1. 分析入口為Activity onCreate調(diào)用的 setContentView(..)方法
//Activity類
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
}
2.Activity類中 setContentView(..)調(diào)用了 getWindow().setContentView(layoutResID), getWindow()獲取了一個Window對象并調(diào)用了Window對象的setContentView（）方法
//Activity類
public void setContentView(@LayoutRes int layoutResID) {
getWindow().setContentView(layoutResID);
initWindowDecorActionBar();
}
Window： 頂級窗口外觀和行為策略的抽象基類哺窄。這個類的一個實例應該被用作添加到窗口管理器的頂層視圖。它提供了標準的UI策略叹侄，如背景，標題區(qū)域，默認密鑰處理等。
3.Window對象是一個抽象了他的唯一實現(xiàn)是PhoneWindow 其中setContentView（...）才是關鍵
//PhoneWindow類
public void setContentView(int layoutResID) {
if (mContentParent == null) {//mContentParent ViewGroup 視圖容器 判斷是否為空 實際是 DecorView 這是頂View
installDecor();//初始化DecorView 設置Activity主題
} else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {//沒有動畫移除所有View
mContentParent.removeAllViews();//移除視圖
}
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {//有過度動畫 執(zhí)行動畫
final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
getContext());
transitionTo(newScene);
} else {//初始化布局
mLayoutInflater.inflate(layoutResID, mContentParent);//解析XML 添加View
}
mContentParent.requestApplyInsets();
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
mContentParentExplicitlySet = true;
}
3.1 初始化頂層容器DecorView 初始化后還要設置當前界面 style（樣式）添加初始化布局
//PhoneWindow類
private void installDecor() {
mForceDecorInstall = false;
if (mDecor == null) {//DecorView為空直接創(chuàng)建
mDecor = generateDecor(-1);
mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
mDecor.setIsRootNamespace(true);
if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
}
} else {
mDecor.setWindow(this);//綁定當前PhoneWindow
}
if (mContentParent == null) {
mContentParent = generateLayout(mDecor);//設置style Activity 樣式 并為DecorView初始布局樣式
.....
}
}
3.2 generateLayout（）Activity style實在這里解析配置
protected ViewGroup generateLayout(DecorView decor) {
TypedArray a = getWindowStyle();//獲取頁面當前樣式數(shù)據(jù) 方法如下：
if (false) {
System.out.println("From style:");
String s = "Attrs:";
for (int i = 0; i < R.styleable.Window.length; i++) {
s = s + " " + Integer.toHexString(R.styleable.Window[i]) + "="
+ a.getString(i);
}
System.out.println(s);
}
mIsFloating = a.getBoolean(R.styleable.Window_windowIsFloating, false);//判斷當前Window是否是浮窗
int flagsToUpdate = (FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR)
& (~getForcedWindowFlags());
if (mIsFloating) {
setLayout(WRAP_CONTENT, WRAP_CONTENT);
setFlags(0, flagsToUpdate);
} else {
setFlags(FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR, flagsToUpdate);
}
//以下都是設置style 的狀態(tài)位
if (a.getBoolean(R.styleable.Window_windowNoTitle, false)) {//是否顯示狀態(tài)欄
requestFeature(FEATURE_NO_TITLE);
} else if (a.getBoolean(R.styleable.Window_windowActionBar, false)) {
// Don't allow an action bar if there is no title.
requestFeature(FEATURE_ACTION_BAR);
}
.....
int layoutResource;//布局文件id
int features = getLocalFeatures()
//根據(jù)主題不一樣加載不同的布局文件
if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
layoutResource = R.layout.screen_swipe_dismiss;
setCloseOnSwipeEnabled(true);
} 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;
}
......
mDecor.startChanging();
mDecor.onResourcesLoaded(mLayoutInflater, layoutResource);//加載主題布局
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);//拿到加載程序員布局父容器
......
return contentParent;//返回程序員布局容器
}
//獲取Style解析樣式數(shù)據(jù)
public final TypedArray getWindowStyle() {
synchronized (this) {
if (mWindowStyle == null) {
mWindowStyle = mContext.obtainStyledAttributes(
com.android.internal.R.styleable.Window);
}
return mWindowStyle;
}
}
Activity布局.png
4.通過以上過程我們拿到了程序源定義布局文件 父容器 mContentParent （ViewGroup ）現(xiàn)在 mLayoutInflater.inflate(layoutResID, mContentParent)接卸自定義布局文件 一直追蹤inflate（）方法會到達LayoutInflater類中
LayoutInflater解析xml生成view
- 先解析布局文件根節(jié)點
//LayoutInflater類
public View inflate(@LayoutRes int resource, @Nullable ViewGroup root, boolean attachToRoot) {
final Resources res = getContext().getResources();
final XmlResourceParser parser = res.getLayout(resource);//Xml解析器
try {
return inflate(parser, root, attachToRoot);//調(diào)用下面方法
} finally {
parser.close();
}
}
//初始化布局文件根節(jié)點
public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {
synchronized (mConstructorArgs) {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "inflate");
final Context inflaterContext = mContext;
final AttributeSet attrs = Xml.asAttributeSet(parser);
Context lastContext = (Context) mConstructorArgs[0];
mConstructorArgs[0] = inflaterContext;
View result = root;
try {
//解析Xml 尋找根節(jié)點
int type;
while ((type = parser.next()) != XmlPullParser.START_TAG &&
type != XmlPullParser.END_DOCUMENT) {
// Empty
}
if (type != XmlPullParser.START_TAG) {
throw new InflateException(parser.getPositionDescription()
+ ": No start tag found!");
}
final String name = parser.getName();//獲取根節(jié)點name
if (TAG_MERGE.equals(name)) {//如果節(jié)點名merge
if (root == null || !attachToRoot) {//沒有根節(jié)點 或者 不加載到父布局中 拋出異常
throw new InflateException("<merge /> can be used only with a valid "
+ "ViewGroup root and attachToRoot=true");
}
rInflate(parser, root, inflaterContext, attrs, false);//根節(jié)點為merge解析
}else{//正常節(jié)點
final View temp = createViewFromTag(root, name, inflaterContext, attrs);//生成view
ViewGroup.LayoutParams params = null;
if (root != null) {
params = root.generateLayoutParams(attrs);//調(diào)用父布局generateLayoutParams獲取LayoutParams
if (!attachToRoot) {//不加入父布局直接設置參數(shù) Adapter因為復用 是由Adapter管理不需要直接加入父布局
temp.setLayoutParams(params);//設置LayoutParams生成的View
}
rInflateChildren(parser, temp, attrs, true);//解析子節(jié)點 這個方法最終調(diào)用 rInflate（）抛杨；
if (root != null && attachToRoot) {//需要加入父布局
root.addView(temp, params);//將改節(jié)點加入父容器
}
.....
}
}
}
}
- 根節(jié)點下的字節(jié)點
void rInflate(XmlPullParser parser, View parent, Context context,
AttributeSet attrs, boolean finishInflate) throws XmlPullParserException, IOException {
final int depth = parser.getDepth();
int type;
boolean pendingRequestFocus = false;
while (((type = parser.next()) != XmlPullParser.END_TAG ||
parser.getDepth() > depth) && type != XmlPullParser.END_DOCUMENT) {
if (type != XmlPullParser.START_TAG) {
continue;
}
final String name = parser.getName();
if (TAG_REQUEST_FOCUS.equals(name)) {
pendingRequestFocus = true;
consumeChildElements(parser);
} else if (TAG_TAG.equals(name)) {
parseViewTag(parser, parent, attrs);
} else if (TAG_INCLUDE.equals(name)) {
if (parser.getDepth() == 0) {
throw new InflateException("<include /> cannot be the root element");
}
parseInclude(parser, context, parent, attrs);
} else if (TAG_MERGE.equals(name)) {
throw new InflateException("<merge /> must be the root element");
} else {
final View view = createViewFromTag(parent, name, context, attrs);
final ViewGroup viewGroup = (ViewGroup) parent;
final ViewGroup.LayoutParams params = viewGroup.generateLayoutParams(attrs);
rInflateChildren(parser, view, attrs, true);
viewGroup.addView(view, params);
}
}
if (pendingRequestFocus) {
parent.restoreDefaultFocus();
}
if (finishInflate) {
parent.onFinishInflate();
}
}
總的邏輯圖
Activity UI加載.png
