Incompatible types: getFragmentManager not working

Question

After importing android.support.v4.app.FragmentManager it still shows an error concerning getFragmentManager. It says Required: android.support.v4.app.Fragmentmanager, but Found: android.app.FragmentManager.

Which is weird because the latter isn't even imported into the library. I'am working in API 15 therefore I read in other topics the reason could be that I have to use getSupportFragmentManager.

Unfortunately, I can't reach SupportFragmentManager what is going wrong? Might be a problem with the import library?

package com.example.slidenerdinterfrag;

import android.app.Activity;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends Activity implements Communicator{

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

    @Override
    public void respond(String data) {
        FragmentManager manager=getFragmentManager();
        FragmentB f2= (FragmentB) manager.findFragmentById(R.id.fragment2);
        f2.changeText(data);
    }
}

Answer 1

Use getSupportFragmentManager instead

@Override public void respond(String data) { FragmentManager 
manager=getSupportFragmentManager(); FragmentB f2= 
(FragmentB) manager.findFragmentById(R.id.fragment2); 
f2.changeText(data); }