I'm trying to display a JTable as a grid, with lines between the cells. I've only been able to add borders within individual cells, though, which never looks correct; if I add full borders, I get a bunch of disconnected boxes, which looks ugly and wrong. Using MatteBorders (as the below code) looks a little better, but results in gaps where border lines don't quite meet.
public Component prepareRenderer(TableCellRenderer renderer, int row, int column) {
Component stamp = super.prepareRenderer(renderer, row, column);
int top = 1;
int left = 1;
int bottom = row == 7 ? 1 : 0; //Grid is always 8x8, this ensures the bottom/right will have full borders.
int right = column == 7 ? 1 : 0;
MatteBorder border = new MatteBorder(top, left, bottom, right, Color.BLACK);
if (stamp instanceof JComponent) {
((JComponent) stamp).setBorder(border);
}
return stamp;
}
I feel like there must be some way to do this properly, so that I just get grid lines between cell elements. What am I missing? If nothing else, is there a way to get MatteBorder to stretch across the gaps, or to push a normal border out slightly further so that the borders of adjacent cells overlap?
EDIT: Got it working with setShowGrid(true) and setGridColor(Color.BLACK).
Use JTable.setShowGrid(true) to show default border or use setShowHorizontalLines(boolean showHorizontalLines) or setShowVerticalLines(boolean showVerticalLines) to show only horizontal or vertical lines
Related
I need to show multi-line content in a JTable. The actual content is a collection of objects maintained in a custom model, which extends DefaultTableModel and generates cell content on the fly by overriding getValueAt().
In order to have multi-line content, I have implemented a custom TableCellRenderer:
private class MultiLineCellRenderer extends JTextArea implements TableCellRenderer {
public MultiLineCellRenderer() {
setLineWrap(true);
setWrapStyleWord(true);
setOpaque(true);
setBorder(new EmptyBorder(-1, 2, -1, 2));
setRows(1);
}
public Component getTableCellRendererComponent(JTable table, Object value,
boolean isSelected, boolean hasFocus, int row, int column) {
String text = value == null ? "" : value.toString();
if (!getText().equals(text)) {
setText(text);
int newHeight = table.getRowHeight() * getLineCount();
if (table.getRowHeight(row) != newHeight)
table.setRowHeight(row, newHeight);
}
if (isSelected) {
setForeground(table.getSelectionForeground());
setBackground(table.getSelectionBackground());
} else {
setForeground(table.getForeground());
setBackground(table.getBackground());
}
return this;
}
}
Now if I populate the table with a few hundred rows (column count is 2), I see the AWT worker thread starting to max out one CPU core. At the same time, memory consuption goes up from ~100 MB to ten times that amount and further. That happens even if the application is not actually doing anything (no data loaded in the background, no user interaction) and stops only when I clear the collection from which the table gets its content.
By commenting out select sections of code, I have identified these lines as the culprit:
int newHeight = table.getRowHeight() * getLineCount();
if (table.getRowHeight(row) != newHeight)
table.setRowHeight(row, newHeight);
If I comment out this section, all table rows have the same height (1 row of text), but memory consumption stays around ~100 MB.
If I replace these lines with a single call to table.setRowHeight(row, 32), i.e. with a fixed value, memory consumption starts going up again indefinitely.
The following modification works, at the expense of all rows having the same height:
int newHeight = getRowHeight() * getLineCount();
if (table.getRowHeight() < newHeight)
table.setRowHeight(newHeight);
Bottom line: it seems setting individual row heights in a JTable creates a massive memory leak. Am I doing something wrong, or have I encountered an actual bug? In the latter case, are there any known fixes/workarounds?
Setting the row height triggers a redraw, which in turn triggers another call to the renderer. Therefore, it is important to set the row height only if it is different from the current one, in order to avoid an endles loop. This is what happens when you call setRowHeight() unconditionally, even with a fixed value.
A second issue is that each row comprises two cells, which may have different heights. The code above will set the row height to match the cell being rendered right now. When the other cell of that row gets rendered and has a different height, the row height gets changed again. That will trigger a redraw, also of the first column in the row. Since that will result in another height change, there’s the infine loop again.
Proof: the following code fixes this:
int newHeight = table.getRowHeight() * getLineCount();
if (table.getRowHeight(row) < newHeight)
table.setRowHeight(row, newHeight);
Now the row height will only increase, but never decrease, thus breaking the infinite loop. Side effect: if the cell contents change and now occupy fewer rows than before, the row height will not change to reflect this.
Bottom line: rendering a JTable with multiline cells is non-trivial, and SO has quite a few buggy examples. The only working example I found (thanks to another SO post) is at https://www.javaspecialists.eu/archive/Issue106.html.
Their solution is to store cell heights internally in the renderer (though this could also be done in the table model, whichever works best for your implementation). When calculating the height of a cell, store it, then get the maximum height of any cell in the row and use that. Also be sure to set the row height only if it differs from the current one.
That has fixed the memory leak/processor consumption issue, in addition to finally giving me a working example of how to calculate cell height properly.
i have a problem, basically my program looks like this:
the thing is, it works, it is supposed to color the rows that have "N" in green, but the first time it loads the values, as you can see, the first row have bits of white, but for some reason if i click the list it fixes the issue, i need the rows to be colored properly without the user needing to click on the list to fix the issue, this is my Render code:
public class Render extends JTable {
#Override
public Component prepareRenderer(TableCellRenderer renderer, int rowIndex,
int columnIndex){
Component componente = super.prepareRenderer(renderer, rowIndex, columnIndex);
String val = getValueAt(rowIndex, columnIndex).toString();
if(val.equals("N")){
componente.setBackground(Color.GREEN);
}
return componente;
}
}
I figured i could use Repaint(); in the MouseMoved event in the JTable, but i think is not a proper way to fix it... Any help is appreciated, cheers!
Start by changing
String val = getValueAt(rowIndex, columnIndex).toString();
to
String val = getValueAt(rowIndex, 3).toString();
This will ensure that no matter what column the cell represents, you are checking the appropriate columns value - this is why the leading cells are white
You should also consider providing a default color for when the column values doesn't match
if (val.equals("N")) {
componente.setBackground(Color.GREEN);
} else {
componente.setBackground(getBackground());
}
The scenario: I have a UI that contains a JPanel (call it topGrid) with a grid layout in a JFrame at the top level. Within topGrid, I have placed another JPanel (midGrid) with grid layout. Inside midGrid, is another JPanel (bottomGrid) that has a JLabel that I populate with images depending on an array and what their instance is within that array.
The goal: I would like the topGrid to center its view on a specific object found in bottomGrid. (Picture a game that as the player icon moves, the game's grid moves to center on that icon and also when the game is started it is already centered for the user.)
I've considered getting the Point from bottomGrid and trying to pass it over to topGrid but doesn't seem to pull the correct information. The only way i know to find where the player is, is to iterate through all the components and check instances. this would have to be done once for the topGrid and again for midGrid to find the player at bottomGrid. then pass the Point data. Then use setLocation() on the appropriate JPanel minus the distance from the center.
Has anyone else tried this and have a more effective or elegant way to go about it? What other options could I explore?
Thanks for any feedback.
Creating the grid within topGrid's JPanel:
public void createTopGrid()
{
int rows = galaxy.getNumRows();
int columns = galaxy.getNumColumns();
pnlGrid.removeAll();
pnlGrid.setLayout(new GridLayout(rows, columns));
for (int row = 0; row < rows; row++)
{
for (int col = 0; col < columns; col++)
{
Position pos = new Position(galaxy, row, col);
Sector sector = galaxy.getSector(pos);
GalaxySector sectorUI = new GalaxySector(sector);
pnlGrid.add(sectorUI);
}
}
}
Creating the grid within midGrid's JPanel:
public void createOccupantIcons()
{
pnlGridOccupants.removeAll();
Occupant[] occs = sector.getOccupantsAsArray();
for ( Occupant occ : occs )
{
GalaxyOccupant occupant = new GalaxyOccupant(occ, sector);
pnlGridOccupants.add(occupant);
}
}
The Image icons for each occupant in the midGrid are pulled from an IconRep String in the model in the bottomGrid class' JPanel and added into a JLabel as needed in FlowLayout.
For visual reference:
Where green square is topGrid JPanel, red squares are midGrid JPanel, and the black square is the bottomGrid JPanel with the white circle for the player image inside a JLabel. The blue circle represents a viewport the user will see the game through and is where I want the player icon to be centered to. Currently the user can move the grid's using very inelegant buttons in the area around the viewport. That might be sufficient but at the start of the game the player has to move the grid around until they can locate their icon.
You might also look at JScrollNavigator, examined here. It would allow you to navigate on a thumbnail image of your entire world, seen at full size in an adjacent scroll pane.
Off the top of my head, I would store all the references you want to in some kind of model.
You could use this model to update the views based on selection requirements.
This allows the you to centralise the logic for finding and updating the elements without knowing or caring out the other UI elements
I am using a Swing JTable, and i want to force scroll to a specific row inside it. That is simple using scrollRowToVisible(...), but i want first to check this row is not already visible on the screen before scrolling to it, as if it is already visible there is no need to force scroll.
How can i do that ?
The link below is to an article that determines if a cell is visible. You could use that - if the cell is visible, then the row is visible. (But of course, possibly not the entire row, if horizontal scrolling is also present.)
However, I think this will fail when the cell is wider than the viewport. To handle this case, you change the test to check if the top/bottom of the cell bounds is within the vertical extent of the viewport, but ignore the left/right part of the cell. It is simplest to set the left and width of the rectangle to 0. I've also changed the method to take just the row index (no need for column index) and it returns true if the table is not in a viewport, which seems to align better with your use-case.
public boolean isRowVisible(JTable table, int rowIndex)
{
if (!(table.getParent() instanceof JViewport)) {
return true;
}
JViewport viewport = (JViewport)table.getParent();
// This rectangle is relative to the table where the
// northwest corner of cell (0,0) is always (0,0)
Rectangle rect = table.getCellRect(rowIndex, 1, true);
// The location of the viewport relative to the table
Point pt = viewport.getViewPosition();
// Translate the cell location so that it is relative
// to the view, assuming the northwest corner of the
// view is (0,0)
rect.setLocation(rect.x-pt.x, rect.y-pt.y);
rect.setLeft(0);
rect.setWidth(1);
// Check if view completely contains the row
return new Rectangle(viewport.getExtentSize()).contains(rect);
}
Determining if a cell is visible in JTable
I want to design a JPanel which should have the color coding as shown in the following diagram:
(source: compendiumblog.com)
How can I code the colors of a JPanel. What I think is that add 5 JPanels (for 5 blocks shown above) on a main JPanel. Set the background of each JPanel to light Gray.
But then how can I achieve the dark color lines as shown in the diagram.
Any hints or suggestions?
Try using a JTable and then alternating the colors of the row. This way you can write a generic JComponent (AlternatingColorTable) and use it just like a regular JTable in those 4 panels.
Something like this maybe:
public class AlternatingColorTable extends JTable {
public AlternatingColorTable () {
super();
}
public AlternatingColorTable(TableModel tableModel) {
super(tableModel);
}
/** Extends the renderer to alternate row colors */
public Component prepareRenderer(TableCellRenderer renderer, int row, int col) {
Component returnComp = super.prepareRenderer(renderer, row, col);
Color alternateColor = Color.GRAY;
Color mainColor = Color.DARK_GRAY;
if (!returnComp.getBackground().equals(getSelectionBackground())) {
Color background = (row % 2 == 0 ? alternateColor : mainColor );
returnComp.setBackground(background);
background = null;
}
return returnComp;
}
}
Just make each of the colored bars themselves panels with a different background color. Don't forget to make the panels explicitly opaque with setOpaque(true) - panels are transparent by default transparent in most look and feels.
A note on aesthetics; I would start with the first line in each group shaded differently.