Add documentation for com.android.location.provider shared library.

Change-Id: I222d61811c88272e84a85512623210c0238337e5

Author: Nick Pelly

location/lib/README.txt

@@ -0,0 +1,30 @@
+This library (com.android.location.provider.jar) is a shared java library
+containing classes required by unbundled location providers.
+
+--- Rules of this library ---
+o This library is effectively a PUBLIC API for unbundled location providers
+  that may be distributed outside the system image. So it MUST BE API STABLE.
+  You can add but not remove. The rules are the same as for the
+  public platform SDK API.
+o This library can see and instantiate internal platform classes (such as
+  ProviderRequest.java), but it must not expose them in any public method
+  (or by extending them via inheritance). This would break clients of the
+  library because they cannot see the internal platform classes.
+
+This library is distributed in the system image, and loaded as
+a shared library. So you can change the implementation, but not
+the interface. In this way it is like framework.jar.
+
+--- Why does this library exists? ---
+
+Unbundled location providers (such as the NetworkLocationProvider)
+can not use internal platform classes.
+
+So ideally all of these classes would be part of the public platform SDK API,
+but that doesn't seem like a great idea when only applications with a special
+signature can implement this API.
+
+The compromise is this library.
+
+It wraps internal platform classes (like ProviderRequest) with a stable
+API that does not leak the internal classes.

location/lib/java/com/android/location/provider/GeocodeProvider.java

@@ -25,12 +25,14 @@
 import java.util.List;
 
 /**
- * An abstract superclass for geocode providers that are implemented
- * outside of the core android platform.
- * Geocode providers can be implemented as services and return the result of
+ * Base class for geocode providers implemented as unbundled services.
+ *
+ * <p>Geocode providers can be implemented as services and return the result of
  * {@link GeocodeProvider#getBinder()} in its getBinder() method.
  *
- * @hide
+ * <p>IMPORTANT: This class is effectively a public API for unbundled
+ * applications, and must remain API stable. See README.txt in the root
+ * of this package for more information.
  */
 public abstract class GeocodeProvider {
 

location/lib/java/com/android/location/provider/LocationProviderBase.java

@@ -34,10 +34,22 @@
 import com.android.internal.location.ProviderProperties;
 import com.android.internal.location.ProviderRequest;
 
-
 /**
- * Base class for location providers implemented as services.
- * @hide
+ * Base class for location providers implemented as unbundled services.
+ *
+ * <p>The network location provider must export a service with action
+ * "com.android.location.service.v2.NetworkLocationProvider"
+ * and a valid minor version in a meta-data field on the service, and
+ * then return the result of {@link #getBinder()} on service binding.
+ *
+ * <p>The fused location provider must export a service with action
+ * "com.android.location.service.FusedLocationProvider"
+ * and a valid minor version in a meta-data field on the service, and
+ * then return the result of {@link #getBinder()} on service binding.
+ *
+ * <p>IMPORTANT: This class is effectively a public API for unbundled
+ * applications, and must remain API stable. See README.txt in the root
+ * of this package for more information.
  */
 public abstract class LocationProviderBase {
     private final String TAG;

location/lib/java/com/android/location/provider/ProviderPropertiesUnbundled.java

@@ -19,9 +19,11 @@
 import com.android.internal.location.ProviderProperties;
 
 /**
- * This class is a public API for unbundled providers,
- * that hides the (hidden framework) ProviderProperties.
- * <p>Do _not_ remove public methods on this class.
+ * This class is an interface to Provider Properties for unbundled applications.
+ *
+ * <p>IMPORTANT: This class is effectively a public API for unbundled
+ * applications, and must remain API stable. See README.txt in the root
+ * of this package for more information.
  */
 public final class ProviderPropertiesUnbundled {
     private final ProviderProperties mProperties;

location/lib/java/com/android/location/provider/ProviderRequestUnbundled.java

@@ -23,9 +23,11 @@
 import com.android.internal.location.ProviderRequest;
 
 /**
- * This class is a public API for unbundled providers,
- * that hides the (hidden framework) ProviderRequest.
- * <p>Do _not_ remove public methods on this class.
+ * This class is an interface to Provider Requests for unbundled applications.
+ *
+ * <p>IMPORTANT: This class is effectively a public API for unbundled
+ * applications, and must remain API stable. See README.txt in the root
+ * of this package for more information.
  */
 public final class ProviderRequestUnbundled {
     private final ProviderRequest mRequest;