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Android Studio – How can you call a method of an activity from another activity?

Here is my first activity

public class FirstActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_first);
    }

    public void addNumbers() {
        ////
    }

}


public class SecondActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
    }

     // I need to call addNumbers() from here
}

I have tried instantiating FirstActivity in SecondActivity like so but I get an error. And I also heard its not the best practice to instantiate the whole activity.

FirstActivity firstActivity = new FirstActivity();
firstActivity.addNumbers();
Tags:

3

Answers


  1. 0

    Instead of calling method in second activity, create a separate public class e.g. Functions.java, and implement it as

    public class Functions {
    public void addNumbers() {
        ////
    }
}

    Now in your second activity where you want to call the method

    public class SecondActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
        // Calling addNumbers() from here
        new Functions().addNumbers();
    }
}
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  2. 0

    Add the static keyword to your shared methods

    public static void addNumbers()

    Then use:

    FirstActivity.addNumbers();

    For more details check out this answer

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  3. 0

    It is better to put the mathematical operations in a repository and, if necessary, find the instance of that repository each time by calling its instance.
    You can use these codes.

    First Make this Repository

    public class CalculatorRepository {
    private static CalculatorRepository calculatorRepository = null;

    private CalculatorRepository() {

    }

    public static CalculatorRepository getInstance() {
        if (calculatorRepository == null) {
            synchronized (CalculatorRepository.class) {
                if (calculatorRepository == null) {
                    calculatorRepository = new CalculatorRepository();
                }
            }
        }
        return calculatorRepository;
    }

    public int AddFunction(int number1, int number2) {
        try {   // for  better handler (Optional)
            return number1 + number2;
        } catch (Exception e) {
            return 0;
        }
    }

    //  another function
    //  .
    //  .
    //  .
}

    Second Call Method

    Now you can easily use other methods inside by calling this class

    int result = CalculatorRepository.getInstance().AddFunction(nmuber1,nmunber2);
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