最后再安装一遍 。 很容易就成功了。
大功告成。
建立虚拟机，正常。
在xamarin studio 内建立android应用，正常，试做了一个应用，能部署到自己的手机上。
在Visual Studio 2015内建立 android应用，正常。
一点疑惑，按照 XamarinInstaller的提示，似乎要安装 Java JDK v1.6，但没有安装也没有出现问题，也许今后会出现问题，那时再来安装，提示如下：
It is very important to install the 32-bit version of Java JDK even if you're using 64-bit Windows. It is also important that Java JDK v1.6 is installed (although it is fine to have Java JDK 1.7 or newer installed at the same time)
总结：由于网上没有完整的资料，所以走了不少弯路。也怪自己粗心，如果完全按照Xamarininstaller的提示来进行安装并仔细检查，也许会少走些弯路。完整的提示如下：
It was not possible to complete an automatic installation. This might be due to a problem with your network, proxy servers or an unsolvable installation conflict. At this point, you can continue the installation by manually downloading and installing the independent pieces. The list below shows each component that you need to install.
Java JDK
Download the Java JDK v1.7.0 installer to any directory on your disk, double-click the downloaded file and follow the on-screen instructions.
It is very important to install the 32-bit version of Java JDK even if you're using 64-bit Windows. It is also important that Java JDK v1.6 is installed (although it is fine to have Java JDK 1.7 or newer installed at the same time)
Android SDK
Download the Android SDK for Windows version 22.0.0 to any directory on your disk and double-click it to start main SDK installation process. You can install the SDK either system wide or only for your account. You will need to point your IDE to that location after the installation is completed.
Click here in order to start the Android SDK Manager application. In the GUI make sure the following components are installed or selected for installation:
· Android SDK Tools
· Android SDK Platform-tools
· Android SDK Build-tools
· Android API 15
· Android API 19
· Android API 21
Once all the required components are selected (you can select others as well, if you wish) start the installation. Click here to open target dir
Download the Android NDK for Windows version r10d to any directory on your disk and double-click it to start the NDK installation.
When the Android SDK installation is finished you might want to start the Android Emulator Manager and create as many emulator images as you might need for your development. This step can be performed at any time, on an as-needed basis.
GTK#
Download the GTK# v2.12.26 installer to any directory on your disk, double-click the downloaded file and follow the on-screen instructions.
Xamarin Studio
Download the Xamarin Studio v5.9.3 installer to any directory on your disk, double-click it and follow the on-screen instructions.
Xamarin
Download the Xamarin v3.11.590 installer to any directory on your disk, double-click it and follow the on-screen instructions.
After installation, restart your Windows workstation to make sure all of the installed system services are running.
顺带将API15的安装包的下载地址记录如下：
/android/repository/sys-img/google_apis/sysimg_arm-21_r07.zip
/android/repository/sys-img/android/sysimg_x86_64-21_r03.zip
/android/repository/sys-img/google_apis/sysimg_x86_64-21_r07.zip
/android/repository/sys-img/android/sysimg_x86-21_r03.zip
/android/repository/sys-img/android-wear/sysimg_wear_x86-21_r03.zip
/android/repository/sys-img/android/sysimg_arm-21_r03.zip
/android/repository/sys-img/android-wear/sysimg_wear_arm-21_r03.zip
/android/repository/sources-21_r01.zip
/android/repository/samples-21_r04.zip
/android/repository/android-21_r02.zip
/android/repository/google_apis-21_r01.zip
/android/repository/sys-img/google_apis/sysimg_x86-21_r07.zip
/android/repository/sys-img/android-tv/sysimg_atv_x86-21_r03.zip
/android/repository/sys-img/android-tv/sysimg_atv_arm-21_r03.zip