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。
时间： 2024-10-10 21:55:28