I'm new with fragments and I try to use these.
My xml from activity is:

```
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".Loguin"
tools:ignore="MergeRootFrame">

    <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Fragment Test"
    android:id="@+id/btn_FragmentTest"
    android:layout_gravity="center_horizontal"
    android:layout_marginTop="20dp"
    android:layout_marginBottom="0dp" />

    <LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:id="@+id/frgContainer"
    android:layout_marginTop="20dp">

    <fragment
        android:id="@+id/frgLoguin"
        android:layout_marginTop="20dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:name="habitatprojects.hubbuildings.Loguin$PlaceholderFragment"
        tools:layout="@layout/fragment_loguin" />

    </LinearLayout>

</LinearLayout>

```

And I want to change the fragment inside of LinearLayout, my class of mainActivity is:

```
public class Loguin extends Activity {

private int num = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_loguin);
    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
    }

    Button btnBoton1 = (Button)findViewById(R.id.btn_FragmentTest);

    btnBoton1.setOnClickListener(new View.OnClickListener() {
        public void onClick(View arg0)
        {
            FragmentManager fragmentManager = getFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

            if(num==0)
            {
                fragmentTransaction.replace(R.id.frgContainer, new PlaceholderFragment())
                        .commit();

                num++;
            }
            else{
                if(num==1)
                {
                    fragmentTransaction.replace(R.id.frgContainer, new PlaceholderFragment2())
                            .commit();

                    num++;
                }
                else{
                    fragmentTransaction.replace(R.id.frgContainer, new PlaceholderFragment3())
                            .commit();

                    num = 0;
                }
            }
        }
    });
 }

```

And my PlaceHolderFunctions are:

```
public static class PlaceholderFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_loguin, container, false);
    }
}

public static class PlaceholderFragment2 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return  inflater.inflate(R.layout.fragment_blank, container, false);
    }
}

public static class PlaceholderFragment3 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_blank2, container, false);
    }
}

```

Why doesn't work when I press the button? What do I doing bad? Srry for my english and thanks in advance!

PD: If you need more code or info advise me, thanks!

PD1: When I debug with my device the log cat just say me:

> 
> 11-18 11:33:30.775 6065-6065/habitatprojects.hubbuildings
>  I/ViewRootImpl﹕ ViewRoot's Touch Event : Touch Down 11-18 11:33:30.835
>  6065-6065/habitatprojects.hubbuildings I/ViewRootImpl﹕ ViewRoot's
>  Touch Event : Touch UP
> 
> 
>