Solution To: Error Class Not Found Widget.CardView

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Solution To: Error "the following classes could not be found android.support.v7.widget.cardview"
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This error may occur if you add a cardview widget in layout file without adding the compile class reference in the build.gradle

1) Add the codes "compile 'com.android.support:cardview-v7:21.0.+'" to the dependencies section of the file build.gradle (module:app)

2) Rebuild your project.

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