setContentView 就从我们自己新建的一个Activity开始
public class ActivityTest extends AppCompatActivity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
}
}
↓
↓ setContentView(R.layout.activity_test);
↓
public class AppCompatActivity extends ... {
public void setContentView(@LayoutRes int layoutResID) {
this.getDelegate().setContentView(layoutResID);
}
↓
↓ getDelegate().setContentView(layoutResID);先找getDelegate()
↓ getDelegate()也在AppCompatActivity 中
↓
@NonNull
public AppCompatDelegate getDelegate() {
if (mDelegate == null) {
mDelegate = AppCompatDelegate.create(this, this);
}
return mDelegate;
}
}
↓
↓ getDelegate() = AppCompatDelegate.create(this, this);
↓
public abstract class AppCompatDelegate {
public static AppCompatDelegate create(Activity activity, AppCompatCallback callback) {
return new AppCompatDelegateImpl(activity, activity.getWindow(), callback);
}
}
所以最后调用的是 AppCompatDelegateImpl 中的 setContentView 方法：
class AppCompatDelegateImpl extends ...{
public void setContentView(int resId) {
this.ensureSubDecor();
ViewGroup contentParent = (ViewGroup)this.mSubDecor.findViewById(16908290);
contentParent.removeAllViews();
LayoutInflater.from(this.mContext).inflate(resId, contentParent);
this.mOriginalWindowCallback.onContentChanged();
}
}接着去看 ensureSubDecor 方法：
ensureSubDecor
private void ensureSubDecor() {
if (!this.mSubDecorInstalled) {
this.mSubDecor = this.createSubDecor();//核心代码
//省略其它代码。。。
}
}createSubDecor
private ViewGroup createSubDecor() {
TypedArray a = this.mContext.obtainStyledAttributes(styleable.AppCompatTheme);
if (!a.hasValue(styleable.AppCompatTheme_windowActionBar)) {
a.recycle();
throw new IllegalStateException("You need to use a Theme.AppCompat theme (or descendant) with this activity.");
} else {
this.mIsFloating = a.getBoolean(styleable.AppCompatTheme_android_windowIsFloating, false);
a.recycle();
this.mWindow.getDecorView(); ---> 核心代码 1 创建DecirView
LayoutInflater inflater = LayoutInflater.from(this.mContext);
ViewGroup subDecor = null;
if (!this.mWindowNoTitle) {
if (this.mIsFloating) {
subDecor = (ViewGroup)inflater.inflate(layout.abc_dialog_title_material, (ViewGroup)null);
} else if (this.mHasActionBar) {
subDecor = (ViewGroup)LayoutInflater.from((Context)themedContext).inflate(layout.abc_screen_toolbar, (ViewGroup)null);
}
} else {
if (this.mOverlayActionMode) {
subDecor = (ViewGroup)inflater.inflate(layout.abc_screen_simple_overlay_action_mode, (ViewGroup)null);
} else {
subDecor = (ViewGroup)inflater.inflate(layout.abc_screen_simple, (ViewGroup)null);
}
//其它代码省略...
}
通过上面subDecor = inflate(布局文件)可以看出,subDecor 的布局文件是下面四种布局文件之一：
1 abc_dialog_title_material
2 abc_screen_toolbar
3 abc_screen_simple_overlay_action_mode
4 abc_screen_simple
if (subDecor == null) {
如果subDecor为空就抛出异常
throw new IllegalArgumentException("AppCompat does not support the current theme features: { windowActionBar: " + this.mHasActionBar + ", windowActionBarOverlay: " + this.mOverlayActionBar + ", android:windowIsFloating: " + this.mIsFloating + ", windowActionModeOverlay: " + this.mOverlayActionMode + ", windowNoTitle: " + this.mWindowNoTitle + " }");
} else {
if (this.mDecorContentParent == null) {
this.mTitleView = (TextView)subDecor.findViewById(id.title);
}
ViewUtils.makeOptionalFitsSystemWindows(subDecor);
// 上面说了 subDecor 是四个布局文件中的一个创建，
// 每个布局文件都有一action_bar_activity_content
ContentFrameLayout contentView = (ContentFrameLayout)subDecor.findViewById(id.action_bar_activity_content);
ViewGroup windowContentView = (ViewGroup)this.mWindow.findViewById(16908290);
if (windowContentView != null) {
while(windowContentView.getChildCount() > 0) {
View child = windowContentView.getChildAt(0);
windowContentView.removeViewAt(0);
contentView.addView(child);
}
windowContentView.setId(-1);
contentView.setId(16908290);---> 核心代码 2 contentView的id被设置成16908290
if (windowContentView instanceof FrameLayout) {
((FrameLayout)windowContentView).setForeground((Drawable)null);
}
}
this.mWindow.setContentView(subDecor);---> 核心代码 3 把subDecor填到mWindow中
contentView.setAttachListener(new OnAttachListener() {
public void onAttachedFromWindow() {
}
public void onDetachedFromWindow() {
AppCompatDelegateImpl.this.dismissPopups();
}
});
return subDecor;
}
}
}总结一下createSubDecor方法：
1 this.mWindow.getDecorView(); 创建Decorview,下面详细说明
2 加载 subDecor 是一个ViewGroup，加载完成以后进行：
ContentFrameLayout contentView = (ContentFrameLayout)subDecor.findViewById(id.action_bar_activity_content);
ViewGroup windowContentView = (ViewGroup)this.mWindow.findViewById(16908290);
3 this.mWindow.setContentView(subDecor); 将subDecor设置到this.mWindow
下面分析这三步骤
先看 1 this.mWindow.getDecorView(); ，this.mWindow 这个是啥呢？看下面
AppCompatDelegateImpl(Context context, Window window, AppCompatCallback callback) {
......
mWindow 的初始化是在AppCompatDelegateImpl构造函数里
↓
this.mWindow = window;
.....
}
想要知道mWindow是啥就要找到AppCompatDelegateImpl(context,window,callback)这个
构造函数初始化的时候传入的window是啥
还记得最开始我们从setContentView点进来的代码么
↓
↓
↓
***********************************************************************
public class ActivityTest extends AppCompatActivity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
}
}
↓
↓ setContentView(R.layout.activity_test);
↓
public class AppCompatActivity extends ... {
public void setContentView(@LayoutRes int layoutResID) {
this.getDelegate().setContentView(layoutResID);
}
↓
↓ getDelegate().setContentView(layoutResID);先找getDelegate()
↓ getDelegate()也在AppCompatActivity 中
↓
@NonNull
public AppCompatDelegate getDelegate() {
if (mDelegate == null) {
mDelegate = AppCompatDelegate.create(this, this);
}
return mDelegate;
}
}
↓
↓ getDelegate() = AppCompatDelegate.create(this, this);
↓
public abstract class AppCompatDelegate {
public static AppCompatDelegate create(Activity activity, AppCompatCallback callback) {
在这里初始化的，activity就是AppCompatActivity ，window就是activity.getWindow()
return new AppCompatDelegateImpl(activity, activity.getWindow(), callback);
}
}
***************************************************************************************
window就是AppCompatActivity.getWindow(),但是AppCompatActivity中没有getWindow()方法，
getWindow()是在其父类Activity中实现
public class Activity extends ... ... {
private Window mWindow;
final void attach(Context context, ......) {
attachBaseContext(context);
mWindow = new PhoneWindow(this, window, activityConfigCallback);
......
}
public @Nullable Window getWindow() {
return mWindow;
}
}
最后找到window就是PhoneWindow对象。
接着我们就到PhoneWindow中查看关键的this.mWindow.getDecorView();
1 this.mWindow.getDecorView();
@Override
public final View getDecorView() {
if (mDecor == null || mForceDecorInstall) {
installDecor(); ---> 核心代码
}
return mDecor;
}
private void installDecor() {
mForceDecorInstall = false;
if (mDecor == null) {
mDecor = generateDecor(-1); ---> 核心代码
....省略其它代码....
} else {
mDecor.setWindow(this);
}
if (mContentParent == null) {
mContentParent = generateLayout(mDecor); ---> 核心代码
....省略其它代码.....
}
}首先来看 mDecor = generateDecor(-1); generateDecor方法很简单就是创建了一个DecorView对象并返回赋值给 mDecor
protected DecorView generateDecor(int featureId) {
...其它代码省略...
return new DecorView(context, featureId, this, getAttributes());
}接着看 mContentParent = generateLayout(mDecor);
1：mContentParent是一个ViewGroup；
2 ：generateLayout(mDecor);将上面刚刚创建的DecorView作为参数传了进去
protected ViewGroup generateLayout(DecorView decor) {
...其它代码省略...
// Inflate the window decor.
这里精简保留的，layoutResource = R.layout.布局文件
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) {
layoutResource = res.resourceId;
} else {
layoutResource = R.layout.screen_title_icons;
}
} else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0
&& (features & (1 << FEATURE_ACTION_BAR)) == 0) {
layoutResource = R.layout.screen_progress;
} else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) {
if (mIsFloating) {
layoutResource = res.resourceId;
} else {
layoutResource = R.layout.screen_custom_title;
}
} else if ((features & (1 << FEATURE_NO_TITLE)) == 0) {
if (mIsFloating) {
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;
}
} else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) {
layoutResource = R.layout.screen_simple_overlay_action_mode;
} else {
layoutResource = R.layout.screen_simple;
}
mDecor.startChanging();
layoutResource就是上面布局文件之中的一个，加载到mDecor即DecorView中
↓
mDecor.onResourcesLoaded(mLayoutInflater, layoutResource);
而上面布局文件中它们都有一个id是content的
而且这个findViewById是在PhoneWindow直接使用？它是Activity?文章最后分析
↓
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
if (contentParent == null) {
throw new RuntimeException("Window couldn't find content container view");
}
return contentParent; ← 返回DecorView的布局文件中id为content的控件
}总结一下generateLayout(mDecor)方法，就是将一个布局文件加载到DecorView中，并将布局中的id为content的控件返回赋值给mContentParent。这样PhoneWindow就新建了DecorView对象，并为其加载了布局文件，并将布局文件的content容器准备好。
到这里 1 this.mWindow.getDecorView() 就完成了。
2 就是准备好加载我们自己创建的布局文件的容器
ContentFrameLayout contentView = (ContentFrameLayout)subDecor.findViewById(id.action_bar_activity_content);
ViewGroup windowContentView = (ViewGroup)this.mWindow.findViewById(16908290);
windowContentView.setId(-1);
contentView.setId(16908290); //其实这个就是加载我们自己创建的Activity的布局文件的容器
接着我们就来看看3 this.mWindow.setContentView(subDecor);同样是this.mWindow我们就到PhoneWindow中找setContentView方法
3 this.mWindow.setContentView(subDecor)
@Override
public void setContentView(View view) {
setContentView(view, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
}
@Override
public void setContentView(View view, ViewGroup.LayoutParams params) {
// 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)) {
view.setLayoutParams(params);
final Scene newScene = new Scene(mContentParent, view);
transitionTo(newScene);
} else {
核心方法
↓
mContentParent.addView(view, params);
}
mContentParent.requestApplyInsets();
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
mContentParentExplicitlySet = true;
}mContentParent.addView(view, params);
|--- mContentParent 就是上面DecorView中加载布局文件的 content 控件
|--- view 就是我们传递进来的subDecor
将subDecor加载到DecorView 布局文件的 content 控件中。还记得subDecor布局文件中 action_bar_activity_content 么:
ContentFrameLayout contentView = (ContentFrameLayout)subDecor.findViewById(id.action_bar_activity_content);
contentView.setId(16908290);
再来看最开始的setContentView
public void setContentView(int resId) {
this.ensureSubDecor();
ViewGroup contentParent = (ViewGroup)this.mSubDecor.findViewById(16908290);
contentParent.removeAllViews();
LayoutInflater.from(this.mContext).inflate(resId, contentParent);
this.mOriginalWindowCallback.onContentChanged();
}我们自己的布局文件被加载到了subDecor布局中id为 action_bar_activity_content的 ContentFrameLayout中。
而subDecor被加载到了DecorView布局中id为content的FrameLayout中；
DecorView是由PhoneWindow 创建
PhoneWindow 在Activity attach方法中初始化。
这样整个加载过程就串起来了。
是时候放上这样一张图了
DecorView加载的xml文件为下面中的一个：
screen_swipe_dismiss
screen_title_icons
screen_progress
screen_custom_title
screen_action_bar
screen_title
screen_simple_overlay_action_mode
screen_simple
而他们都有一个id为content的FrameLayout控件用来加载subDcor.
subDcor加载的xml文件为下面中的一个：
abc_dialog_title_material
abc_screen_toolbar
abc_screen_simple_overlay_action_mode
abc_screen_simple
而他们都有一个id为action_bar_activity_content 的 ContentFrameLayout 控件用来加载我们自定义的布局文件，就是我们创建Activity时候创建的xml文件。
上面还有一个问题PhoneWindow为啥可以直接findViewById? 点进去就会发现是在其父类Window中实现的
public abstract class Window {
@Nullable
public <T extends View> T findViewById(@IdRes int id) {
return getDecorView().findViewById(id);
}
public abstract View getDecorView();
}getDecorView的具体实现又回到了PhoneWindow 中；
@Override
public final View getDecorView() {
if (mDecor == null || mForceDecorInstall) {
installDecor();
}
return mDecor;
}这个方法看起来是不是很熟悉，就是我们初始化DecorView对象的方法，返回的就是我们初始化并加载了布局的DecorView.
所以PhoneWindow进行findViewById其实就是对其持有的DecorView进行操作。