[Android FrameWork 6.0源码学习]ViewGroup的addView函数分析 _源码学习

【[Android FrameWork 6.0源码学习]ViewGroup的addView函数分析】提兵百万西湖上，立马吴山第一峰！这篇文章主要讲述[Android FrameWork 6.0源码学习]ViewGroup的addView函数分析相关的知识，希望能为你提供帮助。
android中整个的View的组装是采用组合模式。
ViewGroup就相当与树根，各种Layout就相当于枝干，各种子View，就相当于树叶。
至于View类。我们就当它是个种子吧。哈哈！
ViewGroup属于树根，可以生长数很多枝干（继承自定义Layout）而枝干上有可以长出很多叶子（TextView,ImageVIew......）
好，闲话少叙，接下来步入正题！
首先，关于View的操作方法，被定义在一个叫做ViewManager的接口中，接口中还有两个方法，分别是移除和更新，这次主要分析addView

public interface ViewManager { /** * Assign the passed LayoutParams to the passed View and add the view to the window. * < p> Throws {@link android.view.WindowManager.BadTokenException} for certain programming * errors, such as adding a second view to a window without removing the first view. * < p> Throws {@link android.view.WindowManager.InvalidDisplayException} if the window is on a * secondary {@link Display} and the specified display can‘t be found * (see {@link android.app.Presentation}). * @param view The view to be added to this window. * @param params The LayoutParams to assign to view. */ public void addView(View view, ViewGroup.LayoutParams params); public void updateViewLayout(View view, ViewGroup.LayoutParams params); public void removeView(View view) }

addView在ViewGroup中实现，接下来贴出代码进行分析

public void addView(View child, LayoutParams params) { addView(child, -1, params); }

这个方法中调用了自身的addView方法，并且多传递了一个-1，这个-1是View的索引，要插入的位置

public void addView(View child, int index, LayoutParams params) { if (DBG) { System.out.println(this + " addView"); }if (child == null) { throw new IllegalArgumentException("Cannot add a null child view to a ViewGroup"); }// addViewInner() will call child.requestLayout() when setting the new LayoutParams // therefore, we call requestLayout() on ourselves before, so that the child‘s request // will be blocked at our level requestLayout(); invalidate(true); addViewInner(child, index, params, false); }

这个方法先是重绘了一下布局，然后调用了addViewInner(child, index, params, false); 方法，来把View插入到相应的位置

private void addViewInner(View child, int index, LayoutParams params, boolean preventRequestLayout) {if (mTransition != null) { // Don‘t prevent other add transitions from completing, but cancel remove // transitions to let them complete the process before we add to the container mTransition.cancel(LayoutTransition.DISAPPEARING); }if (child.getParent() != null) { throw new IllegalStateException("The specified child already has a parent. " + "You must call removeView() on the child‘s parent first."); }if (mTransition != null) { mTransition.addChild(this, child); }if (!checkLayoutParams(params)) { params = generateLayoutParams(params); }if (preventRequestLayout) { child.mLayoutParams = params; } else { child.setLayoutParams(params); }if (index < 0) { index = mChildrenCount; }//ViewGroup用一个View类型的数组去维护下边的子view，这个方法就是把view添加到响应的位置上 addInArray(child, index); //绑定插入的view的父容器为当前group // tell our children if (preventRequestLayout) { child.assignParent(this); } else { child.mParent = this; }if (child.hasFocus()) { requestChildFocus(child, child.findFocus()); }AttachInfo ai = mAttachInfo; if (ai != null & & (mGroupFlags & FLAG_PREVENT_DISPATCH_ATTACHED_TO_WINDOW) == 0) { boolean lastKeepOn = ai.mKeepScreenOn; ai.mKeepScreenOn = false; child.dispatchAttachedToWindow(mAttachInfo, (mViewFlags& VISIBILITY_MASK)); if (ai.mKeepScreenOn) { needGlobalAttributesUpdate(true); } ai.mKeepScreenOn = lastKeepOn; }if (child.isLayoutDirectionInherited()) { child.resetRtlProperties(); }dispatchViewAdded(child); if ((child.mViewFlags & DUPLICATE_PARENT_STATE) == DUPLICATE_PARENT_STATE) { mGroupFlags |= FLAG_NOTIFY_CHILDREN_ON_DRAWABLE_STATE_CHANGE; }if (child.hasTransientState()) { childHasTransientStateChanged(child, true); }if (child.getVisibility() != View.GONE) { notifySubtreeAccessibilityStateChangedIfNeeded(); }if (mTransientIndices != null) { final int transientCount = mTransientIndices.size(); for (int i = 0; i < transientCount; ++i) { final int oldIndex = mTransientIndices.get(i); if (index < = oldIndex) { mTransientIndices.set(i, oldIndex + 1); } } } }

这个方法先检查一下LayoutParams，看看插入的该view是否存在长宽，如果没有就生成一个默认的LayoutParams
然后判断index是否小于0，小于0就赋值为当前容器中的个数，代表插入到最后一项
随后就调用addInArray方法，来插入View到当前ViewGroup中，插入完成后给该view绑定一下父容器（getParent的值）
随后就是一些焦点，监听的分发，我们仔细分析一下插入方法就好了，就是addInArray

private void addInArray(View child, int index) { View[] children = mChildren; final int count = mChildrenCount; final int size = children.length; if (index == count) { if (size == count) { mChildren = new View[size + ARRAY_CAPACITY_INCREMENT]; System.arraycopy(children, 0, mChildren, 0, size); children = mChildren; } children[mChildrenCount++] = child; } else if (index < count) { if (size == count) { mChildren = new View[size + ARRAY_CAPACITY_INCREMENT]; System.arraycopy(children, 0, mChildren, 0, index); System.arraycopy(children, index, mChildren, index + 1, count - index); children = mChildren; } else { System.arraycopy(children, index, children, index + 1, count - index); } children[index] = child; mChildrenCount++; if (mLastTouchDownIndex > = index) { mLastTouchDownIndex++; } } else { throw new IndexOutOfBoundsException("index=" + index + " count=" + count); } }

mChildren是ViewGroup中的一个View类型的数组，里边存放了该Group下的所有子View
ARRAY_CAPACITY_INCREMENT这个常量的值是12
首先判断一下mChildren的位置还是否充足，不充足就继续扩充12个位置出来，copy源数组内容进到新数组里，然后再把本次要添加的view放到最后
如果index比count小，说明是插入操作，也是先判断位置是否充足，不充足就扩充并且copy到index处，然后在把剩下的copy到index+1到末尾
这样就把index位置空了出来。就完成了插入操作
插入完成后，系统会重绘界面，你就可以看到你插入的view了。

addView这个方法就分析完了，有什么疑问就可以指出来，错误也一样。共同学习共同进步。