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This article mainly introduces the Android how to learn the relevant knowledge, the content is detailed and easy to understand, the operation is simple and fast, has a certain reference value, I believe you will have a harvest after reading this Android how to learn the article, let's take a look.

Week 1 Android System Architecture (Android system Architecture)

Android is an open source, Linux-based software stack created for a wide array of devices and form factors.

Android is an open source, Linux-based software stack for creating interfaces for mobile devices of different sizes.

System architecture:

System Apps

Java API Framework

View System

Resource Manager

Notification Manager

Activity Manager

Content Providers

Native Cpico + Libraries

Android Runtime

Hardware Abstraction Layer (HAL)

Linux Kernel

Power Management

Application layer: that is, the application layer, including not only system-level applications such as SMS contacts, but also some third-party applications installed by users themselves.

Framework layer: most of this layer is written in Java, including system services and four major components

Library layer: most of this layer is written by CumberCraft +, mainly virtual machines, as well as some third-party libraries such as SQLite and WebKit

HAL layer: hardware abstraction layer

Linux kernel layer: contains the Linux kernel and some drivers, such as Bluetooth driver, Camera driver, etc., this Binder driver is also in this layer

Android Platform

The Android platform provides a framework API that applications can use to interact with the underlying Android system.

The framework API consists of:

A core set of packages and classes

A set of XML elements and attributes for declaring a manifest file

A set of XML elements and attributes for declaring and accessing resources

A set of Intents

A set of permissions that applications can request, as well as permission enforcements included in the system

Android platform provides an API framework that allows applications to interact with the underlying Android system.

Android Platform Updates

Updates to the framework API are designed so that the new API remains compatible with earlier versions of the API.

Two case:

Most changes in the API are additive and introduce new or replacement functionality = = > In this case, the older replaced parts are deprecated but are not removed

In a very small number of cases, parts of the API may be modified or removed = = > In this case, typically such changes are only needed to ensure API robustness and application or system security

The updated API framework is designed to make the new and old API compatible.

There are two situations:

The vast majority of API updates add or replace new features.

In rare cases, partial API is removed or modified.

API Levels and Android Platform VersionsAPI Level

An integer value

It uniquely identifies the framework API revision offered by a version of the Android platform

API Level ≠ Android Platform Version

Uses of API Level in Android

MinSdkVersion: the smallest API Level.

TargetSdkVersion: target SDK version, it is recommended to use the latest.

CompileSdkVersion: compile the SDK version of the project. Should not be lower than targetSdkVersion.

MaxSdkVersion: the largest API Level.

Week 2 An Overview of Layouts (layout Overview) Views and ViewGroups

A layout defines the structure for a user interface in your app

All elements in the layout are build using a hierarchy of View and

ViewGoup objects

The layout defines the structure of the user interface in the application

All elements in the layout are built using a hierarchy of views and ViewGoup objects

Layout Resources (layout Resources)

A layout resource defines the architecture for the UI in an Activity or a component of a UI

Layout resources define the architecture of UI in Activity or UI components

Several Important Classes (several important classes) View Class

The View class represents the basic building block for UI components.

There are many specialized subclasses of views that act as controls or are capable of displaying text, images, or other content.

The View class represents the basic building block of the UI component.

There are many specialized view subclasses that can act as controls or be able to display text, images, or other content.

Common properties of View Class:

IDs:

"@ + id/idName"-for example, @ + id/mybutton

"@ id/idName"-such as @ id/mybutton

Android:layout_height and android:layout_width

Dimension value:

The unit based on the physical size of the screen: in,mm,pt. 1 in = 25.4 mm = 72 pt. They cannot function properly on all devices.

Based on pixel: Pixel (pixel), Resolution (resolution), Pixel Density: (pixel density dpi)

Px,dp,sp . Px = dp * (dpi / 160)

Match_parent: this view wants to be as large as the parent view (minus the padding of the parent view, if any)

Wrap_content: the view should be large enough to surround its contents (considering its own filling)

Padding

It defines the space between the edge of the view and the content of the view

On android:paddingTop

Under android:paddingBottom

Android:paddingLeft left

Android:paddingRight right

Android:paddingStart is based on ui settings

Andorid:paddingEnd is based on ui settings

View Group Class

View Group Class contains special views of other views

Attributes:

Paddings and Margins

LinearLayout

Android:orientation

Android:orientation= "vertical" vertical alignment

Android:orientation= "horizontal" horizontal alignment

Android:gravity

It specifies how the object should position its contents on the X and Y axes within its own scope.

Its value can be one or more of the following constant values (separated by "|"):

TextView and Button

Attributes:

Android:textColor

Android:textStyle

Android:textSize

Week 3 Introduction to ActivitiesActivities concept

Understand the life cycle of an activity:

This is the end of the article on "how to learn Android". Thank you for reading! I believe you all have a certain understanding of "how to learn Android". If you want to learn more, you are welcome to follow the industry information channel.

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