2020-09-22

Activity KEEP_SCREEN_ON原理

我们都支持如果要保持activity界面常亮，在activity的onCreate中加入如下代码即可：

getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

底层的最终实现是WMS中的WakeLock实现的，变量WindowManagerService中的mHoldingScreenWakeLock。

WMS的源码路径是：

/frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java

那从addflag到mHoldingScreenWakeLock底做经历了什么，流程又是怎么样的呢？
先上图：
!

某某activity

getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

PhoneWindow

    public void addFlags(int flags) {
        setFlags(flags, flags);
    }
    public void setFlags(int flags, int mask) {
		...
        dispatchWindowAttributesChanged(attrs);
    }

    protected void dispatchWindowAttributesChanged(WindowManager.LayoutParams attrs) {
        if (mCallback != null) {
            mCallback.onWindowAttributesChanged(attrs);
        }
    }

Activity

    public void onWindowAttributesChanged(WindowManager.LayoutParams params) {
			...
               getWindowManager().updateViewLayout(decor, params);
           	...
        }
    }

WindowManagerImpl

    @Override
    public void updateViewLayout(@NonNull View view, @NonNull ViewGroup.LayoutParams params) {
		...
        mGlobal.updateViewLayout(view, params);
    }

WindowManagerGlobal

    public void updateViewLayout(View view, ViewGroup.LayoutParams params) {
			...
            root.setLayoutParams(wparams, false);
			...
    }

ViewRootImpl

	    void setLayoutParams(WindowManager.LayoutParams attrs, boolean newView) {
	        synchronized (this) {
	        	...
	
	            if (newView) {
	                mSoftInputMode = attrs.softInputMode;
	                requestLayout();
	            }
	            ...
	            scheduleTraversals();
	        }
	    }
	    @Override
	    public void requestLayout() {
	        if (!mHandlingLayoutInLayoutRequest) {
	            checkThread();
	            mLayoutRequested = true;
	            scheduleTraversals();
	        }
	    }
        void scheduleTraversals() {
			...
            mChoreographer.postCallback(
                    Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
			...
    	}
	    final class TraversalRunnable implements Runnable {
	        @Override
	        public void run() {
	            doTraversal();
	        }
	    }
	    final TraversalRunnable mTraversalRunnable = new TraversalRunnable();
	    void doTraversal() {
	           ....
	            performTraversals();
				....
	    }
	    private void performTraversals() {
			...
	
			performDraw();
	        ...
	     }
    private void performDraw() {
			...
            try {
                mWindowSession.finishDrawing(mWindow);
            } catch (RemoteException e) {
            }
        }
    }
   

Session

    @Override
    public void finishDrawing(IWindow window) {
        mService.finishDrawingWindow(this, window);
    }

WindowManagerService

    public void finishDrawingWindow(Session session, IWindow client) {
		...
        mWindowPlacerLocked.requestTraversal();
        ...
    }

WindowSurfacePlacer

    void requestTraversal() {
        if (!mTraversalScheduled) {
            mTraversalScheduled = true;
            mService.mH.sendEmptyMessage(DO_TRAVERSAL);
        }
    }

WindowManagerService

                case DO_TRAVERSAL: {
                    synchronized(mWindowMap) {
                        mWindowPlacerLocked.performSurfacePlacement();
                    }
                } break;

WindowSurfacePlacer

    final void performSurfacePlacement() {
			...
            performSurfacePlacementLoop();
			...
    }
   	private void performSurfacePlacementLoop() {
        	....
            performSurfacePlacementInner(recoveringMemory);
            ...
    }
   private void performSurfacePlacementInner(boolean recoveringMemory) {
        ...
        mService.setHoldScreenLocked(mHoldScreen);
		...
    }    

WindowManagerService

    void setHoldScreenLocked(final Session newHoldScreen) {
		...
                mHoldingScreenWakeLock.acquire();
		...
    }

至此，整个KEEP_SCREEN_ON的代码执行流程完毕。
如有问题，请联系博主～欢迎指正

本文地址：https://blog.csdn.net/dadan_jiku/article/details/108734472