Message doesnt display continuously

[miguel lisboa]

i'm using the code bellow (written a couple of years ago) to display a message to a jLabel, for a few seconds
yet, the message does display but with "hicups", not permanently: for example - shows for 4 seconds, then disappears for a fraction of second, then resumes displaying...
i tried several combinations for sleep value and for var i, but the present combination looks like the best so far
is there something wrong with the code?

the code:

 
	public void mostraMensagem(final JLabel label, final String mensagem) {
		Runnable mostraMensagem = new Runnable() {
			public void run() {
				Thread thread = new Thread() {
					public void run() {
						int i = 15;
						while( i > 0) {
							label.setText(mensagem);
							try {
								sleep(100);
								i--;
								label.setText("");// funciona como stop
							}
							catch(InterruptedException e) {
								throw new RuntimeException(e);
							}
						}
					}};
					thread.start(); 
			}};
			SwingUtilities.invokeLater(mostraMensagem);
	}   

[Henry Wong]

Swing isn't thread safe. You are not allowed to change swing components in any thread but the event dispatching thread.

Henry

[Rok Štelcer]

Hi,

Any method call that affects the visualization in any way, should(must) be executed from the EDT.
In your case it's not.
The thing is, that you've just created a new worker/background thread on the EDT.
The same result would be achieved, if you'd comment the following lines: 3,4,21 & 22.

The "visual" call in your example is setText(...).
Put it on the EDT like:

SwingUtilities.invokeAndWait( //in case this code is called from synchronized block, use invokeLater
  new Runnable()
  {
      public void run()
      {
          label.setText("foo"); // mensagem vs. ""
      }
  });

Regards,
Rok

[miguel lisboa]

this isnt the first time it happens: i rely on email notification and when i notice, several hours elapsed since first answer
anyway thank you both for your answers
using the (new) code bellow i dont perceive any irregularity in display
please fell free to comment what i wrote:

	public void mostraMensagem(final JLabel label, final String mensagem) {
		Runnable mostraMensagem = new Runnable() {
			public void run() {
				Thread thread = new Thread() {
					public void run() {
						int i = 15;
						while( i > 0) {
							label.setText(mensagem);
							try {
								sleep(100);
								i--;
								SwingUtilities.invokeAndWait(  
										new Runnable() {   
											public void run() {   
												label.setText("");
											}   
										});
							} 
							catch (InterruptedException e1) {
								e1.printStackTrace();
							} 
							catch (InvocationTargetException e1) {
								e1.printStackTrace();
							}
						}
					}};
					thread.start(); 
			}};
			SwingUtilities.invokeLater(mostraMensagem);
	}
}    

[Paul Clapham]

That sort of thing is exactly what javax.swing.Timer is meant for. Try that instead.

[miguel lisboa]

thank you for the idea!
i came up to the following code, but for somw reason, when i hover out of rhe button that triggers the method, the message vanishes... i kmow i have some code for hovering, but with the other method that didnt happen

please comment in case you find something wrong

 
		final  ActionListener listener2 = new ActionListener() {
		      public void actionPerformed(ActionEvent evt) {
		    	  label.setText("");
		      }
		  };
		  ActionListener listener1 = new ActionListener() {
		      public void actionPerformed(ActionEvent e) {
		    	  label.setText(mensagem);
		    	  Timer timer2 = new Timer(5000, listener2);
		  		timer2.setRepeats(false);
				timer2.start();
		      }
		  };

		Timer	timer = new Timer(0, listener1);
		timer.setRepeats(false);
		timer.start();
	}   

[Rob Spoor]

Moving to our GUI forum.

[Rok Štelcer]

Post deleted. ;)

[Mikko Kohtamäki]

Are you trying to flash the text or what?

  Timer timer = null;
  ActionListener listener = new ActionListener() {
  int i = 0;
  boolean flash = true;
  public void actionPerformed(ActionEvent evt) {
    if(flash) {
      label.setText(mensagem);
      flash = false;
    }else {
      label.setText("");
      flash = true;
    }
    if(++i == 15) {
      timer.stop;
    }
  }
};
timer = new Timer(500, listener);
timer.setRepeats(true);
timer.start();

OR

public void mostraMensagem(final JLabel label, final String mensagem) {
  Runnable mostraMensagem = new Runnable() {
    public void run() {
      int i = 15;
      while( i > 0) {
        SwingUtilities.invokeAndWait(new Runnable() {     
          public void run() {     
            label.setText(mensagem);
          }     
        });
        try {
          sleep(100);
        }catch (InterruptedException e1) {
          e1.printStackTrace();
        }catch (InvocationTargetException e1) {
          e1.printStackTrace();
        }
        SwingUtilities.invokeAndWait(new Runnable() {     
          public void run() {     
            label.setText("");  
          }     
        });
    }
  };
  (new Thread(mostraMensagem)).start();
}

[miguel lisboa]

Mikko: i'm trying not to flash
anyway, among others, i get an error message using your code in line 12, saying:

the method sleep(int) is undefined for the type new Runnable(){}

[Rob Spoor]

It's a static method in Thread.

[miguel lisboa]

i'm feeling a bit embarrassed because i cant write it in order to compile:

			  Runnable mostraMensagem = new Runnable() {
			    public void run() {
			      int i = 15;
			      while( i > 0) {
			        SwingUtilities.invokeAndWait(new Runnable() {     
			          public void run() {     
			            label.setText(mensagem);
			          }     
			        });
			        try {
Thread.sleep(100);
			        }
			        catch (InterruptedException e1) {
			          e1.printStackTrace();
			        }
			        catch (InvocationTargetException e1) {
			          e1.printStackTrace();
			        }
			        SwingUtilities.invokeAndWait(new Runnable() {     
			          public void run() {     
			            label.setText("");  
			          }     
			        });
			    }
			  };// line 92
			  (new Thread(mostraMensagem)).start();
			}    

Exception in thread "AWT-EventQueue-0" java.lang.Error: Unresolved compilation problems:
Syntax error on token ";", { expected after this token
Syntax error, insert "}" to complete ClassBody
Syntax error, insert ";" to complete BlockStatements

at util.Util.mostraMensagem(Util.java:92)

[Rob Spoor]

You're missing a }.

[miguel lisboa]

Rob Prime wrote:You're missing a }.

yes, that's what the compiler says
but i just cant figure out where, because if i added it here, gives an error there, and viceversa, and so on - believe me i tried a lot indeed, wtill with no results

[Rob Spoor]

Line 25 here ends the while loop, and line 26 ends the anonymous inner class. You don't close the run method.

[miguel lisboa]

the code below does compile and run, at last
thanks to everyone!

		Runnable mostraMensagem = new Runnable() {
			public void run() {
				int i = 15;
				while( i > 0) {
					try {
						SwingUtilities.invokeAndWait(new Runnable() {     
							public void run() {     
								label.setText(mensagem);
							}     
						});
					} 
					catch (InterruptedException e) {
						e.printStackTrace();
					} 
					catch (InvocationTargetException e) {
						e.printStackTrace();
					}
					try {
						Thread.sleep(300);
						i--;
					}
					catch (InterruptedException e1) {
						e1.printStackTrace();
					}

					try {
						SwingUtilities.invokeAndWait(new Runnable() {     
							public void run() {     
								label.setText("");  
							}     
						});
					} catch (InterruptedException e) {
						e.printStackTrace();
					} catch (InvocationTargetException e) {
						e.printStackTrace();
					}
				}    
			}  
		};
		(new Thread(mostraMensagem)).start();