further improvements:

- the day of week are evenly spread across the screen in the alarms detail activity
- the alarms are stored in a single shared preference (as a set) NB: you'll have to reset your alarms if you used a previous version (and also manually clean the shared preferences, but this is not needed)
- the list of alarms gets correctly updated after editing a specific alarm
- the actionbar back button saves the alarm status, the device back button doesn't. I'm not sure if it's a bug or a feature :)

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/GBAlarm.java

@@ -6,10 +6,14 @@ import android.os.Parcelable;
 import android.preference.PreferenceManager;
 
 import java.util.Calendar;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.Set;
 
-import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARM_PREFIX;
+import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARMS;
 
-public class GBAlarm implements Parcelable {
+
+public class GBAlarm implements Parcelable, Comparable {
 
     private int index;
     private boolean enabled;
@@ -27,9 +31,8 @@ public class GBAlarm implements Parcelable {
     public static final byte ALARM_SAT = 32;
     public static final byte ALARM_SUN = 64;
 
-    public static final String DEFAULT_ALARM1 = "0,false,true,31,7,30";
+    public static final String[] DEFAULT_ALARMS = {"2,false,false,0,15,30","1,false,false,96,8,0","0,false,true,31,7,30"};
-    public static final String DEFAULT_ALARM2 = "1,false,false,96,8,00";
+
-    public static final String DEFAULT_ALARM3 = "2,false,false,0,15,30";
 
     public GBAlarm(int index, boolean enabled, boolean smartWakeup, byte repetition, int hour, int minute) {
         this.index = index;
@@ -38,7 +41,6 @@ public class GBAlarm implements Parcelable {
         this.repetition = repetition;
         this.hour = hour;
         this.minute = minute;
-        store();
     }
 
     public GBAlarm(String fromPreferences){
@@ -50,7 +52,6 @@ public class GBAlarm implements Parcelable {
         this.repetition =  Integer.parseInt(tokens[3]);
         this.hour = Integer.parseInt(tokens[4]);
         this.minute = Integer.parseInt(tokens[5]);
-        store();
     }
 
     private static GBAlarm readFromParcel(Parcel pc) {
@@ -73,6 +74,11 @@ public class GBAlarm implements Parcelable {
         }
     }
 
+    @Override
+    public int hashCode() {
+        return getIndex();
+    }
+
     @Override
     public int describeContents() {
         return 0;
@@ -88,6 +94,16 @@ public class GBAlarm implements Parcelable {
         dest.writeInt(this.minute);
     }
 
+    @Override
+    public int compareTo(Object another) {
+        if (this.getIndex() < ((GBAlarm)another).getIndex()) {
+            return -1;
+        }else if (this.getIndex() > ((GBAlarm)another).getIndex()) {
+            return 1;
+        }
+        return 0;
+    }
+
     public int getIndex() {
         return this.index;
     }
@@ -137,7 +153,6 @@ public class GBAlarm implements Parcelable {
 
     public void setSmartWakeup(boolean smartWakeup) {
         this.smartWakeup = smartWakeup;
-        store();
     }
 
     public void setRepetition(boolean mon, boolean tue, boolean wed, boolean thu, boolean fri, boolean sat, boolean sun) {
@@ -149,29 +164,37 @@ public class GBAlarm implements Parcelable {
                 (fri ? ALARM_FRI : 0) |
                 (sat ? ALARM_SAT : 0) |
                 (sun ? ALARM_SUN : 0);
-        store();
     }
 
     public void setHour(int hour) {
         this.hour = hour;
-        store();
     }
 
     public void setMinute(int minute) {
         this.minute = minute;
-        store();
     }
 
     public void setEnabled(boolean enabled) {
         this.enabled = enabled;
-        store(); // TODO: if we have many setters, this may become a bottleneck
     }
 
-    private void store() {
+    public void store() {
-        //TODO: I don't like to have the alarm index both in the preference name and in the value
         SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(GBApplication.getContext());
-        String pref = PREF_MIBAND_ALARM_PREFIX +(this.index+1);
+        Set<String> preferencesAlarmListSet = sharedPrefs.getStringSet(PREF_MIBAND_ALARMS, new HashSet<String>());
-        sharedPrefs.edit().putString(pref, this.toPreferences()).apply();
+        //the old Set cannot be updated in place see http://developer.android.com/reference/android/content/SharedPreferences.html#getStringSet%28java.lang.String,%20java.util.Set%3Cjava.lang.String%3E%29
+        Set<String> newPrefs = new HashSet<String>(preferencesAlarmListSet);
+
+        Iterator<String> iterator = newPrefs.iterator();
+
+        while (iterator.hasNext()) {
+            String alarmString = iterator.next();
+            if(this.equals(new GBAlarm(alarmString))) {
+                iterator.remove();
+            }
+        }
+        newPrefs.add(this.toPreferences());
+        sharedPrefs.edit().putStringSet(PREF_MIBAND_ALARMS, newPrefs).commit();
+        return;
     }
 
     public static final Creator CREATOR = new Creator() {

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/AlarmDetails.java

@@ -1,29 +1,20 @@
 package nodomain.freeyourgadget.gadgetbridge.activities;
 
 import android.app.Activity;
-import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.os.Parcelable;
-import android.preference.PreferenceManager;
 import android.text.format.DateFormat;
+import android.view.MenuItem;
 import android.view.View;
 import android.widget.CheckedTextView;
 import android.widget.TimePicker;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import nodomain.freeyourgadget.gadgetbridge.GBAlarm;
 import nodomain.freeyourgadget.gadgetbridge.GBApplication;
 import nodomain.freeyourgadget.gadgetbridge.R;
 
-import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARM_PREFIX;
-
 public class AlarmDetails extends Activity {
 
-    private static final Logger LOG = LoggerFactory.getLogger(AlarmDetails.class);
-
-
     private GBAlarm alarm;
     private TimePicker timePicker;
     //using CheckedTextView allows for vertically aligned text
@@ -121,13 +112,23 @@ public class AlarmDetails extends Activity {
 
     }
 
-
     @Override
-    protected void onDestroy() {
+    public boolean onOptionsItemSelected(MenuItem item) {
-        super.onDestroy();
+        switch (item.getItemId()) {
+            case android.R.id.home:
+                // back button
+                updateAlarm();
+                finish();
+                return true;
+        }
+        return super.onOptionsItemSelected(item);
+    }
+
+    private void updateAlarm() {
         alarm.setSmartWakeup(ctvSmartWakeup.isChecked());
         alarm.setRepetition(ctvMonday.isChecked(), ctvTuesday.isChecked(), ctvWednesday.isChecked(), ctvThursday.isChecked(), ctvFriday.isChecked(), ctvSaturday.isChecked(), ctvSunday.isChecked());
         alarm.setHour(timePicker.getCurrentHour());
         alarm.setMinute(timePicker.getCurrentMinute());
+        alarm.store();
     }
 }

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/ConfigureAlarms.java

@@ -1,57 +1,86 @@
 package nodomain.freeyourgadget.gadgetbridge.activities;
 
+import android.app.ListActivity;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Bundle;
-import android.app.Activity;
 import android.preference.PreferenceManager;
-import android.widget.ListView;
+import android.view.MenuItem;
 
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
 
 import nodomain.freeyourgadget.gadgetbridge.BluetoothCommunicationService;
 import nodomain.freeyourgadget.gadgetbridge.GBAlarm;
 import nodomain.freeyourgadget.gadgetbridge.R;
 import nodomain.freeyourgadget.gadgetbridge.adapter.GBAlarmListAdapter;
-import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARM1;
+
-import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARM2;
+import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARMS;
-import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARM3;
 
 
-import java.util.ArrayList;
+public class ConfigureAlarms extends ListActivity {
-import java.util.List;
 
-
-public class ConfigureAlarms extends Activity {
-
-    ListView alarmListView;
     private GBAlarmListAdapter mGBAlarmListAdapter;
-
+    private Set<String> preferencesAlarmListSet;
-    final ArrayList<GBAlarm> alarmList = new ArrayList<>();
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
+
         setContentView(R.layout.activity_configure_alarms);
         getActionBar().setDisplayHomeAsUpEnabled(true);
 
         SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
-        //The GBAlarm class initializes the sharedPrefs values if they're missing, no need to handle it here
+        preferencesAlarmListSet = sharedPrefs.getStringSet(PREF_MIBAND_ALARMS, new HashSet<String>());
-        alarmList.add(new GBAlarm(sharedPrefs.getString(PREF_MIBAND_ALARM1, GBAlarm.DEFAULT_ALARM1)));
+        if (preferencesAlarmListSet.isEmpty()) {
-        alarmList.add(new GBAlarm(sharedPrefs.getString(PREF_MIBAND_ALARM2, GBAlarm.DEFAULT_ALARM2)));
+            //initialize the preferences
-        alarmList.add(new GBAlarm(sharedPrefs.getString(PREF_MIBAND_ALARM3, GBAlarm.DEFAULT_ALARM3)));
+            preferencesAlarmListSet = new HashSet<>(Arrays.asList(GBAlarm.DEFAULT_ALARMS));
+            sharedPrefs.edit().putStringSet(PREF_MIBAND_ALARMS, preferencesAlarmListSet).commit();
+        }
+
+        mGBAlarmListAdapter = new GBAlarmListAdapter(this, preferencesAlarmListSet);
+
+        setListAdapter(mGBAlarmListAdapter);
 
-        alarmListView = (ListView) findViewById(R.id.alarmListView);
-        mGBAlarmListAdapter = new GBAlarmListAdapter(this, alarmList);
-        alarmListView.setAdapter(this.mGBAlarmListAdapter);
     }
 
     @Override
-    protected void onDestroy() {
+    protected void onResume() {
-        super.onDestroy();
+        super.onResume();
+
+        SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
+        preferencesAlarmListSet = sharedPrefs.getStringSet(PREF_MIBAND_ALARMS, new HashSet<String>());
+
+        mGBAlarmListAdapter.setAlarmList(preferencesAlarmListSet);
+        mGBAlarmListAdapter.notifyDataSetChanged();
+
+        sendAlarmsToDevice();
+    }
+
+    @Override
+    public boolean onOptionsItemSelected(MenuItem item) {
+        switch (item.getItemId()) {
+            case android.R.id.home:
+                // back button
+                sendAlarmsToDevice();
+                finish();
+                return true;
+        }
+        return super.onOptionsItemSelected(item);
+    }
+
+    public void configureAlarm(GBAlarm alarm) {
+        Intent startIntent;
+        startIntent = new Intent(getApplicationContext(), AlarmDetails.class);
+        startIntent.putExtra("alarm", alarm);
+        startActivity(startIntent);
+    }
+
+    private void sendAlarmsToDevice() {
         Intent startIntent = new Intent(ConfigureAlarms.this, BluetoothCommunicationService.class);
-        startIntent.putParcelableArrayListExtra("alarms", alarmList);
+        startIntent.putParcelableArrayListExtra("alarms", mGBAlarmListAdapter.getAlarmList());
         startIntent.setAction(BluetoothCommunicationService.ACTION_SET_ALARMS);
         startService(startIntent);
     }
-
 }

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/adapter/GBAlarmListAdapter.java

@@ -1,13 +1,9 @@
 package nodomain.freeyourgadget.gadgetbridge.adapter;
 
 
-import android.app.Activity;
 import android.content.Context;
-import android.content.SharedPreferences;
 import android.graphics.Color;
-import android.preference.PreferenceManager;
 import android.view.LayoutInflater;
-import android.content.Intent;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.ArrayAdapter;
@@ -15,30 +11,100 @@ import android.widget.CompoundButton;
 import android.widget.Switch;
 import android.widget.TextView;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.Set;
+
 import nodomain.freeyourgadget.gadgetbridge.GBAlarm;
 import nodomain.freeyourgadget.gadgetbridge.R;
-import nodomain.freeyourgadget.gadgetbridge.activities.AlarmDetails;
+import nodomain.freeyourgadget.gadgetbridge.activities.ConfigureAlarms;
-
-
-import java.util.List;
-
-import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARM1;
-import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARM2;
-import static nodomain.freeyourgadget.gadgetbridge.miband.MiBandConst.PREF_MIBAND_ALARM3;
 
 
 public class GBAlarmListAdapter extends ArrayAdapter<GBAlarm> {
+
+
     private final Context mContext;
+    private ArrayList<GBAlarm> alarmList;
 
-    private List<GBAlarm> alarmList;
+    public GBAlarmListAdapter(Context context, ArrayList<GBAlarm> alarmList) {
-
-    public GBAlarmListAdapter(Context context, List<GBAlarm> alarmList) {
         super(context, 0, alarmList);
 
         this.mContext = context;
         this.alarmList = alarmList;
     }
 
+    public GBAlarmListAdapter(Context context,Set<String> preferencesAlarmListSet) {
+        super(context, 0, new ArrayList<GBAlarm>());
+
+        this.mContext = context;
+        alarmList = new ArrayList<GBAlarm>();
+
+        if (preferencesAlarmListSet != null) {
+            Iterator<String> iterator = preferencesAlarmListSet.iterator();
+
+            while (iterator.hasNext()) {
+                String alarmString = iterator.next();
+                alarmList.add(new GBAlarm(alarmString));
+            }
+        }
+
+        Collections.sort(alarmList);
+    }
+
+    public void setAlarmList(Set<String> preferencesAlarmListSet) {
+        alarmList = new ArrayList<GBAlarm>();
+
+        if (preferencesAlarmListSet != null) {
+            Iterator<String> iterator = preferencesAlarmListSet.iterator();
+
+            while (iterator.hasNext()) {
+                String alarmString = iterator.next();
+                alarmList.add(new GBAlarm(alarmString));
+            }
+        }
+
+        Collections.sort(alarmList);
+    }
+
+    public ArrayList<GBAlarm> getAlarmList() {
+        return alarmList;
+    }
+
+
+    public void update(GBAlarm alarm) {
+        for (GBAlarm a : alarmList) {
+            if(alarm.equals(a)) {
+             a = alarm;
+            }
+        }
+        alarm.store();
+    }
+
+    @Override
+    public int getCount() {
+        if (alarmList != null) {
+            return alarmList.size();
+        }
+        return 0;
+    }
+
+    @Override
+    public GBAlarm getItem(int position) {
+        if (alarmList != null) {
+            return alarmList.get(position);
+        }
+        return null;
+    }
+
+    @Override
+    public long getItemId(int position) {
+        if (alarmList != null) {
+            return alarmList.get(position).getIndex();
+        }
+        return 0;
+    }
+
     @Override
     public View getView(int position, View view, ViewGroup parent) {
 
@@ -66,16 +132,14 @@ public class GBAlarmListAdapter extends ArrayAdapter<GBAlarm> {
             @Override
             public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                 alarm.setEnabled(isChecked);
+                update(alarm);
             }
         });
 
         view.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
-                Intent startIntent;
+                ((ConfigureAlarms)mContext).configureAlarm(alarm);
-                startIntent = new Intent(mContext, AlarmDetails.class);
-                startIntent.putExtra("alarm", alarm);
-                mContext.startActivity(startIntent);
             }
         });
         alarmTime.setText(alarm.getTime());

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/miband/MiBandConst.java

@@ -15,10 +15,7 @@ public final class MiBandConst {
     public static final String PREF_USER_WEIGHT_KG = "mi_user_weight_kg";
     public static final String PREF_MIBAND_WEARSIDE = "mi_wearside";
     public static final String PREF_MIBAND_ADDRESS = "development_miaddr";  // FIXME: should be prefixed mi_
-    public static final String PREF_MIBAND_ALARM_PREFIX = "mi_alarm";
+    public static final String PREF_MIBAND_ALARMS = "mi_alarms";
-    public static final String PREF_MIBAND_ALARM1 = PREF_MIBAND_ALARM_PREFIX +"1";
-    public static final String PREF_MIBAND_ALARM2 = PREF_MIBAND_ALARM_PREFIX +"2";
-    public static final String PREF_MIBAND_ALARM3 = PREF_MIBAND_ALARM_PREFIX +"3";
 
     public static final String ORIGIN_SMS = "sms";
     public static final String ORIGIN_INCOMING_CALL = "incoming_call";

app/src/main/res/layout/activity_alarm_details.xml

@@ -18,7 +18,9 @@
             android:layout_height="wrap_content"
             android:id="@+id/alarm_time_picker"
             android:layout_alignParentTop="true"
-            android:layout_alignParentStart="true" />
+            android:layout_alignParentStart="true"
+            android:timePickerMode="clock"
+            android:layout_weight="1" />
 
         <CheckedTextView
             android:layout_width="wrap_content"
@@ -28,20 +30,18 @@
             android:id="@+id/alarm_ctv_smart_wakeup"
             android:checked="false"
             android:drawableTop="@drawable/abc_btn_check_material"
-            android:layout_toEndOf="@+id/alarm_time_picker"
+            android:layout_gravity="center_vertical"
-            android:layout_gravity="center_vertical" />
+            android:gravity="center_horizontal"
+            android:layout_weight="1" />
     </LinearLayout>
 
     <LinearLayout
         android:orientation="horizontal"
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
-        android:layout_below="@+id/alarm_time_picker"
-        android:layout_alignParentStart="true"
         android:id="@+id/dowSelector">
 
         <CheckedTextView
-            android:layout_marginLeft="4dp"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:text="@string/alarm_mon_short"
@@ -50,10 +50,12 @@
             android:checked="false"
             android:clickable="true"
             android:focusable="true"
-            android:drawableTop="@drawable/abc_btn_check_material"/>
+            android:drawableTop="@drawable/abc_btn_check_material"
+            android:layout_weight="1"
+            android:enabled="true"
+            android:gravity="center_horizontal" />
 
         <CheckedTextView
-            android:layout_marginLeft="4dp"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:text="@string/alarm_tue_short"
@@ -62,10 +64,12 @@
             android:checked="false"
             android:clickable="true"
             android:focusable="true"
-            android:drawableTop="@drawable/abc_btn_check_material"/>
+            android:drawableTop="@drawable/abc_btn_check_material"
+            android:layout_weight="1"
+            android:enabled="true"
+            android:gravity="center_horizontal" />
 
         <CheckedTextView
-            android:layout_marginLeft="4dp"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:text="@string/alarm_wed_short"
@@ -74,10 +78,12 @@
             android:checked="false"
             android:clickable="true"
             android:focusable="true"
-            android:drawableTop="@drawable/abc_btn_check_material"/>
+            android:drawableTop="@drawable/abc_btn_check_material"
+            android:layout_weight="1"
+            android:enabled="true"
+            android:gravity="center_horizontal" />
 
         <CheckedTextView
-            android:layout_marginLeft="4dp"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:text="@string/alarm_thu_short"
@@ -86,10 +92,12 @@
             android:checked="false"
             android:clickable="true"
             android:focusable="true"
-            android:drawableTop="@drawable/abc_btn_check_material"/>
+            android:drawableTop="@drawable/abc_btn_check_material"
+            android:layout_weight="1"
+            android:enabled="true"
+            android:gravity="center_horizontal" />
 
         <CheckedTextView
-            android:layout_marginLeft="4dp"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:text="@string/alarm_fri_short"
@@ -98,10 +106,12 @@
             android:checked="false"
             android:clickable="true"
             android:focusable="true"
-            android:drawableTop="@drawable/abc_btn_check_material"/>
+            android:drawableTop="@drawable/abc_btn_check_material"
+            android:layout_weight="1"
+            android:enabled="true"
+            android:gravity="center_horizontal" />
 
         <CheckedTextView
-            android:layout_marginLeft="4dp"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:text="@string/alarm_sat_short"
@@ -110,10 +120,12 @@
             android:checked="false"
             android:clickable="true"
             android:focusable="true"
-            android:drawableTop="@drawable/abc_btn_check_material"/>
+            android:drawableTop="@drawable/abc_btn_check_material"
+            android:layout_weight="1"
+            android:enabled="true"
+            android:gravity="center_horizontal" />
 
         <CheckedTextView
-            android:layout_marginLeft="4dp"
             android:layout_width="wrap_content"
             android:layout_height="fill_parent"
             android:text="@string/alarm_sun_short"
@@ -122,7 +134,10 @@
             android:checked="false"
             android:clickable="true"
             android:focusable="true"
-            android:drawableTop="@drawable/abc_btn_check_material"/>
+            android:drawableTop="@drawable/abc_btn_check_material"
+            android:layout_weight="1"
+            android:enabled="true"
+            android:gravity="center_horizontal" />
     </LinearLayout>
 
 

app/src/main/res/layout/activity_configure_alarms.xml

@@ -10,7 +10,7 @@
         android:descendantFocusability="blocksDescendants"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:id="@+id/alarmListView"
+        android:id="@android:id/list"
         android:layout_alignParentTop="true"
         android:layout_centerHorizontal="true" />
 </RelativeLayout>