Android Studio 2.2 - What SDK components to download and install

This is a quick summary of what SDK components to download and install for Android Studio 2.2.

Below is a diagram that shows the distribution of various Android platforms and their API levels. When you click on a platform on the left in Android Studio, the features available since that platform are shown on the right.

The percentage figures under Cumulative Distribution indicate the percentage of Android devices supported by a given platform. For example, an App. could support 73.9% of the Android devices on the market if it's targeting at KitKat (API Level 19). However, if it's only targeting at Marshmallow (API Level 23), it could only support 4.7% of the Android devices.

Note, the above diagram can be obtained by clicking on the "Help me choose" link when creating a new project (see below photo) in Android Studio.

Launching the SDK Manager

In Android Studio, go to Tools -> Android -> SDK Manager.

Click on "Launch Standalone SDK Manager".

Select the SDK components to download and install 

There is no need to download all the platforms. Download only those platforms which you are targeting for your apps and which you intend to test your app with.

The photos below show the Tools, Platforms, and the Extras that I downloaded and installed in SDK Manager.

Tools

Select the followings components.

- Android SDK Tools;
- Android SDK Platform-tools;
- Android SDK Build-tools.

Android 7.0 (API 24) to Android 4.4.2 (API 19)

Select all but those for Android TV, Android Wear, and Glass Development Kit Preview if the focus is on developing Apps. for Android Phones and Tablets. However, you need to select those for Android TV, Android Wear, or Glass Development Kit Preview if you plan to develop software for them.

Note that in the photo below Android 4.3.1 (API 18) to Android 2.1 (API 7) are not selected as I don't plan to target those platforms.

Extras

Select the components shown in the below photo.

Download and install the selected SDK components

After selecting the components shown above, click on the button "Install Packages" on the bottom right corner to start download and install the selected components.

Depending on the network connection and how busy the server is, it may take up to hours to complete this process.

Reference:

Android App Development Tutorial <-- Very good source of info.!!
https://youtu.be/lApbZO7J7ZI?list=PLHs_NFdr_LaHmEh7hV-wPyS-gKnAVPzBU

Android SDK Manager - Do you need to install all android platforms?
http://stackoverflow.com/questions/28896828/android-sdk-manager-do-you-need-to-install-all-android-platforms