Hi I am working on swing application but I am facing one problem.
When I first run application JPanel is positioned at proper position
where I decided to set with components inside. But problem occur when
I minimize & again maximize frame window jpanel automatically changes
it's position.
Below images shows that difference
As we can see on second image components changes it's position automatically.
For this I written below code,
jpanel_addPurchase = new JPanel();
jpanel_addPurchase.setLayout(null);
jpanel_addPurchase.setBounds(400, 0, 500, 500);
jpanel_addPurchase.setBackground(Color.white);
JLabel lbl_title = new JLabel("Purchase Form");
lbl_title.setBounds(90, 20, 100, 100);
jpanel_addPurchase.add(lbl_title);
And added this panel in frame using,
setContentPane(getJPanel());
Where I am going wrong?
I think the original (non-broken) layout looks quirky and would make it difficult for the end user to follow the rows and labels/fields. I suggest instead using a GroupLayout to right align the labels, and left align the fields that contain the values. Like this:
import java.awt.*;
import java.util.HashMap;
import java.util.Map;
import javax.swing.*;
class TwoColumnLayoutWithHeader {
/**
* Provides a JPanel with two columns (labels & fields) laid out using
* GroupLayout. The arrays must be of equal size.
*
* Typical fields would be single line textual/input components such as
* JTextField, JPasswordField, JFormattedTextField, JSpinner, JComboBox,
* JCheckBox.. & the multi-line components wrapped in a JScrollPane -
* JTextArea or (at a stretch) JList or JTable.
*
* @param labels The first column contains labels.
* @param fields The last column contains fields.
* @param addMnemonics Add mnemonic by next available letter in label text.
* @return JComponent A JPanel with two columns of the components provided.
*/
public static JComponent getTwoColumnLayout(
JLabel[] labels,
JComponent[] fields,
boolean addMnemonics) {
if (labels.length != fields.length) {
String s = labels.length + " labels supplied for "
+ fields.length + " fields!";
throw new IllegalArgumentException(s);
}
JComponent panel = new JPanel();
GroupLayout layout = new GroupLayout(panel);
panel.setLayout(layout);
// Turn on automatically adding gaps between components
layout.setAutoCreateGaps(true);
// Create a sequential group for the horizontal axis.
GroupLayout.SequentialGroup hGroup = layout.createSequentialGroup();
GroupLayout.Group yLabelGroup = layout.createParallelGroup(GroupLayout.Alignment.TRAILING);
hGroup.addGroup(yLabelGroup);
GroupLayout.Group yFieldGroup = layout.createParallelGroup();
hGroup.addGroup(yFieldGroup);
layout.setHorizontalGroup(hGroup);
// Create a sequential group for the vertical axis.
GroupLayout.SequentialGroup vGroup = layout.createSequentialGroup();
layout.setVerticalGroup(vGroup);
int p = GroupLayout.PREFERRED_SIZE;
// add the components to the groups
for (JLabel label : labels) {
yLabelGroup.addComponent(label);
}
for (Component field : fields) {
yFieldGroup.addComponent(field, p, p, p);
}
for (int ii = 0; ii < labels.length; ii++) {
vGroup.addGroup(layout.createParallelGroup().
addComponent(labels[ii]).
addComponent(fields[ii], p, p, p));
}
if (addMnemonics) {
addMnemonics(labels, fields);
}
return panel;
}
private final static void addMnemonics(
JLabel[] labels,
JComponent[] fields) {
Map<Character, Object> m = new HashMap<Character, Object>();
for (int ii = 0; ii < labels.length; ii++) {
labels[ii].setLabelFor(fields[ii]);
String lwr = labels[ii].getText().toLowerCase();
for (int jj = 0; jj < lwr.length(); jj++) {
char ch = lwr.charAt(jj);
if (m.get(ch) == null && Character.isLetterOrDigit(ch)) {
m.put(ch, ch);
labels[ii].setDisplayedMnemonic(ch);
break;
}
}
}
}
/**
* Provides a JPanel with two columns (labels & fields) laid out using
* GroupLayout. The arrays must be of equal size.
*
* @param labelStrings Strings that will be used for labels.
* @param fields The corresponding fields.
* @return JComponent A JPanel with two columns of the components provided.
*/
public static JComponent getTwoColumnLayout(
String[] labelStrings,
JComponent[] fields) {
JLabel[] labels = new JLabel[labelStrings.length];
for (int ii = 0; ii < labels.length; ii++) {
labels[ii] = new JLabel(labelStrings[ii]);
}
return getTwoColumnLayout(labels, fields);
}
/**
* Provides a JPanel with two columns (labels & fields) laid out using
* GroupLayout. The arrays must be of equal size.
*
* @param labels The first column contains labels.
* @param fields The last column contains fields.
* @return JComponent A JPanel with two columns of the components provided.
*/
public static JComponent getTwoColumnLayout(
JLabel[] labels,
JComponent[] fields) {
return getTwoColumnLayout(labels, fields, true);
}
public static String getProperty(String name) {
return name + ": \t"
+ System.getProperty(name)
+ System.getProperty("line.separator");
}
public static void main(String[] args) {
Runnable r = new Runnable() {
@Override
public void run() {
JComponent[] components = {
new JTextField(15),
new JTextField(10),
new JTextField(8),
new JSpinner(new SpinnerNumberModel(1,0,10,1)),
new JSpinner(new SpinnerNumberModel(9.95,0d,100d,.01)),
new JSpinner(new SpinnerNumberModel(9.95,0d,1000d,.01)),
new JSpinner(new SpinnerNumberModel(9.95,0d,100d,.01)),
new JSpinner(new SpinnerNumberModel(9.95,0d,1000d,.01)),
new JSpinner(new SpinnerNumberModel(9.95,0d,100d,.01)),
new JSpinner(new SpinnerNumberModel(9.95,0d,1000d,.01))
};
String[] labels = {
"Product Name:",
"Product Unit Name:",
"Purchase Date:",
"Quantity:",
"Price Per Unit:",
"Total Price:",
"Discount:",
"Total:",
"VAT:",
"Grand Total:"
};
JComponent labelsAndFields = getTwoColumnLayout(labels,components);
JComponent orderForm = new JPanel(new BorderLayout(5,5));
orderForm.add(new JLabel("Purchase Form", SwingConstants.CENTER),
BorderLayout.PAGE_START);
orderForm.add(labelsAndFields, BorderLayout.CENTER);
JOptionPane.showMessageDialog(null, orderForm);
}
};
// Swing GUIs should be created and updated on the EDT
// http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html
SwingUtilities.invokeLater(r);
}
}
来源：https://stackoverflow.com/questions/21658144/jpanel-components-change-position-automatically