public class Activity2 extends Activity{

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        //

        setContentView(R.layout.layout2);

        System.out.println("这是我运行的第一个Activity");

        Log.d("text","Log输出的信息");

    }

}

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent">//匹配父窗口

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="大家好"

        />//内容包裹

</LinearLayout>