I have JFrame, and I added my JPanel class with paintComponent() method. For example I drawed red rectangle, and after some action I want to draw green oval. I tried to call repaint() method in JPanel but nothing happens. Help me please!
UPDATE: It's just example code
public class Test extends JFrame implements ActionListener{
private Container content;
private MyPanel em;
private JButton btn;
Test() {
super("test");
content = getContentPane();
em = new MyPanel();
conent.add(em);
btn = new JButton("Draw");
btn.addActionListener(this);
content.add(btn);
}
public void actionPerformed(ActionEvent e) {
em.setShape("oval");
}
public class MyPanel extends JPanel {
private String shape = "rectangle";
MyPanel()
{
}
setShape(String shape){
this.shape = shape;
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
if(shape == "rectanle")
g.drawRectangle(100,25,100,200);
}
else if(shape == "oval"){
g.drawOval(100, 25, 175, 175);
}
}
Try calling markCompletelyDirty(myComponent) on javax.swing.RepaintManager.
Try replacing shape == "oval" with "oval".equals(shape). In Java, Strings that are equal according to equals() are not necessarily equal according to ==.
Also, I'd suggest you replace the string literals with constants:
class Whatever {
private final static String OVAL = "oval";
public void process(String arg) {
if (OVAL.equals(arg)) {
// Do something
}
}
}
to avoid problems with spelling mistakes (like you have with "rectangle" and "rectanle").
You could add debugging statements to check that the actionPerformed method is actually being called, and to see when paintComponent is executed and trace what path it takes through your code.
By the way, the code as posted shouldn't compile: you have mismatched braces.
Related
I am trying to to set up a KeyListener to respond to my keystrokes. I have already setup a mouselistener but for some reason I am un-able to get the keylistener to respond to any keystrokes.
I have created a class that implements KeyListener and overridden the functions. I then created an instance of the new class and added the handler to the JPanel and JFrame. Still no dice
public class main_program extends JFrame {
private int mX_cord, mY_cord,prior_selected_vertex, current_selected_vertex;
private int verticies_to_edge1, verticies_to_edge2;
private int radius =10;
private boolean vertex_selected1 = false, vertex_selected2 = false, edge_ready = false,delete_vertex_ready = false;
private Edge tempEdge = null;
private ArrayList<Integer> vertex_xcord = new ArrayList<Integer>();
private ArrayList<Integer> vertex_ycord = new ArrayList<Integer>();
private ArrayList<Edge> edge = new ArrayList<Edge>();
HandlerMouse handler = new HandlerMouse();
HandlerKey keyhand = new HandlerKey();
private JPanel masterPanel;
private JTextArea masterTextArea;
private JScrollPane masterScrollPane;
private Point point1, point2;
Graphics g;
public main_program(){
setTitle("Graph");
setSize(600, 400);
setDefaultCloseOperation(new JFrame().EXIT_ON_CLOSE);
//this must be set for custom layout of components
setLayout(null);
masterPanel = new JPanel();
masterPanel.setSize(600,300);
masterPanel.setLocation(0, 0);
masterPanel.setBackground(Color.WHITE);
masterPanel.addMouseListener(handler);
masterPanel.addMouseMotionListener(handler);
masterPanel.addKeyListener(keyhand);
masterTextArea = new JTextArea();
masterTextArea.setBackground(Color.green);
masterScrollPane = new JScrollPane();
masterScrollPane.add(masterTextArea);
masterScrollPane.setSize(600, 100);
masterScrollPane.setLocation(0, 300);
masterScrollPane.addMouseListener(handler);
masterScrollPane.addMouseListener(handler);
masterScrollPane.addKeyListener(keyhand);
add(masterPanel);
add(masterScrollPane);
setLocationRelativeTo(null);
setVisible(true);
}
public void paint(Graphics g){
super.paint(g);
for(int i = 0 ; i < vertex_xcord.size(); i++){
g.fillOval(vertex_xcord.get(i), vertex_ycord.get(i), radius, radius);
}
for(int i = 0 ; i<edge.size(); i++){
tempEdge = edge.get(i);
g.drawLine(vertex_xcord.get(tempEdge.vertex1), vertex_ycord.get(tempEdge.vertex1), vertex_xcord.get(tempEdge.vertex2), vertex_ycord.get(tempEdge.vertex2));
}
//g.fillOval(mX_cord, mY_cord, radius, radius);
//repaint();
}
private class HandlerKey implements KeyListener{
public void keyPressed(KeyEvent evt){
System.out.println("key pressed");
if(evt.getKeyCode() == KeyEvent.VK_ENTER && edge_ready){
edge.add(new Edge(prior_selected_vertex, current_selected_vertex));
edge_ready = false;
repaint();
}
}
public void keyReleased(KeyEvent evt){
System.out.println("key rel");
}
public void keyTyped(KeyEvent evt){
System.out.println("key type");
}
}
private class HandlerMouse implements MouseListener, MouseMotionListener{
public void mouseClicked(MouseEvent evt){
mX_cord = evt.getX()-5;
mY_cord = evt.getY()+15;
if( evt.getClickCount() == 1){
//mX_cord = evt.getX();
//mY_cord = evt.getY();
vertex_xcord.add(mX_cord);
vertex_ycord.add(mY_cord);
repaint();
}
else{
for(int i = 0 ; i < vertex_xcord.size(); i++){
if(Math.abs(vertex_xcord.get(i) - mX_cord ) < 15 && Math.abs(vertex_ycord.get(i) - mY_cord ) < 15 ){
if(vertex_selected1 == false){
prior_selected_vertex = i;
vertex_selected1 = true;
}
else{
current_selected_vertex = i;
vertex_selected2 = true;
}
System.out.println("YOU HAVE SELECTED A VERTEX: " + i);
break;
}
}
}
if(vertex_selected2 == true){
edge_ready = true;
verticies_to_edge1 = prior_selected_vertex;
verticies_to_edge2 = current_selected_vertex ;
vertex_selected1 = vertex_selected2 = false;
System.out.println("Ready for edge!");
}
else{
delete_vertex_ready = true;
}
}
public void mouseEntered(MouseEvent arg0)
{
}
public void mouseExited(MouseEvent arg0)
{
}
public void mousePressed(MouseEvent evt)
{
}
public void mouseReleased(MouseEvent arg0)
{
}
public void mouseDragged(MouseEvent e)
{
}
public void mouseMoved(MouseEvent e)
{
}
}
class Edge {
int vertex1, vertex2;
public Edge(int v1, int v2){
vertex1 = v1;
vertex2 = v2;
}
}
public static void main(String[] args){
main_program circle = new main_program();
}
}
You've got several problems with that program, and it suggests that you'd do well to read many of the Swing Q&A's on this site, because these problems (and your main problem) are quite common, and solutions are often posted.
As to your main problem, the problem again is very common: KeyListeners only work if the listened to component has focus. If it loses focus or is not focusable, then you're out of luck. The best solution is often not to use a KeyListener but rather the higher level and more flexible Key Bindings. Google will find the tutorials for you for this.
As for other problems with your code:
You're using null layout, a layout that leads to inflexible GUI's that are very difficult to upgrade and enhance, and that look terrible on all but your current platform and screen resolution. Solution: study and use the layout managers.
You're drawing directly into a JFrame's paint(Graphics g) method, which has risks as you risk messing up the painting of any and all of the JFrame's constituents by doing this. Much better to draw in a JPanel's paintComponent(Graphics g) method, and gain the benefit of Swing (rather than AWT) graphics including automatic double buffering.
Your class has a Graphics variable, g, which suggests that you're contemplating using a stored Graphics object either from a component or from the JVM. This increases the risk of your program throwing a NullPointerException when that Graphics object no longer exists, either that or drawing with it and but not seeing any effect. Solution: draw inside the painting method (again better with a JComponent's paintComponent method) only, or with the Graphics object from a BufferedImage.
You're adding a MouseListener directly to a JPanel but are drawing in a different component, the JFrame, and by doing so without taking insets into account, are placing points in the wrong location. Use the MouseListener on the same component that you're drawing on.
Again, please have a look around here, as I think you'll find a lot of treasures on this site that can be used to enhance your program.
public class TesterApplication {
static JPanel CenterPanel;
public static void main(String[] args){
/* get image MapImg */
JFrame frame=new JFrame();
CenterPanel = new JPanel(){
#Override
protected void paintComponent(Graphics g){
g.drawImage(MapImg, 0, 0, null);
}
};
CenterPanel.addMouseListener(new LineBuildListener(new TesterApplication()));
frame.getContentPane().add(BorderLayout.CENTER, CenterPanel);
frame.setSize(x, y);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
}
}
now inner class
class LineBuildListener implements MouseListener {
TesterApplication TA;
int xFirstClick;
int yFirstClick;
int ClickCounter=0;
int xClick;
int yClick;
LineBuildListener(TesterApplication TA){
this.TA=TA;
}
#Override
public void mouseClicked(MouseEvent e) {
xFirstClick=xClick;
yFirstClick=yClick;
xClick=e.getX();
yClick=e.getY();
TA.CenterPanel.getGraphics().fillOval(xClick, yClick, 10, 10);
if(ClickCounter!=0){
SecondClick();
ClickCounter++;
}else{
ClickCounter++;
}
System.out.println(ClickCounter);
}
public void SecondClick(){
TA.CenterPanel.getGraphics().drawLine(xClick, yClick, xFirstClick,yFirstClick);
}
}
meanwhile I make first click, my GUI blink, Click Counter print that i have made 1 click, but yet i don't get my first circle. If i keep clicking everything work fine, it prints next circle, increase Counter and draw line between them, so i dont get why first circle is missing
Look at this:
xFirstClick=xClick;
yFirstClick=yClick;
xClick=e.getX();
yClick=e.getY();
xClick and yClick are not initialized the first time
I'm using java trying to make a basic game but am having some trouble with a KeyAdapter. I've used a very similar format before and thought I understood it, but this has me stumped.
Any help would be appreciated, here is the main code I'm working with
public class Board extends JPanel implements ActionListener{
Timer timer;
Tank tank = new Tank();
boolean boardset;
public Board(){
setBackground(Color.BLACK);
ImageIcon alien1ii = new ImageIcon(this.getClass().getResource("si_Alien1.png"));
Image alien1 = alien1ii.getImage();
ImageIcon alien2ii = new ImageIcon(this.getClass().getResource("si_Alien2.png"));
Image alien2 = alien2ii.getImage();
ImageIcon alien3ii = new ImageIcon(this.getClass().getResource("si_Alien3.png"));
Image alien3 = alien3ii.getImage();
timer = new Timer(5, this);
timer.start();
addKeyListener(new TAdapter());
JButton button = new JButton(new AbstractAction("hello2"){
#Override
public void actionPerformed(ActionEvent e){
boardset = false;
}
});
this.add(button);
//actual game
setFocusable(true);
setDoubleBuffered(true);
}
public void paint(Graphics g){
super.paint(g);
g.setColor(Color.WHITE);
Graphics2D g2d = (Graphics2D) g;
g2d.drawImage(tank.getTank(), tank.getx(), tank.getY(), this);
g2d.drawLine(0, (tank.getY()+25), 400, (tank.getY()+25));
Toolkit.getDefaultToolkit().sync();
g.dispose();
}
public class TAdapter extends KeyAdapter{
public void keyPressed(KeyEvent e){
tank.keyPressed(e);
System.out.println("pressedddddddddddddddddd");
}
public void keyReleased(KeyEvent e){
tank.keyReleased(e);
}
}
public void setBoardset(boolean x){
boardset = x;
}
public boolean getBoardset(){
return boardset;
}
#Override
public void actionPerformed(ActionEvent e) {
repaint();
tank.move();
}
}
Seems to me like this should be pretty straightforward, right now I'm using this print statement to see if the class is actually recognizing key strokes at all:
public class TAdapter extends KeyAdapter{
public void keyPressed(KeyEvent e){
tank.keyPressed(e);
System.out.println("pressedddddddddddddddddd");
}
However, there is no output. So I suspect it is not recognizing any keystrokes at all. But I can't figure out why. If anybody has any suggestions I would appreciate it. Obviously I have more code I can share if anybody thinks it would be useful in figuring out this bug.
1)Use KeyBindings KeyListener has 2 big issues,first you listen to all keys and second you have to have focus and be focusable. Instead KeyBinding you bind for a key and you don't have to be in focus.
Simple Example:
AbstractAction escapeAction = new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
//code here example
((JComponent)e.getSource()).setVisible(Boolean.FALSE);
}};
String key = "ESCAPE";
KeyStroke keyStroke = KeyStroke.getKeyStroke(key);
component.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(keyStroke, key);
component.getActionMap().put(key, escapeAction);
You can use these JComponent constants
WHEN_ANCESTOR_OF_FOCUSED_COMPONENT
WHEN_FOCUSED
WHEN_IN_FOCUSED_WINDOW
2) Don't use concrete inheritance if it isn't necessary at all.
3) Don't implement ActionListener in top classes, see Single Responsability Principle
Example
Change this:
public class Board extends JPanel implements ActionListener{
to:
public class Board{
private JPanel panel;
private class MyActionListener implements ActionListener{
//code here
}
}
4) Don't use inheritance if it's just the same for example in your KeyAdapter , you don't add nothing to it, just use KeyAdapter (Now you are gonna to use keybinding so this is useless but to know :) ).
5) Add #Override annotation when you do overriding , also you should override paintComponent(..) instead of paint(..) in swing.
KeyListener suffers from focus issues. The component needs to be both focusable and have focus in order for the listener to be notified of key events.
A better solution would be to use Key Bindings which don't suffer from these constraints.
I never get "paint" written to my command line window when I use Eclipse and Run->cmd to run the program. It works fine if I run System.out.print() from paintComponent in another program. Someone who can help?
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class GUI extends JPanel implements KeyListener, ActionListener
{
private static final long serialVersionUID = 1L;
JFrame frmMain = new JFrame("Kodning");
JTextField text = new JTextField();
JPanel pan = new JPanel();
static char bokstav;
static int x=10, y=80;
boolean convert = false;
String s;
Timer t = new Timer(10, this);
public static void main(String[] args)
{
#SuppressWarnings("unused")
GUI g = new GUI();
}
public GUI()
{
frmMain.setSize(600, 120);
frmMain.setLayout(new GridLayout(2, 1));
frmMain.addWindowListener(hornStang());
frmMain.add(text);
frmMain.add(pan);
frmMain.setFocusable(true);
frmMain.setVisible(true);
frmMain.addKeyListener(this);
text.addKeyListener(this);
pan.addKeyListener(this);
t.start();
}
private static WindowAdapter hornStang()
{
return new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
System.exit(0);
}
};
}
public void keyPressed(KeyEvent e)
{
if(e.getKeyCode()== KeyEvent.VK_ENTER)
{
System.out.println("dechifrera");
repaint();
deshiffrera(text.getText());
}
}
public void keyReleased(KeyEvent arg0){}
public void keyTyped(KeyEvent arg0){}
public void deshiffrera(String s)
{
s = this.s;
repaint();
}
#override
public void paintComponent(Graphics g)
{
System.out.println("paint");
for(int i=0;i<s.length();i++)
{
bokstav = s.charAt(i);
switch (bokstav)
{
case 'a':nere(g); hoger(g); prick(g, 0); break;
//en massa case
default:break;
}
x=x+12;
}
}
#Override
public void actionPerformed(ActionEvent e)
{
repaint();
}
}
The component must be added to a visible window/frame/component for it's paintComponent to be called.
GUI is only added as a KeyListener but is neither added to the JFrame, nor any other visible component in the code above. There is no reason for calling paintComponent since the component is not being displayed at all.
There are a number of issues with your code:
Your GUI panel is not in the frame (shouldn't it be added instead of pan?)
String s is uninitialized, which causes a NullPointerException
paint should be overridden instead of paintComponents
paint should not change the state of the component, because it can be called any time.
etc...
You probably miss the output of "System.out.println("paint");" ?
GUI-Apps under Windows cant write to the console (they dont have a console, because it would suck if every GUI-App would also open a black window).
There are two java-interpreters under windows: "javaw.exe" which is a GUI-App and silently discards any System.out-writes. And "java.exe" which is a console-app and allows writing to the console. Try to start your program with "java.exe"
I use this with AWT (not 100% sure whether it's working in Swing too...)
Graphics g = _yourcomponent_.getGraphics();
if (g != null) {
_yourcomponent_.paint(g);
// below the estimated code for Swing:
_yourcomponent_.paintComponent(g);
}
I've a class which extends JPanel. I overwrote protected void paintComponent(Graphics g).
There is a variable which has to be recalculated when the panel's dimensions change. How do I do that in a proper way?
Like Adam Paynter suggested, you can also add an inner class to your code, like this:
class ResizeListener extends ComponentAdapter {
public void componentResized(ComponentEvent e) {
// Recalculate the variable you mentioned
}
}
The code you have entered between the innermost brackets will be executed everytime the component get resized.
Then you add this listener to your component with
myJPanel.addComponentListener(new ResizeListener());
You can get your component by using e.getComponent(). This way you can call any method of your component from inside the inner class like
e.getComponent().getWeight();
I suppose you could override the various setSize and resize methods and perform the calculation there. However, you may not find all the places where the size can be changed. You may want to have your class implement ComponentListener and simply listen to itself for resize events.
Warning: I am not a Swing expert.
Warning: I have not compiled this code.
public class MyJPanel extends JPanel implements ComponentListener {
public MyJPanel() {
this.addComponentListener(this);
}
public void paintComponent(Graphics g) {
// Paint, paint, paint...
}
public void componentResized(ComponentEvent e) {
// Perform calculation here
}
public void componentHidden(ComponentEvent e) {}
public void componentMoved(ComponentEvent e) {}
public void componentShown(ComponentEvent e) {}
}
If I understand the question correctly then you should read the section from the Swing tutorial on How to Write a Component Listener which shows you how to listen for a change in a components size.
If the calculation isn't time consuming, I would just re-calculate the value each time in paintComponent().
Otherwise, you can save a value that is the size of the component and check it against the new size in paintComponent. If the size changed, then recalculate, otherwise don't.
private Dimension size;
protected void paintComponent(Graphics g){
if (!size.equals(getSize())){
size = getSize();
// recalculate value
}
}
Or, you can do the calculation on a resize event.
//in the constructor add the line
addComponentListener(resizeListener);
private ComponentListener resizeListener = new ComponentAdapter(){
public void componentResized(ActionEvent e){
// recalculate value
}
};
The simplest way is to implement a ComponentListener:
myjpanel.addComponentListener(new ComponentAdapter() {
#Override
public void componentResized(ComponentEvent e) {
//recalculate variable
}
});
Here, I have used a ComponentAdapter because I only intend on overriding componentResized().
Here's what I use (where CoordinatePlane is a JPanel):
I'm not an expert
public CoordinatePlane() {
setBackground(Color.WHITE);
this.addComponentListener(new ComponentAdapter(){
public void componentResized(ComponentEvent e) {
//YOUR CODE HERE
}
});
}
It resizes automatically if it's
inside a BorderLayout panel and
put there as BorderLayout.CENTER component.
If it doesn't work, you probably have forgotten one of these two.
This simple example is drawing a red circle in the resized frame....
import java.awt.*;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import javax.swing.*;
import java.awt.geom.*;
public class RedCircle extends JFrame implements ComponentListener {
int getWidth;
int getHeight;
public RedCircle() {
super("Red Circle");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addComponentListener(this);
pack();
setVisible(true);
}
public void componentResized(ComponentEvent e) {
getWidth = e.getComponent().getWidth();
getHeight = e.getComponent().getHeight();
Panel pane = new Panel(getWidth,getHeight);
add(pane);
}
public static void main(String[] args) {
RedCircle rc = new RedCircle();
}
public void componentMoved(ComponentEvent e) {
}
public void componentShown(ComponentEvent e) {
}
public void componentHidden(ComponentEvent e) {
}
}
class Panel extends JPanel {
int panelWidth;
int panelHeight;
public Panel(Integer getWidth,Integer getHeight) {
panelWidth = getWidth;
panelHeight = getHeight;
}
public void paintComponent(Graphics comp) {
super.paintComponent(comp);
Graphics2D comp2D = (Graphics2D) comp;
int realWidth = panelWidth - 17;
int realHeight = panelHeight - 40;
float Height = (realHeight);
float Width = (realWidth);
// draw the Red Circle
comp2D.setColor(Color.red);
Ellipse2D.Float redCircle = new Ellipse2D.Float(0F, 0F, Width, Height);
comp2D.fill(redCircle);
}
}