Error:(26, 0) Gradle DSL method not found: 'runProguard()'

Instead of using runProguard in your gradle file, try using minifyEnabled. This should fix the issue. runProguard is deprecated and soon be stop working.

EDIT

To use minifyEnabled, gradle should be updated to version 2.2 or above.

Change in the app build.gradle file may help:

old:

buildTypes {
    release {

        runProguard false // this line has to be changed

        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

new:

buildTypes {
    release {

        minifyEnabled false // new version

        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

As far as I know runProguard was replaced with minifyEnabled. I am still not sure how to define the config for proguard but a Google search should help you to find out.

Edit:

For the outFile read here: https://groups.google.com/forum/#!topic/adt-dev/4_-5NvxuFB0 how they do it.

In short: they used a more complex version:

applicationVariants.all { variant ->

    variant.outputs.each { output ->

        def apk = output.outputFile;
        def newName;

        // newName = apk.name.replace(".apk", "-v" + defaultConfig.versionName + "-" + variant.buildType.name.toUpperCase() + ".apk");
        if (variant.buildType.name == "release") {
            newName = apk.name.replace(".apk", "-v" + defaultConfig.versionName + "-release.apk");
        } else {
            newName = apk.name.replace(".apk", "-v" + defaultConfig.versionName + "-beta.apk");
        }

        output.outputFile = new File(apk.parentFile, newName);

        if (output.zipAlign) {
            output.outputFile = new File(apk.parentFile, newName.replace("-unaligned", ""));
        }

        logger.info('INFO: Set outputFile to ' + output.outputFile + " for [" + output.name + "]");
    }
}