The Problem
When learning Android development, we may want to check Android source code once in a while.

When we click on a method of Android class, we may not see its source code like below: 
public void recycle() { /* compiled code */ }
The Solution
Install Android SDK Source Code in SDK Manager
Go to Tools -> Android -> SDK Manager.

In the Android SDK Manager panel, go to the Android SDK Version: 4.4.2(API 19) in this case, select “Source for Android SDK”, this will download Android source code to android-studio\sdk\sources\android-19.

We can also select “Samples for SDK”, “Documents dor Android SDK”. Then click “Install packages…”, select “Accept Licenese” in next dialogue, and click install.

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Wait until the install operation complete.

Attach Android SDK Source Code to Sourcepath
Go to File -> Other Settings -> Default Project Structure…

Select SDKs, in the middle panel, select the Android version(API 19 in this case), in the right panel, click the “Sourcepath” tab, click + button, then browse to your SKD path: C:\Programs Files\Android\android-studio\sdk\sources\android-19, then click OK.

Now use Ctrl+N to open class android.os.Message, click Ctrl+F12, then type recycle, press enter, this will navigate to recycle method.

Now you can see the source code and javadoc of Android source code.

* Return a Message instance to the global pool.  You MUST NOT touch
* the Message after calling this function -- it has effectively been
* freed.
public void recycle() {
  synchronized (sPoolSync) {
	if (sPoolSize < MAX_POOL_SIZE) {
		next = sPool;
		sPool = this;

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