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grasshopper · Guest

Hi,
I am trying to write a method that toggles the display of a Swing
component(e.g. a JButton) inside a container (e.g. a JPanel).
The method below essentially does a depth-first search until it
reaches a
container with no child components (since e.g. a JButton is actually a
java.awt.Container this was the only way I could think of to
differentiate it
from e.g. a JPanel) and is supposed to remove the child component from
the parent container and place it in a holder vector, or if it is not
found in
the container, remove it from the holder and place it in the
container.

If the component is present in the container, the method presently
succeeds in placing it in the holder and then removing it from the
container.
The problem occurs when the component is not present in the container
and it
is added to the container from the holder. The next step, removing the
component from the holder, is executed twice despite the presence of a
return
statement which I assumed would terminate the method. I can't figure
out what
is causing the problem. I've included a log of the console output,
hopefully
someone may be able to shed some light on this, I'm stumped.

Thanks,

Brian

public void toggleComponent(String id, Container c) {
System.out.println("toggleComponent("+id+","+c+")");
Component[] children = c.getComponents();
Component cur; // current component

for (int i = 0; i < children.length; i++) {
System.out.println("inside for, i="+i);
cur = children[i];

if ((cur instanceof Container) &&
( ((Container) cur).getComponentCount() > 0 ) ) {

// current component is a non-empty container
toggleComponent(id, (Container)cur);
} else {

// current component is either
// a) an empty container, or
// b) not a container
// in any case, we want to compare it to the specified
// component specified by the 'id' argument
if (pruneXY(cur.toString()).compareTo(id) == 0) {
// the current component matches the supplied argument
// so add current componentto holder & remove from container
found = true;
Container parent = cur.getParent();
//System.out.println("Add to holdernid =t"+cur.toString());
componentHolder.add(cur);
parent.remove(cur);
// redraw
//parent.repaint();
//parent.validate();

// exit method
//System.out.println("about to return from method");
//System.out.println(found);
return;
}
}
}
System.out.println(found);
if (!found) {
// after iterating thru all child components of container c,
// target component not found. Therefore remove from holder
// and add to container c.
System.out.println("Remove from holdernid =t"+id);
c.add(componentHolder.get(id));
//c.repaint();
//c.validate();
System.out.println("about to return from method");
return;
}
System.out.println("after return statement");
}

-------
Output:

toggleComponent(javax.swing.JLabel[,50x16,alignmentX=0.0,alignmentY=null,border=,flags=0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizontalAlignment=LEADING,horizontalTextPosition=TRAILING,iconTextGap=4,labelFor=,text=My
Label,verticalAlignment=CENTER,verticalTextPosition=CENTER],javax.swing.JPanel[,86,40,606x426,alignmentX=null,alignmentY=null,border=,flags=9,maximumSize=,minimumSize=,preferredSize=])
inside for, i=0
toggleComponent(javax.swing.JLabel[,50x16,alignmentX=0.0,alignmentY=null,border=,flags=0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizontalAlignment=LEADING,horizontalTextPosition=TRAILING,iconTextGap=4,labelFor=,text=My
Label,verticalAlignment=CENTER,verticalTextPosition=CENTER],SimplePanel[,0,0,300x200,layout=java.awt.FlowLayout,alignmentX=null,alignmentY=null,border=,flags=9,maximumSize=,minimumSize=,preferredSize=])
inside for, i=0
true
after return statement
toggleComponent(javax.swing.JLabel[,50x16,alignmentX=0.0,alignmentY=null,border=,flags=0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizontalAlignment=LEADING,horizontalTextPosition=TRAILING,iconTextGap=4,labelFor=,text=My
Label,verticalAlignment=CENTER,verticalTextPosition=CENTER],javax.swing.JPanel[,86,40,606x426,invalid,alignmentX=null,alignmentY=null,border=,flags=9,maximumSize=,minimumSize=,preferredSize=])
inside for, i=0
toggleComponent(javax.swing.JLabel[,50x16,alignmentX=0.0,alignmentY=null,border=,flags=0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizontalAlignment=LEADING,horizontalTextPosition=TRAILING,iconTextGap=4,labelFor=,text=My
Label,verticalAlignment=CENTER,verticalTextPosition=CENTER],SimplePanel[,0,0,300x200,invalid,layout=java.awt.FlowLayout,alignmentX=null,alignmentY=null,border=,flags=9,maximumSize=,minimumSize=,preferredSize=])
inside for, i=0
inside for, i=1
false
Remove from holder
id = javax.swing.JLabel[,50x16,alignmentX=0.0,alignmentY=null,border=,flags=0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizontalAlignment=LEADING,horizontalTextPosition=TRAILING,iconTextGap=4,labelFor=,text=My
Label,verticalAlignment=CENTER,verticalTextPosition=CENTER]
about to return from method
false
Remove from holder
id = javax.swing.JLabel[,50x16,alignmentX=0.0,alignmentY=null,border=,flags=0,maximumSize=,minimumSize=,preferredSize=,defaultIcon=,disabledIcon=,horizontalAlignment=LEADING,horizontalTextPosition=TRAILING,iconTextGap=4,labelFor=,text=My
Label,verticalAlignment=CENTER,verticalTextPosition=CENTER]
java.lang.NullPointerException

Andrew Hobbs · Guest

"grasshopper" <googleN0SPAM (AT) eyeonik (DOT) com> wrote