How can I create a multiple jLabel using the result set from database column?
I spent almost 2 days trying to solve but unfortunately i still didn't get it correct. please help me.
Here's my codes:
String[] arr = null;
try{
String sql = "SELECT * FROM Position";
pst = conn.prepareStatement(sql);
rs = pst.executeQuery();
while(rs.next()){
String s1 = rs.getString("PositionName");
arr = s1.split("\n");
int v = 50;
for (int i = 0; i < arr.length; i++){
JLabel[] labels = new JLabel[i];
labels[i] = new JLabel();
labels[i].setBounds(50,v,80,20);
labels[i].setText(arr[i]);
jPanel3.add(labels[i]);
v+=40;
System.out.println(arr[i]);
}
jPanel3.repaint();
}
I want a result something like this, (in a jLabel)
President
Vice-President
Secretary
if i make int i = 0 the output is "java.lang.ArrayIndexOutOfBoundsException:0"
if i make it int i = 1, there's no error but not created jLabel at all.
When i == 0, then
JLabel[] labels = new JLabel[i];
creates an array which can't hold anything since it's size is 0. So then
labels[i] = new JLabel();
attempts to set the element at index 0 which causes the exception.
The code is attempting to do too much which can make it difficult to find bugs. Try separating the code into single responsibility methods such as:
List<String> getAvailablePositions() {
// get the positions from the database
}
and
void addPositionLabels(List<String> availablePositions) {
// add the positions to the JPanel
}
initialize JLabel array outside the for-loop
JLabel[] labels = new JLabel[arr.length];
for (int i = 0; i < arr.length; i++){
labels[i] = new JLabel();
labels[i].setBounds(50,v,80,20);
labels[i].setText(arr[i]);
jPanel3.add(labels[i]);
v+=40;
}
**here is the sample code **
JFrame frame = new JFrame();
frame.setSize(300,300);
JPanel panel = new JPanel();
panel.setLayout(null);
int v = 50;
JLabel[] labels = new JLabel[3];
for (int i = 0; i < 3; i++){
labels[i] = new JLabel();
labels[i].setBounds(50,v,80,20);
labels[i].setText("hi");
panel.add(labels[i]);
v+=40;
}
frame.add(panel);
frame.setVisible(true);
**you will get the following result
hi
hi
hi**
I'm fairly new to GUI programming, and I've been trying to replicate an example where I want to have an array of JButtons right next to each other.
I set the vertical and horizontal gaps both to 0 in the grid layout and still there are spaces between the buttons. On Windows this problem doesn't really exist and you can get the buttons right next to each other.
Can someone help me with this please?
buttons = new JButton[3][3];
buttonP = new JPanel(new GridLayout(3,3,0,0));
for(int i = 0; i < 3; ++i){
for(int j = 0; j < 3; ++j){
buttons[i][j] = new JButton();
buttonP.add(buttons[i][j]);
}
}
add(buttonP);
I am trying to create a grid of buttons.
This is my code to create the grid (which works), but if I want to access a single button later on how would I go about doing that?
for(int i = 1; i<= row; i++){
for( int p=1; p<= col; p++){
boardPanel.add(new JButton());
}
}
Many Thanks
A Clements;
From your question title I'm assuming that you want to be able to access these buttons from a 2d array, but in your code the button is not in an array. If you did something like the following:
JButton[][] buttons = new JButton[row][col];
for(int i = 1; i<= row; i++){
for( int p=1; p<= col; p++){
buttons[i][p] = new JButton();
boardPanel.add(buttons[i][p]);
}
}
Then you are maintaining a 2d array that contains references to the buttons in your JPanel. So now you can access the buttons from the array like this:
buttons[i][j];
I want to add 70 labels and 70 checkboxes in an applet I takes lot of code when we write normally . how to add these labels using for loop
You could use a for loop to add Labels to an array. Something like
List<Label> li = new List<Label>();
for(int i = 0; i < 70; i++)
{
li.add(new Label("label " + i));
}
If you don't want to use an array just you could just add the labels directly to your layout.
FlowLayout fl = new FlowLayout(FlowLayout.CENTER, 10, 10);
for(int i = 0; i < 70; i++)
{
fl.add(new Label("label " + i));
}
I'm working through a JPanel exercise in a Java book. I'm tasked with creating a 5x4 grid using GridLayout.
When I loop through the container to add panels and buttons, the first add() throws the OOB exception. What am I doing wrong?
package mineField;
import java.awt.*;
import javax.swing.*;
#SuppressWarnings("serial")
public class MineField extends JFrame {
private final int WIDTH = 250;
private final int HEIGHT = 120;
private final int MAX_ROWS = 5;
private final int MAX_COLUMNS = 4;
public MineField() {
super("Minefield");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container mineFieldGrid = getContentPane();
mineFieldGrid.setLayout(new GridLayout(MAX_ROWS, MAX_COLUMNS));
// loop through arrays, add panels, then add buttons to panels.
for (int i = 0; i < MAX_ROWS; i++) {
JPanel[] rows = new JPanel[i];
mineFieldGrid.add(rows[i], rows[i].getName());
rows[i].setBackground(Color.blue);
for (int j = 0; j < MAX_COLUMNS; j++) {
JButton[] buttons = new JButton[i];
rows[i].add(buttons[j], buttons[j].getName());
}
}
mineFieldGrid.setSize(WIDTH, HEIGHT);
mineFieldGrid.setVisible(true);
}
public int setRandomBomb(Container con)
{
int bombID;
bombID = (int) (Math.random() * con.getComponentCount());
return bombID;
}
/**
* #param args
*/
public static void main(String[] args) {
//int randomBomb;
//JButton bombLocation;
MineField minePanel = new MineField();
//minePanel[randomBomb] = minePanel.setRandomBomb(minePanel);
}
}
I'm sure I'm over-engineering a simple nested for loop. Since I'm new to Java, please be kind. I'm sure I'll return the favor some day.
JPanel[] rows = new JPanel[i];
i is 0 in the first iteration, which isn't what you want. Make that:
JPanel[] rows = new JPanel[MAX_ROWS];
Also, I think you want to take that completely outside the for loop, since you seem to be using its elements, which would be uninitialised...
This is also wrong:
JButton[] buttons = new JButton[i];
i can be 0 when j is 2 for example, in which case there's no such thing as a buttons[j]. Make them all MAX_* and I think you want to take them out of the loop, since I don't see the point in recreating them at every iteration. Also, you need to instantiate the individual array elements as well.
This part doesn't really make sense:
for (int j = 0; j < MAX_COLUMNS; j++) {
JButton[] buttons = new JButton[i];
rows[i].add(buttons[j], buttons[j].getName());
}
You're creating an array of i JButtons, and trying to add the jth to rows, which makes little sense and won't work if j >= i. You probably meant to do:
JButton[] buttons = new JButton[MAX_COLUMNS];
for (int j = 0; j < MAX_COLUMNS; j++) {
rows[i].add(buttons[j], buttons[j].getName());
}
But the array still doesn't contain any buttons, all you did is initialize it. There's really no reason for the array at all; this actually works:
for (int j = 0; j < MAX_COLUMNS; j++) {
JButton button = new JButton("foo");
rows[i].add(button, button.getName());
}
JPanel[] rows = new JPanel[i];
When i is 0, you create an array with 0 elements. You then try to access that array, but it has no elements in it.
The problem is that your button array is of size i, but j can be larger than i. For instance, the first time through, you are making an empty array here:
JButton[] buttons = new JButton[i];
because i is equal to 0. You then attempt to access it at index 0, which doesn't exist (since the array has no size) and you get your exception. Should you instead be doing something like:
JButton[] buttons = new JButton[MAX_COLUMNS];
That way you will have a button for each array location. Also, you will probably need to initialize the individual buttons - i.e. something like this:
for (int k = 0; k < MAX_COLUMNS; k++) {
buttons[k] = new JButton();
}
(disclaimer: code not tested, but pulled out of you-know-where for example purposes only. There could be typos or unseen bugs.)
Good luck.
It looks like you're creating way too many arrays. You're creating your arrays INSIDE the loops, so instead of creating 5 rows, you're creating 5 rows 5 times, or 25 rows.
The other problem is that you aren't actually creating any objects, only the array to hold the objects. For each object in your array, you need another "button[j] = new JButton()" line.