我已经安装了android sdk。安装了Xcode 5.1.1。我不确定为什么通用安装程序不起作用？感谢您的时间！
[2014-06-05 20:34:18.190] [Info] Installation ID: dd344913-5804-4125-bfe5-a09cc1b2c0ea
[2014-06-05 20:34:18.195] [Info] Operating system: Mac OS X v10.9.3 (10.9.3; Mac OS X 10.9.3 (10.9.3 build version: 13D65)), 32-bit
[2014-06-05 20:34:18.197] [Info] Installer product: Xamarin
[2014-06-05 20:34:18.197] [Info] Installer version: 3.2.0.7 (detached from 04514fb) (04514fb54a5884a2182d80bc299383c8d747ed76 on 23/05/2014 14:03:07)
[2014-06-05 20:34:18.197] [Info] Status: in progress
[2014-06-05 20:34:20.616] [Debug] Waiting for manifests to finish downloading.
[2014-06-05 20:34:20.617] [Debug] Initial task executing (WaitingForActivation). Waiting for it to finish.
[2014-06-05 20:34:21.424] [Info] Retrieving installation manifest.
[2014-06-05 20:34:21.424] [Info] Downloading from 'http://xamarin.com/installer_assets/v3/Mac/Universal//InstallationManifest.xml'.
[2014-06-05 20:34:21.426] [Debug] Setting download timeout for 'http://xamarin.com/installer_assets/v3/Mac/Universal//InstallationManifest.xml' to 60s
[2014-06-05 20:34:21.527] [Info] Retrieving installation size manifest.
[2014-06-05 20:34:21.527] [Info] Downloading from 'http://xamarin.com/installer_assets/v3/Mac/Universal//InstallationSizes.xml'.
[2014-06-05 20:34:21.528] [Debug] Setting download timeout for 'http://xamarin.com/installer_assets/v3/Mac/Universal//InstallationSizes.xml' to 60s
[2014-06-05 20:34:21.629] [Info] Installation size manifest not found online, using the bundled copy
[2014-06-05 20:34:21.629] [Info] Installation size manifest: reading from assembly.
[2014-06-05 20:34:21.630] [Info] Determining list of software items to install.
[2014-06-05 20:34:21.731] [Debug] Processing update nodes from the manifest.
[2014-06-05 20:34:21.731] [Debug] Creating and initializing software item 'Mono Framework'
[2014-06-05 20:34:21.933] [Debug] Creating and initializing software item 'Java SDK'
[2014-06-05 20:34:21.933] [Debug] Creating and initializing software item 'Android SDK'
[2014-06-05 20:34:21.935] [Debug] Creating and initializing software item 'Xamarin Studio'
[2014-06-05 20:34:21.935] [Debug] Creating and initializing software item 'Xamarin.Android'
[2014-06-05 20:34:21.935] [Debug] Creating and initializing software item 'Xamarin.iOS'
[2014-06-05 20:34:21.935] [Debug] Detecting software item 'Mono Framework'
[2014-06-05 20:34:21.935] [Info] Checking whether Mono needs update/installation
[2014-06-05 20:34:22.036] [Info] Mono runtime found in /Library/Frameworks/Mono.framework/Versions/3.4.0
[2014-06-05 20:34:22.037] [Info] Mono version 3.4.0 was found in /Library/Frameworks/Mono.framework/Versions
[2014-06-05 20:34:22.038] [Info] Status: successful
[2014-06-05 20:34:22.039] [Info] Component 'Mono Framework' v. 3.4.0 present
[2014-06-05 20:34:22.039] [Info] Software item 'Mono Framework': up to date
[2014-06-05 20:34:22.039] [Debug] Detecting software item 'Java SDK'
[2014-06-05 20:34:22.039] [Info] Checking whether Mac JDK needs update/installation
[2014-06-05 20:34:22.039] [Info] Status: successful
[2014-06-05 20:34:22.039] [Info] Component 'Java SDK' v. 1.6.0 present
[2014-06-05 20:34:22.039] [Info] Software item 'Java SDK': up to date
[2014-06-05 20:34:22.039] [Debug] Detecting software item 'Android SDK'
[2014-06-05 20:34:22.040] [Info] Checking if Android SDK needs to be updated/installed
[2014-06-05 20:34:22.040] [Info] Fetching Android SDK manifest.
[2014-06-05 20:34:22.040] [Info] Manifest URL: http://dl.google.com/android/repository/repository-8.xml
[2014-06-05 20:34:22.040] [Info] Using default samples:
[2014-06-05 20:34:22.040] [Info] Downloading from 'http://dl.google.com/android/repository/repository-8.xml'.
[2014-06-05 20:34:22.040] [Debug] Setting download timeout for 'http://dl.google.com/android/repository/repository-8.xml' to 25s
[2014-06-05 20:34:22.141] [Info] AVD 'MonoForAndroid API 15' needs to be created.
[2014-06-05 20:34:22.141] [Info] AVD 'MonoForAndroid API 14' needs to be created.
[2014-06-05 20:34:22.141] [Info] AVD 'MonoForAndroid API 12' needs to be created.
[2014-06-05 20:34:22.141] [Info] AVD 'MonoForAndroid API 10' needs to be created.
[2014-06-05 20:34:22.142] [Info] AVD 'MonoForAndroid API 8' needs to be created.
[2014-06-05 20:34:22.142] [Info] AVD 'MonoForAndroid API 7' needs to be created.
[2014-06-05 20:34:22.142] [Info] Status: failed.
[2014-06-05 20:34:22.142] [Exception] Failed to detect component 'Android SDK'
[2014-06-05 20:34:22.142] [Exception] System.NullReferenceException: Object reference not set to an instance of an object
[2014-06-05 20:34:22.142] [Exception] at Xamarin.Web.Installer.Installer.AndroidSoftwareItem.Detect () [0x00000] in <filename unknown>:0
[2014-06-05 20:34:22.142] [Exception] at Xamarin.Web.Installer.Installer.AndroidSoftwareItem.NeedsUpdate () [0x00000] in <filename unknown>:0
[2014-06-05 20:34:22.142] [Exception] at Xamarin.Web.Installer.TasksManager.ComponentDetector (ISoftwareItem si) [0x00000] in <filename unknown>:0
[2014-06-05 20:34:22.142] [Error] No selected SDK, cannot enqueue downloads
[2014-06-05 20:34:22.142] [Debug] Detecting software item 'Xamarin Studio'
[2014-06-05 20:34:22.142] [Info] Checking whether Xamarin Studio needs installation/updating
[2014-06-05 20:34:22.142] [Info] Xamarin Studio installation check: app directory does not exist.
[2014-06-05 20:34:22.142] [Info] Xamarin Studio not detected.
[2014-06-05 20:34:22.143] [Info] Xamarin Studio 5.0.0 needs to be installed.
[2014-06-05 20:34:22.143] [Info] Status: successful
[2014-06-05 20:34:22.143] [Info] Software item 'Xamarin Studio': not up to date
[2014-06-05 20:34:22.143] [Info] Component 'Xamarin Studio' v. 5.0.0 absent
[2014-06-05 20:34:22.244] [Debug] Detecting software item 'Xamarin.Android'
[2014-06-05 20:34:22.245] [Info] Checking whether Xamarin.Android SDK needs installation/updating
[2014-06-05 20:34:22.246] [Info] Xamarin.Android build files not found.
[2014-06-05 20:34:22.246] [Info] Base Xamarin.Android directory not found.
[2014-06-05 20:34:22.247] [Info] Xamarin.Android SDK 4.12.4 requires installation.
[2014-06-05 20:34:22.247] [Info] Status: successful
[2014-06-05 20:34:22.247] [Info] Software item 'Xamarin.Android': not up to date
[2014-06-05 20:34:22.247] [Info] Component 'Xamarin.Android' v. 4.12.4 absent
[2014-06-05 20:34:22.247] [Debug] Detecting software item 'Xamarin.iOS'
[2014-06-05 20:34:22.247] [Info] Checking whether Xamarin.iOS needs update/installation
[2014-06-05 20:34:22.248] [Info] MonoTouch base directory not found.
[2014-06-05 20:34:22.248] [Info] Xamarin.iOS 7.2.3.39 needs to be installed.
[2014-06-05 20:34:22.248] [Info] Status: successful
[2014-06-05 20:34:22.248] [Info] Software item 'Xamarin.iOS': not up to date
[2014-06-05 20:34:22.248] [Info] Component 'Xamarin.iOS' v. 7.2.3 absent
[2014-06-05 20:34:22.248] [Info] Detection complete
[2014-06-05 20:34:22.248] [Info] Initial task completed successfully
[2014-06-05 20:34:22.249] [Debug] Detection complete on the introduction page, determining the next step.
答案 0 :(得分：0)
[2014-06-05 20:34:22.142] [Exception] Failed to detect component 'Android SDK'
[2014-06-05 20:34:22.142] [Exception] System.NullReferenceException: Object reference not set to an instance of an object
[2014-06-05 20:34:22.142] [Exception] at Xamarin.Web.Installer.Installer.AndroidSoftwareItem.Detect () [0x00000] in <filename unknown>:0
[2014-06-05 20:34:22.142] [Exception] at Xamarin.Web.Installer.Installer.AndroidSoftwareItem.NeedsUpdate () [0x00000] in <filename unknown>:0
[2014-06-05 20:34:22.142] [Exception] at Xamarin.Web.Installer.TasksManager.ComponentDetector (ISoftwareItem si) [0x00000] in <filename unknown>:0
安装程序抛出NullReferenceException。尝试使用不同版本的安装程序。登录到您的帐户后，您可以在xamarin.com找到可用安装程序的存档。
或者，您可以在尝试安装Xamarin SDK之前尝试安装Android SDK。您可以在Android developer download页面上的仅限SDK工具下找到下载程序。