通过内部类更改外部类成员的值

Question

I am trying to manipulate a an outer class member via an inner class event handling method.

A class MyColorChooser has a private member sliderColor . The default value of sliderColor is set to black in the constructor.

An inner class is used to handle the construction of new colors via user input from JSliders . I then set the value of sliderColor to this new colour via a setter method in the outer class.

Problem is that an instance of the outer class uses its own getColor method which always returns the value set by the constructor (black), and not the new value it has been assigned. How can I make it so that the inner class method is able to directly alter the value in the outer member variable?

UPDATED

yes it seems like it should be working but got me stumped why its not......have posted soem of what i belive are the relevant bits f code:

NB Apologies in advance if code unsuitable as wasnt sure how much to insert....

Debugging: i have debugged and noted that colour is the colour it should be in the inner class and also the setColour outerclass method...so im suspecting its been changed Back to the default constructor value...just not sure where or by what...ill just keep debugging

Class MyColorChooser with which allows creation of color object via input fom JSliders handled by a inner class event hander:

* Part 4 
* JPanel subclass that alloews the user define the color attributes for shapes 
* utlising 3 JSliders 
*/ 
package Assignment2; 

import java.awt.Color; 
import java.awt.GridLayout; 
import javax.swing.JLabel; 
import javax.swing.JPanel; 
import javax.swing.JSlider; 
import javax.swing.JTextField; 
import javax.swing.SwingConstants; 
import javax.swing.event.ChangeEvent; 
import javax.swing.event.ChangeListener; 

/** 
* 
* @author Ciaran Mooney dancingbush@gmail.com 
*/ 
public class MyColorChooser4 extends JPanel { 

//declare instance varibles 
//JSlider colors 
private JSlider blueSlider; 
private JSlider greenSlider; 
private JSlider redSlider; 
//display color chossen by user varibles 
private JTextField redChoice; 
private JTextField greenChoice; 
private JTextField blueChoice; 
private DrawPanel shapeColor = new DrawPanel(); //set color of drawpanel onbject 
//prompts for user input 
private JLabel redInput; 
private JLabel blueInput; 
private JLabel greenInput; 
//color object created 
private Color colorChoice ; ; 
private JTextField theColor; 

//no arg GUI construtor gets user input and constructs color 
public MyColorChooser4() { 

//default layout of panel is set to GridLayout 4 cols 4 rows 
this.setLayout(new GridLayout(4, 4)); 


greenInput = new JLabel("Green: "); 
greenSlider = new JSlider(SwingConstants.HORIZONTAL, 0, 255, 1); 
greenChoice = new JTextField("0", 4);//default text 
greenChoice.setEditable(false); 

add(greenInput); 
add(greenSlider); 
add(greenChoice); 

redInput = new JLabel("Red: "); 
redSlider = new JSlider(SwingConstants.HORIZONTAL, 0, 255, 1); 
redChoice = new JTextField("0", 4);//default text 
redChoice.setEditable(false); 

add(redInput); 
add(redSlider); 
add(redChoice); 

blueInput = new JLabel("Blue: "); 
blueSlider = new JSlider(SwingConstants.HORIZONTAL, 0, 255, 1); 
blueChoice = new JTextField("0", 4);//default text 
blueChoice.setEditable(false); 

add(blueInput); 
add(blueSlider); 
add(blueChoice); 

//set default color black and declare inner class event handlers 
//sliders utlise ChengeListeners 

greenSlider.addChangeListener(new SlideHandler()); 
redSlider.addChangeListener(new SlideHandler()); 
blueSlider.addChangeListener(new SlideHandler()); 

colorChoice = Color.RED; 

//label to diplay color chosen, and blnk JLabel to move color to center 
theColor = new JTextField(4); 
JLabel preview = new JLabel(" "); 
add(preview); 
add(theColor); 
theColor.setBackground(colorChoice); 


}//end GUI constructor 

//set color 
public void setSlideColor(Color colorSlide) { 
colorChoice = colorSlide; 

}//end set colorChoice 

//get methods for fields 
public Color getColor() { 

return colorChoice; 

}//end getColor 

//return slider for red value 
public JSlider getRedSlider() { 
return redSlider; 
}//edn get red slider 

//retirn slider for green value 
public JSlider getGreenSlider() { 
return greenSlider; 
}//edn getGreenSlider 

//return slider for blue value 
public JSlider getBlueSlider() { 
return blueSlider; 
}//end getGreenSlider 

//private inner class for event handliing on sliders & implement abstract class 
private class SlideHandler implements ChangeListener { 

private Color colorSlide; 

@Override 
public void stateChanged(ChangeEvent e) { 

//return integers from sliders 
int blue = blueSlider.getValue(); 
int green = greenSlider.getValue(); 
int red = redSlider.getValue(); 

//now construct a new color based on these values 

colorSlide = new Color(red, green, blue); 
setSlideColor(colorSlide); 


//display integer value of color chosen in relative textfield 
//use String method valueOf to return string rep of integer 
//display chossen color in text area 
redChoice.setText(String.valueOf(red)); 
redChoice.setBackground(new Color(red, 0, 0)); 
greenChoice.setText(String.valueOf(green)); 
greenChoice.setBackground(new Color(0, green, 0)); 
blueChoice.setText(String.valueOf(blue)); 
blueChoice.setBackground(new Color(0, 0, blue)); 

//set chosen color preview 
theColor.setBackground(colorChoice); 
theColor.setText("Preview"); 


}//end stateChanged method 
}//end inner class SlideHandler 
}//end class MyColorChooser4

Then Class ShapePanel which is a menu for which user can select various attributes of a shape to be drawn including colour. Color determined thrught slection via a JComobobox of an array of clolor objects. The colour from MyColorCHooser4 is acquired via an instance of teh class invoking the its getColor method:

declaration and intilisation of the above

public DrawPanel draw = new DrawPanel(); 
private MyColorChooser4 sliderColor = new MyColorChooser4(); 

//array holding color objects 
private Color colors[] = {Color.BLACK, Color.BLUE, Color.CYAN, 

Color.DARK_GRAY, Color.GRAY, Color.GREEN, Color.LIGHT_GRAY, 
Color.MAGENTA, Color.ORANGE, Color.PINK, Color.RED, Color.WHITE, 
Color.YELLOW, sliderColor.getColor()}; 

//array carrying color strings 
private String colorNames[] = {"Black", "Blue", "Cyan", 
"Dark Gray", "Gray", "Green", "Light Gray", "Magenta", 
"Orange", "Pink", "Red", "White", "Yellow", "Slider Color"};

Event handler method of class ShapePanel which allows selection of colour....

color = new JComboBox(colorNames); 
color.setMaximumRowCount(6); 
color.addItemListener(new ItemListener() { 

@Override 
public void itemStateChanged(ItemEvent e) { 

if (e.getStateChange() == ItemEvent.SELECTED) { 
draw.setCurrentColor((colors[color.getSelectedIndex()]));; 

} //end if 
}//end itemStateChnaged 
});//end annmonouys class and action event method 

componments.add(color); 

The instance draw of class DrawPanel sets the colour the shape shoudl be drawn in via the following set method.....

//set current color 
public void setCurrentColor(Color color) { 


//set currentColor from JCombox input handler 
currentColor = color; 


//generate a random startColor for Gradient color 
int red = (int) (Math.random() * 256); 
int green = (int) (Math.random() * 256); 
int blue = (int) (Math.random() * 256); 

//cyclic vs acylic fill 
colorFillStyle = new Random(); 
boolean gradientShift = colorFillStyle.nextBoolean(); 



 //create gradient object 
 Color startColor = new Color(red, green, blue); 
 gradientColor = new GradientPaint(10f, 10f, startColor, 350f, 350f, currentColor,         gradientShift); 


}//end set color method

However when the shape is drawn the colour is always red, reflecting the colour intilization value in the MyColorChooser4 constructor....

Hopefully this is somewhat useful......

Answer 1

Without seeing your code, it is impossible to know for certain what the issue is, but there are a couple of possibilities:

1: The set method in your outer class is incorrect. Seems unlikely, but always worth checking since perhaps it is written as:

public void setColor(Color color)
{
    // Should be this.color =
    color = color;
}

2: Your inner class is not calling the outer classes set method, perhaps the inner class has declared its own set method that takes precedence in your call.

3: The inner class is never actually being called, possibly because your event is not being triggered.

Ultimately, your setMethod is not being called, it is not doing what you think it should be doing, or something else is resetting the value after you call the set method. As far as I can tell, these are the only possibilities for why your value would not be set as expected.

If you post your code then we can arrive at a more specific answer to your problem.

Answer 2

@increment1 I avoided the the singleton tactic and got wat i needed by creating all instances req in the one class and achieved the changes needed by attaching listeners to event handlers . .

My problem was i was expecting the same behaviour from two separate instances of my drawPanel class, not well thought out and inexperience.

Thanks again C