[TOC]
Activity的相关生命周期
ActivityThread中:
private Activity performLaunchActivity(){
...
ContextImpl appContext = createBaseContextForActivity(r);
java.lang.ClassLoader cl = appContext.getClassLoader();
//创建activity对象
Activity activity = null;
activity = mInstrumentation.newActivity(cl, component.getClassName(), r.intent);
Window window = null;
if (r.mPendingRemoveWindow != null && r.mPreserveWindow) {
window = r.mPendingRemoveWindow;
}
//调用Activity的attach()
activity.attach(...,window,...)
//调用Activity的onPerfermCreate()->onCreate()
mInstrumentation.callActivityOnCreate(activity, r.state);
}
- r是ActivityClientRecord对象，每个activity启动前会创建一个，用于保存：
- Binder对象
- Intent对象
- Bundle对象
- Window对象
- ActiityInfo对象，他包含theme，launcherMode，permission，taskAffinity，flags等
- Activity对象本身和上级Activity对象
- 各种Configuration
- 生命周期状态等
Activity的attach()中：
final void attach(...){
mWindow = new PhoneWindow(this, window, activityConfigCallback);
...
//mToken是当前Activity的IBinder对象，传递给WMS进程
mWindow.setWindowManager((WindowManager)context.getSystemService(Context.WINDOW_SERVICE),mToken,...);
if (mParent != null) {
mWindow.setContainer(mParent.getWindow());
}
mWindowManager = mWindow.getWindowManager();
}
View加载
ActivityThread中：
public void handleResumeActivity(...){
final ActivityClientRecord r = mActivities.get(token);
final Activity a = r.activity;
if (r.window == null && !a.mFinished && willBeVisible) {
//获取PhoneWindow对象
r.window = r.activity.getWindow();
//r.window是Window的实现类phoneWindow对象，实现方法getDecorView()中创建了DecorView
//获取DecorView对象
View decor = r.window.getDecorView();
decor.setVisibility(View.INVISIBLE);
//前面Activity的attach()中初始化了WindowManager
//这里获取了WindowManagerImpl的对象
ViewManager wm = a.getWindowManager();
WindowManager.LayoutParams l = r.window.getAttributes();
a.mDecor = decor;
wm.addView(decor, l);
}
}
- WindowManager是个接口，管理window对象，这里调用了实现类WindowManagerImpl的addView(),通过桥接模式又调用了WindowManagerGlobal的addView()
- WindowManagerGlobal是单例，保存了所有Window对象和ViewRootImol对象和LayoutParams对象,通过对比activity的token(Binder)和这3个对象的token判断是哪个activity的
public void addView(View view, ViewGroup.LayoutParams params,...){
ViewRootImpl root = new ViewRootImpl(view.getContext(), display);
view.setLayoutParams(wparams);
final int count = mViews.size();
for (int i = 0; i < count; i++) {
if (mRoots.get(i).mWindow.asBinder() == wparams.token) {
panelParentView = mViews.get(i);
}
}
root.setView(view, wparams, panelParentView);
}
- ViewRootImpl管理view，surface，与WMS通信
ViewRootImpl的setView()
public void setView(View view,...){
...
requestLayout();
//IWindowSession是远程接口代理，WMS的Binder对象,这里是通知WMS渲染
res = mWindowSession.addToDisplay(mWindow, mSeq, mWindowAttributes,
getHostVisibility(), mDisplay.getDisplayId(), mTmpFrame,
mAttachInfo.mContentInsets, mAttachInfo.mStableInsets,
mAttachInfo.mOutsets, mAttachInfo.mDisplayCutout, mInputChannel,
mTempInsets);
setFrame(mTmpFrame);
}
public void requestLayout() {
if (!mHandlingLayoutInLayoutRequest) {
//这里会检查是否主线程
checkThread();
mLayoutRequested = true;
scheduleTraversals();
}
}
//间接调用到
private void performTraversals(){
//生成测量规则，这是一个32位2进制数，前2位表示测量模式，后30位表示大小
int childWidthMeasureSpec = getRootMeasureSpec(mWidth, lp.width);
int childHeightMeasureSpec = getRootMeasureSpec(mHeight, lp.height);
performMeasure(childWidthMeasureSpec, childHeightMeasureSpec);
//调用到View的measure方法,这里是DecorView对象,所以调用到FrameLayout的onMeasure()
//mView.measure(childWidthMeasureSpec, childHeightMeasureSpec);
performLayout(lp, mWidth, mHeight);
//mView.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight());
performDraw();
}
Framelayout中:
onMeasure
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int count = getChildCount();
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (mMeasureAllChildren || child.getVisibility() != GONE) {
//这里传入子view和父容器的测量规则，调用子view的测量方法
//child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, 0);
final LayoutParams lp = (LayoutParams) child.getLayoutParams();
//FrameLayout的宽高是child中最宽或最高的那个
maxWidth = Math.max(maxWidth,child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin);
maxHeight = Math.max(maxHeight,child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin);
}
}
setMeasuredDimension(resolveSizeAndState(maxWidth, widthMeasureSpec, childState),resolveSizeAndState(maxHeight, heightMeasureSpec,childState << MEASURED_HEIGHT_STATE_SHIFT));
//如果Framelayout不是精确模式,即宽高是Wrap，宽或高为Match的child会受他的最终大小影响，所以在此调用这些child的再次测量
for (int i = 0; i < count; i++) {
final View child = mMatchParentChildren.get(i);
...
child.measure(childWidthMeasureSpec, childHeightMeasureSpec);
}
}
onLayout
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
layoutChildren(left, top, right, bottom, false);
}
void layoutChildren(int left, int top, int right, int bottom, boolean forceLeftGravity) {
final int count = getChildCount();
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
...
child.layout(childLeft, childTop, childLeft + width, childTop + height);
}
}
onDraw
ViewRootImpl的performDraw()会调用到
public final Surface mSurface = new Surface();
private boolean drawSoftware(Surface surface,Rect dirty,...){
final Canvas canvas;
//view绘制用的画布，是在Surface对象上截取的一个rect范围
//mDirty.set(0, 0, mWidth, mHeight);DecorView的范围是Window的宽高
canvas = mSurface.lockCanvas(dirty);
canvas.setDensity(mDensity);
//这里会调用onDraw(),容器是空实现，非容器View绘制视图
mView.draw(canvas);
}
draw方法6步：
* 1. Draw the background
* 2. If necessary, save the canvas' layers to prepare for fading
* 3. Draw view's content
* 4. Draw children
* 5. If necessary, draw the fading edges and restore layers
* 6. Draw decorations (scrollbars for instance)
关键环节
- Activity创建后调用的attach方法中，初始化了PhoneWindow对象，WindowManager对象
- WindowManager初始化时，赋值的是WindowManagerImpl对象
- PhoneWindow实现了Window的getDecorView方法，这里创建了DecorView对象
- handleResumeActivity()中获取了decorView对象和wm的params，由wm开始addView，wm是window的管理器，addview中创建了ViewRootImpl对象，这是view树的根和管理器
- ViewRootImpl的setView被wm触发后，调用requestLayout，这里开始view三步骤
关于测量2次
performTranversal被执行2次
关于测量模式
- EXACTLY：表示设置了精确的值，一般当View或childView设置其宽、高为精确值、match_parent时，会将其设置为EXACTLY
- AT_MOST：表示子布局被限制在一个最大值内，一般当View或childView设置其宽高为wrap_content时，会将其设置为AT_MOST
- UNSPECIFIED：表示子布局想多大多大，一般出现在AadapterView的item的heightMode中、ScrollView的childView的heightMode中
