null pointer exception on calling interface method implemented in other class

Question

I am trying to call the method getFailureDialog() of the interface OnSelectedListener. The method is implemented in MainActivity.java.

Answer 1

You need to modify Common and MainActivity. In Common add a basic constructor. Then activate the callback as shown in startMyCallback.

Common.java

public class Common
{

 public Common() {}

 OnSelectedListener mCallback;


 public interface OnSelectedListener 
 {
    public void getFailureDialog();
 }

 public void myRecord(String email)
 {
    mCallback.getFailureDialog();  //null pointer exception here
 }
}

MainActivity.java

public class MainActivity implements Common.OnSelectedListener
{

    Common common = new Common();

    public MainActivity()
    {

    }

    public void startMyCallback()
    {
        common.mCallback = this;
    }

    @Override
    public void getFailureDialog()
    {
        RecordFailure fd = new RecordFailure(); 
        fd.show(getSupportFragmentManager(), "dialog");
    }
}