adjusting bar in java (GUI)

[it2512]

hei, good day everyone.

I want to draw an GUI that can let the user input the value by adjusting the bar. The bar is similiar to normal volume bar (adjusting the value by draging the pointer to the specific scale.), anyone know the name of the GUI component ? Somemore what is the name of the Listener that should be used to register with the component?

Thanks in advance.

[camickr]

Sounds like you want a JSlider. Read the section from the Swing tutorial on How to Use Sliders for an example.

[Norm]

what is the name of the Listener that should be used to register with the component

Different components have different listeners. Read the API doc for the component to see which one to use.

[it2512]

To camickr: thanks, JSlider is the component that i want.

Now, i know how to use JSlider already. But one things make me so curious:

slider.addChangeListener(new ChangeListener() {
  public void stateChanged(ChangeEvent e) {
     JSlider source = (JSlider)e.getSource();  // get the slider
     if (!source.getValueIsAdjusting()) {
        val = source.getValue();  // get slider value
        
     }
  }
});

The code above, there is one statement like:

 JSlider source = (JSlider)e.getSource();  // get the slider

Why we need to cast it to JSlider? ( I have compiled it, without it i get error)
But when i do the checking i get no error, like

 if( e.getSource == slider)

hmmmm, so strange...

[Norm]

Why we need to cast it to JSlider

You don't have to cast it for: e.getSource == slider
because that statement is comparing if two object references are the same.
You do have to cast it for:

JSlider source = (JSlider)e.getSource(); // get the slider
if (!source.getValueIsAdjusting()) {
val = source.getValue(); // get slider value

Because source needs to be a reference to a class that has a getValue() method.

[it2512]

Sorry previous post i forgot declare:

 JSlider slider = new JSlider();

So, slider should be JSlider type. Since we can compare them e.getSource == slider, this should mean they are same type?

Once after i wrote the statement:

 JSlider source = e.getSource();

, and i compile i got the error. Error happen before i call the getValue() function.

Is e.getSouce() don't return JSlider type object? hmmm...... it should return it.........

[Fubarable]

per the API (which you should probably read), getSource returns an object of Object type which you will need to cast to a JSlider -- if you know for certain that it is in fact a JSlider object.

[it2512]

how can i change this thread to "solved". The title cannot be modified anymore.