User Interfaces-Basics of UI Design

• You can use two ways to creating Views

1. Dynamically Add By Coding

              LinearLayout ll = new LinearLayout(getApplicationContext());

2. Statically Define in XMLs

     
              <android:layout_width=”fill_parent”
              android:layout_height=”fill_parent”
              android:orientation=”vertical” >
     

If you define it in XML you should call setContentView() method to load that XML in Activity.

    public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main_layout);
   }

• Every View and View Group object supports their own variety of XML attributes. Some attributes are specific to a View object (for example, Text View supports the text Size attribute)
• Some are common to all View objects, Like id , layout parameters and etc.

  ID Attribute

• Any View object may have an integer ID associated with it, to uniquely identify the View within the tree. 

      android:id=”@+id/my_button”

  Define & Retrieve

 Define in XML

      <android:layout_width=”wrap_content”
        android:layout_height=”wrap_content”
        android:text=”@string/btn_login_text”/>

   Retrieve By Activity

   Button btnLogin= (Button) findViewById(R.id.btn_login);