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Android Build an Interactive Story App (Retired) User Input Using RelativeLayouts and ImageViews

Rashad Hill
Rashad Hill
1,708 Points
Posted by Rashad Hill
Rashad Hill
1,708 Points

Question regarding syntax of xml code

The challenge asked me to use "@id" as opposed to "@+id" and I see some parts of the code that uses the latter as opposed to the former, what's the difference?

activity_main.xml 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <EditText
        android:id="@+id/captionField"
        android:layout_alignParentTop="true"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:hint="Enter a caption" />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:src="@drawable/grumpy_cat"
        android:layout_below="@id/captionField"/>

</RelativeLayout>
Ryan Sheets
Ryan Sheets
5,337 Points

@+id is used to define a new identifier and must be used at the first occurrence of each identifier in the layout. @id simply references an existing identifier and should be used for all subsequent instances of that identifier.

1 Answer

alladin
alladin
2,873 Points
alladin
alladin
2,873 Points

@+id: is used when we have to create an id and add it to the R file for the first time for a new element. @id if an id has already been created. As shown in the code snippet above @+id : <EditText android:id="@+id/captionField" when creating id for this EditText to be referred from here onwards.

Inside ImageView android:layout_below="@id/captionField"/> this line now just referring to the id captionField and not creating it again to be added to R file