### 计算机代写|app代写安卓代写,Android代写|Understanding the Declarative Paradigm

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• Statistical Inference 统计推断
• Statistical Computing 统计计算
• Advanced Probability Theory 高等概率论
• Advanced Mathematical Statistics 高等数理统计学
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 计算机代写|app代写安卓代写,Android代写|Technical requirements

Jetpack Compose marks a fundamental shift in Android UI development. While the traditional view-based approach is centered around components and classes, the new framework follows a declarative approach.
In Chapter 1, Building Your First Compose App, I introduced you to composable functions, the basic building blocks of a Compose-based UI. In this chapter, we will briefly review how Android UIs are implemented with traditional classes and techniques. You will learn about some issues of this approach, and how a declarative framework helps overcome them.
The main sections of this chapter are as follows:

• Looking at the Android view system
• Moving from components to composable functions
• Examining architectural concepts

We’ll start by looking at my second sample app, Hello View. It is a re-implementation of the Hello app from Chapter 1, Building Your First Compose App. Hello View uses views, an XML layout file, and view binding.
Next, we will cover key aspects of components, which are UI building blocks in the view-based world. You will learn about the similarities and differences of composable functions, and we will find out how composable functions can overcome some of the limitations of component-centric frameworks.
Finally, we will look at the different layers of the Android framework and how they relate to building UIs. By the end of this chapter, you will have gathered enough background information to explore the key principles of Jetpack Compose, which is the topic of the next chapter.

## 计算机代写|app代写安卓代写,Android代写|Looking at the Android view system

The traditional approach to building Android UIs is to define component trees and modify them during runtime. While this can be done completely programmatically, the preferred way is to create layout files. They use XML tags and attributes to define which UI elements should be presented on screen. Let’s take a look:
$<$ ? xml version= “1. $0^{\prime \prime}$ encoding $=”$ “utf $-8^{\prime \prime}$ ? ><TextView
android: id= “@+id/message”
style=”@style/TextAppearance. AppCompat. Medium”
android: layout_width= “wrap_content”

$<$ /androidx. constraintlayout. widget. ConstraintLayout>
Layout files define a hierarchical structure (a tree). In the previous XML snippet, the root node (ConstraintLayout) contains only one child (TextView). The complete XML file of Hello View has two more children, an EditText component and a Button component. Layout files of real-world apps can be quite nested, containing dozens of children.

Generally speaking, … Layout elements are responsible for sizing and positioning their children. While they may have a visual representation (for example, background color or a border), they usually don’t interact with the user. Scrollview is one of the exceptions to that rule. All other (non … Layout) elements such as buttons, checkboxes, and editable text fields not only allow for user interaction – it’s their purpose.
Both layout and non-layout elements are called components. We will return to this term in the Moving from components to composable functions section. But before that, let’s see how layout files are used in apps.

## 计算机代写|app代写安卓代写,Android代写|Inflating layout files

Activities are one of the core building blocks of an Android app. They implement a quite sophisticated lifecycle, which is reflected by a couple of methods we can override.
Typically, oncreate () is used to prepare the app and to show the UI by invoking setContentView (). This method can receive an ID representing a layout file, for example, R. layout. main. Because of this, you must define variables pointing to the UI elements you wish to access. This may look like the following:
private lateinit var doneButton: Button
val doneButton = findViewById(R. id. done)

It turned out that this doesn’t scale well for bigger apps. There are two important issues to remember:

• You may face crashes during runtime if the variable is accessed before it has been initialized.
• The code quickly becomes lengthy if you have more than a few components.
Sometimes, you can prevent the first issue by using local variables, as follows:
val doneButton = findViewById (R.id.done)
This way, you can access the UI element immediately after the declaration. But the variable exists only in the scope in which it has been defined – a block or a function. This may be problematic because you often need to modify a component outside oncreate (). That’s because in a component-based world, you modify the UI by modifying the properties of a component. It turned out that often the same set of changes are necessary for different parts of the app, so to avoid code duplication, they are refactored into methods, which need to know the component to change it.
To solve the second issue – that is, to spare the developer from the task of keeping references to components – Google introduced view binding. It belongs to Jetpack and debuted in Android Studio 3.6. Let’s see how it is used:
class MainActivity : AppcompatActivity() {
private lateinit var binding: MainBinding
override fun onCreate (savedInstancestate: Bundle?) {
super. oncreate (savedInstancestate)
binding = MainBinding. inflate (layout Inflater)
setContentView (binding . root)
enableOrDisableButton()
}
$\ldots$
}

## 计算机代写|app代写安卓代写,Android代写|Technical requirements

Jetpack Compose 标志着 Android UI 开发的根本转变。虽然传统的基于视图的方法以组件和类为中心，但新框架遵循声明性方法。

• 看Android视图系统
• 从组件到可组合函数
• 检查架构概念

## 计算机代写|app代写安卓代写,Android代写|Looking at the Android view system

<? xml版本=“1。0′′编码=”“utf−8′′? ><TextView
android: id= “@+id/message”
style=”@style/TextAppearance. 应用兼容性。中”
android: layout_width= “wrap_content”

</安卓x。约束布局。小部件。ConstraintLayout>

## 计算机代写|app代写安卓代写,Android代写|Inflating layout files

private lateinit var doneButton: Button
val doneButton = findViewById(R. id. done)

• 如果变量在初始化之前被访问，您可能会在运行时遇到崩溃。
• 如果您有多个组件，代码很快就会变得冗长。
有时，您可以通过使用局部变量来防止第一个问题，如下所示：
val doneButton = findViewById (R.id.done)
这样，您可以在声明后立即访问 UI 元素。但是变量只存在于它被定义的范围内——一个块或一个函数。这可能是有问题的，因为您经常需要在 oncreate() 之外修改组件。这是因为在基于组件的世界中，您通过修改组件的属性来修改 UI。事实证明，对于应用程序的不同部分，通常需要进行相同的更改集，因此为了避免代码重复，将它们重构为方法，这些方法需要知道要更改它的组件。
为了解决第二个问题——也就是说，让开发人员免于保留对组件的引用的任务——谷歌引入了视图绑定。它属于 Jetpack，在 Android Studio 3.6 中首次亮相。让我们看看它是如何使用的：
class MainActivity : AppcompatActivity() {
private lateinit var binding: MainBinding
override fun onCreate (savedInstancestate: Bundle?) {
super. oncreate (savedInstancestate)
绑定 = MainBinding。inflate ( layout Inflater)
setContentView (binding . root)
enableOrDisableButton()
}

}

## 有限元方法代写

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。