Android 9 Development Cookbook - Third Edition

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If you click the Set Alarm button and wait for thirty minutes, you will see the Toast when the alarm triggers. If you are too impatient to wait and click the Set Alarm button again before the first alarm is triggered, you won't get two alarms. Instead, the OS will replace the first alarm with the new alarm, since they both use the same Pending Intent. (If you need multiple alarms, you need to create different Pending Intents, such as using different Actions.)