在Java NetBeans中创建自己的GUI构建器

Question

I want to create a gui builder(like the one in NetBeans) in the following way : I have made a JSplitPane where in left side I have a JTextField where I write the name of a Swing Component and in the right side I want to appear that component. Something like this :

I want to make that using Reflections . This is first time using it, so please be kind with me and explain me how to make it.

Thank you!

Answer 1

in left side I have a JTextField where I write the name of a Swing Component

Well, you really shouldn't be use a JTextField. The user will not know what valid values are. Instead you should probably be using a JCombobox. Then you just get the component name from the selected item

I want to make that using Reflections.

The basic code for creating a component given a String value can be something like:

try
{
    String componentName = "Button";
    String classname = "javax.swing.J" + componentName;
    JComponent component = (JComponent)Class.forName(classname).newInstance();
    // add component to your panel

}
catch(Exception e) { System.out.println(e); }

However, if you use the above code the component is created without any parameters, so when you add it to the panel it will be very small. So you will need extra code to set some of the properties of the component.

Not this code is not really reflection since you are not examining the class for possible different constructors to use. It is just a simple way to create an Object given a String name.

For a more flexible approach that does use reflection you can start to specify parameters. Here is an example that will pass a String in the creation of a JButton:

String componentName = "Button";
String classname = "javax.swing.J" + componentName;
Class<?> type = Class.forName(classname);
Class[] argTypes = new Class[]{String.class};
Constructor constructor = type.getConstructor(argTypes);
Object[] parameters = new Object[]{"Button Text"};
JComponent component = (JComponent)constructor.newInstance(parameters);
add( component );

Here is a more general implementation that will allow you to create components with specific parameters as you create the component:

import java.awt.*;
import java.util.*;
import javax.swing.*;
import java.lang.reflect.*;

public class SwingComponentInfo
{
    private String name;
    private ArrayList<Class> types = new ArrayList<Class>();
    private ArrayList<Object> values = new ArrayList<Object>();

    public SwingComponentInfo(String name)
    {
        this.name = name;
    }

    public SwingComponentInfo(String name, Class type, Object value)
    {
        this.name = name;
        addParameter(type, value);
    }

    public void addParameter(Class type, Object value)
    {
        types.add(type);
        values.add(value);
    }

    public String getName()
    {
        return name;
    }

    public JComponent createComponent()
    {
        try
        {
            String classname = "javax.swing.J" + name;
            Class<?> type = Class.forName(classname);
            Constructor constructor = type.getConstructor( types.toArray( new Class[types.size()] ) );
            JComponent component = (JComponent)constructor.newInstance( values.toArray() );

            return component;
        }
        catch(Exception e) { e.printStackTrace(); }

        return null;
    }

    private static void createAndShowGUI()
    {
        JFrame frame = new JFrame("SwingComponent");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.setLayout( new FlowLayout() );
        SwingComponentInfo button = new SwingComponentInfo("Button", String.class, "New Button");
        frame.add(button.createComponent());

        SwingComponentInfo textField = new SwingComponentInfo("TextField", int.class, 10);
        frame.add(textField.createComponent());

        SwingComponentInfo textArea = new SwingComponentInfo("TextArea", int.class, 5);
        textArea.addParameter(int.class, 30);
        frame.add(textArea.createComponent());

        frame.setLocationByPlatform( true );
        frame.pack();
        frame.setVisible( true );
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater( () -> createAndShowGUI() );
/*
        EventQueue.invokeLater(new Runnable()
        {
            public void run()
            {
                createAndShowGUI();
            }
        });
*/
    }
}

So now you can add any number of SwingComponentInfo Objects to a combo box. Then in your ActionListener for the combo box you get the Item selected and create the Swing component and then add it to your panel.

You will need to create a custom renderer when you add the SwingComponentInfo object to the combo box to that the component name is displayed. Check out Combo Box With Custom Renderer for an easy way to do this.