Android windowTranslucentStatus屬性原始碼分析
簡介
我們在設定系統樣式時，將windowTranslucentStatus和windowTranslucentNavigation屬性設定為true後，Activity就會顯示為如下效果：
狀態列和導航欄都會顯示成半透明的狀態。並且佈局會拓展到系統欄的後面。本文就是要從原始碼分析windowTranslucentStatus的實現原理。因為windowTranslucentNavigation是一樣的原理所以就不再去分析，我們只要理解了windowTranslucentStatus實現流程，自然而然也就知道了windowTranslucentNavigation的實現原理。當然，這是Android 4.4後才有的屬性介面，需要注意！！！
res/values/styles.xml
<style name="FullscreenTheme" parent="AppTheme">
<item name="android:windowTranslucentStatus">true</item>
<item name="android:windowTranslucentNavigation">true</item>
</style>當然也可以在程式碼中動態設定
MainActivity.java
@Override
protected 原始碼分析
因為講的東西比較多，跨度比較大，程式碼量也比較大，先來一張時序圖，有一個大概的印象。然後，再一一分解之。
上圖是個人根據程式碼呼叫的流程畫的一張時序圖，可以不是很規範。大概還是能表現出整個SystemUI變化呼叫的流程的，先湊合著看。
第一步，我們在styles.xml中設定了windowTranslucentStatus為true。它真正的實現是在PhoneWindow.java的generateLayout方法中。程式碼如下:
frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindow.java
protected ViewGroup generateLayout(DecorView decor) {
// Apply data from current theme.
TypedArray a = getWindowStyle();
if (a.getBoolean(com.android.internal.R.styleable.Window_windowTranslucentStatus, false)) {
setFlags(FLAG_TRANSLUCENT_STATUS, FLAG_TRANSLUCENT_STATUS
& (~getForcedWindowFlags()));
}
}frameworks/base/core/java/android/view/Window.java
public void setFlags(int flags, int mask) {
final WindowManager.LayoutParams attrs = getAttributes();
attrs.flags = (attrs.flags&~mask) | (flags&mask);
if ((mask&WindowManager.LayoutParams.FLAG_NEEDS_MENU_KEY) != 0) {
attrs.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_SET_NEEDS_MENU_KEY;
}
mForcedWindowFlags |= mask;
if (mCallback != null) {
mCallback.onWindowAttributesChanged(attrs);
}
}上面程式碼可以看出我們在styles.xml中設定的屬性，會通過setFlags設定下去。而setFlags其實就是將屬性設定給了WindowManager.LayoutParams。也就是說，我們設定的windowTranslucentStatus屬性，最終變成WindowManager.LayoutParamsflags屬性中FLAG_TRANSLUCENT_STATUS。那麼這個flags屬性對於我們的狀態列有什麼實際影響呢，接著往下看。
第二步，更新狀態列的狀態變化。在PhoneWindowManager.java中updateSystemUiVisibilityLw方法是處理系統狀態列變化的地方。在其內部它會呼叫updateSystemBarsLw方法，然後，根據其返回值設定給SystemUI。而updateSystemBarsLw中mStatusBarController才是真正管理狀態列的例項類。在updateSystemBarsLw中，它會呼叫mStatusBarController的applyTranslucentFlagLw和updateVisibilityLw的方法。這兩個方法就會返回相應的顯示狀態。SystemUI就是根據這個顯示狀態值，做相應的變化。
frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindowManager.java
private final BarController mStatusBarController = new BarController("StatusBar",
View.STATUS_BAR_TRANSIENT,
View.STATUS_BAR_UNHIDE,
View.STATUS_BAR_TRANSLUCENT,
StatusBarManager.WINDOW_STATUS_BAR,
WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
private int updateSystemUiVisibilityLw() {
...
final int visibility = updateSystemBarsLw(win, mLastSystemUiFlags, tmpVisibility);
mFocusedApp = win.getAppToken();
mHandler.post(new Runnable() {
@Override
public void run() {
try {
IStatusBarService statusbar = getStatusBarService();
if (statusbar != null) {
//改變SystemUI的地方
statusbar.setSystemUiVisibility(visibility, 0xffffffff);
statusbar.topAppWindowChanged(needsMenu);
}
} catch (RemoteException e) {
// re-acquire status bar service next time it is needed.
mStatusBarService = null;
}
}
});
}
private int updateSystemBarsLw(WindowState win, int oldVis, int vis) {
// apply translucent bar vis flags
WindowState transWin = mKeyguard != null && mKeyguard.isVisibleLw() && !mHideLockScreen ? mKeyguard : mTopFullscreenOpaqueWindowState;
vis = mStatusBarController.applyTranslucentFlagLw(transWin, vis, oldVis);
...
vis = mStatusBarController.updateVisibilityLw(transientStatusBarAllowed, oldVis, vis);
...
return vis;
}
上面的程式碼主要是通過mStatusBarController來處理狀態列的顯示狀態。現在我們來看看它對應的實現方法。在applyTranslucentFlagLw方法中，就真正的聯絡上了，我們之前設定的windowTranslucentStatus屬性。為什麼這麼說？因為applyTranslucentFlagLw方法體有一個if ((win.getAttrs().flags & mTranslucentWmFlag) != 0)判斷。這個判斷其實就是判斷我們有沒有把windowTranslucentStatus屬性設定為true。win.getAttrs().flags對應的我們設定的WindowManager.LayoutParams的flags，而mTranslucentWmFlag就等於WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS。所以，這裡就和第一步聯絡起來了。如果我們設定了windowTranslucentStatus為true。這個if判斷就為true,vis就增加一個mTranslucentFlag標誌，其值為View.STATUS_BAR_TRANSLUCENT。這個標誌很重要，我們現在先放到這，後面會用這個標誌。這個新vis就會返回回去。updateVisibilityLw方法沒有做什麼很重要的事情就忽略不分析了。
frameworks/base/policy/src/com/android/internal/policy/impl/BarController.java
public BarController(String tag, int transientFlag, int unhideFlag, int translucentFlag, int statusBarManagerId, int translucentWmFlag) {
mTag = "BarController." + tag; //tag="StatusBar"
mTransientFlag = transientFlag; //transientFlag=View.STATUS_BAR_TRANSIENT
mUnhideFlag = unhideFlag; //unhideFlag=View.STATUS_BAR_UNHIDE
mTranslucentFlag = translucentFlag;//translucentFlag=View.STATUS_BAR_TRANSLUCENT,
mStatusBarManagerId = statusBarManagerId; //statusBarManagerId=StatusBarManager.WINDOW_STATUS_BAR
mTranslucentWmFlag = translucentWmFlag; //translucentWmFlag=WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS
mHandler = new Handler();
}
public int applyTranslucentFlagLw(WindowState win, int vis, int oldVis) {
if (mWin != null) {
if (win != null && (win.getAttrs().privateFlags
& WindowManager.LayoutParams.PRIVATE_FLAG_INHERIT_TRANSLUCENT_DECOR) == 0) {
//mTranslucentWmFlag=WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS
//如果我們設定了FLAG_TRANSLUCENT_STATUS屬性，vis就會新增一個mTranslucentFlag標記，即View.STATUS_BAR_TRANSLUCENT
if ((win.getAttrs().flags & mTranslucentWmFlag) != 0) {
vis |= mTranslucentFlag;
} else {
vis &= ~mTranslucentFlag;
}
} else {
vis = (vis & ~mTranslucentFlag) | (oldVis & mTranslucentFlag);
}
}
return vis;
}
public int updateVisibilityLw(boolean transientAllowed, int oldVis, int vis) {
if (mWin == null) return vis;
if (isTransientShowing() || isTransientShowRequested()) { // transient bar requested
if (transientAllowed) {
vis |= mTransientFlag;
if ((oldVis & mTransientFlag) == 0) {
vis |= mUnhideFlag; // tell sysui we're ready to unhide
}
setTransientBarState(TRANSIENT_BAR_SHOWING); // request accepted
} else {
setTransientBarState(TRANSIENT_BAR_NONE); // request denied
}
}
if (mTransientBarState != TRANSIENT_BAR_NONE) {
vis |= mTransientFlag; // ignore clear requests until transition completes
vis &= ~View.SYSTEM_UI_FLAG_LOW_PROFILE; // never show transient bars in low profile
}
if ((vis & mTranslucentFlag) != 0 || (oldVis & mTranslucentFlag) != 0) {
mLastTranslucent = SystemClock.uptimeMillis();
}
return vis;
}第三步，updateSystemBarsLw呼叫結束後，接下來就是呼叫statusbar.setSystemUiVisibility(visibility, 0xffffffff);，這才是真正改變SystemUI狀態的介面。visibility就是updateSystemBarsLw的返回值，其實也就是mStatusBarController.applyTranslucentFlagLw和mStatusBarController.updateVisibilityLw的返回值。而statusbar呼叫的是StatusBarManagerService.java中的setSystemUiVisibility方法，它最終呼叫的是mBar.setSystemUiVisibility(vis, mask)，那這個mBar又是誰傳過來的呢？從程式碼可以看出，這個mBar是通過registerStatusBar註冊而來的。哪誰又呼叫了這個registerStatusBar方法？
frameworks/base/services/java/com/android/server/StatusBarManagerService.java
public void registerStatusBar(IStatusBar bar, StatusBarIconList iconList, List<IBinder> notificationKeys, List<StatusBarNotification> notifications, int switches[], List<IBinder> binders) {
enforceStatusBarService();
Slog.i(TAG, "registerStatusBar bar=" + bar);
mBar = bar;
}
public void setSystemUiVisibility(int vis, int mask) {
// also allows calls from window manager which is in this process.
enforceStatusBarService();
if (SPEW) Slog.d(TAG, "setSystemUiVisibility(0x" + Integer.toHexString(vis) + ")");
synchronized (mLock) {
updateUiVisibilityLocked(vis, mask);
disableLocked(mCurrentUserId, vis & StatusBarManager.DISABLE_MASK, mSysUiVisToken, "WindowManager.LayoutParams");
}
}
private void updateUiVisibilityLocked(final int vis, final int mask) {
if (mSystemUiVisibility != vis) {
mSystemUiVisibility = vis;
mHandler.post(new Runnable() {
public void run() {
if (mBar != null) {
try {
mBar.setSystemUiVisibility(vis, mask);
} catch (RemoteException ex) {
}
}
}
});
}
}第四步，SystemUI閃亮登場，真正實現SystemUI變化的主角。它在BaseStatusBar.java中呼叫了StatusBarManagerService.java的registerStatusBar將CommandQueue註冊到StatusBarManagerService與其產生關聯。所以StatusBarManagerService中setSystemUiVisibility最終呼叫的是CommandQueue.java中方法。而CommandQueue.java和BaseStatusBar.java是通過介面回撥實現對應關係的，PhoneStatusBar.java繼承自BaseStatusBar.java。所以CommandQueue呼叫setSystemUiVisibility方法，最終呼叫的是PhoneStatusBar中的setSystemUiVisibility方法。
frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/BaseStatusBar.java
public void start() {
...
// Connect in to the status bar manager service
StatusBarIconList iconList = new StatusBarIconList();
ArrayList<IBinder> notificationKeys = new ArrayList<IBinder>();
ArrayList<StatusBarNotification> notifications = new ArrayList<StatusBarNotification>();
mCommandQueue = new CommandQueue(this, iconList);
try {
mBarService.registerStatusBar(mCommandQueue, iconList, notificationKeys, notifications, switches, binders);
} catch (RemoteException ex) {
// If the system process isn't there we're doomed anyway.
}
...
}frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/CommandQueue.java
public CommandQueue(Callbacks callbacks, StatusBarIconList list) {
mCallbacks = callbacks;
mList = list;
}
public void setSystemUiVisibility(int vis, int mask) {
synchronized (mList) {
mHandler.removeMessages(MSG_SET_SYSTEMUI_VISIBILITY);
mHandler.obtainMessage(MSG_SET_SYSTEMUI_VISIBILITY, vis, mask, null).sendToTarget();
}
}
private final class H extends Handler {
public void handleMessage(Message msg) {
final int what = msg.what & MSG_MASK;
switch (what) {
case MSG_SET_SYSTEMUI_VISIBILITY:
mCallbacks.setSystemUiVisibility(msg.arg1, msg.arg2);
break;
...
}
}
}第五步，PhoneStatusBar.java中setSystemUiVisibility的實現。這個方法真正關鍵地方是在呼叫barMode這個方法中獲取最新的mode狀態。它會用vis比較各個flag，vis就是我們在PhoneWindowManager.java中傳入的引數。我們知道在第二步後面增加了View.STATUS_BAR_TRANSLUCENT這個標誌，說了很重要。在這裡才真正的體現出來了。barMode方法通過比較得到mode為MODE_TRANSLUCENT。然後，通過checkBarModes應用相應的mode。
frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBar.java
@Override // CommandQueue
public void setSystemUiVisibility(int vis, int mask) {
final int oldVal = mSystemUiVisibility;
final int newVal = (oldVal&~mask) | (vis&mask);
final int diff = newVal ^ oldVal;
...
// update status bar mode
final int sbMode = computeBarMode(oldVal, newVal, mStatusBarView.getBarTransitions(), View.STATUS_BAR_TRANSIENT, View.STATUS_BAR_TRANSLUCENT);
final boolean sbModeChanged = sbMode != -1;
boolean checkBarModes = false;
if (sbModeChanged && sbMode != mStatusBarMode) {
mStatusBarMode = sbMode;
checkBarModes = true;
}
if (checkBarModes) {
checkBarModes();
}
}
private int computeBarMode(int oldVis, int newVis, BarTransitions transitions, int transientFlag, int translucentFlag) {
final int oldMode = barMode(oldVis, transientFlag, translucentFlag);
final int newMode = barMode(newVis, transientFlag, translucentFlag);
if (oldMode == newMode) {
return -1; // no mode change
}
return newMode;
}
private int barMode(int vis, int transientFlag, int translucentFlag) {
return (vis & transientFlag) != 0 ? MODE_SEMI_TRANSPARENT
: (vis & translucentFlag) != 0 ? MODE_TRANSLUCENT
: (vis & View.SYSTEM_UI_FLAG_LOW_PROFILE) != 0 ? MODE_LIGHTS_OUT
: MODE_OPAQUE;
}
private void checkBarModes() {
if (mDemoMode) return;
int sbMode = mStatusBarMode;
if (panelsEnabled() && (mInteractingWindows & StatusBarManager.WINDOW_STATUS_BAR) != 0) {
// if panels are expandable, force the status bar opaque on any interaction
sbMode = MODE_OPAQUE;
}
checkBarMode(sbMode, mStatusBarWindowState, mStatusBarView.getBarTransitions());
if (mNavigationBarView != null) {
checkBarMode(mNavigationBarMode,
mNavigationBarWindowState, mNavigationBarView.getBarTransitions());
}
}
private void checkBarMode(int mode, int windowState, BarTransitions transitions) {
final boolean anim = (mScreenOn == null || mScreenOn) && windowState != WINDOW_STATE_HIDDEN;
transitions.transitionTo(mode, anim);
}在checkBarMode中transitions是從PhoneStatusBarView中建立的PhoneStatusBarTransitions。
frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBarView.java
public PhoneStatusBarView(Context context, AttributeSet attrs) {
super(context, attrs);
mBarTransitions = new PhoneStatusBarTransitions(this);
}
public BarTransitions getBarTransitions() {
return mBarTransitions;
}frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBarTransitions.java
public PhoneStatusBarTransitions(PhoneStatusBarView view) {
super(view, R.drawable.status_background);
mView = view;
}PhoneStatusBarTransitions繼承自BarTransitions。通過PhoneStatusBarTransitions的建構函式，我們看到其呼叫了父類的構造方法super(view, R.drawable.status_background);。在其父類的構造方法中會將R.drawable.status_background這個資源圖片設定到view的背景中去。那R.drawable.status_background是個什麼樣的圖片呢？如下圖：
是不是恍然大悟，原來我們看到的狀態漸變效果就是因為設定這張點9的背景圖片。那問題來，我們的狀態列不應該一直都是這種漸變效果嗎？哈哈，是不是被忽悠了，客官別急，還有最後一步。
frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/BarTransitions.java
public BarTransitions(View view, int gradientResourceId) {
mTag = "BarTransitions." + view.getClass().getSimpleName();
mView = view;
mBarBackground = new BarBackgroundDrawable(mView.getContext(), radientResourceId);
if (HIGH_END) {
mView.setBackground(mBarBackground);
}
}
public void transitionTo(int mode, boolean animate) {
// low-end devices do not support translucent modes, fallback to opaque
if (!HIGH_END && (mode == MODE_SEMI_TRANSPARENT || mode == MODE_TRANSLUCENT)) {
mode = MODE_OPAQUE;
}
if (mMode == mode) return;
int oldMode = mMode;
mMode = mode;
if (DEBUG) Log.d(mTag, String.format("%s -> %s animate=%s",
modeToString(oldMode), modeToString(mode), animate));
onTransition(oldMode, mMode, animate);
}
protected void onTransition(int oldMode, int newMode, boolean animate) {
if (HIGH_END) {
applyModeBackground(oldMode, newMode, animate);
}
}
protected void applyModeBackground(int oldMode, int newMode, boolean animate) {
if (DEBUG) Log.d(mTag, String.format("applyModeBackground oldMode=%s newMode=%s animate=%s",
modeToString(oldMode), modeToString(newMode), animate));
mBarBackground.applyModeBackground(oldMode, newMode, animate);
}
private static class BarBackgroundDrawable extends Drawable {
public BarBackgroundDrawable(Context context, int gradientResourceId) {
final Resources res = context.getResources();
mGradient = res.getDrawable(gradientResourceId);
mInterpolator = new LinearInterpolator();
}
public void applyModeBackground(int oldMode, int newMode, boolean animate) {
if (mMode == newMode) return;
mMode = newMode;
mAnimating = animate;
if (animate) {
long now = SystemClock.elapsedRealtime();
mStartTime = now;
mEndTime = now + BACKGROUND_DURATION;
mGradientAlphaStart = mGradientAlpha;
mColorStart = mColor;
}
invalidateSelf();
}
@Override
public void draw(Canvas canvas) {
int targetGradientAlpha = 0, targetColor = 0;
if (mMode == MODE_TRANSLUCENT) {
targetGradientAlpha = 0xff;
} else if (mMode == MODE_SEMI_TRANSPARENT) {
targetColor = mSemiTransparent;
} else {
targetColor = mOpaque;
}
if (!mAnimating) {
mColor = targetColor;
mGradientAlpha = targetGradientAlpha;
} else {
...
}
if (mGradientAlpha > 0) {
mGradient.setAlpha(mGradientAlpha);
mGradient.draw(canvas);
}
if (Color.alpha(mColor) > 0) {
canvas.drawColor(mColor);
}
if (mAnimating) {
invalidateSelf(); // keep going
}
}
}最後，我們再來看下PhoneStatusBar.java中checkBarMode方法的transitions.transitionTo呼叫。這個transitionTo最終呼叫的是BarTransitions.java中的transitionTo方法，通過上面的原始碼可以知道它其實最後呼叫就是BarBackgroundDrawable中的applyModeBackground方法。會傳入mode，·並呼叫invalidateSelf方法。最終在draw中，根據mode顯示對應的背景效果。這裡因為我們的mode為MODE_TRANSLUCENT，所以，最終會呼叫mGradient.draw(canvas);。而mGradient就是這個R.drawable.status_background圖片的drawable，所以我們在mode為MODE_TRANSLUCENT就會顯示為一個漸變的效果。而在其它mode時候顯示一個rgb顏色背景。
額外補充
有沒有發現我們在設定windowTranslucentStatus和windowTranslucentNavigation為ture後，我們的佈局也會拓展到狀態列和導航欄後面去。原因在這:
frameworks/base/core/java/android/view/ViewRootImpl.java
private int getImpliedSystemUiVisibility(WindowManager.LayoutParams params) {
int vis = 0;
// Translucent decor window flags imply stable system ui visibility.
if ((params.flags & WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS) != 0) {
vis |= View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN;
}
if ((params.flags & WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION) != 0) {
vis |= View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION;
}
return vis;
}系統在我們新增windowTranslucentStatus和windowTranslucentNavigation屬性時候，會自動為我們增加View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION屬性。
那要怎麼解決我們的佈局會被拓展到系統欄後面的效果。在layout.xml增加android:fitsSystemWindows="true"即可。效果如下：
總結
寫這篇文章中途有很多次試圖放棄了，因為要把這些知識用文字表達出來確實很為難自己啊。表達能力本來就不是特別好，再加上用文字的方法更難了。自己雖然已經明白了整個實現流程。但是變向讓自己去把他們寫出來還是難以下筆。最終還是咬咬牙寫下來了，算是對這個知識點的一個總結吧。