Welcome to Clendy's blog

Android-电池省点优化

2019-02-01

Clendy

Android
电池省点优化（Doze和Standby模式）

从Android6.0开始,系统提供了两种省电功能(延长电池寿命和使用时间):Doze和App Standby Doze和App Standby模式会延缓CPU和网络活动实现节能;

Doze模式
1. 进入Doze模式，在手机未充电,完全静止且熄屏一段时间后,Android系统会自动进入Doze模式；
2. Doze模式效果
  1. 网络访问被挂起；
  2. Wake Locks被无视；
  3. AlarmManager被推迟到下一个maintenance window窗口, 除非使用AlarmManager新方法: setAndAllowWhileIdle(),setExactAndAllowWhileIdle(),setAlarmClock();
  4. WiFi扫描被停止;
  5. SyncAdapter同步工作被停止;
  6. JobScheduler定时任务被停止：
3. 退出Doze模式
  1. 手机充电
  2. 手机移动
  3. 手机屏幕打开
App Standby模式
1. 进入App Standby模式长时间未被用户使用的App,将进入App Standby状态(被标志为空闲状态)
2. 退出App Standby模式
  1. 用户主动启动该App
  2. 该App有前台进程(前台activity/前台service),被其它前台进程启动
  3. 该App在锁屏或通知栏有可见的Notification
  4. Android设备充电时,会将所有Standby状态的App释放,处理挂起任务
  5. 如果App空闲时间很长,系统将允许App一天一次访问网络
3. App Standby和Doze区别 App Standby不需要屏幕关闭,App进入后台一段时间,网络也会受到限制 Doze模式需要屏幕关闭(通常晚上睡觉或长时间屏幕关闭才会进入)
阻止电池优化(白名单)

Android6.0及更高版本提供电池优化白名单,App加入白名单可逃脱Doze和App Standby限制, 处于白名单中的App也会受到一定限制: Jobs和Syncs以及常规Alarms也会被推迟；

用户手动设置App进入白名单: 设置>电池>电池优化白名单

App检测是否在白名单: PowerManager.isIgnoringBatteryOptimizations()

App请求加入白名单:
```
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
	PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
	if (pm != null && !pm.isIgnoringBatteryOptimizations(getPackageName())) {
		//1.进入系统电池优化设置界面,把当前APP加入白名单
		//startActivity(new Intent(Settings.ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS));
		
		//2.弹出系统对话框,把当前APP加入白名单(无需进入设置界面)
		//在manifest添加权限 <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS"/>
		Intent intent = new Intent(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS);
		intent.setData(Uri.parse("package:" + getPackageName()));
		startActivity(intent);
	}
}
```
AlarmManager定时闹钟失效
1. App被Kill后，AlarmManager失效(只有App进程在运行时，才会收到系统定时AlarmManager通知) 添加守护进程,相互监听重启; 提醒用户加入锁屏清理白名单
2. 手机重启，AlarmManager任务失效监听重启广播,重新设置定时闹钟
3. 从Android4.4(API19)开始，AlarmManager机制修改,set(),setRepeating()定时不再精确，甚至setRepeating只生效一次(不会重复) 新增精确定时方法: setExact()，setWindow()，setAlarmClock()；
4. 从Android6.0(API23)开始,进入Doze模式(省电优化),AlarmManager被延缓新增精确定时方法: setAndAllowWhileIdle(),setExactAndAllowWhileIdle()；
从Android4.4(API19)开始,新增精准定时方法都是一次性闹钟,没有重复定时的方法, 所以当需要重复周期闹钟,只能在下一次唤醒时重新设置定时,间接实现重复闹钟。

精确定时一次Demo如下：
```
void setWakeAtTime(Context cxt, int delay) {
	PendingIntent pi = PendingIntent.getService(cxt,0,new Intent(cxt, xxService.class),PendingIntent.FLAG_UPDATE_CURRENT); 
    AlarmManager alarm = (AlarmManager) cxt.getSystemService(Context.ALARM_SERVICE);
	if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) //Android 6，针对省电优化
		alarm.setExactAndAllowWhileIdle(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime() + delay, pi);
	else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) //Android 4.4，针对set不准确
		alarm.setExact(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime() + delay, pi);
	else
		alarm.set(AlarmManager.ELAPSED_REALTIME_WAKEUP, SystemClock.elapsedRealtime() + delay, pi);   
}
```
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Kotlin Coroutines

2018-01-07

Clendy

Kotlin
Kotlin协程和作用

一些耗时操作(网络IO、文件IO、CPU/GPU密集型任务)会阻塞线程直到操作完成， Kotlin的协程提供一种避免阻塞且更廉价可控的操作: 协程挂起(coroutine suspension), 协程将复杂异步操作放入底层库中,程序逻辑可顺序表达,以此简化异步编程，该底层库将用户代码包装为回调/订阅事件,在不同线程(甚至不同机器)调度执行!

Kotlin的协程还能实现其它语言的异步机制(asynchronous mechanisms), 例如源于C#和ECMAScript(js)的async/await机制，源于Go的channel/select机制,源于C#和Python的generators/yield机制。

线程阻塞和协程挂起的区别(Blocking VS Suspending)

协程是通过编译技术实现(不需要虚拟机VM/操作系统OS的支持),通过插入相关代码来生效！与之相反,线程/进程是需要虚拟机VM/操作系统OS的支持,通过调度CPU执行生效!

线程阻塞的代价昂贵, 尤其在高负载时的可用线程很少,阻塞线程会导致一些重要任务缺少可用线程而被延迟!

协程挂起几乎无代价,无需上下文切换或涉及OS, 最重要的是,协程挂起可由用户控制:可决定挂起时发生什么,并根据需求优化/记录日志/拦截!

另一个不同之处是,协程不能在随机指令中挂起,只能在挂起点挂起(调用标记函数)!

挂起函数(Suspending functions)

当调用[suspend修饰的函数]时会发生协程挂起：
```
    suspend fun doSomething(foo: Foo): Bar {           
    }        
```
该函数称为挂起函数,调用它们可能挂起协程(如果调用结果已经可用,协程库可决定不挂起) 挂起函数能像普通函数获取参数和返回值,但只能在协程/挂起函数中被调用!

启动协程,至少要有一个挂起函数,通常是匿名的(即挂起lambda表达式),一个简化的async函数(源自kotlinx.coroutines库)：
```
    //async函数是一个普通函数(不是挂起函数)
    //block参数有suspend修饰,是一个匿名的挂起函数(即挂起lambda表达式)
    fun <T> async(block: suspend () -> T)

    async {
        //doSomething在挂起函数(挂起lambda)中被调用
        doSomething(foo)
        ...
    }

    async {
        ...
        //await()是挂起函数,该函数挂起一个协程,直到执行完成返回结果
        val result = computation.await()  
```
挂起函数不能在普通函数中被调用：
```
    fun main(args: Array<String>) {
        doSomething() //错误: 挂起函数不能在非协程中被调用
    }
```
挂起函数可以是虚拟的,当覆盖它们时,必须指定suspend修饰符：
```
    interface Base {
        suspend fun foo()
    }

    class Derived: Base {
        override suspend fun foo() {                
        }
    }
```
协程内部机制原理(inner workings)

粗略地认识协程机制原理是相当重要的!

协程是通过编译技术实现(不需要虚拟机VM/操作系统OS的支持),通过插入相关代码来生效！与之相反,线程/进程是需要虚拟机VM/操作系统OS的支持,通过调度CPU执行生效!

基本上,每个挂起函数都转换为状态机,对应于挂起调用; 在挂起协程前,下一状态和相关局部变量等被存储在编译器生成的类字段中; 在恢复协程时,状态机从下一状态进行并恢复局部变量！

一个挂起的协程可作为保存挂起状态和局部变量的对象,对象类型是Continuation, 在底层,挂起函数有一个Continuation类型的额外参数

关于协程工作原理的更多细节可查看: https://github.com/Kotlin/kotlin-coroutines/blob/master/kotlin-coroutines-informal.md
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Markdown Beginner

2017-09-25

Clendy

Markdown

前言
- Tools
Markdown: Syntax
- 目录
- 标题
- 列表
- 引用
- 图片
- 链接
- 索引链接
- 本身就是链接
- 分割线
- 表格
- 代码块
- 转义
- Others
Reference

前言

阶段性总结有利于精确自己的目标, 以及为后续的想法开辟空间.

因此开始有必要整理记录.

但是因为没必要像写paper那样规范使用latex, 因此就选择了Markdown.

Tools

Windows - MarkdownPad

Github Pages - (If you have one)

Markdown: Syntax

标题

# content
## content
### content
......

一共可以设置六级标题

列表

无序

* 1
* 2
* 3 * 1 * 2 * 3

有序

1
2
3 1. 1 2. 2 3. 3

嵌套列表

- AAA
  + A
    - a
      1. contentA
      2. contentB

AAA
- A
  - a
    1. contentA
    2. contentB

引用

> contentA
  >> contentB

contentA

contentB

之后的文本内容需要插入空行

图片

！[icon](link to the picture)

链接

[content](link to the content)

索引链接

[content][1]
[1]:Url [content][1] [1]:Url

本身就是链接

<url>

https://xinyao1994.github.io/

分割线

***
---

表格

| Tables        | Are           | Cool  |
| ------------- |:-------------:| -----:|
| col 3 is      | right-aligned | $1600 |
| col 2 is      | centered      |   $12 |
| zebra stripes | are neat      |    $1 |

Tables	Are	Cool
col 3 is	right-aligned	$1600
col 2 is	centered	$12
zebra stripes	are neat	$1

代码块

``` [python]
@requires_authorization
def add(a, b): # add a and b
    return a+b
class TA:
```

@requires_authorization
def add(a, b): # add a and b
	return a+b
class TA:

or 每行文字前加4个空格或者1个Tab

转义

Others

粗体

**content** **content**

__content__ __content__

斜体

*content* *content*

_content_ _content_

字体, 字号, 和颜色

<font face="黑体">我是黑体字</font>
<font face="微软雅黑">我是微软雅黑</font>
<font face="Verdana">I like Verdana format</font>

我是黑体字我是微软雅黑 I like Verdana format

Reference

Read All

Git Beginner

2016-06-18

Clendy

git
What is a git
```
 git 帮助我们进行代码的版本控制，我于2015/10/1花费一天时间学习一个关于git的视频,然后再参考几篇博客,将git的使用方法全部弄清楚。let's begin!
```
##Preparation

History
1. *SCCS Source Code Control System *
  - 1972， closed source, free with Unix
2. *RCS Revision Control System *
  - 1982， open source.
3. *CVS Concurrent Versions System *
  - 1986 - 1990, open source
4. *SVN *
  - 2000, open source
5. BitKeeper SCM
  - distributed version
6. *GIT *
  - github come out
    Install
    
    参考官网的安装方法 —— [git web]
7. download the tar.gz or some package[your linux]
8. tar zxvf *.tar.gz
9. /configure
10. make && make install
11. finish. or you can try:
  - apt-get install git
  - yum install -y git
  - pacman -S git ###configuration
12. git config –global user.name [your name]
13. git config –global user.email [your email]
14. git config –global core.editor “vim”
15. git config –global color.ui true
16. use bash config
  - wget https://github.com/git/git/raw/master/contrib/completion/git-completion.bash * ls * mv git-completion.bash ~/.git-completion.bash * add to .bashrc that if exist this bash, source it.
17. help
  Begin
  
  init the git
18. mkdir dir1
19. cd dir1
20. git init
21. add one file (make change)
22. git add . (add change)
23. git commit -m “some word” (commit change)
24. git log -n/ –since/ –until/ –grep
  stream
  
  working -add file- staging index -commit- repositiry
File Operations

Add (git status to check)
- git add .
- git commit -m “”
- git diff
- git commit -ma “”
  Remove(git status to check)
- git rm filename
- git commit -m “”
  Rename(git status to check)
- git add file
- git rm file
- git commit -m “”
- or you can use git mv file1 file2
  Rollback
  
  git diff to check to change
  1. git checkout – file(before add) it can return the status of the workspace.
  2. git reset HEAD file (after add)
  - unstage the file -> before add
  - git checkout – file
    1. git (after commit)
  - find the Hash value of commit
  - git comment –amend append to the same commit
  - git diff –staged
  - return the commit status
    
    git checkout [commit hash] – file
Warning [git reset]
1. –soft not change staging index & workspace
2. –mixed(default) change staging & not workspace
3. –hard change staging & change workspace
  
  usage : git reset –soft [commit hash] git reset HEAD file -n try to do -f force to do
  
  .gitignore
  
  it can help us to ignore some file or dir reference :
4. help.github.com/articles/ignoring-files
5. github.com/github/gitignore git config –global core.excludesfile pathtofile
  - git rm –cached file
    .gitkeep
    
    git log –oneline/ –graph/ –all/ –decorate
    
    Other options
  - git show [hash]
  - git diff [hash] & git diff [hash1]..[hash2]
    Branch
    
    branch is needed, cheap, try
6. try new ideas
7. isolate the workspace
8. fast context switching
  operations
  - git branch
  - create -> git branch new_branch_name
  - switch -> git checkout branch_name
  - git checkout -b new_branch_name
  - git diff [branch1]..[branch2] (use –color-words)
  - git branch –merged
  - git branch -m old_name new_name (–move)
  - git barnch -d(–delete) name (-D to delete a non-empty branch)
  - prompt
    
    export PS1=’$(__git_ps1 “(%s)”) > ‘
    
    export PS1=’\W$(__git_ps1 “(%s)”) > ‘
    
    export PS1=$PS1’$(__git_ps1 “(%s)”) > ‘ (it’s cool !)
Attantion: barnch is a stack mode, current branch can’t be delete

Merge
- git merge exist_branch
- git branch –merged
- conflict
  - change by yourselt
  - git log –graph –oneline –all –decorate
  - git mergetool –tool=
Attention:
- keep lines short
- commits small focused
- merge often
  stash
  1. git stash save “changed mission …”
  2. git stash list
  3. git stash show stash@{0} (you may use -p option)
  4. git stash apply
  5. git stash pop
  6. git stash drop stash@{0}
    Remote (link to the github or others)
    
    Easily, this can be changed to
    
    Set up a github account
  7. you set up a account
  8. Create a repository
  9. look at the code following
    echo # >> README.md git init git add README.md git commit -m "first commit" git remote add origin https://github.com/[User account]/[project name].git git push -u origin master
- you can easy use git remote rm origin
- git branch -a/-r
- git push -f
- git fetch
  - fetch before work
  - fetch before push
  - fetch often
- git pull = git fetch + git merge
- git push origin :your branch
- git push origin [–delete] branch
  
  [远程分支的使用] git checkout -b [new_branch] (make some change) git commit -am “word” git push [远程仓库名] [远程分支名(new_branch)]
  
  password caching
  
  Password Caching or save the ssh key.
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1/1

Welcome to Clendy's blog

Android-电池省点优化

电池省点优化（Doze和Standby模式）

Doze模式

App Standby模式

阻止电池优化(白名单)

AlarmManager定时闹钟失效

Kotlin Coroutines

Kotlin协程和作用

线程阻塞和协程挂起的区别(Blocking VS Suspending)

挂起函数(Suspending functions)

协程内部机制原理(inner workings)

Markdown Beginner

前言

Tools

Markdown: Syntax

目录

标题

列表

无序

有序

嵌套列表

引用

图片

链接

索引链接

本身就是链接

分割线

表格

代码块

转义

Others

粗体

斜体

字体, 字号, 和颜色

Reference

Git Beginner

What is a git

History

Install

Begin

init the git

stream

File Operations

Add (git status to check)

Remove(git status to check)

Rename(git status to check)

Rollback

git diff to check to change

Warning [git reset]

.gitignore

.gitkeep

Other options

Branch

branch is needed, cheap, try

operations

Merge

stash

Remote (link to the github or others)

Set up a github account

password caching