Posts Tagged 'id'

Give an ID to your view in android xml file

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Give an ID to your view object is very useful if you want to refer to that view later in source code. For example you want to set text of a TextView in source code. To do that, put [cci]android:id[/cci] attibute to your view.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
         />
</RelativeLayout>

In above code, you can see I have put an [cci]android:id=”@+id/textView1″[/cci]. This line defines an [cci]id[/cci] of our [cci]TextView[/cci] to [cci]textView1[/cci].

Refers view from activity

After you have defined an id, now you can refer to your [cci]TextView[/cci] in an activity like this

TextView textView = (TextView) findViewById(R.id.textView1);

Now, with your [cci]TextView[/cci] in hand, you can set text to it as you want like this

if(textView != null) textView.setText("new text");

 

Refers view in xml file

Sometimes we need to refers to our view in the xml layout file. For example you want to align top another [cci]TextView[/cci] to other. To achieve this, you can refer to our last [cci]TextView[/cci] like this [cci]@id/textView1[/cci]. Note you must replace ‘+’ sign when referring to already defined [cci]id[/cci]. Use ‘+’ sign only in first time when you define an [cci]id[/cci].

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@id/textView1"/>
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