Java 获取 JPanel 组件

Question

I have a JPanel full of JTextFields...

for (int i=0; i<maxPoints; i++) {
    JTextField textField = new JTextField();
    points.add(textField);
}

How do I later get the JTextFields in that JPanel? Like if I want their values with

TextField.getText();

Thanks

Answer 1

Every JPanel in Java is also an AWT container. Thus, you should be able to use getComponents to get the array of contained components in the panel, iterate over them, check their types (To make sure you didn't get other controls), and do whatever you need with them.

However, this is generally poor design. If you know that you will need to access specific components, it is better to maintain an array of those text fields and pass it around, even though they are visually contained within the container.

If this is a recurrent task or could be done from multiple points, it may even make sense to have a special class representing a panel with text fields, that will then provide through its interface means of accessing these fields.

Answer 2

Well bear in mind they didn't get there by them selves ( I think a read some questions about dynamically creating these panels at runtime )

In the answers posted there, someone said you should kept reference to those textfields in an array. That's exactly what you need here:

List<JTextField> list = new ArrayLists<JTextField>();

// your code...
for (int i=0; i<maxPoints; i++) { 
    JTextField textField = new JTextField();
    points.add(textField);
    list.add( textField ); // keep a reference to those fields.
}

// Later

for( JTextField f : list ) { 
   System.out.println( f.getText() ) ;
}

Wasn't that easy?

Just remember to keep these kinds of artifacts ( list ) as private as possible. They are for your control only, I don't think they belong to the interface.

Let's say you want to get the array of texts, instead of

 public List<JTextField> getFields();

You should consider:

 public List<String> getTexts(); // get them from the textfields ... 

Answer 3

This is what I did to recursively go through the container and get the textfields that are on the JPanels.

private void ClearAllFields(Container myContainer) {

    Component myComps[] = myContainer.getComponents();

    for (int i=0; i<myComps.length; i++) {
      if(myComps[i] instanceof JPanel) {
          JPanel myPanel = (JPanel) myComps[i];
          ClearAllFields(myPanel);
      }
      if(myComps[i] instanceof JTextField) {
        JTextField myTextField = (JTextField) myComps[i];
        myTextField.setText("");
      }
    }        
}

And then to use it, you call it this way

ClearAllFields([jdialog or jframe etc].getContentPane());

Answer 4

You should call the getComponents method this returns with an array of all elements on your JPanel. After you can iterate on the array and check if its equals with the sought after component.

List<JTextField> list = new ArrayLists<JTextField>();
Component[] components = panel.getComponents();

for (Component component : components) {
    if (component.getClass().equals(JTextField.class)) {
        list.add((JTextField)component);
    }
}

Answer 5

    //una forma de recorer todos los elementos dentro de un jpanel
    Component[] components = jPanelX.getComponents();

    for (int i = 0; i < components.length; i++) {

        if(components[i].getClass().getName().toString().equals("javax.swing.JTextField")){
            components[i].setEnabled(false);
        }
    }

Answer 6

Dynamicly give it a name during creation and then do this.

    Component[] components = panel.getComponents();
    for (Component component: components) {
        var name = component.getName();  
        if(name != null){    
            if(name.equals("textfield 1")){
                var field = (JTextField)component;
                field.setText("whatever you want / same for options and other components")
            }
        }

    }

Answer 7

Your problem is writing the tedious code text. Why not just generate it and paste in the program!!...

for(int i=1 ; i<=maxpoints ;i++){
   System.out.println("JTextField tf"+i+" = new JTextField()"+";");
   System.out.println("points.add(tf"+i+")"+";");
}

Paste the output of the above code in your program and you are done. Now, to access the content of text fields you can generate the tedious code text in a similar way....

for(int i=1 ; i<=maxpoints ;i++){
   System.out.println("String s"+i+" = JTextField tf"+i+".getText()"+";");
}

Answer 8

public Component getComponentByName(Container parent,String name) {
        java.util.List<Component> clist = new ArrayList<>();
        listAllComponentsIn(parent,clist);
        for (Component c : clist) {
            System.out.println(c.getName());
            String s = c.getName();
            if(s!=null){
                if(s.equals(name)){
                    return c;
                }
            }
        }
        return null;
    }
    public void listAllComponentsIn(Container parent,java.util.List<Component> components)
    {
        for (Component c : parent.getComponents()) {
            components.add(c);
            if (c instanceof Container) {
                listAllComponentsIn((Container) c,components);
            }
        }
    }

if you have parent then you can get your textField anytime, anywhere. for example, i have added my textField on a JPanel named searchBar. first i gave a name ("txt_search_box") to textField and then i was able to get this textField from anywhere because i had reference to JPanel(searchBar) by using this-

searchBar.setVisible(true);
                        JTextField jTextField = (JTextField) getComponentByName(searchBar,"txt_search_box");
                        if(jTextField!=null){
                            jTextField.requestFocusInWindow();
                        }