics2D g2d = (Graphics2D) g

Space button size on my layout keyboard won't resize

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问题 I am working on a typing app which includes the a keyboard but I have found a bit hard to re-size the space button to make it wider than the other buttons.. This is the way I am displaying and organizing my layout.. I can resize the whole buttons but its NOT what I want.. the whole point is to be resize just the space bar.. :) import java.awt.BorderLayout; import java.awt.Color; import java.awt.Dimension; import java.awt.Font; import java.awt.GridLayout; import java.awt.event.ActionListener;

How to draw grid using swing class Java and detect mouse position when click and drag

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I am trying to create a grid UI (5*5) using Swing classes. I tried a nested loop and adding a jPanel dynamically to the jFrame. And I also tried to change the background colour of each jPanel when user clicks and drops over it. But with my code there are huge gaps between each cell and I can't get the drag event to work. public class clsCanvasPanel extends JPanel { private static final int intRows = 5; private static final int intCols = 5; private List<JPanel> jpllist = new ArrayList<JPanel>(); public clsCanvasPanel() { /* * * Add eventListener to individual JPanel within CanvasPanel * * *

Java JPanel getGraphics()

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问题 Since Java only supports single inheritance , I desire to paint directly on an instance of a JPanel that is a member of the class Panel . I grab an instance of Graphics from the member and then paint whatever I desire onto it. How can I not inherit from JComponent or JPanel and still utilize getGraphics() for painting on this without overriding public void paintComponent(Graphics g) ? private class Panel { private JPanel panel; private Grahics g; public Panel() { panel = new JPanel(); }

What is the relation between ContentPane and JPanel?

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I found one example in which buttons are added to panels (instances of JPanel ) then panels are added to the the containers (instances generated by getContentPane() ) and then containers are, by the construction, included into the JFrame (the windows). I tried two things: I got rid of the containers. In more details, I added buttons to a panel (instance of JPanel ) and then I added the panel to the windows (instance of JFrame ). It worked fine. I got rid of the panels. In more details, I added buttons directly to the container and then I added the container to the window (instance of JFrame ).