Gradle Build Android Project "Could not resolve all dependencies" error

I'm trying to build my first project with Gradle and I think my gradle files and settings are correct.

I'm using only one module and Support V4 + AppCompatBar libraries.

Project - build.gradle

allprojects {
    repositories {
        mavenCentral()
    }
}

Project - settings.gradle

include ':AssignmentTempos21'

Main module - build.gradle

buildscript {
    repositories {
        mavenCentral()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:0.5.+'
    }
}

apply plugin: 'android'

repositories {
    mavenCentral()
}

android {
    compileSdkVersion 17
    buildToolsVersion "17.0.0"

    defaultConfig {
        minSdkVersion 8
        targetSdkVersion 17
    }
}

dependencies {
    compile "com.android.support:support-v4:18.0.+"
    compile "com.android.support:appcompat-v7:18.0.+"
}

Console output with -i flag:

MacBook-Air-de-Cesar-2:AssignmentTempos21 menor$ ./gradlew -i clean assemble
Starting Build
Settings evaluated using settings file '/Users/menor/workspace_android/AssignmentTempos21/settings.gradle'.
Projects loaded. Root project using build file '/Users/menor/workspace_android/AssignmentTempos21/build.gradle'.
Included projects: [root project 'AssignmentTempos21', project ':AssignmentTempos21']
Evaluating root project 'AssignmentTempos21' using build file '/Users/menor/workspace_android/AssignmentTempos21/build.gradle'.
Compiling build file '/Users/menor/workspace_android/AssignmentTempos21/build.gradle' using BuildScriptClasspathScriptTransformer.
Compiling build file '/Users/menor/workspace_android/AssignmentTempos21/build.gradle' using BuildScriptTransformer.
Evaluating project ':AssignmentTempos21' using build file '/Users/menor/workspace_android/AssignmentTempos21/AssignmentTempos21/build.gradle'.
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/support-v4/maven-metadata.xml]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/support-v4/]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/support-v4/maven-metadata.xml]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/support-v4/]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/support-v4/maven-metadata.xml]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/support-v4/]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/support-v4/maven-metadata.xml]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/support-v4/]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/appcompat-v7/maven-metadata.xml]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/appcompat-v7/]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/appcompat-v7/maven-metadata.xml]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/appcompat-v7/]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/appcompat-v7/maven-metadata.xml]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/appcompat-v7/]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/appcompat-v7/maven-metadata.xml]
Resource missing. [HTTP GET: http://repo1.maven.org/maven2/com/android/support/appcompat-v7/]

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring project ':AssignmentTempos21'.
> Failed to notify project evaluation listener.
   > Could not resolve all dependencies for configuration ':AssignmentTempos21:_DebugCompile'.
      > Could not find any version that matches com.android.support:support-v4:18.0.+.
        Required by:
            AssignmentTempos21:AssignmentTempos21:unspecified
      > Could not find any version that matches com.android.support:appcompat-v7:18.0.+.
        Required by:
            AssignmentTempos21:AssignmentTempos21:unspecified

* Try:
Run with --stacktrace option to get the stack trace. Run with --debug option to get more log output.

BUILD FAILED

Total time: 40.787 secs

As Peter says, they won't be in Maven Central

from the Android SDK Manager download the 'Android Support Repository' and a Maven repo of the support libraries will be downloaded to your Android SDK directory (see 'extras' folder)

to deploy the libraries to your local .m2 repository you can use maven-android-sdk-deployer

2017 edit:

you can now reference the Google online M2 repo

repositories {
google()
jcenter()
}

Go to wherever you installed Android Studio (for me it's under C:\Users\username\AppData\Local\Android\android-studio\) and open sdk\tools, then run android.bat. From here, update and download any missing build-tools and make sure you update the Android Support Repository and Android Support Library under Extras. Restart Android Studio after the SDK Manager finishes.

It seems that Android Studio completely ignores any installed Android SDK files and keeps a copy of its own. After running an update, everything compiled successfully for me using compile com.android.support:appcompat-v7:18.0.+

If you are running on headless CI and are installing the Android SDK through command line, make sure to include the m2repository packages in the --filter argument:

android update sdk --no-ui --filter platform-tools,build-tools-19.0.1,android-19,extra-android-support,extra-android-m2repository,extra-google-m2repository

Update

As of Android SDK Manager rev. 22.6.4 this does not work anymore. Try this instead:

android list sdk --all

You will get a list of all available SDK packages. Look up the numerical values of the components from the first command above ("Google Repository" and others you might be missing).

Install the packages using their numerical values:

android update sdk --no-ui --all --filter <num>

Update #2 (Sept 2017)

With the "new" Android SDK tools that were released earlier this year, the android command is now deprecated, and similar functionality has been moved to a new tool called sdkmanager:

List installed components:

sdkmanager --list

Update installed components:

sdkmanager --update

Install a new component (e.g. build tools version 26.0.0):

sdkmanager 'build-tools;26.0.0'