【移动应用开发技术】Activity怎么显示界面

【移动应用开发技术】Activity怎么显示界面

动画展示/upload/information/20210522/379/525107.png源码解析从小爱诞生说起//ActivityThread.java

private

Activity

performLaunchActivity(ActivityClientRecord

r,

Intent

customIntent)

{

//创建ContextImpl

ContextImpl

appContext

=

createBaseContextForActivity(r);

Activity

activity

=

null;

try

{

java.lang.ClassLoader

cl

=

appContext.getClassLoader();

//创建Activity

activity

=

mInstrumentation.newActivity(

cl,

component.getClassName(),

ent);

}

try

{

if

(activity

!=

null)

{

//完成activity的一些重要数据的初始化

activity.attach(appContext,

this,

getInstrumentation(),

r.token,

r.ident,

app,

ent,

r.activityInfo,

title,

r.parent,

r.embeddedID,

r.lastNonConfigurationInstances,

config,

r.referrer,

r.voiceInteractor,

window,

r.configCallback,

r.assistToken);

//调用activity的onCreate方法

if

(r.isPersistable())

{

mInstrumentation.callActivityOnCreate(activity,

r.state,

r.persistentState);

}

else

{

mInstrumentation.callActivityOnCreate(activity,

r.state);

}

}

}

return

activity;

}给小爱找个和View交互的帮手(PhoneWindow)//Activity.java

final

void

attach()

{

//创建PhoneWindow

mWindow

=

new

PhoneWindow(this,

window,

activityConfigCallback);

mWindow.setCallback(this);

mWindow.setWindowManager(

(WindowManager)context.getSystemService(Context.WINDOW_SERVICE),

mToken,

mComponent.flattenToString(),

(info.flags

&

ActivityInfo.FLAG_HARDWARE_ACCELERATED)

!=

0);

}加载布局文件(DecorView)//Activity.java

public

void

setContentView(@LayoutRes

int

layoutResID)

{

getWindow().setContentView(layoutResID);

initWindowDecorActionBar();

}//PhoneWindow.java

@Override

public

void

setContentView(int

layoutResID)

{

if

(mContentParent

==

null)

{

installDecor();

}

if

(!hasFeature(FEATURE_CONTENT_TRANSITIONS))

{

mLayoutInflater.inflate(layoutResID,

mContentParent);

}

}

private

void

installDecor()

{

if

(mDecor

==

null)

{

mDecor

=

generateDecor(-1);

}

else

{

mDecor.setWindow(this);

}

if

(mContentParent

==

null)

{

mContentParent

=

generateLayout(mDecor);

}

}

protected

DecorView

generateDecor(int

featureId)

{

return

new

DecorView(context,

featureId,

this,

getAttributes());

}//加载xml布局文件

mLayoutInflater.inflate(layoutResID,

mContentParent);

public

View

inflate(@LayoutRes

int

resource,

@Nullable

ViewGroup

root,

boolean

attachToRoot)

{

final

Resources

res

=

getContext().getResources();

final

XmlResourceParser

parser

=

res.getLayout(resource);

try

{

return

inflate(parser,

root,

attachToRoot);

}

finally

{

parser.close();

}

}显示出这个View(ViewRootImpl)@Override

public

void

handleResumeActivity()

{

//onResume

final

ActivityClientRecord

r

=

performResumeActivity(token,

finalStateRequest,

reason);

//addView

if

(r.window

==

null

&&

!a.mFinished

&&

willBeVisible)

{

r.window

=

r.activity.getWindow();

View

decor

=

r.window.getDecorView();

ViewManager

wm

=

a.getWindowManager();

WindowManager.LayoutParams

l

=

r.window.getAttributes()

wm.addView(decor,

l);

}//WindowManagerGlobal.java

public

void

addView()

{

synchronized

(mLock)

{

root

=

new

ViewRootImpl(view.getContext(),

display);

view.setLayoutParams(wparams);

mViews.add(view);

mRoots.add(root);

mParams.add(wparams);

try

{

root.setView(view,

wparams,

panelParentView);

}

}

}

public

ViewRootImpl(Context

context,

Display

display)

{

mContext

=

context;

mWindowSession

=

WindowManagerGlobal.getWindowSession();

mThread

=

Thread.currentThread();

}//ViewRootImpl.java

public

void

setView()

{

synchronized

(this)

{

//绘制

requestLayout();

//调用WMS的addWindow方法

res

=

mWindowSession.addToDisplay(mWindow,

mSeq,

mWindowAttributes,

getHostVisibility(),

mDisplay.getDisplayId(),

mWinFrame,

mAttachInfo.mContentInsets,

mAttachInfo.mStableInsets,

mAttachInfo.mOutsets,

mAttachInfo.mDisplayCutout,

mInputChannel);

//设置this(ViewRootImpl)为view(decorView)的parent

view.assignParent(this);

}

}//ViewRootImpl.java

@Override

public

void

requestLayout()

{

if

(!mHandlingLayoutInLayoutRequest)

{

checkThread();

mLayoutRequested

=

true;

scheduleTraversals();

}

}