編程生活

如下代碼會(huì)出問題
public class C {
    private String c1;

    private String c2;

    public void setC1(String c1) {
        this.c1 = c1;
    }

   public String getC1() {
        return this.c1;
    }

    public void setC2(String c2) {
        this.c2 = c2;
    }

   public String getC2() {
        return this.c2;
    }
}

public abstract class A extends Composite {
    public A(Composite parent, int style) {
        super(parent, style);
        createMainBody(parent);
        createOtherBox();
    }
    
    protected abstract void createMainBody(Composite parent);
    protected abstract void createOtherBox(Composite parent);
}

public class B extends A{
    private Text b1 = null; //VE生成的
    ...
    private C c = new C();

    public B(Composite parent, int style) {
        super(parent, style);
    }
    
    protected void createMainBody(Composite parent) {
        b1 = new Text(parent, SWT.NONE);
        b1.addModifyListener(new ModifyListener() {
            public void modifyText(ModifyEvent e) {
                c.setC1(b1.getText());
                fireFormDataChange();
            }
        });
        b1.setText("Hello...");
        ...
    }
    ...
}
一運(yùn)行代碼出錯(cuò)了，經(jīng)過調(diào)試才發(fā)現(xiàn)B初始化時(shí)，在super(..)執(zhí)行完之前并沒有初始化本類（這是對(duì)的），自己的代碼實(shí)現(xiàn)有問題．
注意：類初始化時(shí)，首先初始化父類，再初始化本類的變量聲明部分，初始化父類時(shí)如果回調(diào)到子類的某些類的實(shí)現(xiàn)，而這些實(shí)現(xiàn)方法又完成了對(duì)聲明變量的創(chuàng)建，再回來初始化本類時(shí)，如果聲明變量有初始值，又會(huì)將這些變量設(shè)置到初始值狀態(tài)，因此，會(huì)發(fā)現(xiàn)這些變量無法訪問了．一切都是對(duì)的，只是自己太相信ＶＥ生成的代碼了．
改動(dòng)很簡(jiǎn)單，只是將
public class B extend   A { 
    private Text b1;    
    ...
    private C c;

    public B(Composite parent, int style) {
        super(parent, style);
    }
    
    protected void createMainBody(Composite parent) {
        c = new C();
        ...
    }
}
好，這樣就一切OK．類的初始化過程的學(xué)習(xí)還是很重要的．