gradle project sync always failed, i have installed sdk 19, 20 as the hints

I think like me, you'd also have the build tools ver 22 installed. Just change your build.gradle(app) to the one I am pasting here. Major changes are:-

1. compileSdkVersion 22

2. buildToolsVersion '22.0.1'

3. targetSdkVersion 22

4. minifyEnabled false (Resolvs the ProGuard() error)

5. compile 'com.android.support:support-v13:22.0.+'

apply plugin: 'android'

android {
    compileSdkVersion 22
    buildToolsVersion '22.0.1'
    defaultConfig {
        applicationId 'com.teamtreehouse.mememaker'
        minSdkVersion 16
        targetSdkVersion 22
        versionCode 1
        versionName '1.0'
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    productFlavors {
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile files('libs/commons-io-2.4.jar')
    compile 'com.android.support:support-v13:22.0.+'
}

The Starter Files provided by Treehouse in this case is generated with Version 0.8.6. So if you are using a newer version of Android Studio (Version 1.0 and above), you need to read the following blog:

http://www.goprogramming.space/importing-older-android-studio-code-example-projects-into-android-studio-1-1-0-step-by-step-guide/

It is a step-by-step guide for importing projects created by older Android Studio versions:

"People started making Android Apps with Android Studio 2 years ago when the first Pre-Developer-Not-At-All-Ready-Version was released.

The developing process of Android Studio took about 1 1/2 years before the first 1.0 version was finished. In this time, many things have changed all the time. Developers made apps during the whole time with a bunch of different versions of Android Studio.

Many of this Source Code examples have never been updated and most of them are not compatible with the recent version of Android Studio....."