Eclipse update failed folder in use

UNEXPECTED TOP-LEVEL EXCEPTION:
java.lang.IllegalArgumentException: already added: Lcz/okhelp/MyMathClass;

First try this solution!!!!!
Select your project in project tree and go to the Eclipse menu Project » Clean » Clean projects selected below » select your project and click OK.

If you create *.apk package with proguard sometimes you must back up the project, delete project, and create new project if you are unable to create *.apk file.

Check your AndroidManifest.xml if all Activity is correctly inserted. If you add a library project to Main project you have to insert Activity from library to Main project AndroidManifest.xml


Problem with the library.
I deleted library project from project tree and again put the _library project into the main project. This problem was resolved.
1.)Go to Project » Properties » Java Build Path » Libraries and remove (your projects) click OK.
2.)Go to Project » Clean » Clean projects selected below » select your project and click OK.
3.)Add again your LIBRARY project to your MAIN project Project » Properties » Java Build Path » Libraries.
See image below.

Problem with a *.apk file
If you create signed *.apk, you have to delete previous *.apk from your PC folder.

Problem: erroneous entry of id

<RadioButton android:id="idRadio"
                android:text="My radio button"/>

Solution: @+id/

<RadioButton android:id="@+id/idRadio"
                android:text="My radio button"/>

Try set bigger line-height of links and font size for example:

/*in css*/
.links{
line-height: 48px;
font-size: 20px;
background-color: rgb(255,204,0);
}

/* in html page set class of link*/
<a class="links" href="m.mydomen.com/mypage.html">Blah blah mypage</a>

// or in css for all links on page
a {
line-height: 48px;
font-size: 20px;
}

/*html page*/
<a href="m.mydomen.com/mypage.html">Blah blah mypage</a>

build.gradle in module have higher priority then AndrodiManifest.xml
Try this.
AndroidManifest.xml have code:

    <uses-sdk
        android:minSdkVersion="9"
        android:targetSdkVersion="23" />

build.gradle have code:

   defaultConfig {
        applicationId "cz.okhelp.words"
        minSdkVersion 9
        targetSdkVersion 19
        versionCode 107
        versionName "1.0.7"
    }

Warning in AndroidManifest.xml:
This targetSdkVersion value (23) is not used; it is always overridden by the value specified in the Gradle build script (19) less... (Ctrl+F1)
The value of (for example) minSdkVersion is only used if it is not specified in the build.gradle build scripts. When specified in the Gradle build scripts, the manifest value is ignored and can be misleading, so should be removed to avoid ambiguity.

Warning in AndroidManifest.xml:
tag should specify a target API level (the highest verified version; when running on
later versions, compatibility behaviors may be enabled) with android:targetSdkVersion="?"

Solution:

    <uses-sdk android:minSdkVersion="4"
         android:targetSdkVersion="16" />