All users must have the Signal app installed to communicate with each other. Encrypted calls and messages use your data connection; therefore both parties to the conversation must have Internet access on their mobile devices. On Android, Signal can replace your default text messaging application, so within Signal it is still possible to send unencrypted SMS messages.
Unencrypted SMS messages go through your mobile plan and may incur fees as set by your plan. Download Location : The app can be downloaded from the Google Play store. This will allow you to more easily discover which of your contacts you can communicate with over Signal.
You will also be prompted to allow Signal to make and manage phone calls. As a result, any incoming Signal call may interrupt your regular phone calls. You will now see the following screen. In order to verify your phone number, you will be sent an SMS text with a six-digit code. You will now be prompted to enter that code. The profile image and name you choose will be shown to any contacts you have saved in your address book, when you initiate or accept new chats, and when you join new groups.
A first name either genuine or made up is required, the image and last name are optional. You will be asked to confirm your pin. In order to use Signal, the person that you are contacting must have Signal installed. If you try to send a message to someone using Signal and they do not have the Signal app installed, it will attempt to send a standard, non-encrypted text message.
The standard text message will only be sent if Signal set as the default SMS app. If you try to call the person, it will place a standard phone call. Warning: Signal provides you with a list of other Signal users in your contacts. To do this, data representing the phone numbers in your contact list is uploaded to the Signal servers, although this data is deleted almost immediately.
This may be an issue for those with particularly sensitive threat models. If sharing your contacts with Signal is a concern, you can deny the contacts permission during setup as described above. They use Google on Android and Apple on iPhone.
That means information about who is receiving messages and when they were received may leak to these companies. Task: Populate the GameViewModel The ViewModel survives configuration changes, so it's a good place for data that needs to survive configuration changes: Put data to be displayed on the screen, and code to process that data, in the ViewModel. The ViewModel should never contain references to fragments, activities, or views, because activities, fragments, and views do not survive configuration changes.
For comparison, here's how the GameFragment UI data is handled in the starter app before you add ViewModel , and after you add ViewModel : Before you add ViewModel : When the app goes through a configuration change such as a screen rotation, the game fragment is destroyed and re-created.
The data is lost. When the app goes through a configuration change, the ViewModel survives, and the data is retained. Make sure word and score are not private. In the GameViewModel , make sure the onSkip and onCorrect methods are not private , because you will reference these methods from the fragment. Remove the code to update the score and instead call the corresponding onSkip and onCorrect methods on viewModel. Because you moved the nextWord method to the ViewModel , the game fragment can no longer access it.
These methods are now being called from the GameFragment. Build the app and make sure there are no errors. If you have errors, clean and rebuild the project. Run the app and play the game through some words. While you are in the game screen, rotate the device. Notice that the current score and the current word are retained after the orientation change. Task: Implement click listener for the End Game button In this task, you implement the click listener for the End Game button.
In GameFragment , add a method called onEndGame. The onEndGame method will be called when the user taps the End Game button. Just beneath these two lines, set a click listener for the End Game button. Use the binding variable, binding. Inside the click listener, call the onEndGame method. Pass in the score as an argument, using Safe Args. Tap the End Game button. Notice that the app navigates to the score screen, but the final score is not displayed.
You fix this in the next task. Under the score package, create a new Kotlin class called ScoreViewModel. This class will be the ViewModel for the score fragment. Add a constructor parameter for the final score. Add an init block with a log statement. In the ScoreViewModel class, add a variable called score to save the final score. This class will be responsible for instantiating the ScoreViewModel object. To resolve the error, override the create method. In the create method, return the newly constructed ScoreViewModel object.
Use the ScoreViewModelFactory. Pass in the final score from the argument bundle, as a constructor parameter to the ScoreViewModelFactory.
Call the ViewModelProvider. This will create the ScoreViewModel object using the factory method defined in the viewModelFactory class. Cycle through some or all the words and tap End Game. Notice that the score fragment now displays the final score. The score value should be displayed. Solution code Congratulations! Android Studio project: GuessTheWord Summary The Android app architecture guidelines recommend separating classes that have different responsibilities.
UI controllers should only contain logic that handles UI and operating system interactions; they shouldn't contain data to be displayed in the UI. Put that data in a ViewModel. The ViewModel class stores and manages UI-related data. The ViewModel class allows data to survive configuration changes such as screen rotations. ViewModel is one of the recommended Android Architecture Components.
Factory is an interface you can use to create a ViewModel object. Doesn't contain any data to be displayed in the UI. Contains data that the UI controller displays in the UI. Contains code for displaying data, and user-event code such as click listeners. Contains code for data processing. Destroyed and re-created during every configuration change.
Contains views. Contains a reference to the associated ViewModel. In the dialog that opens, change the class name HelloDroidActivity and click Refactor :. All references to this class will be updated automatically, and your application's source code will look as follows:. Replace the code in HelloDroid. Note that the identifiers we've used in the source code correspond to those we've set in our layout definition file, otherwise our code would not work.
First of all, to be able to run our application, we need to configure a virtual device. On the first step of the wizard, click Create Virtual Device :. On the next step, we need to select the hardware that our virtual device will emulate.
Let's select Phone on the left, and choose Pixel 2 as the target device:. Click the Download link next to the system image you want to mimic on the virtual device. For this tutorial, we've chosen to download the R system image.
In the License Agreement dialog that opens, read the license agreement and accept it, then click Next and wait for the download to finish. When the system image has been downloaded, select it and click Next in the System Image step of the wizard.
On the last step, you can modify your virtual device name and select the startup size and orientation of the screen. Choose the portrait layout and click Finish :.
The newly configured device appears in the Android Virtual Device Manager. On the main IntelliJ IDEA toolbar, make sure the automatically created Run configuration and the virtual device we've just configured are selected and click :. The Android emulator will launch after the build has successfully finished, with our application started:. Click the droid image and see how the application processes the tap events, counts them and returns the corresponding message:.
Tutorial: Create your first Android application In this tutorial, we will create a simple yet fully-functional Android application that counts how many times you tap a droid image. Optionally, modify the location for the Android SDK, and click Next : Review the installation settings and click Finish to start the download: When all components have been downloaded and installed, click Finish : Select Empty Activity as the project template: On the last step, type HelloDroid as the project name and select Java as the language: Configure project JDK Now that we have created our first project, let's make sure it uses the correct JDK.
Note that it hides project files and directories that you don't commonly use to see them, choose the Project view : The app folder consists of the following subfolders: manifests : contains the AndroidManifest.
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