Android : Android Sweet Alert Dialog dependencies

thanks for read my post.

i read this tutorial:

https://android-arsenal.com/details/1/1065

and i add dependencies to my project this way:

1-select Build.Gradle (Module:app) and open 2-go to this line:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])

}

and change to:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'cn.pedant.sweetalert:library:1.3'
}

3-Run the my app.but i get this error:

Error:A problem occurred configuring project ':app'.
> Could not resolve all dependencies for configuration ':app:_debugCompile'.
   > Could not find com.android.support:appcompat-v7:21.0.0.
     Searched in the following locations:
         https://jcenter.bintray.com/com/android/support/appcompat-v7/21.0.0/appcompat-v7-21.0.0.pom
         https://jcenter.bintray.com/com/android/support/appcompat-v7/21.0.0/appcompat-v7-21.0.0.jar
         file:/D:/sdk/ADT-Bundle-Windows-x86-20140702.Full_p30download.com/sdk/extras/android/m2repository/com/android/support/appcompat-v7/21.0.0/appcompat-v7-21.0.0.pom
         file:/D:/sdk/ADT-Bundle-Windows-x86-20140702.Full_p30download.com/sdk/extras/android/m2repository/com/android/support/appcompat-v7/21.0.0/appcompat-v7-21.0.0.jar
         file:/D:/sdk/ADT-Bundle-Windows-x86-20140702.Full_p30download.com/sdk/extras/google/m2repository/com/android/support/appcompat-v7/21.0.0/appcompat-v7-21.0.0.pom
         file:/D:/sdk/ADT-Bundle-Windows-x86-20140702.Full_p30download.com/sdk/extras/google/m2repository/com/android/support/appcompat-v7/21.0.0/appcompat-v7-21.0.0.jar
     Required by:
         MyApplication:app:unspecified > cn.pedant.sweetalert:library:1.3 > com.pnikosis:materialish-progress:1.0

and when i add appcompat-v7-21.0.0.jar i get this error:

Error:Failed to find: com.android.support:appcompat-v7:21.0.0
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