core: ui: Add IntSeekBarPreference

Signed-off-by: Carlos Rafael Giani <crg7475@mailbox.org>

core/ui/src/main/java/info/nightscout/core/ui/elements/IntSeekBarPreference.kt

@@ -0,0 +1,49 @@
+package info.nightscout.core.ui.elements
+
+import android.content.Context
+import android.util.AttributeSet
+import androidx.core.content.edit
+import androidx.preference.SeekBarPreference
+
+/**
+ * Variant of SeekBarPreference with built-in string->int conversion.
+ *
+ * The normal SeekBarPreference crashes if the associated value in the
+ * SharedPreferences is not an int. This is a problem, because AAPS
+ * exports all settings as strings. When importing settings again,
+ * the former int value becomes a string value as a consequence.
+ *
+ * For this reason, this variant exists. It tries to first read the
+ * initial preference value from the preferences as an int. If it is
+ * not an int, ClassCastException is thrown. This is caught, and the
+ * value is re-read as a string and then converted to an int.
+ *
+ * To use this in fragment XMLs, replace "SeekBarPreference" in them
+ * with "info.nightscout.core.ui.elements.IntSeekBarPreference".
+ */
+class IntSeekBarPreference @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null) : SeekBarPreference(context, attrs) {
+    override fun onSetInitialValue(defaultValue: Any?) {
+        val actualDefaultValue = if (defaultValue == null)
+            0
+        else
+            (defaultValue as Int?) ?: 0
+
+        val storedValue = try {
+            getPersistedInt(actualDefaultValue)
+        } catch (_: ClassCastException) {
+            val keyToDelete = key
+            // Remove the key manually. The setValue() function that is
+            // used in the "value" property assignment below tries to look
+            // up the existing stored value if it exists. If it does exist,
+            // it tries to read the value - as an int. We then get another
+            // ClassCastException. To avoid that, first delete the existing
+            // value. This prevents setValue() from doing that int lookup.
+            sharedPreferences?.edit {
+                remove(keyToDelete)
+            }
+            getPersistedString(actualDefaultValue.toString()).toInt()
+        }
+
+        value = storedValue
+    }
+}