Hey there! Let's break down your two Android development questions one by one, with practical code snippets to help you implement them smoothly:

Setting a custom date/time alarm involves working with AlarmManager, PendingIntent, and handling Android version-specific requirements. Here's how to do it:

• Step 1: Declare Required Permissions
  For Android 12 (API 31) and above, you need the SCHEDULE_EXACT_ALARM permission to set precise alarms. Add these to your AndroidManifest.xml:

  <uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
  <uses-permission android:name="android.permission.WAKE_LOCK" /> <!-- Optional: Wake device when alarm triggers -->
  

  Also, check and request the permission at runtime for API 31+:

  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
      val alarmManager = getSystemService(Context.ALARM_SERVICE) as AlarmManager
      if (!alarmManager.canScheduleExactAlarms()) {
          startActivity(Intent(Settings.ACTION_REQUEST_SCHEDULE_EXACT_ALARM))
      }
  }
  

• Step 2: Create a BroadcastReceiver for Alarm Triggers
  This component will handle the alarm event (e.g., show a notification). Create a class like:

  class MedicationAlarmReceiver : BroadcastReceiver() {
      override fun onReceive(context: Context?, intent: Intent?) {
          val notificationManager = context?.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
          
          // Create a notification channel (required for Android 8.0+)
          if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
              val channel = NotificationChannel(
                  "MEDICATION_CHANNEL",
                  "Medication Reminders",
                  NotificationManager.IMPORTANCE_HIGH
              )
              notificationManager.createNotificationChannel(channel)
          }
          
          // Build and show the reminder notification
          val notification = NotificationCompat.Builder(context, "MEDICATION_CHANNEL")
              .setContentTitle("Time to take your meds!")
              .setContentText(intent?.getStringExtra("MED_NAME"))
              .setSmallIcon(R.drawable.ic_medication)
              .setPriority(NotificationCompat.PRIORITY_HIGH)
              .build()
          
          notificationManager.notify(System.currentTimeMillis().toInt(), notification)
      }
  }
  

  Register it in your AndroidManifest.xml:

  <receiver android:name=".MedicationAlarmReceiver" />
  

• Step 3: Set the Alarm with Selected Date/Time
  Convert your picked date/time to a timestamp, then use AlarmManager to schedule the alarm:

  // Assume you have selected year, month, day, hour, minute from pickers
  val selectedCalendar = Calendar.getInstance().apply {
      set(selectedYear, selectedMonth, selectedDay, selectedHour, selectedMinute, 0)
      set(Calendar.MILLISECOND, 0)
  }
  val alarmTimestamp = selectedCalendar.timeInMillis
  
  val alarmManager = getSystemService(Context.ALARM_SERVICE) as AlarmManager
  val intent = Intent(this, MedicationAlarmReceiver::class.java).apply {
      putExtra("MED_NAME", "Your Medication") // Pass med details here
  }
  val pendingIntent = PendingIntent.getBroadcast(
      this,
      System.currentTimeMillis().toInt(), // Unique request code for multiple alarms
      intent,
      PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
  )
  
  // Use version-compatible alarm method
  when {
      Build.VERSION.SDK_INT >= Build.VERSION_CODES.S -> {
          alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, alarmTimestamp, pendingIntent)
      }
      Build.VERSION.SDK_INT >= Build.VERSION_CODES.M -> {
          alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, alarmTimestamp, pendingIntent)
      }
      else -> {
          alarmManager.setExact(AlarmManager.RTC_WAKEUP, alarmTimestamp, pendingIntent)
      }
  }
  

For your "SET ALARM" button, we'll use a custom AlertDialog (easier than a raw PopupWindow for this use case) to collect medication details before setting the alarm:

• Step 1: Create a Custom Popup Layout
  Make an XML file popup_add_medication.xml with fields for medication info:

  <?xml version="1.0" encoding="utf-8"?>
  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:orientation="vertical"
      android:padding="16dp">
  
      <TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Add Medication Reminder"
          android:textSize="18sp"
          android:textStyle="bold"/>
  
      <EditText
          android:id="@+id/et_med_name"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:hint="Medication Name"
          android:layout_marginTop="8dp"/>
  
      <EditText
          android:id="@+id/et_med_dosage"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:hint="Dosage (e.g., 1 tablet)"
          android:layout_marginTop="8dp"/>
  
      <Button
          android:id="@+id/btn_save_reminder"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:text="Save & Set Alarm"
          android:layout_marginTop="16dp"/>
  </LinearLayout>
  

• Step 2: Trigger the Popup on Button Click
  In your Activity/Fragment, add a click listener to your "SET ALARM" button:

  btn_set_alarm.setOnClickListener {
      val popupView = LayoutInflater.from(this).inflate(R.layout.popup_add_medication, null)
      val etMedName = popupView.findViewById<EditText>(R.id.et_med_name)
      val etMedDosage = popupView.findViewById<EditText>(R.id.et_med_dosage)
      val btnSave = popupView.findViewById<Button>(R.id.btn_save_reminder)
  
      val dialog = AlertDialog.Builder(this)
          .setView(popupView)
          .create()
  
      btnSave.setOnClickListener {
          val medName = etMedName.text.toString().trim()
          val medDosage = etMedDosage.text.toString().trim()
  
          if (medName.isNotEmpty()) {
              // Save reminder to storage (SharedPreferences/Room) if needed
              saveReminderToStorage(medName, medDosage, selectedCalendar.timeInMillis)
              
              // Set the alarm using the function from question 1
              setMedicationAlarm(medName, selectedCalendar.timeInMillis)
              
              Toast.makeText(this, "Reminder set successfully!", Toast.LENGTH_SHORT).show()
              dialog.dismiss()
          } else {
              Toast.makeText(this, "Please enter a medication name!", Toast.LENGTH_SHORT).show()
          }
      }
  
      dialog.show()
  }
  

• Optional: Save Reminders to Storage
  Use SharedPreferences to store reminders for later reference:

  private fun saveReminderToStorage(name: String, dosage: String, timestamp: Long) {
      val prefs = getSharedPreferences("MedReminders", Context.MODE_PRIVATE)
      val editor = prefs.edit()
      val uniqueKey = "reminder_${System.currentTimeMillis()}"
      editor.putString(uniqueKey, "$name|$dosage|$timestamp")
      editor.apply()
  }
  

内容的提问来源于stack exchange，提问作者Mohammed Rabiul Hossain