Question

我正在尝试从WebView类访问setName方法，但是当我在调用callSetNameFunction中出现错误时出现错误。我创建了新的webview对象并将其存储在webfragment类的对象中，但是无法访问webview类中的方法。我怎样才能做到这一点。我还没有做过很长时间的java，还在学习。

WebView类

public class WebView {

    private String name;

    public WebView (String name) {
        this.name = name;
    }

    public WebView () {
        this.name = name;
    }

    public void setName(String name) {
        if(name != null) {
            this.setName(name);
        } else {
            System.out.println("Thats not his name");
        }
    }

    public String getName() {
        return name;
    }   
}

WebFragment类

public class WebFragment {

    Object myObject;

    public WebFragment() {
        myObject = new WebView();
    }

    public Object getWebView() {
        return myObject; 
    }

    public void callSetNameFunction() {
        myObject.setName();
    }
}

Answer 1

3次更正

Object myObject必须为WebView myObject;
_{如果要使用WebView对象中的方法，如果要使用myObject类，则必须将WebFragment类的WebView属性声明为getter类型它声明的方法。

注意：您还必须将public WebView getWebView() {签名更改为myObject.setName();}
myObject.setName("name");应该收到一个参数，例如：public WebView () { this.name = name; // Warning: The assignment to variable name has no effect }

不带参数的构造函数在设置变量时不起作用：

public WebView () {
}

必须是：

#include <memory>
#include <iostream>
#include <vector>
using std::cout;
using std::endl;
using std::vector;

//base class
class Car
{ public:
    Car(int speed): speed(speed) {};
    Car(const Car& c): speed(c.speed)
    { cout <<"Copy Constructor Car" <<endl;
    }
    virtual void display()
    { cout <<" speed: " <<speed <<endl;
    }
    virtual Car* clone()const =0;  // virtual copy constructor
  private:
    int speed;
};
typedef std::shared_ptr<Car> CarP;
class Garage
{ private:
    vector<CarP> cars;
  public:
    Garage() {}
    //copy constructor of the garage
    Garage(const Garage &toCopy)
    { cout <<"Copy Constructor Garage" <<endl;
      for (CarP c : toCopy.cars)
      { CarP cp(c->clone());
        ReceiveCar(cp);
      }
    }
    void ReceiveCar(CarP toCopy)
    { cars.push_back(toCopy);
    }
    void display()
    { for (CarP c : cars)  c->display();
    }
};
class Saab: public Car
{ public:
    Saab(int speed): Car(speed)
    { cout <<"Constructor Saab" <<endl;
    }
    void display()
    { cout <<"Car: Saab";  Car::display();
    }
    Saab* clone()const
    { return new Saab(*this);
    }
};
class AstonMartin: public Car
{ public:
    AstonMartin(int speed): Car(speed)
    { cout <<"Constructor AstonMartin" <<endl;
    }
    AstonMartin(const AstonMartin& toCopy): Car(toCopy)
    { cout <<"Copy Constructor AstonMartin" <<endl;
    }
    void display()
    { cout <<"Car: AstonMartin";  Car::display();
    }
    AstonMartin* clone()const
    { return new AstonMartin(*this);
    }
};
int main()
{
  CarP saab  =std::make_shared <Saab>(100);
  CarP aston =std::make_shared <AstonMartin>(200);
  Garage montreal;
  montreal.ReceiveCar(saab);
  montreal.ReceiveCar(aston);
  montreal.display();
  Garage miami(montreal);  // your decision to offer the user a copy constructor:
  miami.display();
}

Answer 2

将您的方法更改为以下

public void setName(String name) {
    if(name != null) {
        //this.setName(name);
       this.name=name;
    } else {
        System.out.println("Thats not his name");
    }
}

还有这个：

public void callSetNameFunction() {
    WebView wvob=(WebView)myObject;
    wvob.setName("ola");    
}

setName方法与WebView类有关。对象类引用无法找到它。

此方法是未定义类型的对象

2 个答案: