Taller parte 1: layouts

activity_camera.xml

<TextView
    android:id="@+id/textView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_alignParentTop="true"
    android:text="Camera Activity !"/>

activity_main.xml

<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_alignParentTop="true"
    android:onClick="tomarFoto"
    android:text="Tomar foto"/>

MainActivity.java

import android.content.Intent;
import android.view.View;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    ...  
    public void tomarFoto(View view) {
        Intent intent = new Intent(this, CameraActivity.class);
        startActivity(intent);
    }
}