问题
I am trying to paint JFrame when music is played , these shapes are created on random no calculation and when a there is some music played there pops up a JFrame and these shapes are painted there, problem is that when i run this code there is no musical sound and shapes drawn but just a frame pops up and nothing else , Plase check this code and help me to correct it ..
public class MusicBeatsDrawing {
static JFrame frame;
DrawPanel dp =new DrawPanel();
public static void main(String[] args)
{
MusicBeatsDrawing mbd= new MusicBeatsDrawing();
mbd.go();
}
public void SetGui(){
frame= new JFrame("Simple frame ; ");
frame.setBounds(100, 100, 200, 200);
frame.setContentPane(dp);
frame.setVisible(true);
}
public void go()
{
SetGui();
try
{
Sequencer sequencer = MidiSystem.getSequencer();
sequencer.open();
Sequence seq= new Sequence(Sequence.PPQ, 4);
sequencer.addControllerEventListener(dp,new int [] {127});
Track track = seq.createTrack();
int r = 0;
for (int i = 0; i < 60 ; i+= 4) {
r = (int) Math.random()*50;
track.add(MakeEvent(144,1,r,100,i));
track.add(MakeEvent(176,1,127,0,i));
track.add(MakeEvent(128,1,r,100,i ));
}
sequencer.setSequence(seq);
sequencer.start();
}
catch(Exception e)
{e.printStackTrace(); }
}
public MidiEvent MakeEvent(int one , int two , int three , int four , int tick)
{
MidiEvent event= null;
try
{
ShortMessage sm= new ShortMessage();
sm.setMessage(one,two, three, four);
event= new MidiEvent(sm , tick );
} catch (InvalidMidiDataException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return event;
}
class DrawPanel extends JPanel implements ControllerEventListener
{
boolean msg= false ;
public void paintComponent(Graphics g)
{
if(msg){ Graphics2D g2d= (Graphics2D) g;
int red= (int) (Math.random()*255);
int green= (int) (Math.random()*255) ;
int blue= (int) (Math.random()*255);
g.setColor(new Color(red, green , blue));
int height= (int)Math.random()*255;
int width= (int)Math.random()*255;
int x= (int)Math.random()*255;
int y= (int)Math.random()*255;
g.fillRect(height, width, x, y);
msg = false;
}
}
@Override
public void controlChange(ShortMessage event) {
msg= true;
repaint();
}}
}
回答1:
Swing GUI objects should be constructed and manipulated only on the event dispatch thread. With this change, your program works. A telltale symptom is that the program runs when you resize the frame, which causes the system to invoke repaint() repeatedly.
Addendum: Some additional issues merit attention,
Make
setVisible()last.The sequencer startup latency may be worth moving to the background.
Use named constants, e.g.
ShortMessage.NOTE_ON, rather than magic numbers.Instantiate
Randomfor later use.Follow Java naming conventions.
Revised SSCCE:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.util.Random;
import javax.sound.midi.ControllerEventListener;
import javax.sound.midi.InvalidMidiDataException;
import javax.sound.midi.MidiEvent;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.MidiUnavailableException;
import javax.sound.midi.Sequence;
import javax.sound.midi.Sequencer;
import javax.sound.midi.ShortMessage;
import javax.sound.midi.Track;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
/**
* @see http://stackoverflow.com/a/17767350/230513
*/
public class MidiDrawing {
private static final Random R = new Random();
public static void main(String[] args) {
EventQueue.invokeLater(new MidiDrawing()::display);
}
public void display() {
JFrame frame = new JFrame("Midi Drawing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
DrawPanel dp = new DrawPanel();
frame.add(dp);
Sequencer sequencer = initSequencer(dp);
JPanel p = new JPanel(new FlowLayout(FlowLayout.RIGHT));
p.add(new JButton(new AbstractAction("Start") {
@Override
public void actionPerformed(ActionEvent e) {
sequencer.setTickPosition(0);
sequencer.start();
}
}));
frame.add(p, BorderLayout.SOUTH);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
private Sequencer initSequencer(DrawPanel dp) {
try {
Sequencer sequencer = MidiSystem.getSequencer();
Sequence seq = new Sequence(Sequence.PPQ, 3);
Track track = seq.createTrack();
int n = 60; // middle C
for (int i = 0; i < 3 * 12; i += 3) {
track.add(new MidiEvent(new ShortMessage(ShortMessage.CONTROL_CHANGE, 0, 0, n), i));
track.add(new MidiEvent(new ShortMessage(ShortMessage.NOTE_ON, 0, n, 127), i));
track.add(new MidiEvent(new ShortMessage(ShortMessage.NOTE_ON, 0, n + 3, 127), i));
track.add(new MidiEvent(new ShortMessage(ShortMessage.NOTE_OFF, 0, n, 127), i + 3));
track.add(new MidiEvent(new ShortMessage(ShortMessage.NOTE_OFF, 0, n + 3, 127), i + 3));
n++;
}
sequencer.open();
sequencer.setSequence(seq);
sequencer.addControllerEventListener(dp, new int[]{0});
return sequencer;
} catch (InvalidMidiDataException | MidiUnavailableException e) {
e.printStackTrace(System.err);
}
return null;
}
private static class DrawPanel extends JPanel implements ControllerEventListener {
private final Font font = this.getFont().deriveFont(24f);
private int data;
@Override
public void paintComponent(Graphics g) {
g.setColor(Color.getHSBColor(R.nextFloat(), 1, 1));
g.fillRect(0, 0, getWidth(), getHeight());
g.setFont(font);
g.setColor(Color.black);
g.drawString(String.valueOf(data), 8, g.getFontMetrics().getHeight());
}
@Override
public void controlChange(ShortMessage event) {
data = event.getData2();
repaint();
}
@Override
public Dimension getPreferredSize() {
return new Dimension(256, 128);
}
}
}
来源：https://stackoverflow.com/questions/17765604/java-painting-random-shapes-on-jframe-against-music-played