HashMap.putIfAbsent() requires minSdkVersion>=24

[chaulio]

Platform on which you observed the bug:

• Android
• iOS
• Other
• Platform is not relevant for this bug

Device on which you observed the bug:

• Polar OH1
• Polar Verity Sense
• Polar H10
• Polar H9
• Other
• Device is not relevant for this bug

Describe the bug

A user reported this crash on an Android 5.0 (API 21) device:

Fatal Exception: java.lang.NoSuchMethodError: No virtual method putIfAbsent(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object; in class Ljava/util/HashMap; or its super classes (declaration of 'java.util.HashMap' appears in /system/framework/core-libart.jar)
       at com.androidcommunications.polar.api.ble.model.gatt.BleGattBase.addCharacteristic(BleGattBase.java:306)
       at com.androidcommunications.polar.api.ble.model.gatt.BleGattBase.addCharacteristicNotification(BleGattBase.java:280)
       at com.androidcommunications.polar.api.ble.model.gatt.client.psftp.BlePsFtpClient.<init>(BlePsFtpClient.java:64)
       at com.androidcommunications.polar.api.ble.model.gatt.BleGattFactory.getRemoteServices(BleGattFactory.java:41)
       at com.androidcommunications.polar.enpoints.ble.bluedroid.host.BDDeviceSessionImpl.<init>(BDDeviceSessionImpl.java:80)
       at com.androidcommunications.polar.enpoints.ble.bluedroid.host.BDDeviceListenerImpl.deviceDiscovered(BDDeviceListenerImpl.java:301)
       at com.androidcommunications.polar.enpoints.ble.bluedroid.host.BDScanCallback.onScanResult(BDScanCallback.java:273)
       at android.bluetooth.le.BluetoothLeScanner$BleScanCallbackWrapper$1.run(BluetoothLeScanner.java:337)
       at android.os.Handler.handleCallback(Handler.java:815)
       at android.os.Handler.dispatchMessage(Handler.java:104)
       at android.os.Looper.loop(Looper.java:194)
       at android.app.ActivityThread.main(ActivityThread.java:5537)
       at java.lang.reflect.Method.invoke(Method.java)
       at java.lang.reflect.Method.invoke(Method.java:372)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:956)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:751)

It turns out that calling HashMap.putIfAbsent() requires minSdkVersion>=24, at least according to the warning shown by Android Studio when I try to use that in my code.

In your 'Getting Started' instructions, you set minSdkVersion=21. So I believe it would make sense to either change this to 24, or to stop using putIfAbsent() - it's quite trivial to use containsKey()+put() instead.

Thanks!

How to Reproduce
Try to detect Polar devices on an Android device with Android 5.0, 5.1 or 6.0.

Expected behavior
No crash.

[JOikarinen]

Fix released in 3.2.1