We will not always have an Android device at hand. Even having it, we need verify somehow our app will work fine on as many different Android models as possible. This is where emulators come into the picture. With them we can avoid falling into some frequent errors in development. But, as we will see later, to have greater security it is best to use real devices.
El Android EmulatorIncluded in the Android SDK, it is essentially a virtual device that runs on a computer. Its fundamental purpose is to allow developers to create, debug and test applications without the imperative need to own a physical device for each operating system version or each screen resolution.
Creation and management of emulators
We will access the emulator manager (Android Virtual Device Manager or AVD Manager) via this button:
We will see a window where we can access two lists: the list of the virtual devices that we have created, and that of the device definitionsTo create a virtual device (Avd) new, we will press on New (or Create Virtual Device), and we will follow these detailed steps:
- Hardware Selection: We chose the category (as Phone number o Tablet) and the specific model. It is highly recommended to choose models that include the icon of Google Play Storebecause they allow you to install apps directly from the store and offer a more realistic experience.
- System image: We select the Android version (the System ImageHere we decide the API level. For example, API 16 was used to cover most older devices, but nowadays it's vital to choose recent versions (like Android 10 or higher) depending on the project's needs.
- final configuration: On the last screen we can customize the device name, orientation and the RAM options.
When we need to edit our AVDs, we will select it from the list and press "Edit"In this section we can adjust the frontal cámara y trasera, internal storage (increasing the field Internal Storage (if the app requires a lot of data) and other advanced options. For beginners, we are mainly interested in "Device" (the model) and "Target" (the OS version).
If we need to create a new device definition, we will do so through this screen:
Normally it will not be necessary to create our own definitions, but if we require one specific screen resolutionWe will indicate the name, the size in inches and resolution in pixelsValues ​​such as screen ratio y "density" They are calculated automatically. It is also possible to add hardware such as the GPSaccelerometer or physical keyboard.
Use and execution of emulators
If we're just starting out, the IDE automatically chooses the AVD to run the project. To force a specific device, we need to go to Run → Run Configurations, choose the project and in the tab Target activate the option to always choose the device.
Advanced control via command line
For advanced users or those who wish to save RAM resources by avoiding opening the full IDE, it is possible to manage the emulator from the terminalFirst, it is essential to configure the Environment Variables in the system configuration file (such as .bashrc o .zshrc), declaring the routes of emulator, platform-tools y tools.
To start an emulator From the console, the command is used emulator -avd nombre_del_avd o emulator @nombre_del_avdIf we want to list all available virtual devices, we run emulator -list-avds.
Application installation can also be done using the tool adb (Android Debug Bridge)The general process is: compile the app into a file APKStart the emulator and run adb install nombre_app.apkIf multiple devices are connected, the brand should be used. -d to specify the destination.
Emulator file and directory structure
It is helpful to understand that the emulator is based on the hypervisor. QEMU and organizes its data into two main directories:
- System Directory: It contains read-only system (OS) images. Files such as the following are found here:
kernel-qemu,ramdisk.imgand thesystem.img. - Data Directory (DDA): Specific to each instance and contains the modifiable data. The most critical file is
userdata-qemu.img, which stores the settings and apps installed by the user.
Startup and debugging options
When launching the emulator via console, we can apply various boot options to simulate real-world conditions:
- Network and Latency: With
-netspeedy-netdelaywe can emulate connections GSM, EDGE, LTE or UMTSallowing you to test how the app behaves with slow internet. - Hardware and Camera: The option
-camera-backo-camera-frontIt allows you to define whether the emulator uses a virtual scene, the PC's webcam, or a video file. - Memory and Data: We can force the RAM with
-memory sizeor reset the device to factory settings with -wipe-data. - Acceleration: The use of
-accel autooptimizes performance by KVM (Linux) or HAXM (Windows/Mac).
Advantages and limitations of emulators
An emulator is a very useful approximation, but it's not perfect. There are technical limitations Important: it is not possible to emulate the Bluetooth natively, and some advanced features of Google Maps or games that require intensive use of OpenGL They may exhibit malfunctions or poor performance.
Despite this, the main reason for using them is the management of the different screen sizesIn the Android ecosystem, the aspect ratio And the resolution is extremely variable. If we develop only for our own phone, we run the risk of the interface breaking on other models.
The professional solution is always work with relative measures and scalable, avoiding absolute values. The emulator allows you to validate that the design is adaptable without needing to buy dozens of physical devices.
Resolution of common problems
Many developers encounter difficulties when starting the emulator for the first time. The most frequent errors are usually:
- Virtualization disabled: It is essential to activate the hardware virtualization (VT-x or AMD-V) in the BIOS from the computer. Without this, the emulator will not start or will be extremely slow.
- Conflicts with HAXM: On Intel systems, it may be necessary to reinstall the Intel x86 Emulator Accelerator (HAXM) from the SDK Manager to improve execution speed.
- Slow start-up: To speed up the process, you can use the option
-no-boot-animto disable the startup animation.
Resources and tools for the developer
For those starting out on this path, it is essential to have the Android Studiowhich is the official IDE based on IntelliJ IDEA. Additionally, if you wish to develop high-performance applications (especially games), it is recommended to install the NDK (Native Development Kit) to write code in C or C++.
It is recommended to follow the guidelines of Material Design Google uses this to ensure consistent interaction and visual design across all platforms. For further information, resources such as official code samples and usability tests are available in the Android developer documentation.
For those who use hybrid frameworks such as React nativeThe process is similar: SDK and AVD Manager configuration is required, but execution is usually launched from the terminal using framework-specific commands once the emulator is active and detected by adb.
For more information, you can consult the Basic guide to programming in Android.
The combined use of emulators and physical devices allows for a robust development cycle, where the emulator solves screen fragmentation and the real hardware validates the final performance and sensory functions of the device.
