Google Developers的高级Android Kotlin课程

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"3、使用 Kotlin 进行高级 Android 开发（Codelab）, 这是一份由Google Developers培训团队设计的课程，专注于利用Kotlin进行高级Android应用开发。课程包括一系列Codelab，涵盖了从通知、高级图形、动画到地理位置、测试和依赖项注入以及登录等主题。建议按顺序学习，每个Codelab都有对应的解决方案代码在GitHub上可供参考。" 此课程主要针对已经具备Kotlin编程基础和Android应用开发经验的学习者，要求熟悉Kotlin训练营和基础Android开发的知识，如使用Android Studio、运行应用、创建activity和fragment、遵循Material Design创建界面、处理点击事件、使用ViewModel和LiveData、实现数据绑定、运用Room数据库、使用协程和WorkManager处理后台任务、进行网络连接和数据获取，以及保存和恢复应用状态。课程内容详述如下： 1. **通知**：这节课将深入讲解如何在Android应用中集成和管理通知，包括本地通知和远程通知，以及如何使用通知渠道和通知扩展功能来提升用户体验。 2. **高级图形**：这一部分将介绍如何使用Android的图形库和API创建复杂的2D和3D图形，包括自定义视图、SVG渲染、Path操作、动画效果等，以实现更丰富的视觉呈现。 3. **动画**：学习如何使用Kotlin和Android Animation框架创建流畅的过渡效果和用户交互反馈，包括属性动画、视图动画和过渡动画的使用。 4. **地理位置**：这节课将涉及如何利用GPS和网络定位服务获取用户位置，以及如何处理地理围栏和路径规划，为应用添加基于位置的功能。 5. **测试和依赖项注入**：这部分内容将涵盖单元测试、UI测试、集成测试的基本原则，同时讲解如何使用依赖注入框架（如Dagger或Hilt）来提高代码的可测试性和可维护性。 6. **登录**：最后一课将关注用户认证和授权流程，包括OAuth、JWT等认证机制，以及如何安全地存储用户凭据和实现会话管理。通过这个课程，开发者不仅可以深化对Kotlin在Android开发中的高级用法的理解，还能提升构建复杂、高性能、测试驱动的Android应用的能力。对于想要提升自己Android开发技能的专业人士来说，这是一个不可多得的学习资源。

16. Select Notifications from the list of settings. You should see a new channel named Egg, right

below the Show notifications setting.

When you run the app the notification is now shown. Both you as the app developer and your

users can customize the settings and behavior for all notifications sent on this channel. Congrats,

you created a notification!

Step 3: Add notifications to your app

So far this shows the basic usage of the notifications API, but sending a notification right after

starting the timer doesn't make much sense. Users would probably prefer to be notified when the

egg is ready. In the following part of the codelab, you will fix this and change the toast message

to a notification.

You have already sent the notification and observed how it is shown to the users but this was just

the first step to creating great notifications. In this step, you will change your notification to be

sent at a more appropriate time.

Your app uses AlarmManager to set up an alarm. The code related to AlarmManager is already given

in the starter code and used for showing the toast message. AlarmManager keeps track of the

desired time selection and will trigger the onReceive() function of AlarmReceiver.kt when the time is

up. If you open AlarmReceiver.kt and navigate to onReceive(), you should see the toast message that

is displayed every time you set up an egg timer.

1. Open AlarmReceiver.kt, an instance of NotificationManager, and call the sendNotification() function with

the message text and context parameters.

// AlarmReceiver.kt

// TODO: Step 1.9 add call to sendNotification

val notificationManager = ContextCompat.getSystemService(

context,

NotificationManager::class.java

) as NotificationManager

notificationManager.sendNotification(

context.getText(R.string.eggs_ready).toString(),

context

)

2. Optionally, remove the toast since your app will be sending a notification when the timer is up.

// AlarmReceiver.kt

// TODO: Step 1.10 [Optional] remove toast

// Toast.makeText(

// context,

// context.getText(R.string.eggs_ready),

// Toast.LENGTH_SHORT

// ).show()

3. Run your app . You should see a notification every time you start the timer and every time the

timer is up.

This isn't ideal. You don't want to send too many notifications to your users. You can remove the

first notification which is sent when the user starts the timer.

4. Open EggTimerFragment.kt and remove the notification code for Step 1.5.

// EggTimeViewModel.kt

// TODO: Step 1.5 get an instance of NotificationManager

// and call sendNotification

// val notificationManager = ContextCompat.getSystemService(

You created the intent, but the notification is displayed outside your app. To make an intent work

outside your app, you need to create a new PendingIntent.

PendingIntent grants rights to another application or the system to perform an operation on behalf of

your application. A PendingIntent itself is simply a reference to a token maintained by the system

describing the original data used to retrieve it. This means that, even if its owning application's

process is killed, the PendingIntent itself will remain usable from other processes it has been given

to. In this case, the system will use the pending intent to open the app on behalf of you,

regardless of whether or not the timer app is running.

2. Create a PendingIntent with applicationContext, NOTIFICATION_ID, the contentIntent you created in the

previous step, and the PendingIntent flag. The PendingIntent flag specifies the option to create a

new PendingIntent or use an existing one. You need to set PendingIntent.FLAG_UPDATE_CURRENT as

the flag since you do not want to create a new notification if there is an existing one. This way you

will be modifying the current PendingIntent which is associated with the intent you are supplying.

// NotificationUtils.kt

// TODO: Step 1.12 create PendingIntent

val contentPendingIntent = PendingIntent.getActivity(

applicationContext,

NOTIFICATION_ID,

contentIntent,

PendingIntent.FLAG_UPDATE_CURRENT

)

3. Pass the PendingIntent to your notification. You do this by calling setContentIntent() on

the NotificationBuilder. Now, when you click the notification, the PendingIntent will be triggered,

opening up your MainActivity.

4. Also set setAutoCancel() to true, so that when the user taps on the notification, the notification

dismisses itself as it takes them to the app.

// NotificationUtils.kt

// TODO: Step 1.13 set content intent

.setContentIntent(contentPendingIntent)

.setAutoCancel(true)

5. Run the app again.

6. Set a timer, put the app in the background, and wait for the notification to appear.

7. Once you see the notification, click on the notification by pulling down the status bar, and observe

how the app is brought to the foreground.

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