Unable to solve resource linking failed error

Question

I have a following error and I have no clue why this is happening.All I did was add the flag called "mon" and tried to add it to the custom view in the xml. flags other than "mon" works well. What is the meaning of this error? I would love to hear from you.

Android resource linking failed
Output:  samp/app/src/main/res/layout/layout_mon.xml:2: error: 'mon' is incompatible with attribute mon_type (attr) flags [sol=1, dan=4, tin=2] [weak].
error: failed linking file resources.

Command: /Users/me/.gradle/caches/transforms-1/files-1.1/aapt2-3.2.1-4818971-osx.jar/0c6f710daca8a09e3/aapt2-3.2.1-4818971-osx/aapt2 link -I\
        /Users/me/Library/Android/sdk/platforms/android-26/android.jar\
        --manifest\
      /Users/me/Documents/samp/app/build/intermediates/instant_run_merged_manifests/_stagingDebug/process_stagingDebugManifest/instant-run/AndroidManifest.xml\
        -o\
        /Users/me/Documents/samp/app/build/intermediates/processed_res/_stagingDebug/process_stagingDebugResources/out/resources-_stagingDebug.ap_\
        -R\
        @/Users/me/Documents/samp/app/build/intermediates/incremental/process_stagingDebugResources/resources-list-for-resources-_stagingDebug.ap_.txt\
        --auto-add-overlay\
        --java\
        /Users/me/Documents/samp/app/build/generated/not_namespaced_r_class_sources/_stagingDebug/process_stagingDebugResources/r\
        --custom-package\
        jp.aeonretail.aeon.kidsrepublic\
        -0\
        apk\
        --preferred-density\
        xxhdpi\
        --output-text-symbols\
        /Users/me/Documents/samp/app/build/intermediates/symbols/_st/debug/R.txt\
        --no-version-vectors
Daemon:  AAPT2 aapt2-3.2.1-4818971-osx Daemon #0

//inside the attrs

<declare-styleable name="MonView">
    <attr name="mon_type">
        <flag name="sol" value="0x01"/>
        <flag name="dan" value="0x02"/>
        <flag name="tin" value="0x04"/>
        <flag name="mon" value="0x06"/>
    </attr>
</declare-styleable>

//view

<?xml version="1.0" encoding="utf-8"?>
<example.MonView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/mon_id"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:mon_type="mon">
</example.MonView>

Answer 1

You are missing '>' tag

<example.MonView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/mon_id"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    app:mon_type="mon">

</example.MonView>