dynamicactionadapter.java

learning java的源代码。书中每个实例都有相关的代码example。

//file: DynamicActionAdapter.java
import java.awt.*;
import java.util.Hashtable;
import java.lang.reflect.Method;
import java.awt.event.*;

class DynamicActionAdapter implements ActionListener {
  Hashtable actions = new Hashtable(  );

  public void hookup( Object sourceObject, Object targetObject,
                      String targetMethod ) {
    actions.put(sourceObject,
      new Target(targetObject, targetMethod));
    invokeReflectedMethod( sourceObject, "addActionListener",
      new Object[] {this}, new Class[] {ActionListener.class});
  }

  public void actionPerformed(ActionEvent e) {
    Target target = (Target)actions.get( e.getSource(  ) );
    if ( target == null )
      throw new RuntimeException("unknown source");
    invokeReflectedMethod(target.object, target.methodName,
                          null, null);
  }

  private void invokeReflectedMethod(
    Object target, String methodName,
    Object [] args, Class [] argTypes ) {

    try {
      Method method =
        target.getClass(  ).getMethod( methodName, argTypes );
      method.invoke( target, args );
    }
    catch ( Exception e ) {
      throw new RuntimeException("invocation problem: "+e);
    }
  }

  class Target {
    Object object;
    String methodName;

    Target( Object object, String methodName ) {
      this.object = object;
      this.methodName = methodName;
    }
  }
}