java - Fragment add or replace not working

Question

I'm using the code from this reference.

When I put in that code in my program I get an error as seen in the picture below.

Any reasons for the error? The method replace(int, Fragment) in the type FragmentTransaction is not applicable for the arguments (int, ExampleFragments)

Code from my main activity:

public void red(View view) {
        android.app.FragmentManager fragmentManager = getFragmentManager();
                android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        ExampleFragments fragment = new ExampleFragments();
        fragmentTransaction.replace(R.id.frag, fragment);
        fragmentTransaction.commit();
    }

ExampleFragments.java

package com.example.learn.fragments;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class ExampleFragments extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.blue_pill_frag, container, false);
    }
}

Here:

package com.example.learn.fragments;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;

Answer 1

The problem here is that you're mixing android.support.v4.app.Fragment and android.app.Fragment. You need to convert all uses to use the support library, which also means calling getSupportFragmentManager().

Something like this, for example:

    android.support.v4.app.FragmentManager fragmentManager = getSupportFragmentManager();
    android.support.v4.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    ExampleFragments fragment = new ExampleFragments();
    fragmentTransaction.replace(R.id.frag, fragment);
    fragmentTransaction.commit();

It is important to note that the support library Fragment and the normal Fragment are NOT interchangeable. They achieve the same purpose, but they cannot be replaced with one another in code.