假設有一個對象TFFrame,我要在另一個對象中對他的成員進行操作,可以這樣寫:
class MyMonitor implements ActionListener {
TFFrame ft = null;
public void MyMonitor(TFFrame ft) {
this.ft = ft;
}
public void actionPerformed(ActionEvent e) {
int n1 = Integer.parseInt(ft.num1.getText());
int n2 = Integer.parseInt(ft.num2.getText());
ft.num3.setText("" + (n1 + n2));
}
}
調試時,程式出錯,發現
public void MyMonitor(TFFrame ft)
中的
void
在實作接口的構造函數中是不能用的,删除後正常
下面是完整代碼:
import java.awt.*;
import java.awt.event.*;
public class TestMath {
public static void main(String[] args) {
new TFFrame().launchFrame();
}
}
class TFFrame extends Frame {
TextField num1, num2, num3;
public void launchFrame() {
num1 = new TextField();
num2 = new TextField();
num3 = new TextField();
Label plus = new Label("+");
Button equal = new Button("=");
MyMonitor bf = new MyMonitor(this);
equal.addActionListener(bf);
setLayout(new FlowLayout());
add(num1);
add(plus);
add(num2);
add(equal);
add(num3);
pack();
setVisible(true);
}
}
class MyMonitor implements ActionListener {
TFFrame ft = null;
public MyMonitor(TFFrame ft) {
this.ft = ft;
}
public void actionPerformed(ActionEvent e) {
int n1 = Integer.parseInt(ft.num1.getText());
int n2 = Integer.parseInt(ft.num2.getText());
ft.num3.setText("" + (n1 + n2));
}
}
特别注意,在
class TFFrame extends Frame
對象中聲明的另一個對象
MyMonitor bf = new MyMonitor(this); 用this指向對象自身