Java JSlider和JTextField数组更改侦听器-从内部类引用的局部变量必须是final或有效final
我正在做作业,我必须按照给我的模板来完成这个申请。 我得到了两个数组,一个是JTextField[],另一个是JSlider[] 这就是它报告错误的地方:Java JSlider和JTextField数组更改侦听器-从内部类引用的局部变量必须是final或有效final,java,arrays,swing,jtextfield,jslider,Java,Arrays,Swing,Jtextfield,Jslider,我正在做作业,我必须按照给我的模板来完成这个申请。 我得到了两个数组,一个是JTextField[],另一个是JSlider[] 这就是它报告错误的地方: for (ix = 0; ix < cc.length; ++ix) { gbc.gridy = ix; gbc.gridx = 0; JLabel label = new JLabel(cc[ix]); panel.add(label, gbc); /* create a slider, s
for (ix = 0; ix < cc.length; ++ix)
{
gbc.gridy = ix;
gbc.gridx = 0;
JLabel label = new JLabel(cc[ix]);
panel.add(label, gbc);
/* create a slider, set its options, and add it to the panel */
csld[ix] = new JSlider(0, 255);
csld[ix].addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(ChangeEvent e) {
txt[ix].setText(Integer.toString(e.getSource())); //ERROR
}
});
panel.add(csld[ix], gbc);
gbc.gridx = 2;
/* create a JTextField, set its options, and add it to the panel */
txt[ix] = new JTextField();
txt[ix].setText(Integer.toString(csld[ix].getValue()));
System.out.println(Integer.toString(csld[ix].getValue()));
panel.add(txt[ix], gbc);
/* add a change listener */
txt[ix].addKeyListener(new KeyAdapter() {
@Override
public void keyReleased(KeyEvent e) {
JTextField jtf = (JTextField)e.getSource();
String typed = jtf.getText();
if(!typed.matches("\\d+") || typed.length() > 3) {
return;
}
int value = Integer.parseInt(typed);
csld[ix].setValue(value); //ERROR
}
});`
我不确定为什么会显示此错误,并且没有其他StackOverflow答案帮助我诊断它。我将在此处发布相关代码:
//imports
public class AssignRGBSliders implements Runnable
{
static int width = 320;
static int height = 128;
static String title = "RGB Sliders";
static int FIELD_WIDTH = 3;
static int RED = 0;
static int GREEN = 1;
static int BLUE = 2;
static int MIN = 0;
static int MAX = 1;
static String[] cc = {"Red", "Green", "Blue"};
static int[][] RGB_MNMX = {{0, 255}, {0, 255}, {0, 255}};
JFrame application;
JTextField[] txt;
JSlider[] csld;
JPanel colorPanel;
int[] curColor = {0, 0, 0};
public void run()
{
JPanel panel, panel2;
int ix;
GridBagConstraints gbc = new GridBagConstraints();
gbc.anchor = GridBagConstraints.FIRST_LINE_START;
application = new JFrame();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
application.setTitle(title);
panel = new JPanel();
panel.setBorder(BorderFactory.createEmptyBorder(4, 4, 4, 4));
panel.setLayout(new GridBagLayout());
application.add(panel);
csld = new JSlider[cc.length];
txt = new JTextField[cc.length];
for (ix = 0; ix < cc.length; ++ix)
{
gbc.gridy = ix;
gbc.gridx = 0;
JLabel label = new JLabel(cc[ix]);
panel.add(label, gbc);
gbc.gridx = 1;
/* create a slider, set its options, and add it to the panel */
csld[ix] = new JSlider(0, 255);
csld[ix].addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(ChangeEvent e) {
JSlider slider = (JSlider)e.getSource();
txt[ix].setText(Integer.toString(e.getSource()));
}
});
panel.add(csld[ix], gbc);
gbc.gridx = 2;
/* create a JTextField, set its options, and add it to the panel */
txt[ix] = new JTextField();
txt[ix].setText(Integer.toString(csld[ix].getValue()));
System.out.println(Integer.toString(csld[ix].getValue()));
panel.add(txt[ix], gbc);
/* add a change listener */
txt[ix].addKeyListener(new KeyAdapter() {
@Override
public void keyReleased(KeyEvent e) {
JTextField jtf = (JTextField)e.getSource();
String typed = jtf.getText();
if(!typed.matches("\\d+") || typed.length() > 3) {
return;
}
int value = Integer.parseInt(typed);
csld[ix].setValue(value);
}
});
/* slider.addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(ChangeEvent e) {
jtf.setText(Integer.toString(slider.getValue()));
}
}); */
}
colorPanel = new ColorPanel();
colorPanel.setPreferredSize(new Dimension(width / 2, height / 2));
++gbc.gridy;
gbc.gridx = 0;
gbc.gridwidth = 3;
panel.add(colorPanel, gbc);
application.setSize(width, height);
application.setLocationRelativeTo(null);
application.pack();
application.setVisible(true);
}
public static void main(String[] args)
{
AssignRGBSliders dp = new AssignRGBSliders();
SwingUtilities.invokeLater(dp);
}
class SliderChange implements ChangeListener
{
/* instance variables */
/* constructor */
public SliderChange() {
}
/* implement the interface */
public void stateChanged(ChangeEvent e) {
JSlider source = (JSlider) e.getSource();
System.out.println("Sukurac: " + source);
}
}
class ColorPanel extends JPanel {
public void paint(Graphics gr) {
super.paint(gr);
gr.setColor(new Color(csld[0].getValue(), csld[1].getValue(), csld[2].getValue()));
System.out.println(csld[0].getValue() + " " + csld[1].getValue() + " " + csld[2].getValue());
gr.fillRect(0, 0, this.getWidth(), this.getHeight());
}
}
}
提前谢谢你 您的txt[ix]变量不是最终变量,因此当您在内部类中使用它时,编译器会显示该错误:
csld[ix].addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(ChangeEvent e) {
对于您的问题,我建议您更改代码如下:
csld[ix].addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(ChangeEvent e) {
JSlider slider = (JSlider)e.getSource();
JTextField t = new ...//create instance
t.setText(Integer.toString(e.getSource()));//set text
txt[ix] = t; //add current JTextField to array
}
});
ix是您试图使用它的上下文中的一个局部变量,编译器无法确定将来某个时候它的值,即使可以,它也可能类似于cc.length-1
我的一般建议是使用HashMap将JTextField映射到JSlider
问题是列表很容易不同步,所以我更喜欢地图
我们还没有学会/不允许使用List/ArrayList
好的。我们做得很辛苦
基本上,您有一个对触发事件的JSlider的引用,我们需要知道它在csld中的索引,以便我们可以查找相应的JTextField
所以现在,您不是更新屏幕上的字段,而是更新JTextField的一些新实例。。。这不会显示在屏幕上,所以你用一个问题代替另一个问题。嗨,你的回答真的帮了我很大的忙!我修复了代码中的两个错误:D如果不是问题,我还有一个问题。。。我将ColorPanel设置为使用3个滑块的RGB值绘制一个矩形。但是,当我更新滑块时,paint方法中的值不会!如何调用这些值的更新,从而更改矩形的颜色?我通过添加curColor[index]=slider.getValue;发送到csld侦听器。我没有使用SliderChange类,所以我希望他们不会对此产生问题:/只要在我得到新的curColor[I]值时重新绘制整个颜色面板:D
Map<JSlider, JTextField> fieldMap;
//...
fieldMap = new HashMap<>();
//...
JSlider slider = new JSlider(0, 255);
JTextField field = new JTextField(10);
fieldMap.put(slider, field);
slider.addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(ChangeEvent e) {
JSlider slider = (JSlider) e.getSource();
JTextField field = fieldMap.get(slider);
field.setText(Integer.toString(slider.getValue()));
}
});
List<JTextField> fieldList;
List<JSlider> sliderList;
//...
JSlider slider = new JSlider(0, 255);
JTextField field = new JTextField(10);
fieldList.add(field);
sliderList.add(slider);
slider.addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(ChangeEvent e) {
JSlider slider = (JSlider) e.getSource();
int index = sliderList.indexOf(slider);
JTextField field = fieldList.get(index);
field.setText(Integer.toString(slider.getValue()));
}
});
csld[ix].addChangeListener(new javax.swing.event.ChangeListener() {
public void stateChanged(ChangeEvent e) {
JSlider slider = (JSlider) e.getSource();
for (int index = 0; index < csld.length; index++) {
if (csld[index] == slider) {
txt[index].setText(Integer.toString(slider.getValue()));
break;
}
}
}
});