来自Jframe的Jpanel中的doClick（）和SetText（）

Question

I'm new in Java programming. I developed a GUI in Netbeans (unfortunately using drag and drop).

I created a JFrame and two JPanel (using CardLayout).

JFrame:

private void formKeyPressed(java.awt.event.KeyEvent evt) {                                
    int key=evt.getKeyCode();

    switch (key) {

            case 105: 
                UpdatePanel update=new UpdatePanel(105);
                break;

            case 97:
                CardLayout showPanel = (CardLayout) panelCard.getLayout();
                showPanel.show(panelCard, "Incasso");
                break;

            case 99:
                showPanel = (CardLayout) panelCard.getLayout();
                showPanel.show(panelCard, "Selezione");
                break;

So when I press keycode 99, it shows the panelCard "Selezione" , and with keycode 97, panelCard "Incasso"

This works properly.

With keycode 105 it calls the class UpdatePanel .

public class UpdatePanel {
  public UpdatePanel(int key){
    switch (key) {
        case 105:
            Selezione variabile= new Selezione();

            variabile.fascia.setText("io");

            break;
    }
}

The scope of this class is to update the component inside the panels. In this sample I try to update the text field "fascia" that is a component inside the panel "Selezione" .

I compiled the files without errors. When I press the button (code 105) the class UpdatePanel is instantiated successfully, but the fieldText "fascia" is not updated in the panel.

What am I doing wrong ?

I tried to some modifications, but most of the code was made by the drag and drop wizard, so I do not have direct access.

Answer 1

UpdatePanel does not look like a good class name. It is better good for a method name, to say doSomething . If you are intending to write a class responsible for updating panel, better name it as PanelUpdater .

You could have written the case 105 as

case 105: 
       fascia.setText("io");
       break;

Or if you needed to do this with a class, say PanelUpdater ,

public class PanelUpdater {
  public PanelUpdater (int key, JTextField field){
    switch (key) {
        case 105:
            field.setText("io");
            break;
    }
}

and

case 105: 
                PanelUpdater panelUpdater = new PanelUpdater (105, fascia);
                break;

But I do not recommend this approach of creating an Object unnecessarily.