1.MainActivity 调用
setContentView(R.layout.activity_main);
2.frameworks\base\core\java\android\app\Activity.java
public void setContentView(@LayoutRes int layoutResID) { getWindow().setContentView(layoutResID); initWindowDecorActionBar(); }
getWindow 返回Window类型实例,而Window是抽象类，具体实现是 PhoneWindow
public Window getWindow() { return mWindow; }
final void attach(Context context, ActivityThread aThread, Instrumentation instr, IBinder token, int ident, Application application, Intent intent, ActivityInfo info, CharSequence title, Activity parent, String id, NonConfigurationInstances lastNonConfigurationInstances, Configuration config, String referrer, IVoiceInteractor voiceInteractor, Window window, ActivityConfigCallback activityConfigCallback, IBinder assistToken) { attachBaseContext(context); mWindow = new PhoneWindow(this, window, activityConfigCallback); }
frameworks\base\core\java\android\view\Window.java
frameworks\base\core\java\com\android\internal\policy\PhoneWindow.java
public abstract class Window
@Override public void setContentView(int layoutResID) { // 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(); 创建了一个DecorView，这个DecorView就是Activity中的根View } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) { mContentParent.removeAllViews(); } if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) { final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID, getContext()); transitionTo(newScene); } else { mLayoutInflater.inflate(layoutResID, mContentParent); } mContentParent.requestApplyInsets(); final Callback cb = getCallback(); if (cb != null && !isDestroyed()) { cb.onContentChanged(); } mContentParentExplicitlySet = true; }
private void installDecor() { mForceDecorInstall = false; if (mDecor == null) { mDecor = generateDecor(-1); mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS); mDecor.setIsRootNamespace(true); if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) { mDecor.postOnAnimation(mInvalidatePanelMenuRunnable); } } else { mDecor.setWindow(this); } if (mContentParent == null) { //根据不同的情况加载不同的布局给layoutResource mContentParent = generateLayout(mDecor); }
调用 generateDecor 方法创建DecorView 实例
protected DecorView generateDecor(int featureId) { // System process doesn't have application context and in that case we need to directly use // the context we have. Otherwise we want the application context, so we don't cling to the // activity. Context context; if (mUseDecorContext) { Context applicationContext = getContext().getApplicationContext(); if (applicationContext == null) { context = getContext(); } else { context = new DecorContext(applicationContext, this); if (mTheme != -1) { context.setTheme(mTheme); } } } else { context = getContext(); } return new DecorView(context, featureId, this, getAttributes()); }
frameworks\base\core\java\com\android\internal\policy\DecorView.java
public class DecorView extends FrameLayout implements RootViewSurfaceTaker, WindowCallbacks
DecorView(Context context, int featureId, PhoneWindow window, WindowManager.LayoutParams params) { super(context); mFeatureId = featureId; mShowInterpolator = AnimationUtils.loadInterpolator(context, android.R.interpolator.linear_out_slow_in); mHideInterpolator = AnimationUtils.loadInterpolator(context, android.R.interpolator.fast_out_linear_in); mBarEnterExitDuration = context.getResources().getInteger( R.integer.dock_enter_exit_duration); mForceWindowDrawsBarBackgrounds = context.getResources().getBoolean( R.bool.config_forceWindowDrawsStatusBarBackground) && context.getApplicationInfo().targetSdkVersion >= N; mSemiTransparentBarColor = context.getResources().getColor( R.color.system_bar_background_semi_transparent, null /* theme */); updateAvailableWidth(); setWindow(window); updateLogTag(params); mResizeShadowSize = context.getResources().getDimensionPixelSize( R.dimen.resize_shadow_size); initResizingPaints(); mLegacyNavigationBarBackgroundPaint.setColor(Color.BLACK); }
generateLayout根据不同属性，加载不同style的布局文件。
protected ViewGroup generateLayout(DecorView decor) { // Apply data from current theme. TypedArray a = getWindowStyle(); 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); 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); getAttributes().setFitInsetsSides(0); getAttributes().setFitInsetsTypes(0); } if (a.getBoolean(R.styleable.Window_windowNoTitle, false)) { 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); } if (a.getBoolean(R.styleable.Window_windowActionBarOverlay, false)) { requestFeature(FEATURE_ACTION_BAR_OVERLAY); } if (a.getBoolean(R.styleable.Window_windowActionModeOverlay, false)) { requestFeature(FEATURE_ACTION_MODE_OVERLAY); } if (a.getBoolean(R.styleable.Window_windowFullscreen, false)) { setFlags(FLAG_FULLSCREEN, FLAG_FULLSCREEN & (~getForcedWindowFlags())); } if (a.getBoolean(R.styleable.Window_windowTranslucentStatus, false)) { setFlags(FLAG_TRANSLUCENT_STATUS, FLAG_TRANSLUCENT_STATUS & (~getForcedWindowFlags())); } if (a.getBoolean(R.styleable.Window_windowTranslucentNavigation, false)) { setFlags(FLAG_TRANSLUCENT_NAVIGATION, FLAG_TRANSLUCENT_NAVIGATION & (~getForcedWindowFlags())); } if (a.getBoolean(R.styleable.Window_windowShowWallpaper, false)) { setFlags(FLAG_SHOW_WALLPAPER, FLAG_SHOW_WALLPAPER&(~getForcedWindowFlags())); } if (a.getBoolean(R.styleable.Window_windowEnableSplitTouch, getContext().getApplicationInfo().targetSdkVersion >= android.os.Build.VERSION_CODES.HONEYCOMB)) { setFlags(FLAG_SPLIT_TOUCH, FLAG_SPLIT_TOUCH&(~getForcedWindowFlags())); } a.getValue(R.styleable.Window_windowMinWidthMajor, mMinWidthMajor); a.getValue(R.styleable.Window_windowMinWidthMinor, mMinWidthMinor); if (DEBUG) Log.d(TAG, "Min width minor: " + mMinWidthMinor.coerceToString() + ", major: " + mMinWidthMajor.coerceToString()); if (a.hasValue(R.styleable.Window_windowFixedWidthMajor)) { if (mFixedWidthMajor == null) mFixedWidthMajor = new TypedValue(); a.getValue(R.styleable.Window_windowFixedWidthMajor, mFixedWidthMajor); } if (a.hasValue(R.styleable.Window_windowFixedWidthMinor)) { if (mFixedWidthMinor == null) mFixedWidthMinor = new TypedValue(); a.getValue(R.styleable.Window_windowFixedWidthMinor, mFixedWidthMinor); } if (a.hasValue(R.styleable.Window_windowFixedHeightMajor)) { if (mFixedHeightMajor == null) mFixedHeightMajor = new TypedValue(); a.getValue(R.styleable.Window_windowFixedHeightMajor, mFixedHeightMajor); } if (a.hasValue(R.styleable.Window_windowFixedHeightMinor)) { if (mFixedHeightMinor == null) mFixedHeightMinor = new TypedValue(); a.getValue(R.styleable.Window_windowFixedHeightMinor, mFixedHeightMinor); } if (a.getBoolean(R.styleable.Window_windowContentTransitions, false)) { requestFeature(FEATURE_CONTENT_TRANSITIONS); } if (a.getBoolean(R.styleable.Window_windowActivityTransitions, false)) { requestFeature(FEATURE_ACTIVITY_TRANSITIONS); } mIsTranslucent = a.getBoolean(R.styleable.Window_windowIsTranslucent, false); final Context context = getContext(); final int targetSdk = context.getApplicationInfo().targetSdkVersion; final boolean targetPreL = targetSdk < android.os.Build.VERSION_CODES.LOLLIPOP; final boolean targetPreQ = targetSdk < Build.VERSION_CODES.Q; if (!mForcedStatusBarColor) { mStatusBarColor = a.getColor(R.styleable.Window_statusBarColor, 0xFF000000); } if (!mForcedNavigationBarColor) { mNavigationBarColor = a.getColor(R.styleable.Window_navigationBarColor, 0xFF000000); mNavigationBarDividerColor = a.getColor(R.styleable.Window_navigationBarDividerColor, 0x00000000); } if (!targetPreQ) { mEnsureStatusBarContrastWhenTransparent = a.getBoolean( R.styleable.Window_enforceStatusBarContrast, false); mEnsureNavigationBarContrastWhenTransparent = a.getBoolean( R.styleable.Window_enforceNavigationBarContrast, true); } WindowManager.LayoutParams params = getAttributes(); // Non-floating windows on high end devices must put up decor beneath the system bars and // therefore must know about visibility changes of those. if (!mIsFloating) { if (!targetPreL && a.getBoolean( R.styleable.Window_windowDrawsSystemBarBackgrounds, false)) { setFlags(FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS, FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS & ~getForcedWindowFlags()); } if (mDecor.mForceWindowDrawsBarBackgrounds) { params.privateFlags |= PRIVATE_FLAG_FORCE_DRAW_BAR_BACKGROUNDS; } } if (a.getBoolean(R.styleable.Window_windowLightStatusBar, false)) { decor.setSystemUiVisibility( decor.getSystemUiVisibility() | View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR); } if (a.getBoolean(R.styleable.Window_windowLightNavigationBar, false)) { decor.setSystemUiVisibility( decor.getSystemUiVisibility() | View.SYSTEM_UI_FLAG_LIGHT_NAVIGATION_BAR); } if (a.hasValue(R.styleable.Window_windowLayoutInDisplayCutoutMode)) { int mode = a.getInt(R.styleable.Window_windowLayoutInDisplayCutoutMode, -1); if (mode < LAYOUT_IN_DISPLAY_CUTOUT_MODE_DEFAULT || mode > LAYOUT_IN_DISPLAY_CUTOUT_MODE_ALWAYS) { throw new UnsupportedOperationException("Unknown windowLayoutInDisplayCutoutMode: " + a.getString(R.styleable.Window_windowLayoutInDisplayCutoutMode)); } params.layoutInDisplayCutoutMode = mode; } if (mAlwaysReadCloseOnTouchAttr || getContext().getApplicationInfo().targetSdkVersion >= android.os.Build.VERSION_CODES.HONEYCOMB) { if (a.getBoolean( R.styleable.Window_windowCloseOnTouchOutside, false)) { setCloseOnTouchOutsideIfNotSet(true); } } if (!hasSoftInputMode()) { params.softInputMode = a.getInt( R.styleable.Window_windowSoftInputMode, params.softInputMode); } if (a.getBoolean(R.styleable.Window_backgroundDimEnabled, mIsFloating)) { /* All dialogs should have the window dimmed */ if ((getForcedWindowFlags()&WindowManager.LayoutParams.FLAG_DIM_BEHIND) == 0) { params.flags |= WindowManager.LayoutParams.FLAG_DIM_BEHIND; } if (!haveDimAmount()) { params.dimAmount = a.getFloat( android.R.styleable.Window_backgroundDimAmount, 0.5f); } } if (params.windowAnimations == 0) { params.windowAnimations = a.getResourceId( R.styleable.Window_windowAnimationStyle, 0); } // The rest are only done if this window is not embedded; otherwise, // the values are inherited from our container. if (getContainer() == null) { if (mBackgroundDrawable == null) { if (mFrameResource == 0) { mFrameResource = a.getResourceId(R.styleable.Window_windowFrame, 0); } if (a.hasValue(R.styleable.Window_windowBackground)) { mBackgroundDrawable = a.getDrawable(R.styleable.Window_windowBackground); } } if (a.hasValue(R.styleable.Window_windowBackgroundFallback)) { mBackgroundFallbackDrawable = a.getDrawable(R.styleable.Window_windowBackgroundFallback); } if (mLoadElevation) { mElevation = a.getDimension(R.styleable.Window_windowElevation, 0); } mClipToOutline = a.getBoolean(R.styleable.Window_windowClipToOutline, false); mTextColor = a.getColor(R.styleable.Window_textColor, Color.TRANSPARENT); } // Inflate the window decor. int layoutResource; int features = getLocalFeatures(); // System.out.println("Features: 0x" + Integer.toHexString(features)); 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; } // XXX Remove this once action bar supports these features. removeFeature(FEATURE_ACTION_BAR); // System.out.println("Title Icons!"); } else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0 && (features & (1 << FEATURE_ACTION_BAR)) == 0) { // Special case for a window with only a progress bar (and title). // XXX Need to have a no-title version of embedded windows. layoutResource = R.layout.screen_progress; // System.out.println("Progress!"); } else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) { // Special case for a window with a custom title. // If the window is floating, we need a dialog layout if (mIsFloating) { TypedValue res = new TypedValue(); getContext().getTheme().resolveAttribute( R.attr.dialogCustomTitleDecorLayout, res, true); layoutResource = res.resourceId; } else { layoutResource = R.layout.screen_custom_title; } // XXX Remove this once action bar supports these features. removeFeature(FEATURE_ACTION_BAR); } else if ((features & (1 << FEATURE_NO_TITLE)) == 0) { // If no other features and not embedded, only need a title. // If the window is floating, we need a dialog layout if (mIsFloating) { TypedValue res = new TypedValue(); getContext().getTheme().resolveAttribute( R.attr.dialogTitleDecorLayout, res, true); 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; } // System.out.println("Title!"); } else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) { layoutResource = R.layout.screen_simple_overlay_action_mode; } else { // Embedded, so no decoration is needed. layoutResource = R.layout.screen_simple; // System.out.println("Simple!"); } mDecor.startChanging(); mDecor.onResourcesLoaded(mLayoutInflater, layoutResource); ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT); if (contentParent == null) { throw new RuntimeException("Window couldn't find content container view"); } if ((features & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) { ProgressBar progress = getCircularProgressBar(false); if (progress != null) { progress.setIndeterminate(true); } } // Remaining setup -- of background and title -- that only applies // to top-level windows. if (getContainer() == null) { mDecor.setWindowBackground(mBackgroundDrawable); final Drawable frame; if (mFrameResource != 0) { frame = getContext().getDrawable(mFrameResource); } else { frame = null; } mDecor.setWindowFrame(frame); mDecor.setElevation(mElevation); mDecor.setClipToOutline(mClipToOutline); if (mTitle != null) { setTitle(mTitle); } if (mTitleColor == 0) { mTitleColor = mTextColor; } setTitleColor(mTitleColor); } mDecor.finishChanging(); return contentParent; }
一般加载R.layout.screen_title
文件位于frameworks\base\core\res\res\layout\screen_title.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:fitsSystemWindows="true"> <!-- Popout bar for action modes --> <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" android:theme="?attr/actionBarTheme" /> <FrameLayout android:layout_width="match_parent" android:layout_height="?android:attr/windowTitleSize" style="?android:attr/windowTitleBackgroundStyle"> <TextView android:id="@android:id/title" style="?android:attr/windowTitleStyle" android:background="@null" android:fadingEdge="horizontal" android:gravity="center_vertical" android:layout_width="match_parent" android:layout_height="match_parent" /> </FrameLayout> <FrameLayout android:id="@android:id/content" android:layout_width="match_parent" android:layout_height="0dip" android:layout_weight="1" android:foregroundGravity="fill_horizontal|top" android:foreground="?android:attr/windowContentOverlay" /> </LinearLayout>
ViewStub是用来显示ActionBar的，下面的FrameLayout，一个是title用来显示标题，一个是content用来显示内容。
所以，一个Activity包含一个window对象，这个对象是由PhoneWindow来实现的，PhoneWindow将DecorView做为整个应用窗口的根View，而这个DecorView又将屏幕划分为两个区域一个是TitleView，一个是ContentView，而我们平常做应用所写的布局正是展示在ContentView中的。
