问题
I have a series of components underneath each other in a JPanel set as a GridLayout.
I need to temporarily hide the components but setVisible(false) doesn't cut it, because there is still an empty gap where the components were.
Is there a quick and easy way to do this? Or do I have to stay saving the state of the JPanel, removing the components, then restoring it?
SSCCE:
[GridLayout2.java]
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.GridLayout;
import java.awt.Insets;
public class GridLayout2 extends GridLayout
{
public GridLayout2() {
this(1, 0, 0, 0);
}
public GridLayout2(int rows, int cols) {
this(rows, cols, 0, 0);
}
public GridLayout2(int rows, int cols, int hgap, int vgap) {
super(rows, cols, hgap, vgap);
}
public Dimension preferredLayoutSize(Container parent) {
//System.err.println("preferredLayoutSize");
synchronized (parent.getTreeLock()) {
Insets insets = parent.getInsets();
int ncomponents = parent.getComponentCount();
int nrows = getRows();
int ncols = getColumns();
if (nrows > 0) {
ncols = (ncomponents + nrows - 1) / nrows;
}
else {
nrows = (ncomponents + ncols - 1) / ncols;
}
int[] w = new int[ncols];
int[] h = new int[nrows];
for (int i = 0; i < ncomponents; i ++) {
int r = i / ncols;
int c = i % ncols;
Component comp = parent.getComponent(i);
Dimension d = comp.getPreferredSize();
if (w[c] < d.width) {
w[c] = d.width;
}
if (h[r] < d.height) {
h[r] = d.height;
}
}
int nw = 0;
for (int j = 0; j < ncols; j ++) {
nw += w[j];
}
int nh = 0;
for (int i = 0; i < nrows; i ++) {
nh += h[i];
}
return new Dimension(insets.left + insets.right + nw + (ncols-1)*getHgap(),
insets.top + insets.bottom + nh + (nrows-1)*getVgap());
}
}
public Dimension minimumLayoutSize(Container parent) {
System.err.println("minimumLayoutSize");
synchronized (parent.getTreeLock()) {
Insets insets = parent.getInsets();
int ncomponents = parent.getComponentCount();
int nrows = getRows();
int ncols = getColumns();
if (nrows > 0) {
ncols = (ncomponents + nrows - 1) / nrows;
}
else {
nrows = (ncomponents + ncols - 1) / ncols;
}
int[] w = new int[ncols];
int[] h = new int[nrows];
for (int i = 0; i < ncomponents; i ++) {
int r = i / ncols;
int c = i % ncols;
Component comp = parent.getComponent(i);
Dimension d = comp.getMinimumSize();
if (w[c] < d.width) {
w[c] = d.width;
}
if (h[r] < d.height) {
h[r] = d.height;
}
}
int nw = 0;
for (int j = 0; j < ncols; j ++) {
nw += w[j];
}
int nh = 0;
for (int i = 0; i < nrows; i ++) {
nh += h[i];
}
return new Dimension(insets.left + insets.right + nw + (ncols-1)*getHgap(),
insets.top + insets.bottom + nh + (nrows-1)*getVgap());
}
}
public void layoutContainer(Container parent) {
//System.err.println("layoutContainer");
synchronized (parent.getTreeLock()) {
Insets insets = parent.getInsets();
int ncomponents = parent.getComponentCount();
int nrows = getRows();
int ncols = getColumns();
if (ncomponents == 0) {
return;
}
if (nrows > 0) {
ncols = (ncomponents + nrows - 1) / nrows;
}
else {
nrows = (ncomponents + ncols - 1) / ncols;
}
int hgap = getHgap();
int vgap = getVgap();
// scaling factors
Dimension pd = preferredLayoutSize(parent);
double sw = (1.0 * parent.getWidth()) / pd.width;
double sh = (1.0 * parent.getHeight()) / pd.height;
// scale
int[] w = new int[ncols];
int[] h = new int[nrows];
for (int i = 0; i < ncomponents; i ++) {
int r = i / ncols;
int c = i % ncols;
Component comp = parent.getComponent(i);
Dimension d = comp.getPreferredSize();
d.width = (int) (sw * d.width);
d.height = (int) (sh * d.height);
if (w[c] < d.width) {
w[c] = d.width;
}
if (h[r] < d.height) {
h[r] = d.height;
}
}
for (int c = 0, x = insets.left; c < ncols; c ++) {
for (int r = 0, y = insets.top; r < nrows; r ++) {
int i = r * ncols + c;
if (i < ncomponents) {
parent.getComponent(i).setBounds(x, y, w[c], h[r]);
}
y += h[r] + vgap;
}
x += w[c] + hgap;
}
}
}
}
[SSCCE.java]
import java.awt.Color;
import javax.swing.*;
import javax.swing.border.*;
public class SSCCE extends JFrame{
JPanel innerPane = new JPanel();
JScrollPane scr = new JScrollPane(innerPane);
public static void main(String[] args) {
new SSCCE();
}
public SSCCE() {
setSize(400, 800);
innerPane.setLayout(new GridLayout2(0, 1));
add(scr);
for (int i = 0; i < 30; i++)
{
innerPane.add(getPane());
}
setVisible(true);
try {
Thread.sleep(2000);
} catch (InterruptedException e) {}
for (int i = 0; i < 30; i++)
{
if (i%2==0)
innerPane.getComponent(i).setVisible(false);
}
}
private JPanel getPane()
{
JPanel ret = new JPanel();
JLabel lbl = new JLabel("This is a pane.");
ret.add(lbl);
ret.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
ret.setBackground(Color.gray);
return ret;
}
}
回答1:
because there is still an empty gap where the components were.
Yes, GridLayout is not that smart. It just uses the total number of components to determine the number of row/columns.
Is there a quick and easy way to do this?
I would create a custom layout manager. Just copy the GridLayout code and make a couple of changes. The basic changes would be:
Override the
ncomponentsvariable. Instead of just using the number of components on the panel you would need to loop thorugh all the components and count the visible ones.In the layout code you would need to add an
if (visible)check.
Edit:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class InvisibleGridLayout implements LayoutManager, java.io.Serializable
{
int hgap;
int vgap;
int rows;
int cols;
public InvisibleGridLayout() {
this(1, 0, 0, 0);
}
public InvisibleGridLayout(int rows, int cols) {
this(rows, cols, 0, 0);
}
public InvisibleGridLayout(int rows, int cols, int hgap, int vgap) {
if ((rows == 0) && (cols == 0)) {
throw new IllegalArgumentException("rows and cols cannot both be zero");
}
this.rows = rows;
this.cols = cols;
this.hgap = hgap;
this.vgap = vgap;
}
public int getRows() {
return rows;
}
public void setRows(int rows) {
if ((rows == 0) && (this.cols == 0)) {
throw new IllegalArgumentException("rows and cols cannot both be zero");
}
this.rows = rows;
}
public int getColumns() {
return cols;
}
public void setColumns(int cols) {
if ((cols == 0) && (this.rows == 0)) {
throw new IllegalArgumentException("rows and cols cannot both be zero");
}
this.cols = cols;
}
public int getHgap() {
return hgap;
}
public void setHgap(int hgap) {
this.hgap = hgap;
}
public int getVgap() {
return vgap;
}
public void setVgap(int vgap) {
this.vgap = vgap;
}
public void addLayoutComponent(String name, Component comp) {
}
public void removeLayoutComponent(Component comp) {
}
public Dimension preferredLayoutSize(Container parent) {
synchronized (parent.getTreeLock()) {
Insets insets = parent.getInsets();
// int ncomponents = parent.getComponentCount();
int ncomponents = getVisibleComponents(parent);
int nrows = rows;
int ncols = cols;
if (nrows > 0) {
ncols = (ncomponents + nrows - 1) / nrows;
} else {
nrows = (ncomponents + ncols - 1) / ncols;
}
int w = 0;
int h = 0;
// for (int i = 0 ; i < ncomponents ; i++) {
for (int i = 0 ; i < parent.getComponentCount(); i++) {
Component comp = parent.getComponent(i);
if (!comp.isVisible()) continue; // added
Dimension d = comp.getPreferredSize();
if (w < d.width) {
w = d.width;
}
if (h < d.height) {
h = d.height;
}
}
Dimension d = new Dimension(insets.left + insets.right + ncols*w + (ncols-1)*hgap,
insets.top + insets.bottom + nrows*h + (nrows-1)*vgap);
return d;
}
}
public Dimension minimumLayoutSize(Container parent) {
synchronized (parent.getTreeLock()) {
Insets insets = parent.getInsets();
// int ncomponents = parent.getComponentCount();
int ncomponents = getVisibleComponents(parent);
int nrows = rows;
int ncols = cols;
if (nrows > 0) {
ncols = (ncomponents + nrows - 1) / nrows;
} else {
nrows = (ncomponents + ncols - 1) / ncols;
}
int w = 0;
int h = 0;
// for (int i = 0 ; i < ncomponents ; i++) {
for (int i = 0 ; i < parent.getComponentCount(); i++) {
Component comp = parent.getComponent(i);
if (!comp.isVisible()) continue; // added
Dimension d = comp.getMinimumSize();
if (w < d.width) {
w = d.width;
}
if (h < d.height) {
h = d.height;
}
}
Dimension d = new Dimension(insets.left + insets.right + ncols*w + (ncols-1)*hgap,
insets.top + insets.bottom + nrows*h + (nrows-1)*vgap);
return d;
}
}
public void layoutContainer(Container parent) {
synchronized (parent.getTreeLock()) {
Insets insets = parent.getInsets();
// int ncomponents = parent.getComponentCount();
int ncomponents = getVisibleComponents(parent);
int nrows = rows;
int ncols = cols;
boolean ltr = parent.getComponentOrientation().isLeftToRight();
if (ncomponents == 0) {
return;
}
if (nrows > 0) {
ncols = (ncomponents + nrows - 1) / nrows;
} else {
nrows = (ncomponents + ncols - 1) / ncols;
}
// int w = parent.width - (insets.left + insets.right);
// int h = parent.height - (insets.top + insets.bottom);
int w = parent.getSize().width - (insets.left + insets.right);
int h = parent.getSize().height - (insets.top + insets.bottom);
w = (w - (ncols - 1) * hgap) / ncols;
h = (h - (nrows - 1) * vgap) / nrows;
/*
if (ltr) {
for (int c = 0, x = insets.left ; c < ncols ; c++, x += w + hgap) {
for (int r = 0, y = insets.top ; r < nrows ; r++, y += h + vgap) {
int i = r * ncols + c;
if (i < ncomponents) {
parent.getComponent(i).setBounds(x, y, w, h);
}
}
}
} else {
// for (int c = 0, x = parent.width - insets.right - w; c < ncols ; c++, x -= w + hgap) {
for (int c = 0, x = parent.getSize().width - insets.right - w; c < ncols ; c++, x -= w + hgap) {
for (int r = 0, y = insets.top ; r < nrows ; r++, y += h + vgap) {
int i = r * ncols + c;
if (i < ncomponents) {
parent.getComponent(i).setBounds(x, y, w, h);
}
}
}
}
}
*/
int i = 0;
if (ltr)
{
for (int r = 0, y = insets.top ; r < nrows ; r++, y += h + vgap)
{
int c = 0;
int x = insets.left;
while (c < ncols)
{
if (i >= parent.getComponentCount()) break;
Component component = parent.getComponent(i);
if (component.isVisible())
{
parent.getComponent(i).setBounds(x, y, w, h);
c++;
x += w + hgap;
}
i++;
}
}
}
}}
private int getVisibleComponents(Container parent)
{
int visible = 0;
for (Component c: parent.getComponents())
{
if (c.isVisible())
visible++;
}
return visible;
}
public String toString() {
return getClass().getName() + "[hgap=" + hgap + ",vgap=" + vgap +
",rows=" + rows + ",cols=" + cols + "]";
}
public static void main(String[] args)
{
final JPanel innerPane = new JPanel();
JScrollPane scr = new JScrollPane(innerPane);
innerPane.setLayout(new InvisibleGridLayout(0, 3));
for (int i = 0; i < 30; i++)
{
JPanel ret = new JPanel();
JLabel lbl = new JLabel("This is pane " + i);
ret.add(lbl);
ret.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
ret.setBackground(Color.gray);
innerPane.add(ret);
}
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(scr);
frame.setBounds(400, 0, 400, 700);
frame.setVisible(true);
javax.swing.Timer timer = new javax.swing.Timer(2000, new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
for (int i = 0; i < 30; i++)
{
if (i%2==0)
innerPane.getComponent(i).setVisible(false);
}
}
});
timer.setRepeats(false);
timer.start();
}
}
回答2:
Here are 3 ways off the top of my head.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class HideComponents {
public static void main(String args[]) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JPanel gui = new JPanel(new BorderLayout());
JToolBar tb = new JToolBar();
gui.add(tb, BorderLayout.NORTH);
final JButton openTool = new JButton("Open");
final JButton saveTool = new JButton("Save");
tb.add( openTool );
tb.add( saveTool );
JPanel buttonFlow = new JPanel(new FlowLayout(3));
gui.add(buttonFlow, BorderLayout.CENTER);
final JButton openFlow = new JButton("Open");
final JButton saveFlow = new JButton("Save");
buttonFlow.add( openFlow );
buttonFlow.add( saveFlow );
JPanel buttonBox = new JPanel();
gui.add(buttonBox, BorderLayout.EAST);
BoxLayout bl = new BoxLayout(buttonBox, BoxLayout.Y_AXIS);
buttonBox.setLayout(bl);
final JButton openBox = new JButton("Open");
final JButton saveBox = new JButton("Save");
buttonBox.add( openBox );
buttonBox.add( saveBox );
final JCheckBox openChoice = new JCheckBox("Show open", true);
openChoice.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
openTool.setVisible(openChoice.isSelected());
openFlow.setVisible(openChoice.isSelected());
openBox.setVisible(openChoice.isSelected());
}
});
gui.add(openChoice, BorderLayout.SOUTH);
JOptionPane.showMessageDialog(null, gui);
}
});
}
}
On reflection
Please consider swapping:
button.setVisible(false);
For:
button.setEnabled(false);
This will be more intuitive to most users who view the GUI, and has the same ultimate effect.
Vis:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class DisableComponents {
public static void main(String args[]) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JPanel gui = new JPanel(new BorderLayout());
JToolBar tb = new JToolBar();
gui.add(tb, BorderLayout.NORTH);
final JButton openTool = new JButton("Open");
final JButton saveTool = new JButton("Save");
tb.add( openTool );
tb.add( saveTool );
JPanel buttonFlow = new JPanel(new FlowLayout(3));
gui.add(buttonFlow, BorderLayout.CENTER);
final JButton openFlow = new JButton("Open");
final JButton saveFlow = new JButton("Save");
buttonFlow.add( openFlow );
buttonFlow.add( saveFlow );
JPanel buttonBox = new JPanel();
gui.add(buttonBox, BorderLayout.EAST);
BoxLayout bl = new BoxLayout(buttonBox, BoxLayout.Y_AXIS);
buttonBox.setLayout(bl);
final JButton openBox = new JButton("Open");
final JButton saveBox = new JButton("Save");
buttonBox.add( openBox );
buttonBox.add( saveBox );
final JCheckBox openChoice = new JCheckBox("Enable open", true);
openChoice.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
openTool.setEnabled(openChoice.isSelected());
openFlow.setEnabled(openChoice.isSelected());
openBox.setEnabled(openChoice.isSelected());
}
});
gui.add(openChoice, BorderLayout.SOUTH);
JOptionPane.showMessageDialog(null, gui);
}
});
}
}
回答3:
don't call Thread.sleep(int); during EDT, because block EDT, use javax.swing.Timer
for example
import java.awt.Color;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import javax.swing.*;
import javax.swing.border.*;
public class SSCCE extends JFrame {
private static final long serialVersionUID = 1L;
private JPanel innerPane = new JPanel();
private JScrollPane scr = new JScrollPane(innerPane);
private Timer timer;
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
SSCCE sSCCE = new SSCCE();
}
});
}
private JPanel getPane() {
JPanel ret = new JPanel();
JLabel lbl = new JLabel("This is a pane.");
ret.add(lbl);
ret.setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
ret.setBackground(Color.gray);
return ret;
}
public SSCCE() {
innerPane.setLayout(new GridLayout(0, 1));
add(scr);
for (int i = 0; i < 30; i++) {
innerPane.add(getPane());
}
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setVisible(true);
start();
}
private void start() {
timer = new javax.swing.Timer(2000, updateCol());
timer.start();
timer.setRepeats(false);
}
private Action updateCol() {
return new AbstractAction("Hide Row Action") {
private static final long serialVersionUID = 1L;
@Override
public void actionPerformed(ActionEvent e) {
for (int i = 0; i < 30; i++) {
if (i % 2 == 0) {
innerPane.getComponent(i).setVisible(false);
}
}
}
};
}
}
回答4:
I really don't like the GridLayout. Instead of writing your own layout manager, I would suggest you take a look at the TableLayout. I use it all the time.
The initial learning curve is a bit steeper than the GridLayout, but it is easy to get it to behave the way you want.
http://java.sun.com/products/jfc/tsc/articles/tablelayout/
回答5:
try to use BoxLayout with component alignment. For example:
JPanel innerPane = new JPanel();
BoxLayout innerPaneLayout = new BoxLayout(innerPane,BoxLayout.Y_AXIS);
innerPane.setLayout(innerPaneLayout);
for (int i = 0; i < 30; i++)
{
JPane newPane = getPane();
innerPane.add(newPane);
newPane.setAlignmentY(Component.TOP_ALIGNMENT);
}
for (int i = 0; i < 30; i++)
{
if (i%2==0)
innerPane.getComponent(i).setVisible(false);
}
来源：https://stackoverflow.com/questions/7727728/invisible-components-still-take-up-space-jpanel