【移動應用開發(fā)技術】Android性能優(yōu)化電量的方法是什么

【移動應用開發(fā)技術】Android性能優(yōu)化電量的方法是什么

本文在下為大家詳細介紹“Android性能優(yōu)化電量的方法是什么”，內容詳細，步驟清晰，細節(jié)處理妥當，希望這篇“Android性能優(yōu)化電量的方法是什么”文章能幫助大家解決疑惑，下面跟著在下的思路慢慢深入，一起來學習新知識吧。1)UnderstandingBatteryDrain手機各個硬件模塊的耗電量是不一樣的，有些模塊非常耗電，而有些模塊則相對顯得耗電量小很多。電量消耗的計算與統(tǒng)計是一件麻煩而且矛盾的事情，記錄電量消耗本身也是一個費電量的事情。唯一可行的方案是使用第三方監(jiān)測電量的設備，這樣才能夠獲取到真實的電量消耗。當設備處于待機狀態(tài)時消耗的電量是極少的，以N5為例，打開飛行模式，可以待機接近1個月。可是點亮屏幕，硬件各個模塊就需要開始工作，這會需要消耗很多電量。使用WakeLock或者JobScheduler喚醒設備處理定時的任務之后，一定要及時讓設備回到初始狀態(tài)。每次喚醒蜂窩信號進行數據傳遞，都會消耗很多電量，它比WiFi等操作更加的耗電。2)BatteryHistorianBatteryHistorian是Android5.0開始引入的新API。通過下面的指令，可以得到設備上的電量消耗信息：$

adb

shell

dumpsys

batterystats

>

xxx.txt

//得到整個設備的電量消耗信息

$

adb

shell

dumpsys

batterystats

>

>

xxx.txt

//得到指定app相關的電量消耗信息得到了原始的電量消耗數據之后，我們需要通過Google編寫的一個python腳本把數據信息轉換成可讀性更好的html文件：$

python

historian.py

xxx.txt

>

xxx.html打開這個轉換過后的html文件，可以看到類似TraceView生成的列表數據，這里的數據信息量很大，這里就不展開了。3)TrackBatteryStatus&BatteryManager我們可以通過下面的代碼來獲取手機的當前充電狀態(tài)：//

It

is

very

easy

to

subscribe

to

changes

to

the

battery

state,

but

you

can

get

the

current

//

state

by

simply

passing

null

in

as

your

receiver.

Nifty,

isn't

that?

IntentFilter

filter

=

new

IntentFilter(Intent.ACTION_BATTERY_CHANGED);

Intent

batteryStatus

=

this.registerReceiver(null,

filter);

int

chargePlug

=

batteryStatus.getIntExtra(BatteryManager.EXTRA_PLUGGED,

-1);

boolean

acCharge

=

(chargePlug

==

BatteryManager.BATTERY_PLUGGED_AC);

if

(acCharge)

{

Log.v(LOG_TAG,“The

phone

is

charging!”);

}在上面的例子演示了如何立即獲取到手機的充電狀態(tài)，得到充電狀態(tài)信息之后，我們可以有針對性的對部分代碼做優(yōu)化。比如我們可以判斷只有當前手機為AC充電狀態(tài)時才去執(zhí)行一些非常耗電的操作。/**

*

This

method

checks

for

power

by

comparing

the

current

battery

state

against

all

possible

*

plugged

in

states.

In

this

case,

a

device

may

be

considered

plugged

in

either

by

USB,

AC,

or

*

wireless

charge.

(Wireless

charge

was

introduced

in

API

Level

17.)

*/

private

boolean

checkForPower()

{

//

It

is

very

easy

to

subscribe

to

changes

to

the

battery

state,

but

you

can

get

the

current

//

state

by

simply

passing

null

in

as

your

receiver.

Nifty,

isn't

that?

IntentFilter

filter

=

new

IntentFilter(Intent.ACTION_BATTERY_CHANGED);

Intent

batteryStatus

=

this.registerReceiver(null,

filter);

//

There

are

currently

three

ways

a

device

can

be

plugged

in.

We

should

check

them

all.

int

chargePlug

=

batteryStatus.getIntExtra(BatteryManager.EXTRA_PLUGGED,

-1);

boolean

usbCharge

=

(chargePlug

==

BatteryManager.BATTERY_PLUGGED_USB);

boolean

acCharge

=

(chargePlug

==

BatteryManager.BATTERY_PLUGGED_AC);

boolean

wirelessCharge

=

false;

if

(Build.VERSION.SDK_INT

>=

Build.VERSION_CODES.JELLY_BEAN_MR1)

{

wirelessCharge

=

(chargePlug

==

BatteryManager.BATTERY_PLUGGED_WIRELESS);

}

return

(usbCharge

||

acCharge

||

wirelessCharge);

}4)WakelockandBatteryDrain高效的保留更多的電量與不斷促使用戶使用你的App會消耗電量，這是矛盾的選擇題。不過我們可以使用一些更好的辦法來平衡兩者。假設你的手機里面裝了大量的社交類應用，即使手機處于待機狀態(tài)，也會經常被這些應用喚醒用來檢查同步新的數據信息。Android會不斷關閉各種硬件來延長手機的待機時間，首先屏幕會逐漸變暗直至關閉，然后CPU進入睡眠，這一切操作都是為了節(jié)約寶貴的電量資源。但是即使在這種睡眠狀態(tài)下，大多數應用還是會嘗試進行工作，他們將不斷的喚醒手機。一個最簡單的喚醒手機的方法是使用PowerManager.WakeLock的API來保持CPU工作并防止屏幕變暗關閉。這使得手機可以被喚醒，執(zhí)行工作，然后回到睡眠狀態(tài)。知道如何獲取WakeLock是簡單的，可是及時釋放WakeLock也是非常重要的，不恰當的使用WakeLock會導致嚴重錯誤。例如網絡請求的數據返回時間不確定，導致本來只需要10s的事情一直等待了1個小時，這樣會使得電量白白浪費了。這也是為何使用帶超時參數的wakelock.acquice()方法是很關鍵的。但是僅僅設置超時并不足夠解決問題，例如設置多長的超時比較合適？什么時候進行重試等等？解決上面的問題，正確的方式可能是使用非精準定時器。通常情況下，我們會設定一個時間進行某個操作，但是動態(tài)修改這個時間也許會更好。例如，如果有另外一個程序需要比你設定的時間晚5分鐘喚醒，***能夠等到那個時候，兩個任務捆綁一起同時進行，這就是非精確定時器的核心工作原理。我們可以定制計劃的任務，可是系統(tǒng)如果檢測到一個更好的時間，它可以推遲你的任務，以節(jié)省電量消耗。這正是JobSchedulerAPI所做的事情。它會根據當前的情況與任務，組合出理想的喚醒時間，例如等到正在充電或者連接到WiFi的時候，或者集中任務一起執(zhí)行。我們可以通過這個API實現很多免費的調度算法。5)NetworkandBatteryDrain下面內容來自官方Training文檔中高效下載章節(jié)關于手機(Radio)蜂窩信號對電量消耗的介紹。通常情況下，使用3G移動網絡傳輸數據，電量的消耗有三種狀態(tài)：Fullpower:能量***的狀態(tài)，移動網絡連接被激活，允許設備以***的傳輸速率進行操作。Lowpower:一種中間狀態(tài)，對電量的消耗差不多是Fullpower狀態(tài)下的50%。Standby:***的狀態(tài)，沒有數據連接需要傳輸，電量消耗最少。下圖是一個典型的3GRadioStateMachine的圖示總之，為了減少電量的消耗，在蜂窩移動網絡下，***做到批量執(zhí)行網絡請求，盡量避免頻繁的間隔網絡請求。通過前面學習到的BatteryHistorian我們可以得到設備的電量消耗數據，如果數據中的移動蜂窩網絡(MobileRadio)電量消耗呈現下面的情況，間隔很小，又頻繁斷斷續(xù)續(xù)的出現，說明電量消耗性能很不好：經過優(yōu)化之后，如果呈現下面的圖示，說明電量消耗的性能是良好的：另外WiFi連接下，網絡傳輸的電量消耗要比移動網絡少很多，應該盡量減少移動網絡下的數據傳輸，多在WiFi環(huán)境下傳輸數據。那么如何才能夠把任務緩存起來，做到批量化執(zhí)行呢？下面就輪到JobScheduler出場了。6)UsingJobScheduler使用JobScheduler，應用需要做的事情就是判斷哪些任務是不緊急的，可以交給JobScheduler來處理，JobScheduler集中處理收到的任務，選擇合適的時間，合適的網絡，再一起進行執(zhí)行。下面是使用JobScheduler的一段簡要示例，需要先有一個JobService：public

class

MyJobService

extends

JobService

{

private

static

final

String

LOG_TAG

=

"MyJobService";

@Override

public

void

onCreate()

{

super.onCreate();

Log.i(LOG_TAG,

"MyJobService

created");

}

@Override

public

void

onDestroy()

{

super.onDestroy();

Log.i(LOG_TAG,

"MyJobService

destroyed");

}

@Override

public

boolean

onStartJob(JobParameters

params)

{

//

This

is

where

you

would

implement

all

of

the

logic

for

your

job.

Note

that

this

runs

//

on

the

main

thread,

so

you

will

want

to

use

a

separate

thread

for

asynchronous

work

//

(as

we

demonstrate

below

to

establish

a

network

connection).

//

If

you

use

a

separate

thread,

return

true

to

indicate

that

you

need

a

"reschedule"

to

//

return

to

the

job

at

some

point

in

the

future

to

finish

processing

the

work.

Otherwise,

//

return

false

when

finished.

Log.i(LOG_TAG,

"Totally

and

completely

working

on

job

"

+

params.getJobId());

//

First,

check

the

network,

and

then

attempt

to

connect.

if

(isNetworkConnected())

{

new

SimpleDownloadTask()

.execute(params);

return

true;

}

else

{

Log.i(LOG_TAG,

"No

connection

on

job

"

+

params.getJobId()

+

";

sad

face");

}

return

false;

}

@Override

public

boolean

onStopJob(JobParameters

params)

{

//

Called

if

the

job

must

be

stopped

before

jobFinished()

has

been

called.

This

may

//

happen

if

the

requirements

are

no

longer

being

met,

such

as

the

user

no

longer

//

connecting

to

WiFi,

or

the

device

no

longer

being

idle.

Use

this

callback

to

resolve

//

anything

that

may

cause

your

application

to

misbehave

from

the

job

being

halted.

//

Return

true

if

the

job

should

be

rescheduled

based

on

the

retry

criteria

specified

//

when

the

job

was

created

or

return

false

to

drop

the

job.

Regardless

of

the

value

//

returned,

your

job

must

stop

executing.

Log.i(LOG_TAG,

"Whelp,

something

changed,

so

I'm

calling

it

on

job

"

+

params.getJobId());

return

false;

}

/**

*

Determines

if

the

device

is

currently

online.

*/

private

boolean

isNetworkConnected()

{

ConnectivityManager

connectivityManager

=

(ConnectivityManager)

getSystemService(Context.CONNECTIVITY_SERVICE);

NetworkInfo

networkInfo

=

connectivityManager.getActiveNetworkInfo();

return

(networkInfo

!=

null

&&

networkInfo.isConnected());

}

/**

*

Uses

AsyncTask

to

create

a

task

away

from

the

main

UI

thread.

This

task

creates

a

*

HTTPUrlConnection,

and

then

downloads

the

contents

of

the

webpage

as

an

InputStream.

*

The

InputStream

is

then

converted

to

a

String,

which

is

logged

by

the

*

onPostExecute()

method.

*/

private

class

SimpleDownloadTask

extends

AsyncTask<JobParameters,

Void,

String>

{

protected

JobParameters

mJobParam;

@Override

protected

String

doInBackground(JobParameters...

params)

{

//

cache

system

provided

job

requirements

mJobParam

=

params[0];

try

{

InputStream

is

=

null;

//

Only

display

the

first

50

characters

of

the

retrieved

web

page

content.

int

len

=

50;

URL

url

=

new

URL("");

HttpURLConnection

conn

=

(HttpURLConnection)

url.openConnection();

conn.setReadTimeout(10000);

//10sec

conn.setConnectTimeout(15000);

//15sec

conn.setRequestMethod("GET");

//Starts

the

query

conn.connect();

int

response

=

conn.getResponseCode();

Log.d(LOG_TAG,

"The

response

is:

"

+

response);

is

=

conn.getInputStream();

//

Convert

the

input

stream

to

a

string

Reader

reader

=

null;

reader

=

new

InputStreamReader(is,

"UTF-8");

char[]

buffer

=

new

char[len];

reader.read(buffer);

return

new

String(buffer);

}

catch

(IOException

e)

{

return

"Unable

to

retrieve

web

page.";

}

}

@Override

protected

void

onPostExecute(String

result)

{

jobFinished(mJobParam,

false);

Log.i(LOG_TAG,

result);

}

}

}然后模擬通過點擊Button觸發(fā)N個任務，交給JobService來處public

class

FreeTheWakelockActivity

extends

ActionBarActivity

{

public

static

final

String

LOG_TAG

=

"FreeTheWakelockActivity";

TextView

mWakeLockMsg;

ComponentName

mServiceComponent;

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_wakelock);

mWakeLockMsg

=

(TextView)

findViewById(R.id.wakelock_txt);

mServiceComponent

=

new

ComponentName(this,

MyJobService.class);

Intent

startServiceIntent

=

new

Intent(this,

MyJobService.class);

startService(startServiceIntent);

Button

theButtonThatWakelocks

=

(Button)

findViewById(R.id.wakelock_poll);

theButtonThatWakelocks.setText(R.string.poll_server_button);

theButtonThatWakelocks.setOnClickListener(new

View.OnClickListener()

{

@Override

public

void

onClick(View

v)

{

pollServer();

}

});

}

/**

*

This

method

polls

the

server

via

the

JobScheduler

API.

By

scheduling

the

job

with

this

API,

*

your

app

can

be

confident

it

will

execute,

but

without

the

need

for

a

wake

lock.

Rather,

the

*

API

will

take

your

network

jobs

and

execute

them

in

batch

to

best

take

advantage

of

the

*

initial

network

connection

cost.

*

*

The

JobScheduler

API

works

through

a

background

service.

In

this

sample,

we

have

*

a

simple

service

in

MyJobService

to

get

you

started.

The

job

is

scheduled

here

in

*

the

activity,

but

the

job

itself

is

executed

in

MyJ