// first clears the measured dimension flag mPrivateFlags &= ~PFLAG_MEASURED_DIMENSION_SET;
resolveRtlPropertiesIfNeeded();
int cacheIndex = (mPrivateFlags & PFLAG_FORCE_LAYOUT) == PFLAG_FORCE_LAYOUT ? -1 : mMeasureCache.indexOfKey(key); if (cacheIndex < 0 || sIgnoreMeasureCache) { // measure ourselves, this should set the measured dimension flag back onMeasure(widthMeasureSpec, heightMeasureSpec); mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT; } else { long value = mMeasureCache.valueAt(cacheIndex); // Casting a long to int drops the high 32 bits, no mask needed setMeasuredDimensionRaw((int) (value >> 32), (int) value); mPrivateFlags3 |= PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT; } ...... }
/** * <p> * Measure the view and its content to determine the measured width and the * measured height. This method is invoked by {@link #measure(int, int)} and * should be overridden by subclasses to provide accurate and efficient * measurement of their contents. * </p> * * <p> * <strong>CONTRACT:</strong> When overriding this method, you * <em>must</em> call {@link #setMeasuredDimension(int, int)} to store the * measured width and height of this view. Failure to do so will trigger an * <code>IllegalStateException</code>, thrown by * {@link #measure(int, int)}. Calling the superclass' * {@link #onMeasure(int, int)} is a valid use. * </p> * * <p> * The base class implementation of measure defaults to the background size, * unless a larger size is allowed by the MeasureSpec. Subclasses should * override {@link #onMeasure(int, int)} to provide better measurements of * their content. * </p> * * <p> * If this method is overridden, it is the subclass's responsibility to make * sure the measured height and width are at least the view's minimum height * and width ({@link #getSuggestedMinimumHeight()} and * {@link #getSuggestedMinimumWidth()}). * </p> * * @param widthMeasureSpec horizontal space requirements as imposed by the parent. * The requirements are encoded with * {@link android.view.View.MeasureSpec}. * @param heightMeasureSpec vertical space requirements as imposed by the parent. * The requirements are encoded with * {@link android.view.View.MeasureSpec}. * * @see #getMeasuredWidth() * @see #getMeasuredHeight() * @see #setMeasuredDimension(int, int) * @see #getSuggestedMinimumHeight() * @see #getSuggestedMinimumWidth() * @see android.view.View.MeasureSpec#getMode(int) * @see android.view.View.MeasureSpec#getSize(int) */ protectedvoidonMeasure(int widthMeasureSpec, int heightMeasureSpec){ setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec), getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec)); }
publicstaticintgetDefaultSize(int size, int measureSpec){ int result = size; int specMode = MeasureSpec.getMode(measureSpec); int specSize = MeasureSpec.getSize(measureSpec);
switch (specMode) { case MeasureSpec.UNSPECIFIED: result = size; break; case MeasureSpec.AT_MOST: case MeasureSpec.EXACTLY: result = specSize; break; } return result; }
protectedvoidmeasureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed){ final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
publicstaticintgetChildMeasureSpec(int spec, int padding, int childDimension){ //获取父视图传来的mode和size int specMode = MeasureSpec.getMode(spec); int specSize = MeasureSpec.getSize(spec);
//计算size减去padding的大小，如果小于0就返回0 int size = Math.max(0, specSize - padding);
//最后返回的结果值。 int resultSize = 0; int resultMode = 0;
switch (specMode) { // 父视图指定了一个准确的大小 case MeasureSpec.EXACTLY: if (childDimension >= 0) { //说明开发者在xml文件或者java中设置了一个具体的大于等于0的大小值，所以将这个值设为结果，并且mode为EXACTLY. resultSize = childDimension; resultMode = MeasureSpec.EXACTLY; } elseif (childDimension == LayoutParams.MATCH_PARENT) { // 子视图就设为当前值 resultSize = size; resultMode = MeasureSpec.EXACTLY; } elseif (childDimension == LayoutParams.WRAP_CONTENT) { // 子视图自己决定大小，但是最大是当前这个值。所以mode设为AT_MOST， 大小设为size resultSize = size; resultMode = MeasureSpec.AT_MOST; } break; //以下两种case的逻辑思路和上述的默认case差不多，这里就不再赘述了，大家看代码应该很容易理解。 case MeasureSpec.AT_MOST: if (childDimension >= 0) { // Child wants a specific size... so be it resultSize = childDimension; resultMode = MeasureSpec.EXACTLY; } elseif (childDimension == LayoutParams.MATCH_PARENT) { // Child wants to be our size, but our size is not fixed. // Constrain child to not be bigger than us. resultSize = size; resultMode = MeasureSpec.AT_MOST; } elseif (childDimension == LayoutParams.WRAP_CONTENT) { // Child wants to determine its own size. It can't be // bigger than us. resultSize = size; resultMode = MeasureSpec.AT_MOST; } break; case MeasureSpec.UNSPECIFIED: if (childDimension >= 0) { // Child wants a specific size... let him have it resultSize = childDimension; resultMode = MeasureSpec.EXACTLY; } elseif (childDimension == LayoutParams.MATCH_PARENT) { // Child wants to be our size... find out how big it should be resultSize = View.sUseZeroUnspecifiedMeasureSpec ? 0 : size; resultMode = MeasureSpec.UNSPECIFIED; } elseif (childDimension == LayoutParams.WRAP_CONTENT) { // Child wants to determine its own size.... find out how // big it should be resultSize = View.sUseZeroUnspecifiedMeasureSpec ? 0 : size; resultMode = MeasureSpec.UNSPECIFIED; } break;
protectedbooleansetFrame(int left, int top, int right, int bottom){ boolean changed = false; ...... if (mLeft != left || mRight != right || mTop != top || mBottom != bottom) { changed = true;
// 保存drawn位 int drawn = mPrivateFlags & PFLAG_DRAWN;
int oldWidth = mRight - mLeft; int oldHeight = mBottom - mTop; int newWidth = right - left; int newHeight = bottom - top; boolean sizeChanged = (newWidth != oldWidth) || (newHeight != oldHeight);
if (sizeChanged) { sizeChange(newWidth, newHeight, oldWidth, oldHeight); }
if ((mViewFlags & VISIBILITY_MASK) == VISIBLE || mGhostView != null) { // If we are visible, force the DRAWN bit to on so that // this invalidate will go through (at least to our parent). // This is because someone may have invalidated this view // before this call to setFrame came in, thereby clearing // the DRAWN bit. mPrivateFlags |= PFLAG_DRAWN; invalidate(sizeChanged); // 需要显示列表的父view可能因为子view的边界改变而需要重新创建 invalidateParentCaches(); }
@Override publicfinalvoidlayout(int l, int t, int r, int b){ if (!mSuppressLayout && (mTransition == null || !mTransition.isChangingLayout())) { if (mTransition != null) { mTransition.layoutChange(this); } super.layout(l, t, r, b); } else { // record the fact that we noop'd it; request layout when transition finishes mLayoutCalledWhileSuppressed = true; } }
privatevoiddraw(boolean fullRedrawNeeded){ Surface surface = mSurface; ...... final Rect dirty = mDirty; ...... if (!drawSoftware(surface, mAttachInfo, xOffset, yOffset, scalingRequired, dirty)) { return; } ...... }
我们看到，在draw中关键一步是调用了ViewRootImpl的drawSoftware方法。
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privatebooleandrawSoftware(Surface surface, AttachInfo attachInfo, int xoff, int yoff, boolean scalingRequired, Rect dirty){ final Canvas canvas; try { finalint left = dirty.left; finalint top = dirty.top; finalint right = dirty.right; finalint bottom = dirty.bottom;
/** * Draw one child of this View Group. This method is responsible for getting * the canvas in the right state. This includes clipping, translating so * that the child's scrolled origin is at 0, 0, and applying any animation * transformations. * * @param canvas The canvas on which to draw the child * @param child Who to draw * @param drawingTime The time at which draw is occurring * @return True if an invalidate() was issued */ protectedbooleandrawChild(Canvas canvas, View child, long drawingTime){ return child.draw(canvas, this, drawingTime); }
/** * This method is called by ViewGroup.drawChild() to have each child view draw itself. * * This is where the View specializes rendering behavior based on layer type, * and hardware acceleration. */ booleandraw(Canvas canvas, ViewGroup parent, long drawingTime){ finalboolean hardwareAcceleratedCanvas = canvas.isHardwareAccelerated(); ...... if (!drawingWithDrawingCache) { if (drawingWithRenderNode) { mPrivateFlags &= ~PFLAG_DIRTY_MASK; ((DisplayListCanvas) canvas).drawRenderNode(renderNode); } else { // Fast path for layouts with no backgrounds if ((mPrivateFlags & PFLAG_SKIP_DRAW) == PFLAG_SKIP_DRAW) { mPrivateFlags &= ~PFLAG_DIRTY_MASK; dispatchDraw(canvas); } else { draw(canvas); } } } ...... }