Android Layouts

person DK schedule December 24, 2014
There are two ways to create Layout.
  1. Layouts in XML
  2. Layouts in Code

1. Layouts in XML

Example: main.xml(Layout file)
     <?xml version=”1.0” encoding=”utf-8”?>
     <LinearLayout   xmlns:android=”http://schemas.android.com/apk/res/android”
                                android:orientation=”vertical”
                                android:layout_width=”fill_parent”
                                android:layout_height=”fill_parent” >
     <TextView   android:id=”@+id/mytxt”
                          android:layout_width=”fill_parent”
                          android:layout_height=”wrap_content”
                          android:text=”@string/Write here..” />
     </LinearLayout>

    • It's a preferred way of implementing your user interfaces (UIs) or defining your UI in XML.
    • As it decouples your application logic from your UI design.
    • Keeping the visual design decoupled from the application code, helps keep the code concise.
    • To get access to the UI elements we have to add identifier(id) attributes to them in the XML definition.
                                    android:id=”@+id/mytxt”

    • The above line generates an id named "mytxt" for TextView,which are stored in /gen/packageName/R.java of your poject hierarchy.
           In R.java file, following line generates:
         public final class R {
              public static final class id {
                            public static final int mytxt=0x7f050044;
                                        }
                             }

      2. Layouts in Code

           public class MainActivity extends Activity {
                public void onCreate(Bundle savedInstanceState) {
                     super.onCreate(savedInstanceState);

                    LinearLayout ll = new LinearLayout(this);
                    ll.setOrientation(LinearLayout.VERTICAL);

                    TextView myTxtView = new TextView(this);
                    EditText myEdtText = new EditText(this);
                    myTxtView.setText(“Enter Text”);
                    myEdtText.setText(“Write Text Here!”);

                    int lHeight = LinearLayout.LayoutParams.MATCH_PARENT;
                    int lWidth = LinearLayout.LayoutParams.WRAP_CONTENT;

                    ll.addView(myTxtView, new LinearLayout.LayoutParams(lHeight, lWidth));
                    ll.addView(myEdtText, new LinearLayout.LayoutParams(lHeight, lWidth));
                    setContentView(ll);
       }   }
        It's not a preferred way of implementing your user interfaces (UIs).
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