Introduction

In this chapter, we explore one of the most important parts of an Android app: its design. We’ll look at how to create a basic app flow and then talk about how activities are organized into hierarchies for ease of navigation.

An Activity is a single focused thing that the user can do.

An Activity is a single focused thing that the user can do. It is the fundamental building block of an Android application. Activities are typically presented to the user as full-screen windows, but they can also be used in other ways.

An activity’s primary purpose is to provide a way for its components (such as views) and services (such as network connections) to interact with each other and respond to external events such as user input or changes in device state.

Determining which activities to build is a key step in designing your app.

As you design your app, it’s important to determine what activities you need to build. An activity is a unit of work that performs an action and returns control back to the UI thread.

Organizing your app into a hierarchy of related activities allows for easy navigation within the app and between apps. For example, if you have an Activity for signing into Facebook (a sign-in group), then this can be placed within a Navigation Drawer as its own UI element so that users can easily navigate from one screen to another without having to use any buttons or other interfaces when viewing their account information on another screen like “Settings” or “Messenger.”

In addition, this could also lead users into believing that it’s normal for there not necessarily being anything more than just one thing happening at any given moment – rather than seeing all sorts of things happening simultaneously throughout different screens which could confuse them even more!

The simpler your design, the easier it will be for people to understand.

The simpler your design, the easier it will be for people to understand. This is especially important when you’re designing an app that has multiple screens or features. If there are too many options on one screen, users might get confused and frustrated trying to figure out where they are in order to find what they need.

Don’t try to do too much! Your design should have a clear focus so users can easily navigate through their experience with minimal hassle or confusion—and then move on with their day without having any problems whatsoever (like not being able to find what they were looking for).

You should create a hierarchy of activities (A home screen activity, a detail activity)

The hierarchy of activities is one of the most important concepts to understand when building an Android app. It defines how your app will transition from one activity to another, and it can be thought of as a series of screens that make up your entire user experience (UX).

The first step in creating this hierarchy is defining each activity’s purpose: what does it do? How does it help users complete tasks within your application? What information should they get when they open this particular screen? Once you’ve answered these questions, you can define how each screen should look and feel like by using a layout file (layouts) and create Transition objects (transitions), which connect between different screens based on user input or location changes.

You must typically navigate back to the Home screen activity.

You can navigate back to the Home screen activity

If you are in an activity, then tap on Back button and choose Home screen or any other option.

If you are in a fragment, then hit on Back button twice and return to previous Activity (or start another).

If you are in a service, it does not have an equivalent of “Back” button so there is no way to go back from here other than quitting the app altogether!

Activities are made up of Layouts and Views (and fragments).

An activity is a single focused thing that the user can do. It’s what you’ll see when you launch your app, and it’s where all of your UI elements go.

When you first run an Android app, it will show up as a blank screen with no content on it—no buttons or text boxes yet! This is how Android handles when no activities are created yet: by showing off just one activity in full-screen mode (with no menus).

Activity layout files contain information about how to arrange views on the screen and also define what those views look like. Views are UI elements such as buttons (or other controls) or text boxes; they’re arranged into different positions within an Activity so that they appear correctly when they’re shown during runtime. View objects can also be attached directly onto Views via setContentView() , which makes them easier to reuse across different activities within your APK file—if you want some kind of button but don’t know exactly where it should go yet, just attach one now!

A Layout is an object that organizes how Views appear onscreen.

A Layout is an object that organizes how Views appear onscreen. Each view has a layout, and you can define a new layout for each Activity or Fragment by creating an XML file with the .xml extension.

You can use the Android Layout Editor to create layouts visually, but you also typically write your own layouts from scratch using XML files (or .java files). This chapter covers how to create and modify these files using Eclipse’s graphical user interface (GUI) editor.

View objects are UI elements such as buttons and text boxes.

View objects are UI elements such as buttons and text boxes. They are what the user sees on the screen, and they’re usually created with XML, but you can also create them programmatically.

Android provides several types of layouts (linear, relative …)

LinearLayout: A linear layout is a one-dimensional container that arranges its child views along a single axis. For example, you can use linear layouts to create a horizontal list of items or to wrap around content like a card in an Android app.

RelativeLayout: A relative layout arranges its child views based on the distance from their parent (the top-left corner). It’s useful when you want your elements to align themselves while still allowing them some room around them so they don’t overlap with each other.

You can use Android’s Layout Editor to visually create layouts without writing XML by hand.

You can use Android’s Layout Editor to visually create layouts without writing XML by hand. The Layout Editor is a graphical layout tool for creating and modifying user interfaces in Android.

The Layout Editor makes it easy to create intuitive layouts for your application, with drag-and-drop functionality that lets you quickly add or change elements of the layout.

Intents are the messages between android components (activities, services, Broadcast Receivers and content providers).

Intents are the messages between Android components (activities, services, Broadcast Receivers and content providers).

Intents can be used to start activities, services and broadcast receivers.

Activities are defined in Manifest files and are arranged in hierarchies to make navigation easier

An Activity is a single screen that contains a user interface and can be launched by other activities. Activities are defined in Manifest files and are arranged in hierarchies to make navigation easier.

An Activity can have one or more Views, which are the actual visual elements of an application (e.g., buttons, text boxes). Each View corresponds to a specific UI component on your screen (e.g., an EditText control).

Activities can be nested within other activities as well as within each other’s hierarchy; this allows you to build complex apps with an intuitive organization of screens based on their function rather than just having everything laid out flat like a traditional app might do when it comes time for users to get started interacting with something new!

Conclusion

We hope that you have a better understanding of how Android’s activities work and how they can be used to enhance your app’s overall user experience. We also hope that you now feel more confident using the tools in Android Studio or Eclipse to design your own apps.

USEFUL NOTES FOR:

you will analyze asymmetric and symmetric encryption. Evaluate the differences between the two of them and which one that you would determine is the most secure. The writing assignment requires a minimum of two written pages to evaluate the history.

Introduction

Symmetric encryption is one of the most popular methods for securing data. The basic idea behind it is to use one shared secret key for both encryption and decryption. This makes it very easy to use, but also makes it vulnerable to attack if the key is stolen or leaked.

There are many ways to categorize symmetric algorithms.

The most common way to categorize symmetric algorithms is into three separate groups, which include block ciphers, stream ciphers and hybrid schemes.

The choice between these three types of encryption depends on the type of data to be encrypted. If you want to protect sensitive information such as credit card numbers or passwords then you should use a block cipher because it encrypts each letter in the message individually. However if you have large amounts of data that need to be transmitted quickly over insecure channels such as radio waves then it might be better for this type of transmission not only because it has higher speed than other forms but also because there are no collisions during transmission (where multiple messages can collide). This may lead us into thinking about how different types affect our privacy depending on how we use them:

It is one of the most common encryption methods used in commercial applications.

Symmetric encryption is a common method of encrypting data that is used in many commercial applications. It’s more secure than asymmetric encryption, but slower.

There are over 100 different symmetric key encryption algorithms.

Symmetric key encryption algorithms are used for confidentiality. These algorithms can be divided into three separate groups: block ciphers, stream ciphers and hybrid schemes.

Block cipher algorithms encrypt data using a fixed-size block of bits (the size of two or more blocks). The block size is usually 64 bits in length, but it may vary depending on the algorithm used.

Stream cipher algorithms use keys that change each time they’re used to encrypt or decrypt messages; this makes them much faster than traditional symmetric key methods like DES because it doesn’t require re-encryption of previous messages every time one is sent out over network connections which makes this type ideal for high speed applications like telecommunication systems where latency matters most!

Symmetric (or secret key) algorithms use a single key for both encryption and decryption

Symmetric (or secret key) algorithms use a single key for both encryption and decryption. This is the most common way to encrypt data. The same key must be used for both encryption and decryption, so if someone gets ahold of your private key, they can also decrypt any messages sent using that same private key.

The best type of symmetric algorithm has its own version number, which is different from the version number of open source software like OpenSSL or GnuPG. It also has several other properties:

It uses an underlying hash function called SHA-1 to create hashes; these hashes are used as keys in other operations.

There are multiple ways in which this algorithm can operate – each one creates different hashes based on specific input values (the “key”). For example, if you use one method but not another then your output will differ from what others expect!

Algorithms can be classified as block ciphers, stream ciphers, or hybrid schemes.

You can also classify algorithms as block ciphers, stream ciphers, or hybrid schemes.

Block cipher algorithms encrypt data in fixed size blocks; stream cipher algorithms encrypt small amounts of data. The choice between the two approaches depends on the type of data to be encrypted: if it’s more than one byte long (like an email message), then you should use a block cipher; if it’s less than one byte long (like a password), then you should use a stream cipher.

It is important to note that hybrid schemes are not really symmetric encryption schemes because they combine both approaches into one single algorithm for each end-to-end session.

In general, longer keys are better than shorter ones, since they are more difficult to “crack”.

In general, longer keys are better than shorter ones, since they are more difficult to “crack”. For example:

If you have a four-character password and want to encrypt it with a 128-bit key (i.e., a password of 12 characters), then your encrypted text will be only one character long. The remaining characters would be useless because they can’t be used in any way other than as random numbers. So if someone knows your password and wants access to your account, there’s no way he can get at that last character by trying different combinations until he finds something useful (unless he knows what type of encryption we’re talking about). This is an ideal situation since the longer the key length is meant us greater security but also slower performance when encrypting or decrypting data because there’s more data being stored on our hard drive(s).

Symmetric algorithms can be divided into three separate groups: block ciphers, stream ciphers and hybrid schemes. The choice between block cipher, stream cipher and hybrid scheme depends on the type of data to be encrypted.

Symmetric algorithms can be divided into three separate groups: block ciphers, stream ciphers and hybrid schemes. The choice between block cipher, stream cipher and hybrid scheme depends on the type of data to be encrypted.

Block ciphers work by encrypting a fixed-length block at a time. This approach has been around for many years now because it provides good security for small amounts of data (e.g., passwords). However, if you want something more powerful than that then you might need to consider using a stream cipher instead!

The main advantage of working with streams is that they allow you to send multiple pieces of information through one channel which makes them much faster than traditional methods like XORing together bit strings or adding random numbers together until they reach a certain value (which could take hours). They also require less processing power because they don’t need as many calculations per byte processed compared with traditional methods such as AES since there aren’t too many possible keys combinations being considered here; only one key is required per message being sent.”

Block algorithms encrypt data in fixed size blocks. These algorithms usually operate on very large integers or binary strings and are often used in protocols such as HTTPS, SSH, IPsec and others that do not require hard real-time guarantees. However, they are not suitable for applications that need such guarantees such as VoIP and some video streaming applications.

Block algorithms encrypt data in fixed size blocks. These algorithms usually operate on very large integers or binary strings and are often used in protocols such as HTTPS, SSH, IPsec and others that do not require hard real-time guarantees. However, they are not suitable for applications that need such guarantees such as VoIP and some video streaming applications.

In block ciphers a block is a unit of information (for example 128 bits) that gets encrypted by the ciphertext being generated from plaintext blocks. The number of rounds in a block cipher determines how many times it can be decrypted before failing encryption at all if used with a different key size than what was originally chosen for its round function (e.g., 3 rounds means only 2 cycles will be needed).

Stream algorithms are more adequate for applications that require hard real-time guarantees. They encrypt small amounts of data (usually 8-bit bytes into 8-bit bytes). The disadvantage is that these algorithms tend to have different cryptographic strength per bit than the block ciphers because each byte is encrypted separately from all other bytes.

Stream ciphers encrypt a single bit at a time. Stream ciphers are used in applications that require hard real-time guarantees, such as voice over IP (VoIP) and some video streaming applications.

These algorithms have different cryptographic strength per bit than block ciphers because each byte is encrypted separately from all other bytes.

Conclusion

In conclusion, you should be able to choose the best algorithm for your application depending on what kind of security and performance requirements are needed. The best way to understand these differences is by doing some research and experimenting with different algorithms. We hope this assignment has helped you learn more about symmetric key encryption algorithms and hopefully helped clarify some of the confusion that surrounds them!