Expose cellular signal strength on Android to native

net/android/java/src/org/chromium/net/AndroidCellularSignalStrength.java

Index: net/android/java/src/org/chromium/net/AndroidCellularSignalStrength.java
diff --git a/net/android/java/src/org/chromium/net/AndroidCellularSignalStrength.java b/net/android/java/src/org/chromium/net/AndroidCellularSignalStrength.java
new file mode 100644
index 0000000000000000000000000000000000000000..650e02b7c98c44e57437035d111bede0eaac7552
--- /dev/null
+++ b/net/android/java/src/org/chromium/net/AndroidCellularSignalStrength.java
@@ -0,0 +1,147 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.net;
+
+import android.annotation.SuppressLint;
+import android.content.Context;
+import android.os.Build;
+import android.telephony.CellInfo;
+import android.telephony.CellInfoCdma;
+import android.telephony.CellInfoGsm;
+import android.telephony.CellInfoLte;
+import android.telephony.CellInfoWcdma;
+import android.telephony.CellSignalStrengthCdma;
+import android.telephony.CellSignalStrengthGsm;
+import android.telephony.CellSignalStrengthLte;
+import android.telephony.CellSignalStrengthWcdma;
+import android.telephony.TelephonyManager;
+
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+
+import java.util.List;
+
+/**
+ * This class interacts with the cellular signal strength API provided by Android.
+ */
+@JNINamespace("net::android::cellular_signal_strength")
+public class AndroidCellularSignalStrength {
+    /**
+     * True if the Android API to query the cellular signal strength is available.
+     * getAllCellInfo is only available on API Level JELLY_BEAN_MR1 and higher.
+     */
+    private static boolean sAPIAvailable =

[pauljensen, 2016/04/22 11:54:13]

final

[tbansal1, 2016/04/28 20:12:03]

Done.

+            Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1;
+
+    private AndroidCellularSignalStrength() {}
+
+    /**
+     * @return RSSI (in dbM) for the currently registered cellular network. Returns {@link
+     * invalidValue} if the RSSI is unavailable.
+     */
+    @SuppressWarnings("unused")
+    @SuppressLint("NewApi")
+    @CalledByNative
+    private static long getRssiDbm(Context context, long invalidValue) {
+        if (!sAPIAvailable) {

[pauljensen, 2016/04/22 11:54:12]

how about moving lines 48-60 into a function?  it can return an empty list if
!sAPIAvailable or telephonyManager == null or cellInfos == null.  Then this
function is just:

for (CellInfo cellInfo : getCellInfos(context))
...
return invalidValue;

[tbansal1, 2016/04/28 20:12:02]

Done.

+            return invalidValue;
+        }
+
+        TelephonyManager telephonyManager =
+                (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
+        if (telephonyManager == null) return invalidValue;
+
+        List<CellInfo> cellInfos = telephonyManager.getAllCellInfo();
+        if (cellInfos == null) {
+            return invalidValue;
+        }
+
+        for (CellInfo cellInfo : cellInfos) {
+            if (cellInfo.isRegistered()) {
+                return getRssiDbm(cellInfo, invalidValue);
+            }
+        }
+
+        return invalidValue;
+    }
+
+    /**
+     * @return the signal level (between 0 and 4, both inclusive) for the currently registered
+     * cellular network. Returns {@link invalidValue} if the signal level is unavailable.
+     */
+    @SuppressWarnings("unused")
+    @SuppressLint("NewApi")
+    @CalledByNative
+    private static long getSignalLevel(Context context, long invalidValue) {

[pauljensen, 2016/04/22 11:54:12]

why not return an int?

[tbansal1, 2016/04/28 20:12:02]

Done.

+        if (!sAPIAvailable) {
+            return invalidValue;
+        }
+
+        TelephonyManager telephonyManager =
+                (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
+        if (telephonyManager == null) return invalidValue;
+
+        List<CellInfo> cellInfos = telephonyManager.getAllCellInfo();
+        if (cellInfos == null) {
+            return invalidValue;
+        }
+
+        for (CellInfo cellInfo : cellInfos) {
+            if (cellInfo.isRegistered()) {
+                return getSignalLevel(cellInfo, invalidValue);
+            }
+        }
+
+        return invalidValue;
+    }
+
+    /**
+     * @return RSSI (in dbM) from {@link cellInfo}. Returns {@link invalidValue} if the RSSI is
+     * unavailable.
+     */
+    @SuppressLint("NewApi")
+    private static long getRssiDbm(CellInfo cellInfo, long invalidValue) {

[pauljensen, 2016/04/22 11:54:12]

how about returning an int?  and you could remove invalidValue and just return
Integer.MAX_VALUE for invalid values.

[tbansal1, 2016/04/28 20:12:02]

Done.

+        if (cellInfo instanceof CellInfoCdma) {
+            CellSignalStrengthCdma signalStrength =
+                    ((CellInfoCdma) cellInfo).getCellSignalStrength();
+            return signalStrength.getDbm();
+        } else if (cellInfo instanceof CellInfoGsm) {
+            CellSignalStrengthGsm signalStrength = ((CellInfoGsm) cellInfo).getCellSignalStrength();
+            return signalStrength.getDbm();
+        } else if (cellInfo instanceof CellInfoLte) {
+            CellSignalStrengthLte signalStrength = ((CellInfoLte) cellInfo).getCellSignalStrength();
+            return signalStrength.getDbm();
+        } else if (cellInfo instanceof CellInfoWcdma) {
+            CellSignalStrengthWcdma signalStrength =
+                    ((CellInfoWcdma) cellInfo).getCellSignalStrength();
+            return signalStrength.getDbm();
+        }
+        return invalidValue;
+    }
+
+    /**
+     * @return the signal level from {@link cellInfo}. Returns {@link invalidValue} if the signal
+     * level is unavailable.
+     */
+    @SuppressLint("NewApi")
+    private static long getSignalLevel(CellInfo cellInfo, long invalidValue) {

[pauljensen, 2016/04/22 11:54:13]

why not an int?  I think all the getLevel functions return 0-4

[pauljensen, 2016/04/22 11:54:13]

instead of invalidValue, you could pre-define some invalid value.  if you want
the value shared between native and Java you could use
GENERATED_JAVA_ENUM_PACKAGE

[tbansal1, 2016/04/28 20:12:02]

Done.

[tbansal1, 2016/04/28 20:12:03]

Done.

+        if (cellInfo instanceof CellInfoCdma) {
+            CellSignalStrengthCdma signalStrength =
+                    ((CellInfoCdma) cellInfo).getCellSignalStrength();
+            return signalStrength.getLevel();
+        } else if (cellInfo instanceof CellInfoGsm) {
+            CellSignalStrengthGsm signalStrength = ((CellInfoGsm) cellInfo).getCellSignalStrength();
+            return signalStrength.getLevel();
+        } else if (cellInfo instanceof CellInfoLte) {
+            CellSignalStrengthLte signalStrength = ((CellInfoLte) cellInfo).getCellSignalStrength();
+            return signalStrength.getLevel();
+        } else if (cellInfo instanceof CellInfoWcdma) {
+            CellSignalStrengthWcdma signalStrength =
+                    ((CellInfoWcdma) cellInfo).getCellSignalStrength();
+            return signalStrength.getLevel();
+        }
+        return invalidValue;
+    }
+}