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一般我们都是这样使用setContentView:
@Override
protected onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}但setContentView是怎么把我们的布局加载显示到界面上的呢？我们进去setContentView看一下：
public setContentView( layoutResID) {
getWindow().setContentView(layoutResID);
initWindowDecorActionBar();
}这里的getWindow返回一个Window对象mWindow，然后调用其setContentView方法，不过Window是一个抽象类，因此这个mWindow一定是Window的某个子类对象（你可以打印它的Class对象直接看是什么类型），它在Activity的attach方法（这个方法在ActivityThread启动Activity时会被调用）中被初始化：
final attach(Context context, ActivityThread aThread,
Instrumentation instr, IBinder token, int ident,
mWindow PolicyManagermakeNewWindow(this);
再看PolicyManager的makeNewWindow方法：
public static Window makeNewWindow(Context context) {
return sPolicy.makeNewWindow(context);
}这个sPolicy是通过反射创建的，是一个com.android.internal.policy.impl.Policy对象，它的makeNewWindow方法：
public Window makeNewWindow(Context context) {
return PhoneWindow(context);
}到这里就可以确定Activity的getWindow()返回的其实是一个PhoneWindow对象，注意PhoneWindow所在的包为com.android.internal.policy.impl。也就是说getWindow().setContentView(layoutResID);调用的就是PhoneWindow的setContentView方法：
@Override
public setContentView( layoutResID) {
(mContentParent == ) {
installDecor();
} {
mContentParent.removeAllViews();
}
//把我们的布局添加到mContentParent中
mLayoutInflater.inflate(layoutResID, mContentParent);
//这个cb其实就是我们的Activity对象
final Callback cb = getCallback();
(cb != && !isDestroyed()) {
cb.onContentChanged();
}
}代码逻辑并不复杂，就是把我们的布局添加到mContentParent（ViewGroup对象）中。它的赋值是在installDecor中进行的：
private installDecor() {
(mDecor ) {
mDecor generateDecor();
}
(mContentParent ) {
mContentParent generateLayout(mDecor);
}
}先看mDecor是一个什么东西：
protected DecorView generateDecor() {
return DecorView(getContext(), -);
}原来是一个DecorView对象，DecorView类继承自FrameLayout，它是PhoneWindow的内部类。
再来看generateLayout方法：
protected ViewGroup generateLayout(DecorView decor) {
// Apply data from current theme.
TypedArray a = getWindowStyle();
(false) {
System..println("From style:");
String s = "Attrs:";
( i = ; i < com.android.internal.R.styleable.Window.length; i++) {
s = s + + Integer.toHexString(com.android.internal.R.styleable.Window[i]) +
+ a.getString(i);
}
System..println(s);
}
mIsFloating = a.getBoolean(com.android.internal.R.styleable.Window_windowIsFloating, false);
flagsToUpdate = (FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR)
& (~getForcedWindowFlags());
(mIsFloating) {
setLayout(WRAP_CONTENT, WRAP_CONTENT);
setFlags(, flagsToUpdate);
} {
setFlags(FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR, flagsToUpdate);
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowNoTitle, false)) {
requestFeature(FEATURE_NO_TITLE);
} (a.getBoolean(com.android.internal.R.styleable.Window_windowActionBar, false)) {
// Don't allow an action bar if there is no title.
requestFeature(FEATURE_ACTION_BAR);
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowActionBarOverlay, false)) {
requestFeature(FEATURE_ACTION_BAR_OVERLAY);
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowActionModeOverlay, false)) {
requestFeature(FEATURE_ACTION_MODE_OVERLAY);
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowFullscreen, false)) {
setFlags(FLAG_FULLSCREEN, FLAG_FULLSCREEN & (~getForcedWindowFlags()));
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowTranslucentStatus,
false)) {
setFlags(FLAG_TRANSLUCENT_STATUS, FLAG_TRANSLUCENT_STATUS
& (~getForcedWindowFlags()));
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowTranslucentNavigation,
false)) {
setFlags(FLAG_TRANSLUCENT_NAVIGATION, FLAG_TRANSLUCENT_NAVIGATION
& (~getForcedWindowFlags()));
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowOverscan, false)) {
setFlags(FLAG_LAYOUT_IN_OVERSCAN, FLAG_LAYOUT_IN_OVERSCAN&(~getForcedWindowFlags()));
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowShowWallpaper, false)) {
setFlags(FLAG_SHOW_WALLPAPER, FLAG_SHOW_WALLPAPER&(~getForcedWindowFlags()));
}
(a.getBoolean(com.android.internal.R.styleable.Window_windowEnableSplitTouch,
getContext().getApplicationInfo().targetSdkVersion
>= android.os.Build.VERSION_CODES.HONEYCOMB)) {
setFlags(FLAG_SPLIT_TOUCH, FLAG_SPLIT_TOUCH&(~getForcedWindowFlags()));
}
a.getValue(com.android.internal.R.styleable.Window_windowMinWidthMajor, mMinWidthMajor);
a.getValue(com.android.internal.R.styleable.Window_windowMinWidthMinor, mMinWidthMinor);
(a.hasValue(com.android.internal.R.styleable.Window_windowFixedWidthMajor)) {
(mFixedWidthMajor == ) mFixedWidthMajor = TypedValue();
a.getValue(com.android.internal.R.styleable.Window_windowFixedWidthMajor,
mFixedWidthMajor);
}
(a.hasValue(com.android.internal.R.styleable.Window_windowFixedWidthMinor)) {
(mFixedWidthMinor == ) mFixedWidthMinor = TypedValue();
a.getValue(com.android.internal.R.styleable.Window_windowFixedWidthMinor,
mFixedWidthMinor);
}
(a.hasValue(com.android.internal.R.styleable.Window_windowFixedHeightMajor)) {
(mFixedHeightMajor == ) mFixedHeightMajor = TypedValue();
a.getValue(com.android.internal.R.styleable.Window_windowFixedHeightMajor,
mFixedHeightMajor);
}
(a.hasValue(com.android.internal.R.styleable.Window_windowFixedHeightMinor)) {
(mFixedHeightMinor == ) mFixedHeightMinor = TypedValue();
a.getValue(com.android.internal.R.styleable.Window_windowFixedHeightMinor,
mFixedHeightMinor);
}
final Context context = getContext();
final targetSdk = context.getApplicationInfo().targetSdkVersion;
final boolean targetPreHoneycomb = targetSdk < android.os.Build.VERSION_CODES.HONEYCOMB;
final boolean targetPreIcs = targetSdk < android.os.Build.VERSION_CODES.ICE_CREAM_SANDWICH;
final boolean targetHcNeedsOptions = context.getResources().getBoolean(
com.android.internal.R..target_honeycomb_needs_options_menu);
final boolean noActionBar = !hasFeature(FEATURE_ACTION_BAR) || hasFeature(FEATURE_NO_TITLE);
(targetPreHoneycomb || (targetPreIcs && targetHcNeedsOptions && noActionBar)) {
addFlags(WindowManager.LayoutParams.FLAG_NEEDS_MENU_KEY);
} {
clearFlags(WindowManager.LayoutParams.FLAG_NEEDS_MENU_KEY);
}
(mAlwaysReadCloseOnTouchAttr || getContext().getApplicationInfo().targetSdkVersion
>= android.os.Build.VERSION_CODES.HONEYCOMB) {
(a.getBoolean(
com.android.internal.R.styleable.Window_windowCloseOnTouchOutside,
false)) {
setCloseOnTouchOutsideIfNotSet();
}
}
WindowManager.LayoutParams params = getAttributes();
(!hasSoftInputMode()) {
params.softInputMode = a.getInt(
com.android.internal.R.styleable.Window_windowSoftInputMode,
params.softInputMode);
}
(a.getBoolean(com.android.internal.R.styleable.Window_backgroundDimEnabled,
mIsFloating)) {
/* All dialogs should have the window dimmed */
((getForcedWindowFlags()&WindowManager.LayoutParams.FLAG_DIM_BEHIND) == ) {
params.flags |= WindowManager.LayoutParams.FLAG_DIM_BEHIND;
}
(!haveDimAmount()) {
params.dimAmount = a.getFloat(
android.R.styleable.Window_backgroundDimAmount, f);
}
}
(params.windowAnimations == ) {
params.windowAnimations = a.getResourceId(
com.android.internal.R.styleable.Window_windowAnimationStyle, );
}
// The rest are only done if this window is not embedded; otherwise,
// the values are inherited from our container.
(getContainer() == ) {
(mBackgroundDrawable == ) {
(mBackgroundResource == ) {
mBackgroundResource = a.getResourceId(
com.android.internal.R.styleable.Window_windowBackground, );
}
(mFrameResource == ) {
mFrameResource = a.getResourceId(com.android.internal.R.styleable.Window_windowFrame, );
}
(false) {
System..println("Background: "
+ Integer.toHexString(mBackgroundResource) + " Frame: "
+ Integer.toHexString(mFrameResource));
}
}
mTextColor = a.getColor(com.android.internal.R.styleable.Window_textColor, 0xFF000000);
}
// Inflate the window decor.
layoutResource;
features = getLocalFeatures();
// System.out.println("Features: 0x" + Integer.toHexString(features));
((features & (( << FEATURE_LEFT_ICON) | ( << FEATURE_RIGHT_ICON))) != ) {
(mIsFloating) {
TypedValue res = TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogTitleIconsDecorLayout, res, );
layoutResource = res.resourceId;
} {
layoutResource = com.android.internal.R.layout.screen_title_icons;
}
// XXX Remove this once action bar supports these features.
removeFeature(FEATURE_ACTION_BAR);
// System.out.println("Title Icons!");
} ((features & (( << FEATURE_PROGRESS) | ( << FEATURE_INDETERMINATE_PROGRESS))) !=
&& (features & ( << FEATURE_ACTION_BAR)) == ) {
// Special case for a window with only a progress bar (and title).
// XXX Need to have a no-title version of embedded windows.
layoutResource = com.android.internal.R.layout.screen_progress;
// System.out.println("Progress!");
} ((features & ( << FEATURE_CUSTOM_TITLE)) != ) {
// Special case for a window with a custom title.
// If the window is floating, we need a dialog layout
(mIsFloating) {
TypedValue res = TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogCustomTitleDecorLayout, res, );
layoutResource = res.resourceId;
} {
layoutResource = com.android.internal.R.layout.screen_custom_title;
}
// XXX Remove this once action bar supports these features.
removeFeature(FEATURE_ACTION_BAR);
} ((features & ( << FEATURE_NO_TITLE)) == ) {
// If no other features and not embedded, only need a title.
// If the window is floating, we need a dialog layout
(mIsFloating) {
TypedValue res = TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogTitleDecorLayout, res, );
layoutResource = res.resourceId;
} ((features & ( << FEATURE_ACTION_BAR)) != ) {
layoutResource = com.android.internal.R.layout.screen_action_bar;
} {
layoutResource = com.android.internal.R.layout.screen_title;
}
// System.out.println("Title!");
} ((features & ( << FEATURE_ACTION_MODE_OVERLAY)) != ) {
layoutResource = com.android.internal.R.layout.screen_simple_overlay_action_mode;
} {
// Embedded, so no decoration is needed.
layoutResource = com.android.internal.R.layout.screen_simple;
// System.out.println("Simple!");
}
mDecor.startChanging();
View = mLayoutInflater.inflate(layoutResource, );
decor.addView(, ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
(contentParent == ) {
throw RuntimeException("Window couldn't find content container view");
}
((features & ( << FEATURE_INDETERMINATE_PROGRESS)) != ) {
ProgressBar progress = getCircularProgressBar(false);
(progress != ) {
progress.setIndeterminate();
}
}
// Remaining setup -- of background and title -- that only applies
// to top-level windows.
(getContainer() == ) {
Drawable drawable = mBackgroundDrawable;
(mBackgroundResource != ) {
drawable = getContext().getResources().getDrawable(mBackgroundResource);
}
mDecor.setWindowBackground(drawable);
drawable = ;
(mFrameResource != ) {
drawable = getContext().getResources().getDrawable(mFrameResource);
}
mDecor.setWindowFrame(drawable);
// System.out.println("Text=" + Integer.toHexString(mTextColor) +
// " Sel=" + Integer.toHexString(mTextSelectedColor) +
// " Title=" + Integer.toHexString(mTitleColor));
(mTitleColor == ) {
mTitleColor = mTextColor;
}
(mTitle != ) {
setTitle(mTitle);
}
setTitleColor(mTitleColor);
}
mDecor.finishChanging();
return contentParent;
}这个方法主要做两件事：
1.设置当前窗口的主题样式
2.查找适当的布局作为mDecor的子View，Android中定义了许多这种布局，在~\sdk\platforms\android-19\data\res\layout目录下可以找到，比如一般使用的screen_simple.xml：
<LinearLayout xmlns:android="http://schemas.android.com///android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
android:orientation="vertical">
<ViewStub android:id="@+id/action_mode_bar_stub"
android:inflatedId="@+id/action_mode_bar"
android:layout="@layout/action_mode_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<!-- 这个就是mContentParent,我们的布局添加做为它的子View -->
<FrameLayout
android:id="@android:id/content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:foregroundInsidePadding="false"
android:foregroundGravity="fill_horizontal|top"
android:foreground="?android:attr/windowContentOverlay" />
</LinearLayout>因此平时我们调用setContentView设置显示我们的布局，实际的布局会是这样子：
实际的xml布局文件（采用screen_simple.xml为例）：
<com.android.internal.policy.impl.PhoneWindow$DecorView
android:layout_width="match_parent"
android:layout_height="match_parent">
<!-- screen_simple.xml -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
android:orientation="vertical">
<ViewStub android:id="@+id/action_mode_bar_stub"
android:inflatedId="@+id/action_mode_bar"
android:layout="@layout/action_mode_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<!-- mContentParent实际就是这个FrameLayout -->
<FrameLayout
android:id="@android:id/content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:foregroundInsidePadding="false"
android:foregroundGravity="fill_horizontal|top"
android:foreground="?android:attr/windowContentOverlay">
<!-- 我们的activity_main.xml -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="hello world"/>
</LinearLayout>
</FrameLayout>
</LinearLayout>
</com.android.internal.policy.impl.PhoneWindow>setContentView时序图：
转载请注明出处：blog.csdn.net/u012619640/…[2]
