Get value from different class in android/java

Question

I want to get a return value from a function From CLass A in class B. But i do not want to create a new instance of class A in Class B. Since all the variable value in class a are null if i create a new instance. I also cannot use static in the function because i dont get access to non static varible. I have tried using aync task/ handler to but cannot find any way to return value from handle message>

public class ClassA(){
     List<String> stringlist;

    public List<String> getStringlist() {
    //code  
    return stringlist;
     }
}

public class ClassB(){

    public void getValueFromCLassA {
        ClassA classA = new ClassA();
        List<string> string = classA.getStingList();
    }
}

score 0 · Answer 1 · edited May 23 '17 at 11:50

0

You have 2 ways to do this...

you can send data between activities using parcelable or
you can use Global variables over the hole application.

for the 1st one check my answer here: for the 2nd one: check my answer here:

the 2nd option looks like what you are looking for....

edited May 23 '17 at 11:50

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answered Feb 12 '16 at 16:31

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score 0 · Answer 2 · answered Feb 12 '16 at 16:40

Create your reference to ClassA outside of the getValueFromClassA method. There is no way around "making an instance of class A" to GET a member from class A, unless that member is shared in a different class higher in hierarchy. It's part of the fundamentals of OOP. You can, however, SET ClassB's list by creating a setter method in ClassB and forcing ClassA to send its list to ClassB. The only difference here is now ClassA needs a reference to ClassB and Class *doesn't need a reference to ClassA.

public class ClassA()
{
    List<String> stringList;

    public List<String> getStringlist()
    {
        //code  
        return stringList;
    }
}

public class ClassB()
{
    ClassA classA = new ClassA();
    List<string> stringListB;    

    public void getValueFromClassA()
    {
       stringListB = classA.getStringList();
    }
}

score 0 · Answer 3 · answered Feb 12 '16 at 16:45

Just save the variables that you need as a global variable. I recommend you having something like this:

public class Environment extends Application {

    public String globar_var = null;
}

//Manifest

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme"
    android:name=".Environment">  <---------- where the magic happens



After this, you can access the var like this from anywhere in your app:

((Environment) getApplicationContext()).globar_var == "It should work!!"

Hope it helped, let me know how it went :)

Get value from different class in android/java

3 Answers3