QUESTION 1: WHY CAN NOT I RUN A REGULAR JAVA BYTECODE ON ANDROID?
Answer: Android uses Dalvik Virtual Machine (DVM), for which we do not need a special bytecode. It is necessary to convert a file containing a regular Java bytecode into an executable Dalvik file using a utility called “dx”. Under normal circumstances, developers do not need to use this tool directly, since the reset tools will generate DVM-compatible files for Android.
QUESTION 2: CAN I DOWNLOAD EXECUTABLE JAR FILES TO ANDROID? WHAT TYPE OF PACKAGES DOES ANDROID SUPPORT?
Answer: No, you cannot download executable JAR files to Android. The Android platform will not support the download of the JAR. Applications for Android should be packed in the Android Package (.apk) using the Android Asset Packaging Tool (AAPT) and then downloaded to the Android platform. Google provides development tools for Android, which can be used to create apk-files.
QUESTION 3: APPLICATIONS FOR ANDROID CAN BE WRITTEN ONLY IN JAVA?
Answer: No, you can write Android applications on C / C ++ using NDK.
QUESTION 4: WHICH FILES ARE DALVIK EXECUTABLE FILES?
Answer: Executable Dalvik files have a. dex extension and are packed into a file with the .apk extension when deployed on the device.
QUESTION 5: HOW DOES ANDROID TRACK INSTALLED APPLICATIONS?
Answer: When installing a new application, Android assigns it a unique identifier called the Linux User Id. This ID is used to track each installed application.
QUESTION 6: HOW DOES THE APPLICATION WORK IN ISOLATION FROM OTHER APPLICATIONS?
Answer: Each application has its own Linux User Id, and each Linux User Id has its virtual machine. This means that application code is run in isolation from other applications.
QUESTION 7: WHEN DOES ANDROID START AND STOP THE APPLICATION PROCESS?
Answer: Android generates an application process when any component of the application needs to be used. When the component is no longer needed, the process terminates (garbage collection takes place).
QUESTION 8: IN WHICH CASE TWO ANDROID APPLICATIONS CAN HAVE THE SAME LINUX USER ID AND THE SAME VIRTUAL MACHINE
Answer: Applications must be signed with the same certificate.
QUESTION 9: CAN I CHANGE THE NAME OF THE APPLICATION AFTER INSTALLING IT?
Answer: It is not recommended to change the name of the application after its installation, as this can lead to the inoperability of some of its functionality. For example, application shortcuts may stop working.
QUESTION 10: WHAT ARE ANDRO’S APPLICATION RESOURCE FILES?
Answer: As an Android application developer, you can configure the assembly of the project in such a way that different resource files (XML, JSON, JPEG, etc.) are added to the application so that you can download them at runtime. These files are called resources.
QUESTION 11: WHAT BASIC DIALOG BOXES CAN BE USED IN THE ANDROID APPLICATION?
AlertDialog: a warning dialog box that supports from 0 to 3 buttons and a list of selectable items.
ProgressDialog: extension AlertDialog, you can add additional buttons to it. It shows the indicator in the form of a circle or in the form of a horizontal strip.
DatePickerDialog: used to select the date by the user.
TimePickerDialog: Used to select the time by the user.
QUESTION 12: WHAT IS AN ACTIVITY COMPONENT?
Answer: Activation is used to provide users with an interactive dialog box. It can contain various interface components. A typical Android application consists of several Activities that are loosely related to each other. The developer determines the main Activity, which is launched when the application starts.
QUESTION 13: CAN AN ANDROID APPLICATION ACCESS FILES AND RESOURCES OF ANOTHER ANDROID APPLICATION?
Answer: The system configures the access rights to all files and resources of the application so only the owner application can access them. Other applications cannot access the resources of other applications until the same certificate signs them.
QUESTION 14: THE ANDROID APPLICATION NEEDS ACCESS TO SOME FEATURES OF THE DEVICE, FOR EXAMPLE SENDING SMS MESSAGES OR TO THE CAMERA. WHEN SHOULD THE USER GRANT HIM THE APPROPRIATE RIGHTS?
Answer: The user must provide the access rights to the application during the application installation.