Question

我有一个界面：

public interface ICustomObjectListingViews {
    View createCustomObjectListingView(MyDBObject myDBObject);
}

然后：

public abstract class AbstractICustomObjectListingViews implements ICustomObjectListingViews {

@Override
    public View createCustomObjectListingView(MyDBObject myDBObject) {
        return null;
    }
}

然后我尝试通过扩展抽象类来实现接口：

public class MyCustomObjectListingView extends AbstractICustomObjectListingViews {

@Override
    public VIew createCustomObjectListingView(MyDBObject myDBObject) {
        Log.v("MyApp", ">>>> " + myDBObject.get_myObjectDescription());

        TextView textView = new TextView(mContext);
        textView.setText(myDBObject.get_myObjectDescription());

        return textView;
    }
}

我使用MyObject来映射我的数据库结果：

public class MyDBObject {
    public MyDBObject() {
    }

    private String _myObjectDescription;

    public void set_myObjectDescription(String _myObjectDescription) {
        this._myObjectDescription = _myObjectDescription;
    }

    public String get_myObjectDescription() {
        return _myObjectDescription;
    }
}

但是，每当我尝试调用MyCustomObjectListingView createCustomObjectListingView(MyDBObject myDBObject)的实现时，我都会得到一个空指针。

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String MyDBObject.get_myObjectDescription()' on a null object reference

at：

Log.v("MyApp", ">>>> " + myDBObject.get_myObjectDescription());

这就是我所说的：

MyDBObject myObject = new MyObject();
myObject.set_myObjectDescription("HELLO WORLD");

ICustomObjectListingViews iCustomObjectListingViews = new  MyCustomObjectListingView();
iCustomObjectListingViews.createCustomObjectListingView(myObject);

我错了什么？我应该如何打电话给最重要的班级＆＃39;覆盖方法？我怎样才能使上述尝试奏效？

提前谢谢大家。

Answer 1

如果您不知道如何在createCustomObjectListingView(MyDBObject myDBObject)中实施AbstractICustomObjectListingViews，请直接在具体类MyCustomObjectListingView中实施（以这种方式避免使用null } return。。

从AbstractICustomObjectListingViews中删除该方法，使其显示为

   public abstract class AbstractICustomObjectListingViews implements ICustomObjectListingViews {
     //other methods
}

并保持MyCustomObjectListingView原样。

如何调用具有参数的Abstract类overriden方法

1 个答案: