【移动应用开发技术】怎么浅析Activity的渲染过程

【移动应用开发技术】怎么浅析Activity的渲染过程

今天就跟大家聊聊有关怎么浅析Activity的渲染过程，可能很多人都不太了解，为了让大家更加了解，在下给大家总结了以下内容，希望大家根据这篇文章可以有所收获。####以下代码基于API251.Activity是如何展现在我们眼前的？我大概知道UI方面是和Window相关的，而activity的attach方法会传入一个window对象，所以就从activity的attach方法入手：

attach方法里会创建一个PhoneWindow

activity在执行onCreate方法的时候都会执行一个方法performCreateCommon

点击setEnterActivityOptions方法：

注意window.getDecorView()这个方法/**

*Retrievethetop-levelwindowdecorview(containingthestandard

*windowframe/decorationsandtheclient'scontentinsideofthat),which

*canbeaddedasawindowtothewindowmanager.

*

*<p><em>Notethatcallingthisfunctionforthefirsttime"locksin"

*variouswindowcharacteristicsasdescribedin

*{@link#setContentView(View,android.view.ViewGroup.LayoutParams)}.</em></p>

*

*@returnReturnsthetop-levelwindowdecorview.

*/publicabstractViewgetDecorView();

官方的解释是说这个方法是获取了顶层window的decorview。

这里的window很明显是PhoneWindow,看它对getDecorView的实现。

mDecor其实在PhoneWindow的构造方法里就已经生成了preservedWindow向上追溯其来源：从onCreate里其实根本就找不到activity显示相关的源码，于是只能看看其他人怎么分析的。/jiaocheng/6995.html

（道中重点）/snow-flower/p/6111599.html/monkey646812329/article/details/52885835if

(r.window

==

null

&&

!a.mFinished

&&

willBeVisible)

{

r.window

=

r.activity.getWindow();

View

decor

=

r.window.getDecorView();

decor.setVisibility(View.INVISIBLE);

ViewManager

wm

=

a.getWindowManager();

WindowManager.LayoutParams

l

=

r.window.getAttributes();

a.mDecor

=

decor;

l.type

=

WindowManager.LayoutParams.TYPE_BASE_APPLICATION;

l.softInputMode

|=

forwardBit;

if

(r.mPreserveWindow)

{

a.mWindowAdded

=

true;

r.mPreserveWindow

=

false;

//

Normally

the

ViewRoot

sets

up

callbacks

with

the

Activity

//

in

addView->ViewRootImpl#setView.

If

we

are

instead

reusing

//

the

decor

view

we

have

to

notify

the

view

root

that

the

//

callbacks

may

have

changed.

ViewRootImpl

impl

=

decor.getViewRootImpl();

if

(impl

!=

null)

{

impl.notifyChildRebuilt();

}

}

if

(a.mVisibleFromClient

&&

!a.mWindowAdded)

{

a.mWindowAdded

=

true;

wm.addView(decor,

l);

}

//

If

the

window

has

already

been

added,

but

during

resume

//

we

started

another

activity,

then

don't

yet

make

the

//

window

visible.

}

else

if

(!willBeVisible)

{

if

(localLOGV)

Slog.v(

TAG,

"Launch

"

+

r

+

"

mStartedActivity

set");

r.hideForNow

=

true;

}看上面的源码得到PhoneWindow对象

r.window

=

r.activity.getWindow();

View

decor

=

r.window.getDecorView();

从PhoneWindow获取DecorView并赋值给activity

a.mDecor

=

decor;通过WindowManager添加decorwm.addView(decor,

l);这样activity就展示在我们眼前了。关于WindowManager更加底层的源码后探讨。2.Activity的setContentView方法/**

*

Set

the

activity

content

from

a

layout

resource.

The

resource

will

be

*

inflated,

adding

all

top-level

views

to

the

activity.

*

*

@param

layoutResID

Resource

ID

to

be

inflated.

*

*

@see

#setContentView(android.view.View)

*

@see

#setContentView(android.view.View,

android.view.ViewGroup.LayoutParams)

*/

public

void

setContentView(@LayoutRes

int

layoutResID)

{

getWindow().setContentView(layoutResID);

initWindowDecorActionBar();

}

/**

*

Set

the

activity

content

to

an

explicit

view.

This

view

is

placed

*

directly

into

the

activity's

view

hierarchy.

It

can

itself

be

a

complex

*

view

hierarchy.

When

calling

this

method,

the

layout

parameters

of

the

*

specified

view

are

ignored.

Both

the

width

and

the

height

of

the

view

are

*

set

by

default

to

{@link

ViewGroup.LayoutParams#MATCH_PARENT}.

To

use

*

your

own

layout

parameters,

invoke

*

{@link

#setContentView(android.view.View,

android.view.ViewGroup.LayoutParams)}

*

instead.

*

*

@param

view

The

desired

content

to

display.

*

*

@see

#setContentView(int)

*

@see

#setContentView(android.view.View,

android.view.ViewGroup.LayoutParams)

*/

public

void

setContentView(View

view)

{

getWindow().setContentView(view);

initWindowDecorActionBar();

}

/**

*

Set

the

activity

content

to

an

explicit

view.

This

view

is

placed

*

directly

into

the

activity's

view

hierarchy.

It

can

itself

be

a

complex

*

view

hierarchy.

*

*

@param

view

The

desired

content

to

display.

*

@param

params

Layout

parameters

for

the

view.

*

*

@see

#setContentView(android.view.View)

*

@see

#setContentView(int)

*/

public

void

setContentView(View

view,

ViewGroup.LayoutParams

params)

{

getWindow().setContentView(view,

params);

initWindowDecorActionBar();

}

/**

*

Add

an

additional

content

view

to

the

activity.

Added

after

any

existing

*

ones

in

the

activity

--

existing

views

are

NOT

removed.

*

*

@param

view

The

desired

content

to

display.

*

@param

params

Layout

parameters

for

the

view.

*/

public

void

addContentView(View

view,

ViewGroup.LayoutParams

params)

{

getWindow().addContentView(view,

params);

initWindowDecorActionBar();

}

关于填充view,activity有4种方法。下面先讨论最常用的方法public

void

setContentView(@LayoutRes

int

layoutResID)

{

getWindow().setContentView(layoutResID);

initWindowDecorActionBar();

}第一步调用PhoneWindow的对应的方法（注意观察源码会发现，activity的绝大多数的方法都是在操作PhoneWindow）第二步初始化ActionBar先看看PhoneWindow的源码@Override

public

void

setContentView(int

layoutResID)

{

//

Note:

FEATURE_CONTENT_TRANSITIONS

may

be

set

in

the

process

of

installing

the

window

//

decor,

when

theme

attributes

and

the

like

are

crystalized.

Do

not

check

the

feature

//

before

this

happens.

if

(mContentParent

==

null)

{

installDecor();

}

else

if

(!hasFeature(FEATURE_CONTENT_TRANSITIONS))

{

mContentParent.removeAllViews();

}

if

(hasFeature(FEATURE_CONTENT_TRANSITIONS))

{

final

Scene

newScene

=

Scene.getSceneForLayout(mContentParent,

layoutResID,

getContext());

transitionTo(newScene);

}

else

{

mLayoutInflater.inflate(layoutResID,

mContentParent);

}

mContentParent.requestApplyInsets();

final

Callback

cb

=

getCallback();

if

(cb

!=

null

&&

!isDestroyed())

{

cb.onContentChanged();

}

mContentParentExplicitlySet

=

true;

}最开始程序应该是走了installDecor方法这个方法比较长，它负责的业务主要有以下几项。如果decor为null，创建PhoneWindow的decor，已经存在decor则与PhoneWindow绑定。如果mContentParent为null，通过decor创建mContentParent。转场动画的处理private

void

installDecor()

{

mForceDecorInstall

=

false;

if

(mDecor

==

null)

{

mDecor

=

generateDecor(-1);

mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);

mDecor.setIsRootNamespace(true);

if

(!mInvalidatePanelMenuPosted

&&

mInvalidatePanelMenuFeatures

!=

0)

{

mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);

}

}

else

{

mDecor.setWindow(this);

}

if

(mContentParent

==

null)

{

mContentParent

=

generateLayout(mDecor);

//

Set

up

decor

part

of

UI

to

ignore

fitsSystemWindows

if

appropriate.

mDecor.makeOptionalFitsSystemWindows();

final

DecorContentParent

decorContentParent

=

(DecorContentParent)

mDecor.findViewById(

R.id.decor_content_parent);

if

(decorContentParent

!=

null)

{

mDecorContentParent

=

decorContentParent;

mDecorContentParent.setWindowCallback(getCallback());

if

(mDecorContentParent.getTitle()

==

null)

{

mDecorContentParent.setWindowTitle(mTitle);

}

final

int

localFeatures

=

getLocalFeatures();

for

(int

i

=

0;

i

<

FEATURE_MAX;

i++)

{

if

((localFeatures

&

(1

<<

i))

!=

0)

{

mDecorContentParent.initFeature(i);

}

}

mDecorContentParent.setUiOptions(mUiOptions);

if

((mResourcesSetFlags

&

FLAG_RESOURCE_SET_ICON)

!=

0

||

(mIconRes

!=

0

&&

!mDecorContentParent.hasIcon()))

{

mDecorContentParent.setIcon(mIconRes);

}

else

if

((mResourcesSetFlags

&

FLAG_RESOURCE_SET_ICON)

==

0

&&

mIconRes

==

0

&&

!mDecorContentParent.hasIcon())

{

mDecorContentParent.setIcon(

getContext().getPackageManager().getDefaultActivityIcon());

mResourcesSetFlags

|=

FLAG_RESOURCE_SET_ICON_FALLBACK;

}

if

((mResourcesSetFlags

&

FLAG_RESOURCE_SET_LOGO)

!=

0

||

(mLogoRes

!=

0

&&

!mDecorContentParent.hasLogo()))

{

mDecorContentParent.setLogo(mLogoRes);

}

//

Invalidate

if

the

panel

menu

hasn't

been

created

before

this.

//

Panel

menu

invalidation

is

deferred

avoiding

application

onCreateOptionsMenu

//

being

called

in

the

middle

of

onCreate

or

similar.

//

A

pending

invalidation

will

typically

be

resolved

before

the

posted

message

//

would

run

normally

in

order

to

satisfy

instance

state

restoration.

PanelFeatureState

st

=

getPanelState(FEATURE_OPTIONS_PANEL,

false);

if

(!isDestroyed()

&&

(st

==

null

||

st.menu

==

null)

&&

!mIsStartingWindow)

{

invalidatePanelMenu(FEATURE_ACTION_BAR);

}

}

else

{

mTitleView

=

(TextView)

findViewById(R.id.title);

if

(mTitleView

!=

null)

{

if

((getLocalFeatures()

&

(1

<<

FEATURE_NO_TITLE))

!=

0)

{

final

View

titleContainer

=

findViewById(R.id.title_container);

if

(titleContainer

!=

null)

{

titleContainer.setVisibility(View.GONE);

}

else

{

mTitleView.setVisibility(View.GONE);

}

mContentParent.setForeground(null);

}

else

{

mTitleView.setText(mTitle);

}

}

}

if

(mDecor.getBackground()

==

null

&&

mBackgroundFallbackResource

!=

0)

{

mDecor.setBackgroundFallback(mBackgroundFallbackResource);

}

//

Only

inflate

or

create

a

new

TransitionManager

if

the

caller

hasn't

//

already

set

a

custom

one.

if

(hasFeature(FEATURE_ACTIVITY_TRANSITIONS))

{

if

(mTransitionManager

==

null)

{

final

int

transitionRes

=

getWindowStyle().getResourceId(

R.styleable.Window_windowContentTransitionManager,

0);

if

(transitionRes

!=

0)

{

final

TransitionInflater

inflater

=

TransitionInflater.from(getContext());

mTransitionManager

=

inflater.inflateTransitionManager(transitionRes,

mContentParent);

}

else

{

mTransitionManager

=

new

TransitionManager();

}

}

mEnterTransition

=

getTransition(mEnterTransition,

null,

R.styleable.Window_windowEnterTransition);

mReturnTransition

=

getTransition(mReturnTransition,

USE_DEFAULT_TRANSITION,

R.styleable.Window_windowReturnTransition);

mExitTransition

=

getTransition(mExitTransition,

null,

R.styleable.Window_windowExitTransition);

mReenterTransition

=

getTransition(mReenterTransition,

USE_DEFAULT_TRANSITION,

R.styleable.Window_windowReenterTransition);

mSharedElementEnterTransition

=

getTransition(mSharedElementEnterTransition,

null,

R.styleable.Window_windowSharedElementEnterTransition);

mSharedElementReturnTransition

=

getTransition(mSharedElementReturnTransition,

USE_DEFAULT_TRANSITION,

R.styleable.Window_windowSharedElementReturnTransition);

mSharedElementExitTransition

=

getTransition(mSharedElementExitTransition,

null,

R.styleable.Window_windowSharedElementExitTransition);

mSharedElementReenterTransition

=

getTransition(mSharedElementReenterTransition,

USE_DEFAULT_TRANSITION,

R.styleable.Window_windowSharedElementReenterTransition);

if

(mAllowEnterTransitionOverlap

==

null)

{

mAllowEnterTransitionOverlap

=

getWindowStyle().getBoolean(

R.styleable.Window_windowAllowEnterTransitionOverlap,

true);

}

if

(mAllowReturnTransitionOverlap

==

null)

{

mAllowReturnTransitionOverlap

=

getWindowStyle().getBoolean(

R.styleable.Window_windowAllowReturnTransitionOverlap,

true);

}

if

(mBackgroundFadeDurationMillis

<

0)

{

mBackgroundFadeDurationMillis

=

getWindowStyle().getInteger(

R.styleable.Window_windowTransitionBackgroundFadeDuration,

DEFAULT_BACKGROUND_FADE_DURATION_MS);

}

if

(mSharedElementsUseOverlay

==

null)

{

mSharedElementsUseOverlay

=

getWindowStyle().getBoolean(

R.styleable.Window_windowSharedElementsUseOverlay,

true);

}

}

}

}对上面的方法主要节点剖析

推荐结合这篇博客Andriod中Style/Theme原理以及Activity界面文件选取过程浅析来看这个方法的源码protected

ViewGroup

generateLayout(DecorView

decor)

{

//

Apply

data

from

current

theme.

TypedArray

a

=

getWindowStyle();

...//根据window

style设置window的属性

WindowManager.LayoutParams

params

=

getAttributes();

//

Non-floating

windows

on

high

end

devices

must

put

up

decor

beneath

the

system

bars

and

//

therefore

must

know

about

visibility

changes

of

those.

if

(!mIsFloating

&&

ActivityManager.isHighEndGfx())

{

if

(!targetPreL

&&

a.getBoolean(

R.styleable.Window_windowDrawsSystemBarBackgrounds,

false))

{

setFlags(FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS,

FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS

&

~getForcedWindowFlags());

}

if

(mDecor.mForceWindowDrawsStatusBarBackground)

{

params.privateFlags

|=

PRIVATE_FLAG_FORCE_DRAW_STATUS_BAR_BACKGROUND;

}

}

if

(a.getBoolean(R.styleable.Window_windowLightStatusBar,

false))

{

decor.setSystemUiVisibility(

decor.getSystemUiVisibility()

|

View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR);

}

if

(mAlwaysReadCloseOnTouchAttr

||

getContext().getApplicationInfo().targetSdkVersion

>=

android.os.Build.VERSION_CODES.HONEYCOMB)

{

if

(a.getBoolean(

R.styleable.Window_windowCloseOnTouchOutside,

false))

{

setCloseOnTouchOutsideIfNotSet(true);

}

}

if

(!hasSoftInputMode())

{

params.softInputMode

=

a.getInt(

R.styleable.Window_windowSoftInputMode,

params.softInputMode);

}

if

(a.getBoolean(R.styleable.Window_backgroundDimEnabled,

mIsFloating))

{

/*

All

dialogs

should

have

the

window

dimmed

*/

if

((getForcedWindowFlags()&WindowManager.LayoutParams.FLAG_DIM_BEHIND)

==

0)

{

params.flags

|=

WindowManager.LayoutParams.FLAG_DIM_BEHIND;

}

if

(!haveDimAmount())

{

params.dimAmount

=

a.getFloat(

android.R.styleable.Window_backgroundDimAmount,

0.5f);

}

}

if

(params.windowAnimations

==

0)

{

params.windowAnimations

=

a.getResourceId(

R.styleable.Window_windowAnimationStyle,

0);

}

//

The

rest

are

only

done

if

this

window

is

not

embedded;

otherwise,

//

the

values

are

inherited

from

our

container.

if

(getContainer()

==

null)

{

if

(mBackgroundDrawable

==

null)

{

if

(mBackgroundResource

==

0)

{

mBackgroundResource

=

a.getResourceId(

R.styleable.Window_windowBackground,

0);

}

if

(mFrameResource

==

0)

{

mFrameResource

=

a.getResourceId(R.styleable.Window_windowFrame,

0);

}

mBackgroundFallbackResource

=

a.getResourceId(

R.styleable.Window_windowBackgroundFallback,

0);

if

(false)

{

System.out.println("Background:

"

+

Integer.toHexString(mBackgroundResource)

+

"

Frame:

"

+

Integer.toHexString(mFrameResource));

}

}

if

(mLoadElevation)

{

mElevation

=

a.getDimension(R.styleable.Window_windowElevation,

0);

}

mClipToOutline

=

a.getBoolean(R.styleable.Window_windowClipToOutline,

false);

mTextColor

=

a.getColor(R.styleable.Window_textColor,

Color.TRANSPARENT);

}

//

Inflate

the

window

decor.

int

layoutResource;

int

features

=

getLocalFeatures();

//

System.out.println("Features:

0x"

+

Integer.toHexString(features));

if

((features

&

(1

<<

FEATURE_SWIPE_TO_DISMISS))

!=

0)

{

layoutResource

=

R.layout.screen_swipe_dismiss;

}

else

if

((features

&

((1

<<

FEATURE_LEFT_ICON)

|

(1

<<

FEATURE_RIGHT_ICON)))

!=

0)

{

if

(mIsFloating)

{

TypedValue

res

=

new

TypedValue();

getContext().getTheme().resolveAttribute(

R.attr.dialogTitleIconsDecorLayout,

res,

true);

layoutResource

=

res.resourceId;

}

else

{

layoutResource

=

R.layout.screen_title_icons;

}

//

XXX

Remove

this

once

action

bar

supports

these

features.

removeFeature(FEATURE_ACTION_BAR);

//

System.out.println("Title

Icons!");

}

else

if

((features

&

((1

<<

FEATURE_PROGRESS)

|

(1

<<

FEATURE_INDETERMINATE_PROGRESS)))

!=

0

&&

(features

&

(1

<<

FEATURE_ACTION_BAR))

==

0)

{

//

Special

case

for

a

window

with

only

a

progress

bar

(and

title).

//

XXX

Need

to

have

a

no-title

version

of

embedded

windows.

layoutResource

=

R.layout.screen_progress;

//

System.out.println("Progress!");

}

else

if

((features

&

(1

<<

FEATURE_CUSTOM_TITLE))

!=

0)

{

//

Special

case

for

a

window

with

a

custom

title.

//

If

the

window

is

floating,

we

need

a

dialog

layout

if

(mIsFloating)

{

TypedValue

res

=

new

TypedValue();

getContext().getTheme().resolveAttribute(

R.attr.dialogCustomTitleDecorLayout,

res,

true);

layoutResource

=

res.resourceId;

}

else

{

layoutResource

=

R.layout.screen_custom_title;

}

//

XXX

Remove

this

once

action

bar

supports

these

features.

removeFeature(FEATURE_ACTION_BAR);

}

else

if

((features

&

(1

<<

FEATURE_NO_TITLE))

==

0)

{

//

If

no

other

features

and

not

embedded,

only

need

a

title.

//

If

the

window

is

floating,

we

need

a

dialog

layout

if

(mIsFloating)

{

TypedValue

res

=

new

TypedValue();

getContext().getTheme().resolveAttribute(

R.attr.dialogTitleDecorLayout,

res,

true);

layoutResource

=

res.resourceId;

}

else

if

((features

&

(1

<<

FEATURE_ACTION_BAR))

!=

0)

{

layoutResource

=

a.getResourceId(

R.styleable.Window_windowActionBarFullscreenDecorLayout,

R.layout.screen_action_bar);

}

else

{

layoutResource

=

R.layout.screen_title;

}

//

System.out.println("Title!");

}

else

if

((features

&

(1

<<

FEATURE_ACTION_MODE_OVERLAY))

!=

0)

{

layoutResource

=

R.layout.screen_simple_overlay_action_mode;

}

else

{

//

Embedded,

so

no

decoration

is

needed.

layoutResource

=

R.layout.screen_simple;

//

System.out.println("Simple!");

}

mDecor.startChanging();

mDecor.onResourcesLoaded(mLayout