Can't upload Android app to device (stale dexed jars)

Question

I am using Android Studio to develop this app, and today when I tried to upload it to my device to test I got a popup window saying:

Installation fail

Answer 1

What i did was modified build.gradle (Module:app) file.

Initially it was

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

I changed it to

    buildTypes {
    release {
        minifyEnabled true
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}

Then Rebuild and deploy !