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

Posted by P ruijters
P ruijters
1,217 Points

@+id/ versus @id/ in: android:layout_below="@id/captionField"

Although @+id/ in: ' android:layout_below="@id/captionField" ', gives error in online checker , it does not give error in Android Studio.

In fact using @id/ does give error in Android Studio when using in this layout_below construction: android:layout_below="@id/nameEditText" Namely: Error:(25, 31) No resource found that matches the given name (at 'layout_below' with value '@id/nameEditText').

When changing back to android:layout_below="@+id/nameEditText" it is error free again.

So I do not understand the way it seems necessary having to refer with @+id in Android Studio....I always thought this was only needed to declare a variable name.

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:hint="Enter a caption" 

        android:layout_alignParentTop="true"/>

    <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>

1 Answer

James Simshaw
James Simshaw
28,738 Points
James Simshaw
James Simshaw
28,738 Points

Hello,

You use @id+/ when you are creating a new resource id(typically in the android:id tag of the object like how it is in the EditText view). This tells Android that this is a new resource and it should be added to the main resource file(R.java).

@id/ is used to reference an already created object's id as in the case of using the tag android:layout_below.

If you have any further questions about this please let me know and I will try to clarify further.