JScrollPane Doesn;t appear in JScrollPane?

Question

hi Following is the code of JPanel that contains JScrollPane.
And JScrollPane adds again CompareView Panel
CompareViewPanel is using custom defined Layout CompareViewLayout .
But this as a output this panel is not showing the proper JScrollPane when outer frame size is lesser then the current panel(which contains JScrollPane).
public class GalleryViewRightPanel extends JPanel {
* Layout Manager
private List <CapturedScreenControl> students;
* Scroll Container.
private final JScrollPane compareScrollPane;
private final CompareView screenCtlContainerPanel;
public GalleryViewRightPanel(List <CapturedScreenControl> students)
//TODO - Add in super() Your Own Made Layout that will take care
// of all the selected elements.
//super();
final int unitIncr = 96;
final int blockIncr = 192;
this.students = students;
this.screenCtlContainerPanel = new CompareView(new CompareViewLayout());
this.screenCtlContainerPanel.addComponentArray(this.students);
compareScrollPane = new JScrollPane(screenCtlContainerPanel,
JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED,
JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
compareScrollPane.getVerticalScrollBar().setUnitIncrement(unitIncr);
compareScrollPane.getVerticalScrollBar().setBlockIncrement(blockIncr);
compareScrollPane.getHorizontalScrollBar().setUnitIncrement(unitIncr);
compareScrollPane.getHorizontalScrollBar().setBlockIncrement(blockIncr);
//setSize(compareScrollPane.getPreferredSize());
add(compareScrollPane,BorderLayout.CENTER);
setBorder(BorderFactory.createLineBorder(new Color(0,0,255,2)));
public List<CapturedScreenControl> getStudentList()
return students;
public void setStudentList(final List<CapturedScreenControl> screenControl)
students = screenControl;
screenCtlContainerPanel.addComponentArray(students);
//setSize(compareScrollPane.getPreferredSize());
public void SetInfo()
class CompareView extends JPanel
public CompareView(LayoutManager layout)
super(layout);
public void addComponentArray(List <CapturedScreenControl> screens)
removeComponentList();
//Add Here All Components.
for(CapturedScreenControl s: screens)
//add(s);
Rectangle rect = s.getBounds();
add(new CompareImage(null,null,false,false,rect));
updateUI();
public void singleComponentArray(CapturedScreenControl screen)
//removeComponentList();
//Add here this screen component.
//if(screen != null)
// add(screen);
public void removeComponentList()
removeAll();
class CompareViewLayout implements LayoutManager
private int leftGap,topGap,middleGap,rightGap,bottomGap;
* @param left : Left Gap before arranging Components.
* @param top : Top Gap before arranging Components.
* @param middle : Middle Gap between Components.
* @param right : Right Gap before arranging Components.
* @param bottom : Bottom Gap before arranging Components.
public void setGaps(int left,int top,int middle, int right,int bottom)
this.leftGap = left;
this.topGap = top;
this.middleGap = middle;
this.rightGap = right;
this.bottomGap = bottom;
@Override
public void addLayoutComponent(String name, Component comp)
// TODO Auto-generated method stub
// No need.
@Override
public void layoutContainer(Container parent)
Dimension max = calculateSize(parent);
Dimension size = parent.getSize();
int compCount = parent.getComponentCount();
if ((max.width == 0) || (max.height == 0)) {
return;
int rowCount = compCount/ScreenCaptureConstant.GALLERY_TWO_COMPONENT_SCREEN;
int colCount = 1;
if(rowCount == 0)
rowCount = 1;
if(compCount > ScreenCaptureConstant.GALLERY_MIN_COMPONENT_SCREEN)
colCount = ScreenCaptureConstant.GALLERY_TWO_COMPONENT_SCREEN;
int x = leftGap;
int y = topGap;
int row = 0;
int col = 0;
for(int count=0;count<compCount;count++)
//Here Set XY-position and Size for all the controls.
Component c = parent.getComponent(count);
c.setLocation(x, y);
c.setSize(max);
col++;
if(col >= colCount)
col = 0;
row++;
//Set here other Controls.
x = (col * (max.width + leftGap)) + middleGap;
y = (row * (max.height + topGap)) + middleGap;
@Override
public Dimension minimumLayoutSize(Container parent)
Dimension componentDim = new Dimension(0,0);
int componentCount = parent.getComponentCount();
//Only one component.
if(componentCount == ScreenCaptureConstant.GALLERY_MIN_COMPONENT_SCREEN)
//Considering that device types are of NSpire Device.
componentDim.height = ScreenCaptureConstant.SINGLE_NSPIRE_COMONENT_HEIGHT + topGap + bottomGap;
componentDim.width = ScreenCaptureConstant.SINGLE_NSPIRE_COMPONENT_WIDTH + leftGap + rightGap;
//Two Components.
else if(componentCount == ScreenCaptureConstant.GALLERY_TWO_COMPONENT_SCREEN)
componentDim.height = ScreenCaptureConstant.MULTIPLE_NSPIRE_COMONENT_HEIGHT + topGap + bottomGap;
componentDim.width = (2*ScreenCaptureConstant.MULTIPLE_NSPIRE_COMPONENT_WIDTH) + leftGap + rightGap + middleGap;
//More than Two Components.
else if(componentCount > ScreenCaptureConstant.GALLERY_TWO_COMPONENT_SCREEN &&
componentCount <= ScreenCaptureConstant.GALLERY_MAX_COMPONENT_SCREEN )
componentDim.height = (2*ScreenCaptureConstant.MULTIPLE_NSPIRE_COMONENT_HEIGHT) + topGap + bottomGap + middleGap;
componentDim.width = (2*ScreenCaptureConstant.MULTIPLE_NSPIRE_COMPONENT_WIDTH) + leftGap + rightGap + middleGap;
return componentDim;
@Override
public Dimension preferredLayoutSize(Container parent)
Dimension singleScreenSize = calculateSize(parent);
int cnt = parent.getComponentCount();
if(cnt <= 0)
return new Dimension();
int cols = 1;
if(cnt > ScreenCaptureConstant.GALLERY_MIN_COMPONENT_SCREEN)
cols = ScreenCaptureConstant.GALLERY_MAX_COMPONENT_SCREEN;
int rows = cnt / cols;
if (cnt == 0)
return new Dimension();
else
Dimension ret = new Dimension(singleScreenSize);
ret.width = cols*(ret.width) + leftGap + rightGap + (cols-1)*middleGap;
ret.height = rows*(ret.height) + topGap + bottomGap + (rows-1)*middleGap;
return ret;
@Override
public void removeLayoutComponent(Component comp)
// TODO Auto-generated method stub
* @return
private Dimension getBestFitSize(Dimension crntSize,Dimension maxsize,int nDeviceType)
//Calculate here best fit.
//This will say the best size of the component.
int minWidth = crntSize.width;
int minHeight = crntSize.height;
while(minWidth+4<=maxsize.width && minHeight+3<=maxsize.height)
minWidth = minWidth + 4;
minHeight = minHeight + 3;
return new Dimension(minWidth,minHeight);
* @param parent : Calculate Each Component Size.
* @return
private Dimension calculateSize(Container parent)
int componentCount = parent.getComponentCount();
Dimension parSize = parent.getSize();
Dimension comSize = new Dimension();
if(componentCount == ScreenCaptureConstant.GALLERY_MIN_COMPONENT_SCREEN)
//Logic to get the zoom
//Only For NSpire Device.
comSize.height = ScreenCaptureConstant.SINGLE_NSPIRE_COMONENT_HEIGHT;
comSize.width = ScreenCaptureConstant.SINGLE_NSPIRE_COMPONENT_WIDTH;
parSize.width -= (leftGap + rightGap);
if((parSize.width > comSize.width) &&
(parSize.height > comSize.height))
//Here We Get the size for the One Image.
return getBestFitSize(comSize,parSize,0);
else if(componentCount > ScreenCaptureConstant.GALLERY_MIN_COMPONENT_SCREEN)
//Only Considering for NSpire Devices.
comSize.height = ScreenCaptureConstant.MULTIPLE_NSPIRE_COMONENT_HEIGHT + middleGap;
comSize.width = ScreenCaptureConstant.MULTIPLE_NSPIRE_COMPONENT_WIDTH + middleGap;
//Logic to get the zoom for multiple screens.
parSize.width -= (leftGap + rightGap + middleGap);
parSize.width = parSize.width/2 ;
//Calculate Here the Size of Each Component.
return new Dimension(parSize.width,getHeightFromWidth(parSize.width,0));
return comSize;
private int getHeightFromWidth(int nWidth,int nDeviceType)
int nHeight = (nWidth*3)/4;
return nHeight;
class CompareImage extends Component {
private static final Logger log = Logger.getLogger("gui.capturedScreen.CompareImageComponent");
private Image lastGoodScreenImage;
private Image screenImage;
private boolean loaded;
private boolean hasErrored;
private Rectangle rect;
* @param lastGoodImage
* @param screenImage
* @param loaded
* @param error
* @param rect
public CompareImage(Image lastGoodImage,Image screenImage,boolean loaded, boolean error,Rectangle rect)
super();
this.lastGoodScreenImage = lastGoodImage;
this.screenImage = screenImage;
this.loaded = loaded;
this.hasErrored = error;
this.rect = rect;
public synchronized void paint(Graphics g)
String msg = "Image is Coming soon..." + rect.x + "," + rect.y + "," + rect.width + "," + rect.height;
g.drawString(msg, 20, 20);
Please help me to identify why this is not working??
Thank you.
Ajit.

Answer 1

Hi,
I Had created "class CompareViewLayout implements LayoutManager".
Now you can see its implementation in code. This CompareViewLayout is used in CompareView Panel.
And In compareScrollPane (JScrollPane) takes CompareView Panel as an argument in constructor.
And compareScrollPane is added in Container(Top Level Panel) class.
Now here,
Whenever preferredLayoutSize() function of the LayoutManager is called, that will set the Components.
But this functions is several time not called on resize of the frame..... normally this function called on each resize operation.
In short Anyone Having idea what are the cases when preferredLayoutSize() function of the LayoutManager is not called ??
And what to take care to avoid it??