\*\*\*\* I found the sulotion \*\*\*\*\*
all I add to do is to move all my function from "protected void onCreate(Bundle savedInstanceState)"
and put them in "public static class PlaceholderFragment extends Fragment implements View.OnClickListener". Thank you all.

I really new to all of this and I just can't manage to move from one activity to another...
I don't see why it doesn't work and keeps crashing every time. Can anyone help? 

here's MainActivity code:

```
public class MainActivity extends ActionBarActivity {

Button button1;

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

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }
    button1 = (Button) findViewById(R.id.button1);
    button1.setOnClickListener((OnClickListener) this);
}

private void buttonClick()
{
    startActivity(new Intent("com.example.chaty.SignUpActivity"));
}
public void onClick(View v)
{
    switch (v.getId())
    {
        case R.id.button1:
            buttonClick();
            break;
    }
}

```

here is the Manifest:

```
 <application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.chaty.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity
        android:name="com.example.chaty.SignUpActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="com.example.chaty.SignUpActivity" />

            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
    </activity>

</application>

```

I am really new for all of this...