SurfaceView가 다른 View 클래스와의 차이(updateWindow() method in SurfaceView class)

 안드로이드 UI를 설계할 때 주로 사용되는 View의 경우 화면에 한 번 표출되면 특별한 이펙트를 적용하지 않는 한 Activity에서 생성된 모습 그대로의 모습을 유지하는 경우가 대부분입니다.

 반면 SurfaceView의 경우 화면의 변화가 다른 View들에 비해 거의 실시간으로 화면에 변화를 주어야 하는 특성을 가지고 있기 때문에 이를 실시간으로 적용시킬 수 있는 기능이 필요로 하는데 그 중 하나가 updateWindow() 함수입니다.

 아래 간단한 예제를 통해 알아보도록 하겠습니다.

surfaceView.setVisibility(View.VISIBLE);

 Application 단계에서 SurfaceView를 화면상에서 보이도록 설정하게 되는 순간 SurfaceView는 화면에 비추어지기 시작합니다.

/frameworks/base/core/java/android/view/SurfaceView.java

    @Override
    public void setVisibility(int visibility) {
        super.setVisibility(visibility);
        mViewVisibility = visibility == VISIBLE;
        boolean newRequestedVisible = mWindowVisibility && mViewVisibility;
        if (newRequestedVisible != mRequestedVisible) {
            // our base class (View) invalidates the layout only when
            // we go from/to the GONE state. However, SurfaceView needs
            // to request a re-layout when the visibility changes at all.
            // This is needed because the transparent region is computed
            // as part of the layout phase, and it changes (obviously) when
            // the visibility changes.
            requestLayout();
        }
        mRequestedVisible = newRequestedVisible;
        updateWindow(false, false);
    }

 보시는 바와 같이 SurfaceView를 화면에 비추도록 설정하였을 때 함수 내에 updateWindow() 함수가 호출되고 있는 것을 보실 수 있습니다. 해당 함수는 SurfaceHolder에서 설정한 기능들을 수행하는 데에 사용되며 SurfaceHolder에 대한 자세한 사항은 아래 포스팅을 참조해 주시길 바랍니다.

http://elecs.tistory.com/78

    private void updateWindow(boolean force, boolean redrawNeeded) {
 
        if (!mHaveFrame) {
            return;
        }
        ViewRootImpl viewRoot = getViewRootImpl();
        if (viewRoot != null) {
            mTranslator = viewRoot.mTranslator;
        }
 
        if (mTranslator != null) {
            mSurface.setCompatibilityTranslator(mTranslator);
        }
 
        int myWidth = mRequestedWidth;
        if (myWidth <= 0) myWidth = getWidth();
        int myHeight = mRequestedHeight;
        if (myHeight <= 0) myHeight = getHeight();
 
        getLocationInWindow(mLocation);
        final boolean creating = mWindow == null;
        final boolean formatChanged = mFormat != mRequestedFormat;
        final boolean sizeChanged = mWidth != myWidth || mHeight != myHeight;
        final boolean visibleChanged = mVisible != mRequestedVisible;
 
        if (force || creating || formatChanged || sizeChanged || visibleChanged
            || mLeft != mLocation[0] || mTop != mLocation[1]
            || mUpdateWindowNeeded || mReportDrawNeeded || redrawNeeded) {
 
            if (DEBUG) Log.i(TAG, "Changes: creating=" + creating
                    + " format=" + formatChanged + " size=" + sizeChanged
                    + " visible=" + visibleChanged
                    + " left=" + (mLeft != mLocation[0])
                    + " top=" + (mTop != mLocation[1]));
 
            try {
                final boolean visible = mVisible = mRequestedVisible;
                mLeft = mLocation[0];
                mTop = mLocation[1];
                mWidth = myWidth;
                mHeight = myHeight;
                mFormat = mRequestedFormat;
 
                // Scaling/Translate window's layout here because mLayout is not used elsewhere.
 
                // Places the window relative
                mLayout.x = mLeft;
                mLayout.y = mTop;
                mLayout.width = getWidth();
                mLayout.height = getHeight();
                if (mTranslator != null) {
                    mTranslator.translateLayoutParamsInAppWindowToScreen(mLayout);
                }
 
                mLayout.format = mRequestedFormat;
                mLayout.flags |=WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
                              | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                              | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS
                              | WindowManager.LayoutParams.FLAG_SCALED
                              | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                              | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE
                              ;
                if (!getContext().getResources().getCompatibilityInfo().supportsScreen()) {
                    mLayout.privateFlags |=
                            WindowManager.LayoutParams.PRIVATE_FLAG_COMPATIBLE_WINDOW;
                }
                mLayout.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_NO_MOVE_ANIMATION;
 
                if (mWindow == null) {
                    Display display = getDisplay();
                    mWindow = new MyWindow(this);
                    mLayout.type = mWindowType;
                    mLayout.gravity = Gravity.START|Gravity.TOP;
                    mSession.addToDisplayWithoutInputChannel(mWindow, mWindow.mSeq, mLayout,
                            mVisible ? VISIBLE : GONE, display.getDisplayId(), mContentInsets);
                }
 
                boolean realSizeChanged;
                boolean reportDrawNeeded;
 
                int relayoutResult;
 
                mSurfaceLock.lock();
                try {
                    mUpdateWindowNeeded = false;
                    reportDrawNeeded = mReportDrawNeeded;
                    mReportDrawNeeded = false;
                    mDrawingStopped = !visible;
 
                    if (DEBUG) Log.i(TAG, "Cur surface: " + mSurface);
 
                    relayoutResult = mSession.relayout(
                        mWindow, mWindow.mSeq, mLayout, mWidth, mHeight,
                            visible ? VISIBLE : GONE,
                            WindowManagerGlobal.RELAYOUT_DEFER_SURFACE_DESTROY,
                            mWinFrame, mOverscanInsets, mContentInsets,
                            mVisibleInsets, mConfiguration, mNewSurface);
                    if ((relayoutResult & WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) {
                        mReportDrawNeeded = true;
                    }
 
                    if (DEBUG) Log.i(TAG, "New surface: " + mNewSurface
                            + ", vis=" + visible + ", frame=" + mWinFrame);
 
                    mSurfaceFrame.left = 0;
                    mSurfaceFrame.top = 0;
                    if (mTranslator == null) {
                        mSurfaceFrame.right = mWinFrame.width();
                        mSurfaceFrame.bottom = mWinFrame.height();
                    } else {
                        float appInvertedScale = mTranslator.applicationInvertedScale;
                        mSurfaceFrame.right = (int) (mWinFrame.width() * appInvertedScale + 0.5f);
                        mSurfaceFrame.bottom = (int) (mWinFrame.height() * appInvertedScale + 0.5f);
                    }
 
                    final int surfaceWidth = mSurfaceFrame.right;
                    final int surfaceHeight = mSurfaceFrame.bottom;
                    realSizeChanged = mLastSurfaceWidth != surfaceWidth
                            || mLastSurfaceHeight != surfaceHeight;
                    mLastSurfaceWidth = surfaceWidth;
                    mLastSurfaceHeight = surfaceHeight;
                } finally {
                    mSurfaceLock.unlock();
                }
 
                try {
                    redrawNeeded |= creating | reportDrawNeeded;
 
                    SurfaceHolder.Callback callbacks[] = null;
 
                    final boolean surfaceChanged = (relayoutResult
                            & WindowManagerGlobal.RELAYOUT_RES_SURFACE_CHANGED) != 0;
                    if (mSurfaceCreated && (surfaceChanged || (!visible && visibleChanged))) {
                        mSurfaceCreated = false;
                        if (mSurface.isValid()) {
                            if (DEBUG) Log.i(TAG, "visibleChanged -- surfaceDestroyed");
                            callbacks = getSurfaceCallbacks();
                            for (SurfaceHolder.Callback c : callbacks) {
                                c.surfaceDestroyed(mSurfaceHolder);
                            }
                        }
                    }
 
                    mSurface.transferFrom(mNewSurface);
 
                    if (visible && mSurface.isValid()) {
                        if (!mSurfaceCreated && (surfaceChanged || visibleChanged)) {
                            mSurfaceCreated = true;
                            mIsCreating = true;
                            if (DEBUG) Log.i(TAG, "visibleChanged -- surfaceCreated");
                            if (callbacks == null) {
                                callbacks = getSurfaceCallbacks();
                            }
                            for (SurfaceHolder.Callback c : callbacks) {
                                c.surfaceCreated(mSurfaceHolder);
                            }
                        }
                        if (creating || formatChanged || sizeChanged
                                || visibleChanged || realSizeChanged) {
                            if (DEBUG) Log.i(TAG, "surfaceChanged -- format=" + mFormat
                                    + " w=" + myWidth + " h=" + myHeight);
                            if (callbacks == null) {
                                callbacks = getSurfaceCallbacks();
                            }
                            for (SurfaceHolder.Callback c : callbacks) {
                                c.surfaceChanged(mSurfaceHolder, mFormat, myWidth, myHeight);
                            }
                        }
                        if (redrawNeeded) {
                            if (DEBUG) Log.i(TAG, "surfaceRedrawNeeded");
                            if (callbacks == null) {
                                callbacks = getSurfaceCallbacks();
                            }
                            for (SurfaceHolder.Callback c : callbacks) {
                                if (c instanceof SurfaceHolder.Callback2) {
                                    ((SurfaceHolder.Callback2)c).surfaceRedrawNeeded(
                                            mSurfaceHolder);
                                }
                            }
                        }
                    }
                } finally {
                    mIsCreating = false;
                    if (redrawNeeded) {
                        if (DEBUG) Log.i(TAG, "finishedDrawing");
                        mSession.finishDrawing(mWindow);
                    }
                    mSession.performDeferredDestroy(mWindow);
                }
            } catch (RemoteException ex) {
            }
            if (DEBUG) Log.v(
                TAG, "Layout: x=" + mLayout.x + " y=" + mLayout.y +
                " w=" + mLayout.width + " h=" + mLayout.height +
                ", frame=" + mSurfaceFrame);
        }
    }