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

Steven Sierra Forero
Steven Sierra Forero
3,486 Points
Posted by Steven Sierra Forero
Steven Sierra Forero
3,486 Points

What is the difference between @+id and @id?

The code challenge rejected to use @+id/captionField and instead suggested to use @id/captionField, what is 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_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="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:layout_below="@id/captionField"
        android:src="@drawable/grumpy_cat" />

</RelativeLayout>

1 Answer

Greg Schmidt
Greg Schmidt
5,908 Points
Greg Schmidt
Greg Schmidt
5,908 Points

When you use the +sign you are instructing the parser(or builder) to create a new entry in R.java. Without the + you are referring to an id that has already been created, so the parser links it to the id which has already been created.