提示错误：The method replace in the type.. is not applicable for the argument......

在最近新学fragment的时候出现了一个错误：

The method replace(int, Fragment) in the type FragmentTransaction is not applicable for the arguments (int, MyFragment)

新建fragment的时候

Fragment newfragment =new MyFragment();
fragmentTransaction.replace(R.layout.activity_main,newfragment ).commit();提示错误：The method replace(int, Fragment) in the type FragmentTransaction is not applicable for the arguments (int, MyFragment)
错误代码：

package com.example.testforfragment;import android.os.Bundle;import android.app.Activity;import android.app.FragmentManager;import android.app.FragmentTransaction;import android.support.v4.app.Fragment;import android.support.v4.app.Fragment.*;import android.view.Menu;public class MainActivity extends Activity {

@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction  fragmentTransaction = fragmentManager.beginTransaction();
Fragment newfragment =new MyFragment();
fragmentTransaction.replace(R.layout.activity_main,newfragment ).commit();
}

@Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.main, menu);        return true;
}

}

修改：

package com.example.testforfragment;import android.os.Bundle;import android.app.Activity;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentActivity;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentTransaction;import android.view.Menu;public class MainActivity extends FragmentActivity {

@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction  fragmentTransaction = fragmentManager.beginTransaction();
Fragment newfragment =new MyFragment();
fragmentTransaction.replace(R.layout.activity_main,newfragment ).commit();
}

@Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.main, menu);        return true;
}

}

在出错的时候一直找不到根源，然后网上找了下，找到了问题所在点，转自http://www.cnblogs.com/1114250779boke/p/3867494.html