Java反射调用不起作用

Question

public class RunnableSupport implements Runnable {

private MyClient myClient;
private String frameType;

Method[] methodList;
Constructor<?> constructor;
Class<?> myClass;

private JFrame mainFrame;
private boolean mustClose;
private int width;
private int height;
private int x;
private int y;

public RunnableSupport(MyClient myClient, String frameType, int width,
        int height, int x, int y, boolean mustClose) {
    this.myClient = myClient;
    this.frameType = frameType;
    this.height = height;
    this.width = width;
    this.x = x;
    this.y = y;
    this.mustClose = mustClose;
}

@Override
public void run() {
    try {
        myClass = Class.forName("it.polimi.social.frame." + frameType);
        constructor = myClass
                .getDeclaredConstructor(new Class[] { MyClient.class });
        methodList = myClass.getDeclaredMethods();

        mainFrame = (JFrame) constructor.newInstance(myClient);
        mainFrame.setSize(width, height);
        mainFrame.setLocation(x, y);
        if (mustClose)
            mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainFrame.setVisible(true);
    } catch (InstantiationException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SecurityException e) {
        e.printStackTrace();
    } catch (IllegalArgumentException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    }
}

public JFrame getFrame() {
    return mainFrame;
}

public void invokeMethod(String method) {
    for (int i = 0; i < methodList.length; i++) {
        if (methodList[i].getName() == method) {
            try {
                methodList[i].invoke(mainFrame);
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }
            break;
        }
    }
}

I have a problem with reflection. I use this class as an universal runnable for various JFrame elements. For this reason I need to invoke methods via reflection. When I try to invoke a method I get this error:

Exception in thread "main" java.lang.NullPointerException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at it.polimi.social.frame.RunnableSupport.invokeMethod(RunnableSupport.java:83)
    at it.polimi.social.client.MyClient.main(MyClient.java:56)

even if it seems to be all right. The problem is when I try to invoke the method... I've also checked other questions but they were all different problems, even if similiar. Thank you!

EDIT: I've fixed the problem, thank to everyone.

Now I have another question regarding what I've done. Is it a good idea to have a single runnable that uses reflection instead of having a different runnable for each JFrame class? What concerns me is that using a single class each time that I invoke a method implies searching in the method list.

Answer 1

On this line:

if (methodList[i].getName() == method)

You should never compare strings with ==. Try changing this to .equals() and see if that helps.