Android中View绘制流程详细介绍

final void attach(Context context, ActivityThread aThread, 
    Instrumentation instr, IBinder token, int ident, 
    Application application, Intent intent, ActivityInfo info, 
    CharSequence title, Activity parent, String id, 
    NonConfigurationInstances lastNonConfigurationInstances, 
    Configuration config) { 
  attachBaseContext(context); 
 
  mFragments.attachActivity(this, mContainer, null); 
   
  mWindow = PolicyManager.makeNewWindow(this); 
  mWindow.setCallback(this); 
  mWindow.getLayoutInflater().setPrivateFactory(this); 

protected boolean initializePanelDecor(PanelFeatureState st) { 
  st.decorView = new DecorView(getContext(), st.featureId); 
  st.gravity = Gravity.CENTER | Gravity.BOTTOM; 
  st.setStyle(getContext()); 
 
  return true; 
} 

public void addView(View view, ViewGroup.LayoutParams params, 
    Display display, Window parentWindow) { 
  if (view == null) { 
    throw new IllegalArgumentException("view must not be null"); 
  } 
  if (display == null) { 
    throw new IllegalArgumentException("display must not be null"); 
  } 
  if (!(params instanceof WindowManager.LayoutParams)) { 
    throw new IllegalArgumentException("Params must be WindowManager.LayoutParams"); 
  } 
 
  final WindowManager.LayoutParams wparams = (WindowManager.LayoutParams)params; 
  if (parentWindow != null) { 
    parentWindow.adjustLayoutParamsForSubWindow(wparams); 
  } 
 
  ViewRootImpl root; 
  View panelParentView = null; 
 
  synchronized (mLock) { 
    // Start watching for system property changes. 
    if (mSystemPropertyUpdater == null) { 
      mSystemPropertyUpdater = new Runnable() { 
        @Override public void run() { 
          synchronized (mLock) { 
            for (ViewRootImpl viewRoot : mRoots) { 
              viewRoot.loadSystemProperties(); 
            } 
          } 
        } 
      }; 
      SystemProperties.addChangeCallback(mSystemPropertyUpdater); 
    } 
 
    int index = findViewLocked(view, false); 
    if (index >= 0) { 
      throw new IllegalStateException("View " + view 
          + " has already been added to the window manager."); 
    } 
 
    // If this is a panel window, then find the window it is being 
    // attached to for future reference. 
    if (wparams.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW && 
        wparams.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) { 
      final int count = mViews != null ? mViews.length : 0; 
      for (int i=0; i<count; i++) { 
        if (mRoots[i].mWindow.asBinder() == wparams.token) { 
          panelParentView = mViews[i]; 
        } 
      } 
    } 
 
    root = new ViewRootImpl(view.getContext(), display); 
 
    view.setLayoutParams(wparams); 
 
    if (mViews == null) { 
      index = 1; 
      mViews = new View[1]; 
      mRoots = new ViewRootImpl[1]; 
      mParams = new WindowManager.LayoutParams[1]; 
    } else { 
      index = mViews.length + 1; 
      Object[] old = mViews; 
      mViews = new View[index]; 
      System.arraycopy(old, 0, mViews, 0, index-1); 
      old = mRoots; 
      mRoots = new ViewRootImpl[index]; 
      System.arraycopy(old, 0, mRoots, 0, index-1); 
      old = mParams; 
      mParams = new WindowManager.LayoutParams[index]; 
      System.arraycopy(old, 0, mParams, 0, index-1); 
    } 
    index--; 
 
    mViews[index] = view; 
    mRoots[index] = root; 
    mParams[index] = wparams; 
  } 
 
  // do this last because it fires off messages to start doing things 
  try { 
    root.setView(view, wparams, panelParentView); 
  } catch (RuntimeException e) { 
    // BadTokenException or InvalidDisplayException, clean up. 
    synchronized (mLock) { 
      final int index = findViewLocked(view, false); 
      if (index >= 0) { 
        removeViewLocked(index, true); 
      } 
    } 
    throw e; 
  } 
} 

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); 
    } 
  } 

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
  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; 
   } 
   mMeasuredWidth = measuredWidth; 
   mMeasuredHeight = measuredHeight; 
 
   mPrivateFlags |= PFLAG_MEASURED_DIMENSION_SET; 
 } 

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()); 
 
    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; 
} 

protected void onLayout(boolean changed, int left, int top, int right, int bottom) { 
} 

public void layout(int l, int t, int r, int b) { 
  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) { 
    onLayout(changed, l, t, r, b); 
    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; 
}