Easiest way to return double from another class

Question

I wish to return a double from another class depending on input doubles. Any good links/examples to very simple project structure examples would be appreciated. Am I missing something in manifest. ie. activity 1

import com.example.app.utils.getRhumbLineBearingUtil;


double tbearing =             getRhumbLineBearing(alata,alona,alatb,alonb);

double recipbearing=getRhumbLineBearing(alatb, alonb, alata, alona);

Activity 2 import com.example.app.utils.getRhumbLineBearingUtil;

 double lattocbearing = getRhumbLineBearing(lat,lon,alatc,alonc);

 double bcbearing=getRhumbLineBearing(alatb, alonb, alatc, alonc);

(I do this over many activities with 15 different returns with some inputs ie gps points changing rapidly)

Class package com.example.app.utils;

public class getRhumbLineBearingUtil
{


public double getRhumbLineBearing(double $lat1, double $lon1, double $lat2, double $lon2)
  {Yada=trueRhumb  ;
double Bearing=yada;
Return (bearing);
      }
}

I am not interested in bearingTo which is the initial bearing hearing.

I don't know what you mean. Classes don't return values. Methods do. What are you trying to do? — Simon, Jan 26 '15 at 22:25
Have a method in another class return a value. Is this possible? Or get it back easily or I may have to put this method into every class I use it which will eventually get messy. — Tomsmith, Jan 26 '15 at 22:26
Of course it is. Do you need class instances (objects) or statics? — Simon, Jan 26 '15 at 22:27

richard slond · Accepted Answer · 2015-01-26T22:40:58.747

You should first learn a bit of Java programming and then move-up to android. You cannot do that that way. Try this:

Class GetRhumbLineBearingUtil {    

    public static double getRhumbLineBearing(double lat1, double lon1, double lat2, double lon2) {
        return lat1 + lon1;
    }
}

And then in another class, after import and whatever you wanna use that method for, just call it like this:

double lattocbearing = GetRhumbLineBearingUtil.getRhumbLineBearing(alatb, alonb, alata, alona);

Some notes here: static methods can be accessed via ClassName.methodName

This was what i understood from the question. Now if you want to exchange data between activities, then that is another story, you can use intents.

Some notes tho:

Class names start with upperCase
Classes, methods and method arguments should have a proper name/meaning to make it easier to understand what is being done.
Variable names start lowerCase
There is no $variable in Java, everything is passed by value
If you want to return some value stored in a variable in class GetRhumbLineBearingUtil you need to make that variables static as well.

I am learning, the app works but am trying to make the code and structure more readable and efficient. I spent ages yesterday researching and the last five minutes laughing at myself. So simple. — Tomsmith, Jan 26 '15 at 22:44

score 0 · Answer 2 · answered Jan 26 '15 at 22:29

If what you mean is how to exchange data between two activities and you would like to pass some double values, you should use the method putExtra(String name, double value) or putExtra(String name, double[] value) and get them from the second activity onCreate(Bundle savedInstanceState) method.

Otherwise use a static method that contains your method code.

public class Utils {

public static double getRhumbLineBearing(double latA, double lonA, double latB, double lonB) {
    [your code]
}
}

Easiest way to return double from another class

2 Answers2

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