有关 setter 和 getter 的信息

Question

我正在广泛学习有关 getter 和 setter 的知识，但我似乎没有按我的方式进行。 我有一个名为 Apps_Info 的类，其中包含我的 setter 和 getter，并且我有我的主要活动 FavouriteApps，它有一个使用 Apps_Info 类的列表。
我试图从 FavouriteApps 的列表中获取包的名称，但仍然为 null。
请问有人可以告诉我该怎么做吗？下面是按顺序排列的代码：Apps_Info类和FavouriteApps活动

public class Apps_Info {
    private Bitmap bIcon;
    private String sName;
    private String sPacks_Name;

    public Apps_Info(Bitmap icon, String name, String Packs_Name) {
        bIcon = icon;
        sName = name;
        sPacks_Name = Packs_Name;
    }

    public void setIcon(Bitmap icon) {
        bIcon=icon;
    }

    public Bitmap getIcon() {
        return bIcon;
    }

    public void setName(String name) {
        sName=name;
    }

    public String getName() {
        return sName;
    }

    public void setPacks_Name(String Packs_Name) {
        this.sPacks_Name=Packs_Name;
    }

    public String getPacks_Name() {
        return sPacks_Name;
    }
}

FavouriteApps活动代码（部分）

String packname, packsname, apps_names;
Bitmap app_icon; 
Resources res = getResources();
List<Apps_Info> ListApps_Info = new ArrayList<Apps_Info>();
ListApps_Info.add(new Apps_Info(BitmapFactory.decodeResource(res, R.drawable.browser_app), "Browser", "com.browser"));
ListApps_Info.add(new Apps_Info(BitmapFactory.decodeResource(res, R.drawable.clock_app), "Alarm Clock", "com.alarm.clock"));
ListApps_Info.add(new Apps_Info(BitmapFactory.decodeResource(res, R.drawable.threegplus), "3G Secure Connection", "threeg.secureconnect"));

mGridView.setAdapter(new Apps_Info_Adapter(this, ListApps_Info));
Apps_Info packinfo = new Apps_Info(app_icon, apps_names, packname);
packsname = packinfo.getPacks_Name();
apps_names = packinfo.getName();
Log.i("The Pack_Name is " + packsname, "Pack Name");

Answer 1

你应该这样做。

for (int i = 0; i < ListApps_Info.size(); i++) {
    Apps_Info packinfo = ListApps_Info.item(i);
    packsname = packinfo.getPacks_Name();
    apps_names = packinfo.getName();
    Log.i("The Pack_Name is " + packsname, "Pack Name");
}

Answer 2

这是因为您从未在代码中初始化 packname 变量。

 String packname,packsname,apps_names;

当你这样做时：

 Apps_Info packinfo=new Apps_Info(app_icon, apps_names,packname);
 packsname=packinfo.getPacks_Name();

你的 getter 做得很好，如果它返回 null，这是正常的。