Android初学：联系创建Activity

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>