Android自定义一个view ViewRootImpl绘制流程示例
作者：keen_zuxwang
这篇文章主要为大家介绍了Android自定义一个view ViewRootImpl绘制流程示例，有需要的朋友可以借鉴参考下，希望能够有所帮助，祝大家多多进步，早日升职加薪
Android如何自定义一个view ViewRootImpl绘制流程
1、自定义属性
在res/values/attrs.xml文件里定义一个declare-styleable name：自定义view的名字
<resources>
<declare-styleable name="CustomView">
<attr name="background" format="color"/> //定义属性：名称 + 格式类型---颜色、尺寸、整形、字符串类型
<attr name="size" format="dimension"/>
<attr name="AttrFirst" format="integer"/>
<attr name="AttrSecond" format="string"/>
</declare-styleable>
</resources>
2、在res/layout/activity_main.xml文件里使用自定义view
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:custom="http://schemas.android.com/apk/res-auto" // 自定义的命名空间
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.example.custom.MainActivity">
<com.example.custom.CustomView
android:id="@+id/custom_view"
android:layout_width="100dp"
android:layout_height="100dp"
custom:background="@color/colorPrimary"
custom:size="20dp"
custom:AttrFirst="1"
custom:AttrSecond="CustomView"/>
</LinearLayout>
3、构造CustomView名称的view，读取自定义属性
//通过AttributeSet直接获取
public CustomView(Context context, AttributeSet attrs) {
super(context, attrs);
int n = attrs.getAttributeCount(); //获得自定义view的属性数量
for (int i =0; i < n; i++) {
Log.d("CustomView", "attrs No " + i + ", name: " + attrs.getAttributeName(i) + ", value: " + attrs.getAttributeValue(i));
}
int custon_background = attrs.getAttributeIntValue("http://schemas.android.com/apk/res-auto", "background", Color.BLUE);
int custom_size = attrs.getAttributeIntValue("http://schemas.android.com/apk/res-auto", "size", 10);
int AttrFirst = attrs.getAttributeIntValue("http://schemas.android.com/apk/res-auto", "AttrFirst", 100));
String AttrSecond = attrs.getAttributeValue("http://schemas.android.com/apk/res-auto", "AttrSecond"));
}
//getAttributeName来获取对应index处的属性名称，以sting返回。
//getAttributeValue来获取相应index处属性的值，以string返回。
//getAttributeIntValue来获取相应attribute属性的值
public String getAttributeValue(String namespace, String attribute);
public int getAttributeIntValue(String namespace, String attribute, int defaultValue);
namespace代表自定义属性的命名空间（与xml中的使用方法相同）
public class CustomView extends View {
private Paint mPaint;
private int mHeight;
private int mWidth;
private int custom_size;
private float scale = 1f;
private final int SIZE = 30;
public CustomView(Context context) {
this(context, null);
}
public CustomView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public CustomView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.CustomView, defStyleAttr, R.style.AppTheme); //通过obtainStyledAttributes()方法获取属性值
int custon_background = a.getColor(R.styleable.CustomView_background, Color.BLUE);
custom_size = a.getDimensionPixelSize(R.styleable.CustomView_size, 10);
int AttrFirst = arr.getInt(R.styleable.CustomView_AttrFirst, 100);
String AttrSecond = arr.getString(R.styleable.CustomView_AttrSecond);
a.recycle();
mPaint = new Paint();
mPaint.setColor(custom_background);
mPaint.setAntiAlias(true);
mPaint.setStyle(Paint.Style.FILL);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { //计算出实际的高(mMeasuredHeight)和宽(mMeasureWidth)传入setMeasuredDimension()方法完成单个View的测量
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int widthSize = MeasureSpec.getSize(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int heightSize = MeasureSpec.getSize(heightMeasureSpec);
int measuredHeight, measuredWidth;
if (widthMode == MeasureSpec.EXACTLY) {
measuredWidth = widthSize;
} else {
measuredWidth = SIZE;
}
if (heightMode == MeasureSpec.EXACTLY) {
measuredHeight = heightSize;
} else {
measuredHeight = SIZE;
}
setMeasuredDimension(measuredWidth, measuredHeight);
}
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) { //onLayout决定具体View的大小和位置, 对当前视图和其所有子View设置它们在父视图中具体位置
super.onLayout(changed, left, top, right, bottom);
mHeight = getHeight(); //getWidth,和getLeft等这些函数都是View相对于其父View的位置。而getMeasuredWidth,getMeasuredHeight是测量后该View的实际值
mWidth = getWidth();
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawCircle(mWidth/2, mHeight/2, custom_size * scale, mPaint);
}
private ValueAnimator mAnimator;
public void startAnimation() {
mAnimator = ValueAnimator.ofFloat(1, 2);
mAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
scale = (float) animation.getAnimatedValue();
postInvalidate();
}
});
mAnimator.setRepeatCount(-1); //重复次数，-1表示无限循环
mAnimator.setRepeatMode(ValueAnimator.REVERSE); //重复模式：RESTART---重新开始，REVERSE---恢复初始状态再开始
mAnimator.start();
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
mAnimator.end(); //关闭动画
}
@Override
protected Parcelable onSaveInstanceState() {
return super.onSaveInstanceState();
}
@Override
protected void onRestoreInstanceState(Parcelable state) {
super.onRestoreInstanceState(state);
}
} 4、自定义view应用属性、刷新显示
Android里，一个view的绘制流程包括： Measure、Layout、Draw 测量——onMeasure()：决定View的大小，确定view及它所有子节点需要的尺寸 布局——onLayout()：决定View在ViewGroup中的位置, 当view需要为它的所有子节点指定大小和布局时，调用此方法 绘制——onDraw()：绘制View。 自定义View中，onLayout配合onMeasure方法一起使用，可以实现自定义View的复杂布局。
自定义view，刷新view的方法： requestLayout()、invalidate()、postInvalidate()， 其实invalidate和postInvalidate这两个方法作用是一样的，唯一不同: invalidate用在主线程 postInvalidate用在异步线程，它最后会通过handler调用invalidate实现
requestLayout和invalidate的内部实现： requestLayout 会调用measure和layout 等一系列操作，然后根据布局是否发生改变，surface是否被销毁，来决定是否调用draw，也就是说requestlayout肯定会调用measure和layout， 但不一定调用draw，读者可以试着改下我上面写的那个小程序，将postInvalidate改成requestlayout，动画效果就消失了，因为布局没有发生改变。 invalidate 只会调用draw，而且肯定会调，即使什么都没有发生改变，它也会重新绘制。 所以如果有布局需要发生改变，需要调用requestlayout方法，如果只是刷新动画，则只需要调用invalidate方法
postInvalidate()方法程序调用流程，从View.java到ViewRootImpl.java，最终由performTraversals()实现 postInvalidate => postInvalidateDelayed => dispatchInvalidateDelayed => invalidate => scheduleTraversals() => doTraversal => performTraversals
requestLayout()方法程序调用流程 requestLayout() => scheduleTraversals() => doTraversal => performTraversals
performTraversals()方法调用：（真正实现view的measure、layout、draw） performMeasure(childWidthMeasureSpec, childHeightMeasureSpec); performMeasure() => measure() => onMeasure() 调用该方法来确定view及它所有子节点需要的尺寸 performLayout(lp, desiredWindowWidth, desiredWindowHeight); performLayout() => layout() => onLayout() 当view需要为它的所有子节点指定大小和布局时，调用此方法 performDraw(); performDraw() => draw() => onDraw() => dispatchDraw() (drawSoftware())
onMeasure(int widthMeasureSpec, int heightMeasureSpec) 功能：通过测量知道一个view要占的大小， 参数：宽高测量规格，int型的值（java中int型由4个字节（32bit）组成），在MeasureSpce中，其前两位表示mode，后30位表示size MeasureSpce的mode有三种：EXACTLY、AT_MOST、UNSPECIFIED
1、当父布局是EXACTLY时， 子控件确定大小或者match_parent，mode都是EXACTLY， 子控件是wrap_content时，mode为AT_MOST；
2、当父布局是AT_MOST时， 子控件确定大小，mode为EXACTLY， 子控件wrap_content或者match_parent时，mode为AT_MOST。 所以在确定控件大小时，需要判断MeasureSpec的mode，不能直接用MeasureSpec的size
View.java:
public class View implements Drawable.Callback, KeyEvent.Callback,
AccessibilityEventSource {
...
public void requestLayout() {
if (mMeasureCache != null) mMeasureCache.clear();
if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == null) {
// Only trigger request-during-layout logic if this is the view requesting it,
// not the views in its parent hierarchy
ViewRootImpl viewRoot = getViewRootImpl();
if (viewRoot != null && viewRoot.isInLayout()) {
if (!viewRoot.requestLayoutDuringLayout(this)) {
return;
}
}
mAttachInfo.mViewRequestingLayout = this;
}
mPrivateFlags |= PFLAG_FORCE_LAYOUT;
mPrivateFlags |= PFLAG_INVALIDATED;
if (mParent != null && !mParent.isLayoutRequested()) {
mParent.requestLayout(); //ViewParent接口的requestLayout()方法
}
if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == this) {
mAttachInfo.mViewRequestingLayout = null;
}
}
public final void measure(int widthMeasureSpec, int heightMeasureSpec) { //为整个View树计算实际的大小, 需要递归的去计算每一个子视图的大小
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);
final boolean forceLayout = (mPrivateFlags & PFLAG_FORCE_LAYOUT) == PFLAG_FORCE_LAYOUT;
final boolean isExactly = MeasureSpec.getMode(widthMeasureSpec) == MeasureSpec.EXACTLY && MeasureSpec.getMode(heightMeasureSpec) == MeasureSpec.EXACTLY;
final boolean matchingSize = isExactly &&
getMeasuredWidth() == MeasureSpec.getSize(widthMeasureSpec) &&
getMeasuredHeight() == MeasureSpec.getSize(heightMeasureSpec);
if (forceLayout || !matchingSize && (widthMeasureSpec != mOldWidthMeasureSpec || heightMeasureSpec != mOldHeightMeasureSpec)) {
// first clears the measured dimension flag
mPrivateFlags &= ~PFLAG_MEASURED_DIMENSION_SET;
resolveRtlPropertiesIfNeeded();
int cacheIndex = forceLayout ? -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("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
}
//对于每个View的实际宽高都是由父视图和本身视图决定的
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { //计算出实际的高(mMeasuredHeight)和宽(mMeasureWidth)传入setMeasuredDimension()方法完成单个View的测量
setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),
getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));
}
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;
}
public void layout(int l, int t, int r, int b) { //为整个View树计算实际的位置, 需要递归的去计算每一个子视图的位置
if ((mPrivateFlags3 & PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT) != 0) {
onMeasure(mOldWidthMeasureSpec, mOldHeightMeasureSpec);
mPrivateFlags3 &= ~PFLAG3_MEASURE_NEEDED_BEFORE_LAYOUT;
}
int oldL = mLeft;
int oldT = mTop;
int oldB = mBottom;
int oldR = mRight;
boolean changed = isLayoutModeOptical(mParent) ? setOpticalFrame(l, t, r, b) : setFrame(l, t, r, b);
if (changed || (mPrivateFlags & PFLAG_LAYOUT_REQUIRED) == PFLAG_LAYOUT_REQUIRED) {
//调用onLayout回调方法，具体实现由重写了onLayout方法的ViewGroup的子类去实现
onLayout(changed, l, t, r, b); //l，t，r，b四个值是子View相对于父View的值
mPrivateFlags &= ~PFLAG_LAYOUT_REQUIRED;
ListenerInfo li = mListenerInfo;
if (li != null && li.mOnLayoutChangeListeners != null) {
ArrayList<OnLayoutChangeListener> listenersCopy =
(ArrayList<OnLayoutChangeListener>)li.mOnLayoutChangeListeners.clone();
int numListeners = listenersCopy.size();
for (int i = 0; i < numListeners; ++i) {
listenersCopy.get(i).onLayoutChange(this, l, t, r, b, oldL, oldT, oldR, oldB);
}
}
}
mPrivateFlags &= ~PFLAG_FORCE_LAYOUT;
mPrivateFlags3 |= PFLAG3_IS_LAID_OUT;
}
//onLayout被定义为抽象方法，继承ViewGroup时必须要重写该方法
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
}
public void draw(Canvas canvas) {
final int privateFlags = mPrivateFlags;
final boolean dirtyOpaque = (privateFlags & PFLAG_DIRTY_MASK) == PFLAG_DIRTY_OPAQUE &&
(mAttachInfo == null || !mAttachInfo.mIgnoreDirtyState);
mPrivateFlags = (privateFlags & ~PFLAG_DIRTY_MASK) | PFLAG_DRAWN;
/*
* Draw traversal performs several drawing steps which must be executed
* in the appropriate order:
*
* 1. Draw the background
* 2. If necessary, save the canvas' layers to prepare for fading
* 3. Draw view's content
* 4. Draw children
* 5. If necessary, draw the fading edges and restore layers
* 6. Draw decorations (scrollbars for instance)
*/
// Step 1, draw the background, if needed
int saveCount;
if (!dirtyOpaque) {
drawBackground(canvas);
}
// skip step 2 & 5 if possible (common case)
final int viewFlags = mViewFlags;
boolean horizontalEdges = (viewFlags & FADING_EDGE_HORIZONTAL) != 0;
boolean verticalEdges = (viewFlags & FADING_EDGE_VERTICAL) != 0;
if (!verticalEdges && !horizontalEdges) {
// Step 3, draw the content
if (!dirtyOpaque) onDraw(canvas);
// Step 4, draw the children
dispatchDraw(canvas);
// Step 6, draw decorations (scrollbars)
onDrawScrollBars(canvas);
if (mOverlay != null && !mOverlay.isEmpty()) {
mOverlay.getOverlayView().dispatchDraw(canvas);
}
// we're done...
return;
}
...
// Step 3, draw the content
if (!dirtyOpaque) onDraw(canvas);
// Step 4, draw the children
dispatchDraw(canvas);
// Step 5, draw the fade effect and restore layers
final Paint p = scrollabilityCache.paint;
final Matrix matrix = scrollabilityCache.matrix;
final Shader fade = scrollabilityCache.shader;
if (drawTop) {
matrix.setScale(1, fadeHeight * topFadeStrength);
matrix.postTranslate(left, top);
fade.setLocalMatrix(matrix);
p.setShader(fade);
canvas.drawRect(left, top, right, top + length, p);
}
if (drawBottom) {
...
}
if (drawLeft) {
...
}
if (drawRight) {
...
}
canvas.restoreToCount(saveCount);
// Step 6, draw decorations (scrollbars)
onDrawScrollBars(canvas);
if (mOverlay != null && !mOverlay.isEmpty()) {
mOverlay.getOverlayView().dispatchDraw(canvas); // 核心
}
}
protected void dispatchDraw(Canvas canvas) {
}
public void postInvalidate() {
postInvalidateDelayed(0);
}
public void postInvalidateDelayed(long delayMilliseconds) {
// We try only with the AttachInfo because there's no point in invalidating
// if we are not attached to our window
final AttachInfo attachInfo = mAttachInfo;
if (attachInfo != null) {
attachInfo.mViewRootImpl.dispatchInvalidateDelayed(this, delayMilliseconds);
}
}
...
}
ViewRootImpl.java
public final class ViewRootImpl implements ViewParent,
View.AttachInfo.Callbacks, HardwareRenderer.HardwareDrawCallbacks {
...
final class ViewRootHandler extends Handler {
...
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_INVALIDATE:
((View) msg.obj).invalidate();
break;
case MSG_INVALIDATE_RECT:
final View.AttachInfo.InvalidateInfo info = (View.AttachInfo.InvalidateInfo) msg.obj;
info.target.invalidate(info.left, info.top, info.right, info.bottom);
info.recycle();
break;
case MSG_PROCESS_INPUT_EVENTS:
mProcessInputEventsScheduled = false;
doProcessInputEvents();
break;
case MSG_DISPATCH_APP_VISIBILITY:
handleAppVisibility(msg.arg1 != 0);
break;
case MSG_DISPATCH_GET_NEW_SURFACE:
handleGetNewSurface();
break;
case MSG_RESIZED: {
// Recycled in the fall through...
SomeArgs args = (SomeArgs) msg.obj;
if (mWinFrame.equals(args.arg1)
&& mPendingOverscanInsets.equals(args.arg5)
&& mPendingContentInsets.equals(args.arg2)
&& mPendingStableInsets.equals(args.arg6)
&& mPendingVisibleInsets.equals(args.arg3)
&& args.arg4 == null) {
break;
}
} // fall through...
case MSG_RESIZED_REPORT:
if (mAdded) {
...
requestLayout();
}
break;
case MSG_WINDOW_MOVED:
if (mAdded) {
...
requestLayout();
}
break;
case MSG_WINDOW_FOCUS_CHANGED: {
if (mAdded) {
boolean hasWindowFocus = msg.arg1 != 0;
mAttachInfo.mHasWindowFocus = hasWindowFocus;
profileRendering(hasWindowFocus);
if (hasWindowFocus) {
boolean inTouchMode = msg.arg2 != 0;
ensureTouchModeLocally(inTouchMode);
if (mAttachInfo.mHardwareRenderer != null && mSurface.isValid()){
mFullRedrawNeeded = true;
try {
final WindowManager.LayoutParams lp = mWindowAttributes;
final Rect surfaceInsets = lp != null ? lp.surfaceInsets : null;
mAttachInfo.mHardwareRenderer.initializeIfNeeded(
mWidth, mHeight, mSurface, surfaceInsets);
} catch (OutOfResourcesException e) {
Log.e(TAG, "OutOfResourcesException locking surface", e);
try {
if (!mWindowSession.outOfMemory(mWindow)) {
Slog.w(TAG, "No processes killed for memory; killing self");
Process.killProcess(Process.myPid());
}
} catch (RemoteException ex) {
}
// Retry in a bit.
sendMessageDelayed(obtainMessage(msg.what, msg.arg1, msg.arg2), 500);
return;
}
}
}
mLastWasImTarget = WindowManager.LayoutParams
.mayUseInputMethod(mWindowAttributes.flags);
InputMethodManager imm = InputMethodManager.peekInstance();
if (mView != null) {
if (hasWindowFocus && imm != null && mLastWasImTarget &&
!isInLocalFocusMode()) {
imm.startGettingWindowFocus(mView);
}
mAttachInfo.mKeyDispatchState.reset();
mView.dispatchWindowFocusChanged(hasWindowFocus);
mAttachInfo.mTreeObserver.dispatchOnWindowFocusChange(hasWindowFocus);
}
// Note: must be done after the focus change callbacks,
// so all of the view state is set up correctly.
if (hasWindowFocus) {
if (imm != null && mLastWasImTarget && !isInLocalFocusMode()) {
imm.onWindowFocus(mView, mView.findFocus(),
mWindowAttributes.softInputMode,
!mHasHadWindowFocus, mWindowAttributes.flags);
}
// Clear the forward bit. We can just do this directly, since
// the window manager doesn't care about it.
mWindowAttributes.softInputMode &=
~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
((WindowManager.LayoutParams)mView.getLayoutParams())
.softInputMode &=
~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
mHasHadWindowFocus = true;
}
if (mView != null && mAccessibilityManager.isEnabled()) {
if (hasWindowFocus) {
mView.sendAccessibilityEvent(
AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED);
}
}
}
} break;
...
}
}
}
final ViewRootHandler mHandler = new ViewRootHandler();
public void dispatchInvalidateDelayed(View view, long delayMilliseconds) {
Message msg = mHandler.obtainMessage(MSG_INVALIDATE, view);
mHandler.sendMessageDelayed(msg, delayMilliseconds);
}
@Override
public void requestLayout() {
if (!mHandlingLayoutInLayoutRequest) {
checkThread();
mLayoutRequested = true; //
scheduleTraversals(); // mTraversalRunnable => doTraversal => performTraversals
}
}
@Override
public boolean isLayoutRequested() {
return mLayoutRequested;
}
void invalidate() {
mDirty.set(0, 0, mWidth, mHeight);
if (!mWillDrawSoon) {
scheduleTraversals(); // mTraversalRunnable => doTraversal => performTraversals
}
}
final class TraversalRunnable implements Runnable {
@Override
public void run() {
doTraversal();
}
}
final TraversalRunnable mTraversalRunnable = new TraversalRunnable();
void scheduleTraversals() {
if (!mTraversalScheduled) {
mTraversalScheduled = true;
mTraversalBarrier = mHandler.getLooper().postSyncBarrier();
mChoreographer.postCallback(
Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
if (!mUnbufferedInputDispatch) {
scheduleConsumeBatchedInput();
}
notifyRendererOfFramePending();
}
}
void unscheduleTraversals() {
if (mTraversalScheduled) {
mTraversalScheduled = false;
mHandler.getLooper().removeSyncBarrier(mTraversalBarrier);
mChoreographer.removeCallbacks(
Choreographer.CALLBACK_TRAVERSAL, mTraversalRunnable, null);
}
}
void doTraversal() {
if (mTraversalScheduled) {
mTraversalScheduled = false;
mHandler.getLooper().removeSyncBarrier(mTraversalBarrier);
if (mProfile) {
Debug.startMethodTracing("ViewAncestor");
}
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "performTraversals");
try {
performTraversals();
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
if (mProfile) {
Debug.stopMethodTracing();
mProfile = false;
}
}
}
private void performMeasure(int childWidthMeasureSpec, int childHeightMeasureSpec) {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "measure");
try {
mView.measure(childWidthMeasureSpec, childHeightMeasureSpec); // 调用用View.java的measure()方法
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
}
private void performLayout(WindowManager.LayoutParams lp, int desiredWindowWidth,
int desiredWindowHeight) {
mLayoutRequested = false;
mScrollMayChange = true;
mInLayout = true;
final View host = mView;
if (DEBUG_ORIENTATION || DEBUG_LAYOUT) {
Log.v(TAG, "Laying out " + host + " to (" +
host.getMeasuredWidth() + ", " + host.getMeasuredHeight() + ")");
}
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "layout");
try {
host.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight()); // 调用用View.java的layout()方法
mInLayout = false;
int numViewsRequestingLayout = mLayoutRequesters.size();
if (numViewsRequestingLayout > 0) {
// requestLayout() was called during layout.
// If no layout-request flags are set on the requesting views, there is no problem.
// If some requests are still pending, then we need to clear those flags and do
// a full request/measure/layout pass to handle this situation.
ArrayList<View> validLayoutRequesters = getValidLayoutRequesters(mLayoutRequesters,
false);
if (validLayoutRequesters != null) {
// Set this flag to indicate that any further requests are happening during
// the second pass, which may result in posting those requests to the next
// frame instead
mHandlingLayoutInLayoutRequest = true;
// Process fresh layout requests, then measure and layout
int numValidRequests = validLayoutRequesters.size();
for (int i = 0; i < numValidRequests; ++i) {
final View view = validLayoutRequesters.get(i);
Log.w("View", "requestLayout() improperly called by " + view +
" during layout: running second layout pass");
view.requestLayout();
}
measureHierarchy(host, lp, mView.getContext().getResources(), desiredWindowWidth, desiredWindowHeight);
mInLayout = true;
host.layout(0, 0, host.getMeasuredWidth(), host.getMeasuredHeight());
mHandlingLayoutInLayoutRequest = false;
// Check the valid requests again, this time without checking/clearing the
// layout flags, since requests happening during the second pass get noop'd
validLayoutRequesters = getValidLayoutRequesters(mLayoutRequesters, true);
if (validLayoutRequesters != null) {
final ArrayList<View> finalRequesters = validLayoutRequesters;
// Post second-pass requests to the next frame
getRunQueue().post(new Runnable() {
@Override
public void run() {
int numValidRequests = finalRequesters.size();
for (int i = 0; i < numValidRequests; ++i) {
final View view = finalRequesters.get(i);
Log.w("View", "requestLayout() improperly called by " + view +
" during second layout pass: posting in next frame");
view.requestLayout();
}
}
});
}
}
}
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
mInLayout = false;
}
//performDraw() => draw() => drawSoftware()
private void performDraw() {
if (mAttachInfo.mDisplayState == Display.STATE_OFF && !mReportNextDraw) {
return;
}
final boolean fullRedrawNeeded = mFullRedrawNeeded;
mFullRedrawNeeded = false;
mIsDrawing = true;
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "draw");
try {
draw(fullRedrawNeeded);
// draw()调用 drawSoftware(surface, mAttachInfo, xOffset, yOffset, scalingRequired, dirty)
// private boolean drawSoftware(Surface surface, AttachInfo attachInfo, int xoff, int yoff, boolean scalingRequired, Rect dirty)
} finally {
mIsDrawing = false;
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
// For whatever reason we didn't create a HardwareRenderer, end any
// hardware animations that are now dangling
if (mAttachInfo.mPendingAnimatingRenderNodes != null) {
final int count = mAttachInfo.mPendingAnimatingRenderNodes.size();
for (int i = 0; i < count; i++) {
mAttachInfo.mPendingAnimatingRenderNodes.get(i).endAllAnimators();
}
mAttachInfo.mPendingAnimatingRenderNodes.clear();
}
if (mReportNextDraw) {
mReportNextDraw = false;
if (mAttachInfo.mHardwareRenderer != null) {
mAttachInfo.mHardwareRenderer.fence();
}
if (LOCAL_LOGV) {
Log.v(TAG, "FINISHED DRAWING: " + mWindowAttributes.getTitle());
}
if (mSurfaceHolder != null && mSurface.isValid()) {
mSurfaceHolderCallback.surfaceRedrawNeeded(mSurfaceHolder);
SurfaceHolder.Callback callbacks[] = mSurfaceHolder.getCallbacks();
if (callbacks != null) {
for (SurfaceHolder.Callback c : callbacks) {
if (c instanceof SurfaceHolder.Callback2) {
((SurfaceHolder.Callback2)c).surfaceRedrawNeeded(
mSurfaceHolder);
}
}
}
}
try {
mWindowSession.finishDrawing(mWindow);
} catch (RemoteException e) {
}
}
}
...
}以上就是Android自定义一个view ViewRootImpl绘制流程示例的详细内容，更多关于Android view ViewRootImpl绘制的资料请关注脚本之家其它相关文章！