i'm trying create simple panel 2-dimensional ball bouncing , down. can't work because reason can't call repaint method more once second. design there object can given "an impulse" method move(). everytime evaluateposition method called, current position calculated through time has passed, velocity , acceleration. code panel is:
public class display extends jpanel { private movableobject object = new movableobject(new ellipse2d.double(5,5,50,50)); private static final int delay = 1000; public display(){ object.move(50,50); timer timer = new timer(delay, new actionlistener(){ @override public void actionperformed(actionevent e){ object.evaluateposition(); repaint(); } }); timer.start(); } } @override public void paintcomponent(graphics g){ super.paintcomponent(g); graphics2d g2 = (graphics2d)g; g.setrenderinghint(renderinghints.key_antialiasing, renderinghints.value_antialias_on); g.drawoval((int)object.getposition().getx(), (int)object.getposition.gety() (int)object.getshape().getwidth(), object.getshape().getheight()); } this code works delay=1000 not delay=100 or delay=10 , on. read example code here on seem me did. why code not working?
edit (2016-01-30): since seems performance issue, here's code movableobject (i thought irrelevant , see why):
public class movableobject { // use shape instead of ellipse2d // objects of shape can created private ellipse2d.double shape; private point position; // vector own class. want have easy vector addition , // multiplication , magnitude methods private vector velocity = new vector(0, 0); private vector acceleration = new vector(0, 0); private date lastevaluation = new date(); public movableobject(ellipse2d.double objectshape){ shape = objectshape; } public void evaluateposition(){ date currenttime = new date(); long deltatins = (currenttime.gettime()-lastevaluation.gettime())/1000; // s = s_0 + v*t + 0.5*a*t^2 position = new point((int)position.getx()+ (int)(velocity.getx()*deltatins) + (int)(0.5*acceleration.getx()*deltatins*deltatins), (int)position.gety()+ (int)(velocity.gety()*deltatins) + (int)(0.5*acceleration.gety()*deltatins*deltatins)); lastevaluation = currenttime; } } public void move(vector vector){ velocity = velocity.add(vector); evaluateposition(); } public point getposition(){ return position; } public ellipse2d.double getshape(){ return shape; } my move method not change position velocity. please notice changed shape object shape ellipse2d testing if code has performance issue because of additional code. if think more complex needs be: want add complexity movableobject can have shape of subclass of shape. i've seen lot of code seemed more complex me , rendered fast. i'd know what's wrong (besides fact it's bit complex rendering ellipse).
okay, simple example, based on out-of-context code snippet left doesn't seem have problems. has variable speed controlled simple slider...
import java.awt.borderlayout; import java.awt.dimension; import java.awt.eventqueue; import java.awt.fontmetrics; import java.awt.graphics; import java.awt.graphics2d; import java.awt.point; import java.awt.renderinghints; import java.awt.shape; import java.awt.event.actionevent; import java.awt.event.actionlistener; import java.awt.geom.affinetransform; import java.awt.geom.ellipse2d; import java.awt.geom.generalpath; import java.awt.geom.pathiterator; import java.util.random; import javax.swing.jframe; import javax.swing.jpanel; import javax.swing.jslider; import javax.swing.timer; import javax.swing.uimanager; import javax.swing.unsupportedlookandfeelexception; import javax.swing.event.changeevent; import javax.swing.event.changelistener; public class display extends jpanel { public static void main(string[] args) { eventqueue.invokelater(new runnable() { @override public void run() { try { uimanager.setlookandfeel(uimanager.getsystemlookandfeelclassname()); } catch (classnotfoundexception | instantiationexception | illegalaccessexception | unsupportedlookandfeelexception ex) { ex.printstacktrace(); } jframe frame = new jframe("testing"); frame.setdefaultcloseoperation(jframe.exit_on_close); frame.add(new display()); frame.pack(); frame.setlocationrelativeto(null); frame.setvisible(true); } }); } private movableobject object = new movableobject(new ellipse2d.double(5, 5, 50, 50)); private int delay = 40; private timer timer = new timer(40, new actionlistener() { @override public void actionperformed(actionevent e) { object.evaluateposition(getsize()); repaint(); } }); private jslider slider = new jslider(5, 1000); public display() { object.move(50, 50); slider = new jslider(5, 1000); slider.setsnaptoticks(true); slider.setmajortickspacing(10); slider.setminortickspacing(5); setlayout(new borderlayout()); add(slider, borderlayout.south); // designed put artificate delay between // change listener , time update takes place, intention // stop pausing "main" timer... timer delay = new timer(250, new actionlistener() { @override public void actionperformed(actionevent e) { if (timer != null) { timer.stop(); } timer.setdelay(slider.getvalue()); timer.start(); } }); slider.addchangelistener(new changelistener() { @override public void statechanged(changeevent e) { delay.restart(); repaint(); } }); slider.setvalue(40); } @override public dimension getpreferredsize() { return new dimension(200, 200); } @override public void paintcomponent(graphics g) { super.paintcomponent(g); graphics2d g2 = (graphics2d) g.create(); g2.setrenderinghint(renderinghints.key_antialiasing, renderinghints.value_antialias_on); g2.draw(object.gettranslatedshape()); fontmetrics fm = g2.getfontmetrics(); string text = integer.tostring(slider.getvalue()); g2.drawstring(text, 0, fm.getascent()); g2.dispose(); } public class movableobject { private shape shape; private point location; private int xdelta, ydelta; public movableobject(shape shape) { this.shape = shape; location = shape.getbounds().getlocation(); random rnd = new random(); xdelta = rnd.nextint(8); ydelta = rnd.nextint(8); if (rnd.nextboolean()) { xdelta *= -1; } if (rnd.nextboolean()) { ydelta *= -1; } } public void move(int x, int y) { location.setlocation(x, y); } public void evaluateposition(dimension bounds) { int x = location.x + xdelta; int y = location.y + ydelta; if (x < 0) { x = 0; xdelta *= -1; } else if (x + shape.getbounds().width > bounds.width) { x = bounds.width - shape.getbounds().width; xdelta *= -1; } if (y < 0) { y = 0; ydelta *= -1; } else if (y + shape.getbounds().height > bounds.height) { y = bounds.height - shape.getbounds().height; ydelta *= -1; } location.setlocation(x, y); } public shape gettranslatedshape() { pathiterator pi = shape.getpathiterator(affinetransform.gettranslateinstance(location.x, location.y)); generalpath path = new generalpath(); path.append(pi, true); return path; } } } you have at
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