自定义控件View之onMeasure调用时机源码分析
终于建了一个自己个人小站：https://huangtianyu.gitee.io，以后优先更新小站博客，欢迎进站，O(∩_∩)O~~ 先上测试代码： MainActivity.java import android.app.Activity; import android.os.Bundle; import android.util.Log; public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Log.e("hty", "before setContextView"); setContentView(R.layout.activity_main); Log.e("hty", "after setContextView"); } @Override protected void onResume() { super.onResume(); Log.e("hty", "onResume"); } @Override protected void onDestroy() { super.onDestroy(); Log.e("hty", "onDestroy"); } }MyView.java import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.util.AttributeSet; import android.util.Log; import android.view.View; public class MyView extends View { Paint paint; public MyView(Context context) { this(context, null); } public MyView(Context context, AttributeSet attrs) { super(context, attrs); Log.e("hty","view constructor"); paint = new Paint(); paint.setColor(Color.RED); paint.setTextSize(20); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); Log.e("hty","view onMeasure"); } @Override protected void onLayout(boolean changed, int left, int top, int right, int bottom) { super.onLayout(changed, left, top, right, bottom); Log.e("hty","view onLayout"); } String str = "这里是测试"; @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); Log.e("hty","view onDraw"); canvas.drawText(str, getWidth()/2-paint.measureText(str)/2,getHeight()/2, paint); } } activity_main.xml <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.zqc.mytest.MainActivity"> <com.zqc.mytest.MyView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Hello World!" /> </RelativeLayout> 正常运行后，查看对应的Log： 从Log输出可以看出在一个View的绘制过程中，onMeasure是被多次调用了的。下面通过源码来一步步分析onMeasure(int widthMeasureSpec, int heightMeasureSpec)函数，尤其是传过来的两个参数到底是从哪里来的。 首先看下MainActivity里面的setContentView，进入该函数后，其对应的代码如下： Activity.java public void setContentView(@LayoutRes int layoutResID) { getWindow().setContentView(layoutResID); initWindowDecorActionBar(); } 即调用了getWindow()的setContentView方法，查看getWindow方法，其返还的是类Window的一个实例mWindow，该类是一个抽象类，其具体实现类是PhoneWindow，即调用的是PhoneWindow的setContentView方法，查看相应的代码如下： PhoneWindow.java @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(); } 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(); } } 该方法首先判断mContentParent是否为空，不为空则调用installDecor()方法来初始化mContentParent，查看具体的代码： PhoneWindow.java private void installDecor() { if (mDecor == null) { mDecor = generateDecor();//这里生成了mDecor,它是所有应用窗口的根View 。 mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS); mDecor.setIsRootNamespace(true); if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) { mDecor.postOnAnimation(mInvalidatePanelMenuRunnable); } } if (mContentParent == null) { mContentParent = generateLayout(mDecor);//这里就生成了mContentParent，这个generateLayout会根据设定的style来布局显示的界面 // Set up decor part of UI to ignore fitsSystemWindows if appropriate. mDecor.makeOptionalFitsSystemWindows(); .... } } 其中generateDecor方法就直接返回一个DecorView，代码如下： PhoneWindow.java protected DecorView generateDecor() { return new DecorView(getContext(), -1); } 而generateLayout(mDecor)方法会根据程序Activity设定的style来布局显示的界面，其代码如下： PhoneWindow.java protected ViewGroup generateLayout(DecorView decor) { // Apply data from current theme. TypedArray a = getWindowStyle();//获取窗口的style 。。。。 if (a.getBoolean(R.styleable.Window_windowNoTitle, false)) { requestFeature(FEATURE_NO_TITLE);//看到没，你在xml里面设置的FEATURE_NO_TITLE，在这里生效了 } else if (a.getBoolean(R.styleable.Window_windowActionBar, false)) { // Don't allow an action bar if there is no title. requestFeature(FEATURE_ACTION_BAR); } 。。。。 final Context context = getContext(); 。。。。 WindowManager.LayoutParams params = getAttributes(); 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); } } 。。。。 int layoutResource; int features = getLocalFeatures(); 。。。。 View in = mLayoutInflater.inflate(layoutResource, null);//这里把给定的布局加载出来，然后加到decor中 decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT)); mContentRoot = (ViewGroup) in; ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);//看到没这个ID_ANDROID_CONTENT，也就是一个窗口的根布局 if (contentParent == null) { throw new RuntimeException("Window couldn't find content container view"); } 。。。。 mDecor.finishChanging(); return contentParent; } 通过一张图来分析下一个窗口的布局具体是怎样的。 图上标的很详细，在最外层是一个FramLayout，其实也就是DecorView，是所有窗口的根布局，在该根布局下有一个(0)LinearLayout和一个(1)View，这个(1)View就是状态栏，(0)LinearLayout里面有个FrameLayout，在里面的多个View有固定的id，在图中已经标明，所有在一个Activity通过findViewById获取的ID_ANDROID_CONTENT就是(0)FrameLayout->(0)LinearLayout->(0)FrameLayout->(1)FrameLayout对应的View。要知道onMeasure两个参数到底是从哪里来的，还得再找下View是如何绘制的，上一篇文章有分析。View的绘制从ViewRootImpl的performTraversals()函数开始，下面进入该方法中具体分析下。 ViewRootImpl.java private void performTraversals() { // cache mView since it is used so much below... final View host = mView; 。。。。 mIsInTraversal = true; mWillDrawSoon = true; boolean windowSizeMayChange = false; boolean newSurface = false; boolean surfaceChanged = false; WindowManager.LayoutParams lp = mWindowAttributes; int desiredWindowWidth; int desiredWindowHeight; final int viewVisibility = getHostVisibility(); boolean viewVisibilityChanged = mViewVisibility != viewVisibility || mNewSurfaceNeeded; WindowManager.LayoutParams params = null; if (mWindowAttributesChanged) { mWindowAttributesChanged = false; surfaceChanged = true; params = lp; } 。。。。 Rect frame = mWinFrame; if (mFirst) { mFullRedrawNeeded = true; mLayoutRequested = true; if (lp.type == WindowManager.LayoutParams.TYPE_STATUS_BAR_PANEL || lp.type == WindowManager.LayoutParams.TYPE_INPUT_METHOD) { // NOTE -- system code, won't try to do compat mode. Point size = new Point(); mDisplay.getRealSize(size); desiredWindowWidth = size.x; desiredWindowHeight = size.y; } else { DisplayMetrics packageMetrics = mView.getContext().getResources().getDisplayMetrics(); desiredWindowWidth = packageMetrics.widthPixels; desiredWindowHeight = packageMetrics.heightPixels; } 。。。。 } else { desiredWindowWidth = frame.width(); desiredWindowHeight = frame.height(); if (desiredWindowWidth != mWidth || desiredWindowHeight != mHeight) { if (DEBUG_ORIENTATION) Log.v(TAG, "View " + host + " resized to: " + frame); mFullRedrawNeeded = true; mLayoutRequested = true; windowSizeMayChange = true; } } if (viewVisibilityChanged) { mAttachInfo.mWindowVisibility = viewVisibility; host.dispatchWindowVisibilityChanged(viewVisibility); if (viewVisibility != View.VISIBLE || mNewSurfaceNeeded) { destroyHardwareResources(); } if (viewVisibility == View.GONE) { // After making a window gone, we will count it as being // shown for the first time the next time it gets focus. mHasHadWindowFocus = false; } } 。。。。 boolean layoutRequested = mLayoutRequested && (!mStopped || mReportNextDraw); if (layoutRequested) { final Resources res = mView.getContext().getResources(); if (mFirst) { // make sure touch mode code executes by setting cached value // to opposite of the added touch mode. mAttachInfo.mInTouchMode = !mAddedTouchMode; ensureTouchModeLocally(mAddedTouchMode); } else { 。。。。 if (lp.width == ViewGroup.LayoutParams.WRAP_CONTENT || lp.height == ViewGroup.LayoutParams.WRAP_CONTENT) { windowSizeMayChange = true; if (lp.type == WindowManager.LayoutParams.TYPE_STATUS_BAR_PANEL || lp.type == WindowManager.LayoutParams.TYPE_INPUT_METHOD) { // NOTE -- system code, won't try to do compat mode. Point size = new Point(); mDisplay.getRealSize(size); desiredWindowWidth = size.x; desiredWindowHeight = size.y; } else { DisplayMetrics packageMetrics = res.getDisplayMetrics(); desiredWindowWidth = packageMetrics.widthPixels; desiredWindowHeight = packageMetrics.heightPixels; } } } // Ask host how big it wants to be windowSizeMayChange |= measureHierarchy(host, lp, res, desiredWindowWidth, desiredWindowHeight); } 。。。。 if (!mStopped || mReportNextDraw) { boolean focusChangedDueToTouchMode = ensureTouchModeLocally( (relayoutResult&WindowManagerGlobal.RELAYOUT_RES_IN_TOUCH_MODE) != 0); if (focusChangedDueToTouchMode || mWidth != host.getMeasuredWidth() || mHeight != host.getMeasuredHeight() || contentInsetsChanged) { int childWidthMeasureSpec = getRootMeasureSpec(mWidth, lp.width);//获取 int childHeightMeasureSpec = getRootMeasureSpec(mHeight, lp.height); if (DEBUG_LAYOUT) Log.v(TAG, "Ooops, something changed! mWidth=" + mWidth + " measuredWidth=" + host.getMeasuredWidth() + " mHeight=" + mHeight + " measuredHeight=" + host.getMeasuredHeight() + " coveredInsetsChanged=" + contentInsetsChanged); // Ask host how big it wants to be performMeasure(childWidthMeasureSpec, childHeightMeasureSpec);//看这里，看这里 // Implementation of weights from WindowManager.LayoutParams // We just grow the dimensions as needed and re-measure if // needs be int width = host.getMeasuredWidth(); int height = host.getMeasuredHeight(); boolean measureAgain = false; if (lp.horizontalWeight > 0.0f) { width += (int) ((mWidth - width) * lp.horizontalWeight); childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); measureAgain = true; } if (lp.verticalWeight > 0.0f) { height += (int) ((mHeight - height) * lp.verticalWeight); childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); measureAgain = true; } if (measureAgain) { if (DEBUG_LAYOUT) Log.v(TAG, "And hey let's measure once more: width=" + width + " height=" + height); performMeasure(childWidthMeasureSpec, childHeightMeasureSpec);//看这里，看这里 } layoutRequested = true; } } } 。。。。 mIsInTraversal = false; } private void performMeasure(int childWidthMeasureSpec, int childHeightMeasureSpec) { Trace.traceBegin(Trace.TRACE_TAG_VIEW, "measure"); try { mView.measure(childWidthMeasureSpec, childHeightMeasureSpec); } finally { Trace.traceEnd(Trace.TRACE_TAG_VIEW); } } 看performTraversals方法中调用的performMeasure的地方，performMeasure即调用了View的measure方法，而measure方法会去调用onMeasure方法。 看下如下两行代码 int childWidthMeasureSpec = getRootMeasureSpec(mWidth, lp.width);//获取 int childHeightMeasureSpec = getRootMeasureSpec(mHeight, lp.height); 在这两行代码中获取了child的宽高，使用的方法是getRootMeasureSpec，其中参数lp.width是传入的MATCH_PARENT或者WRAP_CONTENT，mWidth是窗口期望的大小，getRootMeasureSpec代码如下： ViewRootImpl.java private static int getRootMeasureSpec(int windowSize, int rootDimension) { int measureSpec; switch (rootDimension) { case ViewGroup.LayoutParams.MATCH_PARENT: // Window can't resize. Force root view to be windowSize. measureSpec = MeasureSpec.makeMeasureSpec(windowSize, MeasureSpec.EXACTLY); break; case ViewGroup.LayoutParams.WRAP_CONTENT: // Window can resize. Set max size for root view. measureSpec = MeasureSpec.makeMeasureSpec(windowSize, MeasureSpec.AT_MOST); break; default: // Window wants to be an exact size. Force root view to be that size. measureSpec = MeasureSpec.makeMeasureSpec(rootDimension, MeasureSpec.EXACTLY); break; } return measureSpec; } 这里应该很好理解了，其中调用了MeasureSpec类中的方法，关于MeasureSpec类网上资料很多，该类中用一个int值的两部分分别表示Mode和具体的尺寸。其中最高两位表示 Mode，而最低的30位表示具体的尺寸值，这里计算完之后就进入了View的measure函数中，代码如下： View.java public final void measure(int widthMeasureSpec, int heightMeasureSpec) { boolean optical = isLayoutModeOptical(this); if (optical != isLayoutModeOptical(mParent)) { Insets insets = getOpticalInsets(); int oWidth = insets.left + insets.right; int oHeight = insets.top + insets.bottom; widthMeasureSpec = MeasureSpec.adjust(widthMeasureSpec, optical ? -oWidth : oWidth); heightMeasureSpec = MeasureSpec.adjust(heightMeasureSpec, optical ? -oHeight : oHeight); } // Suppress sign extension for the low bytes long key = (long) widthMeasureSpec << 32 | (long) heightMeasureSpec & 0xffffffffL; if (mMeasureCache == null) mMeasureCache = new LongSparseLongArray(2); if ((mPrivateFlags & PFLAG_FORCE_LAYOUT) == PFLAG_FORCE_LAYOUT || widthMeasureSpec != mOldWidthMeasureSpec || heightMeasureSpec != mOldHeightMeasureSpec) { // 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; } // flag not set, setMeasuredDimension() was not invoked, we raise // an exception to warn the developer if ((mPrivateFlags & PFLAG_MEASURED_DIMENSION_SET) != PFLAG_MEASURED_DIMENSION_SET) { throw new IllegalStateException("View with id " + getId() + ": " + getClass().getName() + "#onMeasure() did not set the" + " measured dimension by calling" + " setMeasuredDimension()"); } mPrivateFlags |= PFLAG_LAYOUT_REQUIRED; } mOldWidthMeasureSpec = widthMeasureSpec; mOldHeightMeasureSpec = heightMeasureSpec; mMeasureCache.put(key, ((long) mMeasuredWidth) << 32 | (long) mMeasuredHeight & 0xffffffffL); // suppress sign extension } 该方法是final的，因而不能被继承，但是里面提供了onMeasure回调，这样子类就可以直接继承onMeasure函数来实现相应的操作。这个View类型的，但是还有一种是ViewGroup类型，也就是容器类型的控件，在具体容器类型的控件里面可以通过重写onMeasure来实现，比如FrameLayout中的onMeasure函数如下： FrameLayout.java protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { int count = getChildCount(); final boolean measureMatchParentChildren = MeasureSpec.getMode(widthMeasureSpec) != MeasureSpec.EXACTLY || MeasureSpec.getMode(heightMeasureSpec) != MeasureSpec.EXACTLY; mMatchParentChildren.clear(); int maxHeight = 0; int maxWidth = 0; int childState = 0; for (int i = 0; i < count; i++) { final View child = getChildAt(i); if (mMeasureAllChildren || child.getVisibility() != GONE) { measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, 0); final LayoutParams lp = (LayoutParams) child.getLayoutParams(); maxWidth = Math.max(maxWidth, child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin); maxHeight = Math.max(maxHeight, child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin); childState = combineMeasuredStates(childState, child.getMeasuredState()); if (measureMatchParentChildren) { if (lp.width == LayoutParams.MATCH_PARENT || lp.height == LayoutParams.MATCH_PARENT) { mMatchParentChildren.add(child); } } } } // Account for padding too maxWidth += getPaddingLeftWithForeground() + getPaddingRightWithForeground(); maxHeight += getPaddingTopWithForeground() + getPaddingBottomWithForeground(); // Check against our minimum height and width maxHeight = Math.max(maxHeight, getSuggestedMinimumHeight()); maxWidth = Math.max(maxWidth, getSuggestedMinimumWidth()); // Check against our foreground's minimum height and width final Drawable drawable = getForeground(); if (drawable != null) { maxHeight = Math.max(maxHeight, drawable.getMinimumHeight()); maxWidth = Math.max(maxWidth, drawable.getMinimumWidth()); } setMeasuredDimension(resolveSizeAndState(maxWidth, widthMeasureSpec, childState), resolveSizeAndState(maxHeight, heightMeasureSpec, childState << MEASURED_HEIGHT_STATE_SHIFT)); count = mMatchParentChildren.size(); if (count > 1) { for (int i = 0; i < count; i++) { final View child = mMatchParentChildren.get(i); final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); final int childWidthMeasureSpec; if (lp.width == LayoutParams.MATCH_PARENT) { final int width = Math.max(0, getMeasuredWidth() - getPaddingLeftWithForeground() - getPaddingRightWithForeground() - lp.leftMargin - lp.rightMargin); childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( width, MeasureSpec.EXACTLY); } else { childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, getPaddingLeftWithForeground() + getPaddingRightWithForeground() + lp.leftMargin + lp.rightMargin, lp.width); } final int childHeightMeasureSpec; if (lp.height == LayoutParams.MATCH_PARENT) { final int height = Math.max(0, getMeasuredHeight() - getPaddingTopWithForeground() - getPaddingBottomWithForeground() - lp.topMargin - lp.bottomMargin); childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( height, MeasureSpec.EXACTLY); } else { childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec, getPaddingTopWithForeground() + getPaddingBottomWithForeground() + lp.topMargin + lp.bottomMargin, lp.height); } child.measure(childWidthMeasureSpec, childHeightMeasureSpec); } } }大概也就是回调本容器里面的子View的measure函数实现尺寸计算。这里通过方法ViewGroup类中的getChildMeasureSpec()来获取子类期望自己获取的宽高大小。其代码是 ViewGroup.java public static int getChildMeasureSpec(int spec, int padding, int childDimension) { int specMode = MeasureSpec.getMode(spec); int specSize = MeasureSpec.getSize(spec); int size = Math.max(0, specSize - padding); int resultSize = 0; int resultMode = 0; switch (specMode) { // Parent has imposed an exact size on us case MeasureSpec.EXACTLY: if (childDimension >= 0) { resultSize = childDimension; resultMode = MeasureSpec.EXACTLY; } else if (childDimension == LayoutParams.MATCH_PARENT) { // Child wants to be our size. So be it. resultSize = size; resultMode = MeasureSpec.EXACTLY; } else if (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; // Parent has imposed a maximum size on us case MeasureSpec.AT_MOST: if (childDimension >= 0) { // Child wants a specific size... so be it resultSize = childDimension; resultMode = MeasureSpec.EXACTLY; } else if (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; } else if (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; // Parent asked to see how big we want to be case MeasureSpec.UNSPECIFIED: if (childDimension >= 0) { // Child wants a specific size... let him have it resultSize = childDimension; resultMode = MeasureSpec.EXACTLY; } else if (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; } else if (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; } return MeasureSpec.makeMeasureSpec(resultSize, resultMode); } 在重写onMeasure方法时一定要调用setMeasuredDimension，该方法会将mPrivateFlags经过或使得View知道已经经过了measure这个步骤了。代码如下： View.java protected final void setMeasuredDimension(int measuredWidth, int measuredHeight) { boolean optical = isLayoutModeOptical(this); if (optical != isLayoutModeOptical(mParent)) { Insets insets = getOpticalInsets(); int opticalWidth = insets.left + insets.right; int opticalHeight = insets.top + insets.bottom; measuredWidth += optical ? opticalWidth : -opticalWidth; measuredHeight += optical ? opticalHeight : -opticalHeight; } setMeasuredDimensionRaw(measuredWidth, measuredHeight); } private void setMeasuredDimensionRaw(int measuredWidth, int measuredHeight) { mMeasuredWidth = measuredWidth; mMeasuredHeight = measuredHeight; mPrivateFlags |= PFLAG_MEASURED_DIMENSION_SET; } 至此分析结束，所以说一个View的大小是由自己和父类两者共同决定的。
