First create a frame that has a slider in it which will be used to set transparency amount.

import javax.swing.JFrame;
import javax.swing.JSlider;

public class TransparentFrame extends JFrame {
 public TransparentFrame() {
 setTitle('Transparent Frame');
 setSize(400,400);
 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 JSlider slider = new JSlider(JSlider.HORIZONTAL);
 add(slider);
 setVisible(true);
 }
 public static void main(String[] args) {
 new TransparentFrame();
 }
}

Output of this will be:

Now add a change listener to slider so we can monitor it.

slider.addChangeListener(new ChangeListener() {
 @Override
 public void stateChanged(ChangeEvent e) {
 }
});

Now we will write our transparency logic in this method but before we do that first let’s see how to make a JFrame transparent.

To make a JFrame transparent java has a built in utility class that is AWTUtilities. By using methods provided in this class we can make our JFrame transparent. Following is the code for that:

AWTUtilities.setWindowOpacity(window, floatOpacity);

Arguments:

Window – Your frame/window object.

floatOpactity – between 0 to 1. 1 for no opacity and 0 for fully transparent.

So now we know that we have to add this logic to slider change event and give sliders value as floatOpacity value. So for that change stateChanged() method with following:

@Override
public void stateChanged(ChangeEvent e) {
 JSlider slider = (JSlider) e.getSource();
 if(!slider.getValueIsAdjusting()){
 AWTUtilities.setWindowOpacity(TransparentFrame.this, slider.getValue());
 }
}

Think it’s done. No we still have to make sure that opacity value doesn’t go beyond its limit that is 0.0f to 1.0f. So for that we have to limit our slider to these values. As slider don’t supports point values we will take values in multiple of 10 and then divide them by 100 to get desired value. For this we will change JSlider declaration and stateChanged like follow:

JSlider slider = new JSlider(JSlider.HORIZONTAL, 10, 100, 100);

Change following line in stateChanged method:

AWTUtilities.setWindowOpacity(TransparentFrame.this, slider.getValue()/100f);

So now when we run this program we see a frame with a slider in it which is set to end. And when we change slider the frame accordingly change its transparency.

Output:

Note:

To use AWTUtilities class in eclipse you need to change preference setting or you may have error for accessing restricted classes. To change settings do as follows:

1. Right click on your project. Select properties.
2. Select Java compiler and expand it.
3. Select Errors/Warnings.
4. Enable project specific settings.
5. In Deprecated and Restricted API you will find Forbidden References (access rules.) Change it to Warning or Ignore

Reference: Make JFrame transparent from our JCG partner Harsh Raval at the harryjoy blog.