Improve documentation of ScanResult and WifiInfo.

Valid dBm ranges should *not* be mentioned in the documentation.
Manufacturers should be able to produce devices which can detect
signal strengths with arbitrary sensitivity rather than being forced
to restrict strengths to a certain range.

Adds a reference to WifiManager.calculateSignalLevel(), an
often-useful method to convert these RSSI values into an absolute
signal level that can be displayed to a user as the signal strength.

Bug: 13731529
Change-Id: I0aae85a6d8bc48ffddd1927d816a1dfbf5230f7e

wifi/java/android/net/wifi/ScanResult.java

@@ -18,8 +18,8 @@ package android.net.wifi;
 
 import android.net.wifi.passpoint.WifiPasspointInfo;
 import android.net.wifi.passpoint.WifiPasspointManager;
-import android.os.Parcelable;
 import android.os.Parcel;
+import android.os.Parcelable;
 
 /**
  * Describes information about a detected access point. In addition
@@ -48,7 +48,10 @@ public class ScanResult implements Parcelable {
      */
     public String capabilities;
     /**
-     * The detected signal level in dBm.
+     * The detected signal level in dBm, also known as the RSSI.
+     *
+     * <p>Use {@link android.net.wifi.WifiManager#calculateSignalLevel} to convert this number into
+     * an absolute signal level which can be displayed to a user.
      */
     public int level;
     /**

wifi/java/android/net/wifi/WifiInfo.java

@@ -323,7 +323,11 @@ public class WifiInfo implements Parcelable {
     /**
      * Returns the received signal strength indicator of the current 802.11
      * network, in dBm.
-     * @return the RSSI, in the range -127 to 200
+     *
+     * <p>Use {@link android.net.wifi.WifiManager#calculateSignalLevel} to convert this number into
+     * an absolute signal level which can be displayed to a user.
+     *
+     * @return the RSSI.
      */
     public int getRssi() {
         return mRssi;