从活动引用私有帮助程序类

Question

I need to use some methods from a helper class but having trouble when I try to create a object of the helper class in my activity.

HelperClass helper = new HelperClass();

When I do the above I get an error saying I need to make the visibility of Helper() default. Here is the relevant part of the helper class.

public class HelperClass {

private static HelperClass helperClass;
private String list;

private HelperClass() {
    initialiseHelper();
}

When I take out the private in the HelperClass it is fine but I do not want to edit this class. Is there a way around this?

Answer 1

It looks like you're trying to apply Singleton pattern, but you're missing the getInstance() method, which should look like this:

public static synchronized HelperClass getInstance() {
    if (helperClass == null) {
        helperClass = new HelperClass();
    }
    return helperClass;
}

Now you should use this method everywhere you want to reference an instance of HelperClass . Hope this helps.

Answer 2

如果你想要私有构造函数你可以从HelperClass制作单例。

Answer 3

Your Helper class does not have a public constructor as you have marked it private .

Or

public HelperClass{

   private HelperClass(){
   // do some stuff
   }

   public static HelperClass newInstance(){
       new HelperClass();
   }
}

Or use Singleton Pattern