foreword

Telegram is a powerful end-to-end encrypted IM, focusing on security and speed, supporting platforms such as Android/IOS/Windows/macOS, rich in functions, smooth running, free and open source, and the code is meaningful for learning and research .

Telegram is a cloud-based mobile and desktop messaging app with a focus on security and speed.

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source code compilation

The compilation environment is version Android Studio4.2.1 , JDKusing Android Studiothe built-inOpenJDK 11

Download Telegram source code from github.com/DrKLO/Teleg…
Copy your own release.keystoreto the TMessagesProj/configdirectory
gradle.propertiesFill RELEASE_KEY_PASSWORDin , RELEASE_KEY_ALIAS, in the file RELEASE_STORE_PASSWORD, such as:

RELEASE_KEY_PASSWORD=123456
RELEASE_KEY_ALIAS=jack
RELEASE_STORE_PASSWORD=123456
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Visit console.firebase.google.com , create two android applications, the application ids are org.telegram.messengerand respectively org.telegram.messenger.beta, then download google-services.json and copy it to the TMessagesProj directory

Log in to my.telegram.org , apply for api_id and api_hash , and replace the and fields TMessagesProj/src/main/java/org/telegram/messenger/BuildVars.javain the fileAPP_IDAPP_HASH

Compile and run the program

Source code analysis

Telegram服务端源码不开源，那研究Telegram客户端代码有何意义呢？个人认为Telegram作为世界级IM，研究其源码还是相当有意义的，如下：

学习Telegram优秀的设计&编程思想，如单模块，单Activity架构，动态生成布局等
将Telegram中相对独立的功能如rlottie(贴纸)，MTProto(通信协议)，webrtc(音视频通话)剔除其业务逻辑然后抽出来，集成到自己的项目中

Telegram源码极其庞大和复杂，博大精深(晦涩难懂)，有以下特点：

项目只有一个模块TMessagesProj，没有模块化，没有组件化，没有Kotlin，没有MVVM...
项目极少直接使用第三方类库，没有okhttp，没有glide，包含大量c/c++代码(tgnet，ffmpeg，webrtc，rlottie...)
项目中极少使用xml文件进行布局，基本都是使用代码动态生成界面，采用单Activity+多Fragment(这里的Fragment和Android SDK里的Fragment没有任何关系)
一个java类文件常常多达几千至几万行而没有任何注释说明，阅读起来感觉太爽了_^_

目前仅仅研究了一点点其贴纸使用的类库rlottie，如下：

贴纸尺寸为512*512像素，时长不超过3s，每秒运行60帧
贴纸文件名后缀为.tgs，本地缓存路径为Android/data/org.telegram.messenger/cache
tgs文件可以直接拖放到lottiefiles.com/preview上预览效果

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rlottie代码分析

native代码

TMessagesProj/jni/lottie.cpp rlottie包装类，定义了一些native函数，供java层调用
TMessagesProj/rlottie rlottie核心代码
TMessagesProj/lz4 压缩类库代码

java代码

RLottieImageView 继承于ImageView，内部调用RLottieDrawable展示播放tgs动画
RLottieDrawableInherited from Drawable, calling native code to create rendering animation

//使用文件路径创建动画
public static native long create(String src, String json, int w, int h, int[] params, boolean precache, int[] colorReplacement, boolean limitFps);

//使用json字符串创建动画
protected static native long createWithJson(String json, String name, int[] params, int[] colorReplacement);

//销毁动画
public static native void destroy(long ptr);

//设置指定层次的颜色
private static native void setLayerColor(long ptr, String layer, int color);

//替换颜色
private static native void replaceColors(long ptr, int[] colorReplacement);

//获取一帧动画
public static native int getFrame(long ptr, int frame, Bitmap bitmap, int w, int h, int stride, boolean clear);

//创建缓存
private static native void createCache(long ptr, int w, int h);
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I have extracted the rlottie related code from Telegram and uploaded it to github.com/kongpf8848/…

Other open source IM

Signal , the main focus of privacy, Lao Ma recommends Use Signal, GitHub
Wire , encrypted chat IM, GitHub

Open source IM Telegram source code compilation and partial analysis