匿名 class 实现接口，不能有 arguments

Question

i have some code that i am trying to recompile and understand, but i have a method that does not compile and i wish to find the good work around. the method is as follows.

private void launchEventPanel(String title) { 
    EventQueue.invokeLater(new Runnable(title) { 
        public void run() { 
        JFrame myFrame = new JFrame(); 
        myFrame.setTitle("Conference Call"); 
        myFrame.setIconImage(CallConference.this.myCore.myPanel.myIconManager.getPromptIcon(CallEMart.class.toString())); 
        myFrame.getContentPane().add(CallConference.this.myEventPanel, "Center"); 
        myFrame.pack(); 
        myFrame.setVisible(true); } }); }

the second line of the EventQueue.invokeLater does not compile, i get the error "Anonymous class implements interface, cannot have arguments".

any help and work around is highly appreciated. thanks!

Answer 1

That's because Runnable is just an interface and it doesn't take any argument as an anonymous class. To get around it, you can assign final to the upper parameter:

private void launchEventPanel(final String title) { 
    EventQueue.invokeLater(new Runnable() { 
        public void run() { 
        JFrame myFrame = new JFrame(); 
        myFrame.setTitle("Conference Call");  
        myFrame.setIconImage(CallConference.this.myCore.myPanel.myIconManager.getPromptIcon(CallEMart.class.toString())); 
        myFrame.getContentPane().add(CallConference.this.myEventPanel, "Center"); 
        myFrame.pack(); 
        myFrame.setVisible(true); } }); }

Answer 2

Well, it is what it says, you can't give arguments to a Runnable "constructor" because there is no constructor -- it's an interface.

Instead, declare title final , and use it directly inside the inner class.

Answer 3

private void launchEventPanel(final String title) { 
    EventQueue.invokeLater(new Runnable() { 
        public void run() { 
        JFrame myFrame = new JFrame(); 
        myFrame.setTitle("Conference Call"); 
        myFrame.setIconImage(CallConference.this.myCore.myPanel.myIconManager.getPromptIcon(CallEMart.class.toString())); 
        myFrame.getContentPane().add(CallConference.this.myEventPanel, "Center"); 
        myFrame.pack(); 
        myFrame.setVisible(true); } }); }

And you're done. Although as far as I can see, you're not actually using the value of title anywhere in your code.

Answer 4

You can convert your anonymous class into nested class. It will allow you to pass parameters into constructor.

private static final MyRunnable implements Runnable {

    private final String title;

    public MyRunnable(String title) {
        this.title = title;
    }

    @Override
    public void run() {
        // use title here
    }

}    

Answer 5

Runnable is an interface and so it does not contain a constructor which accepts a string, which you are doing in this line: EventQueue.invokeLater(new Runnable(title) {

If you want to use title in public void run() , just make title a final argument and you are free to use it within that method.

Answer 6

Well, as the message says: java.lang.Runnable is an interface so you cannot pass title to its constructor. Use:

EventQueue.invokeLater(new Runnable() { 

instead.

Note that title isn't used anywhere. If you need it inside the Runnable, you need to declare it final:

private void launchEventPanel(final String title) { 
EventQueue.invokeLater(new Runnable() { 
    public void run() { 
    JFrame myFrame = new JFrame(); 
    myFrame.setTitle(title);