Scrolling to a component
I have a JPanel that contained withn a JScrollPane (called flowchartPane). The JPane contains other JPanels that are arranged with a grid layout.
These JPanels contain graphics and when put together in various combinations make a flowchart.
The actual size of the JPane is larger than the viewport of the JScrollPane. So there are times when I want to scroll to a perticular component that is out of the bounds of the view port rectangle.
I am aware of the scrollRectToVisible method and have been utilising it in my method. However my method seems to be unreliable.
What the method attempts to do is, if a component (comp) has its left, right, top or bottom edge outside the bounds of the viewport scroll the viewport so the component is in view.
However this method is not reliable and does not allways do what is expected. Can anyone think of anyway I can improve it, see what I am doing wrong or help in the writing of a scroll to component method.
Kind regards
Andrew Scott.
publicvoid scrollToComponent( Component comp)
{
int x = comp.getLocation().x;//get x location of the component
int y = comp.getLocation().y;//get the y location of the component
int h = comp.getHeight();//get the height of the component;
int w = comp.getWidth();//get the width of the component
Rectangle vr = flowchartPane.getViewport().getViewRect();
int newY = vr.x;
int newX = vr.y;
//if outside the bounds of the viewport
if ( ((x+w) > (vr.x + vr.width)) | (x < vr.x) |
((y+h) > (vr.y + vr.height)) | (y < (vr.y)))
{
//Do not attempt to scroll to an posision zero or less on the X axis
if (x-w > 0)
newX = x;// - w ;
else
newX = x;
//Do not attempt to sctoll to a position zero or less on the Y axis
if (y - (h/2) > 0)
newY = y;// - (h/2);
else
newY = y;
flowchartPane.getViewport().scrollRectToVisible(new Rectangle(newX,newY,vr.width,vr.height));
}//end if
}//End Scroll to Component
# 3
Cente of view rect must be center point of your component.
So
int centerX=comp.getBounds().getX()+comp.getBounds().getWidth()/2;
int centerY=comp.getBounds().getY()+comp.getBounds().getHeight()/2;
The rect passed in scrollRectToVisible() size (width and height) must be the same as vr size.
And we should define proper x and y.
rect.x=centerX-vr.getWidth()/2;
rect.x=centerY-vr.getHegiht()/2;
Regards,
Stas
# 4
Stanislav,
Close, but no cigar. I will say that is the best solution yet, but its far from perfect.
It does not want to scroll upwards or to the left. It will only scroll to the right or down.
Why is that?
From your ideas Stanislav I developed this method:
public void scrollToComponent( Component comp)
{
Rectangle vr = flowchartPane.getViewport().getViewRect();
int centerX=comp.getBounds().x + comp.getBounds().width/2;
int centerY=comp.getBounds().y + comp.getBounds().height/2;
int newX=centerX-vr.width/2;
int newY=centerY-vr.height/2;
flowchartPane.getViewport().scrollRectToVisible(new Rectangle(newX,newY,vr.width,vr.height));
}//end scroll to component
Kind Regards.
Andrew.
Message was edited by:
scottie_uk
# 5
Strangely is I substitue scrollRectToVisible(new Rectangle(newX,newY,vr.width,vr.height)); withflowchartPane.getViewport().setViewPosition(new Point(newX,newY)); It works but is very jumpy and not very smooth.
How can I makeflowchartPane.getViewport().setViewPosition(new Point(newX,newY)); as visually smooth as scrollRectToVisible(new Rectangle(newX,newY,vr.width,vr.height));
Andrew.
# 8
> But it's rather jerky and not smooth at all when compared with the other way.
Its not a problem with the method. Its a problem with something in your code.
If you need further help then you need to create a [url http://homepage1.nifty.com/algafield/sscce.html]Short, Self Contained, Compilable and Executable, Example Program[/url] (SSCCE) that demonstrates the incorrect behaviour, because I can't guess exactly what you are doing based on the information provided.
Don't forget to use the [url http://forum.java.sun.com/help.jspa?sec=formatting]Code Formatting Tags[/url] so the posted code retains its original formatting.
