上一篇已经对ActionBar的菜单项的执行过程进行了分析，有兴趣的朋友可以看一下android中ActionBar的源代码分析（三），本章对ActionBar的OverflowMenu的运行机制进行分析。
ActionBar的OverflowMenu，就是ActionBar右边的三个小点点，点击以后就出现一个下拉菜单项，如图
OverflowMenu是为了解决ActionBar的菜单项太多，在一个屏幕上显示不出来，而把过多的菜单项放到下拉菜单中显示的问题；在配置菜单属性的时候，把android:showAsAction设为ifRoom或者never，就会利用ActionBar的OverflowMenu特性在下拉菜单显示出来了，当然如果你的机器是带有物理menu键的，还需要进行特殊处理，这个可以看一下我之前写的一篇文章android2.x使用ActionBar-强制显示OverflowButton
溢出菜单按钮的构建
既然我们知道了如何使用OverflowMenu，那这个OverflowMenu在代码层次是如何实现的呢？从上几篇文章我们知道，类ActionMenuPresenter是负责ActionBar菜单项的绘制工作的，其中初始菜单参数的方法是initForMenu()，我们先看一下这个代码是如何实现的吧。
@Override
public void initForMenu(Context context, MenuBuilder menu) {
super.initForMenu(context, menu);
final Resources res = context.getResources();
<span style="white-space:pre"> </span>//是否显示溢出菜单按钮
final ActionBarPolicy abp = ActionBarPolicy.get(context);
if (!mReserveOverflowSet) {
mReserveOverflow = abp.showsOverflowMenuButton();
}
<span style="white-space:pre"> </span>//嵌入菜单最大宽度即放置ActionBar菜单项的最大宽度
if (!mWidthLimitSet) {
mWidthLimit = abp.getEmbeddedMenuWidthLimit();
}
<span style="white-space:pre"> </span>//ActionBar最多显示的按钮数目
// Measure for initial configuration
if (!mMaxItemsSet) {
mMaxItems = abp.getMaxActionButtons();
}
<span style="white-space:pre"> </span>//初始化溢出菜单按钮，并计算溢出菜单按钮宽度
int width = mWidthLimit;
if (mReserveOverflow) {
if (mOverflowButton == null) {
mOverflowButton = new OverflowMenuButton(mSystemContext);
final int spec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
mOverflowButton.measure(spec, spec);
}
width -= mOverflowButton.getMeasuredWidth(); //显示的菜单按钮宽度需要减掉溢出菜单按钮的宽度
} else {
mOverflowButton = null;
}
mActionItemWidthLimit = width;
mMinCellSize = (int) (ActionMenuView.MIN_CELL_SIZE * res.getDisplayMetrics().density);
// Drop a scrap view as it may no longer reflect the proper context/config.
mScrapActionButtonView = null;
}溢出菜单按钮（OverflowMenuButton）什么时候放置到ActionBar上的呢？从android中ActionBar的源代码分析（二）我们可以看出，系统在创建菜单时，会调用ActionMenuPresenter的updateMenuView()方法，我们看一下这个方法的实现逻辑：
@Override
public void updateMenuView(boolean cleared) {
final ViewGroup menuViewParent = (ViewGroup) ((View) mMenuView).getParent();
if (menuViewParent != null) {
<span style="white-space:pre"> </span> // 使用ActionBar的淡出淡入效果，其实系统本身并没有启用该效果
ActionBarTransition.beginDelayedTransition(menuViewParent);
}
super.updateMenuView(cleared); //使用父类的方法，构建ActionBar的按钮并添加到ActionMenuView上
((View) mMenuView).requestLayout();
<span style="white-space:pre"> </span>//判断菜单是否配置了ActionProvider，如果有则设置ActionProvider的子菜单侦听事件
if (mMenu != null) {
final ArrayList<MenuItemImpl> actionItems = mMenu.getActionItems();
final int count = actionItems.size();
for (int i = 0; i < count; i++) {
final ActionProvider provider = actionItems.get(i).getActionProvider();
if (provider != null) {
provider.setSubUiVisibilityListener(this);
}
}
}
final ArrayList<MenuItemImpl> nonActionItems = mMenu != null ?
mMenu.getNonActionItems() : null;
<span style="white-space:pre"> </span>//判断是否存在溢出菜单
boolean hasOverflow = false;
if (mReserveOverflow && nonActionItems != null) {
final int count = nonActionItems.size();
if (count == 1) {
hasOverflow = !nonActionItems.get(0).isActionViewExpanded(); //如果只有一个菜单按钮，并且该菜单按钮是个可扩展按钮，则不显示溢出菜单按钮
} else {
hasOverflow = count > 0;
}
}
<span style="white-space:pre"> </span>//如果需要显示溢出菜单，则初始化溢出菜单按钮，并添加到ActionMenuView中
if (hasOverflow) {
if (mOverflowButton == null) {
mOverflowButton = new OverflowMenuButton(mSystemContext);
}
ViewGroup parent = (ViewGroup) mOverflowButton.getParent();
if (parent != mMenuView) {
if (parent != null) {
parent.removeView(mOverflowButton);
}
ActionMenuView menuView = (ActionMenuView) mMenuView;
menuView.addView(mOverflowButton, menuView.generateOverflowButtonLayoutParams());
}
} else if (mOverflowButton != null && mOverflowButton.getParent() == mMenuView) {
((ViewGroup) mMenuView).removeView(mOverflowButton);
}
((ActionMenuView) mMenuView).setOverflowReserved(mReserveOverflow);
}溢出菜单弹出执行过程分析
溢出菜单按钮点击以后，就会弹出下拉菜单来，这个过程在代码层次上具体是怎么实现的呢？这就需要我们看一下类OverflowMenuButton的具体实现了，OverflowMenuButton继承于类ImageButton，也就是说它实际就是一个图片按钮；我们先看一下OverflowMenuButton的构造方法吧
public OverflowMenuButton(Context context) {
super(context, null, com.android.internal.R.attr.actionOverflowButtonStyle);
<span style="white-space:pre"> </span> //设置控件可点击、可设置焦点、可用和可见性
setClickable(true);
setFocusable(true);
setVisibility(VISIBLE);
setEnabled(true);
<span style="white-space:pre"> </span> //侦听控件本身的touch事件
setOnTouchListener(new ForwardingListener(this) {
@Override
public ListPopupWindow getPopup() {
if (mOverflowPopup == null) {
return null;
}
return mOverflowPopup.getPopup();
}
@Override
public boolean onForwardingStarted() { // touch事件转发开始后，显示溢出菜单
showOverflowMenu();
return true;
}
@Override
public boolean onForwardingStopped() { // 溢出菜单显示后再次touch该控件，则隐藏溢出菜单
// Displaying the popup occurs asynchronously, so wait for
// the runnable to finish before deciding whether to stop
// forwarding.
if (mPostedOpenRunnable != null) {
return false;
}
hideOverflowMenu();
return true;
}
});
}- onForwardingStarted()表示当手指在触摸溢出菜单按钮时回调该方法，这里是执行了showOverflowMenu()方法，按照字面的意思应该就是显示溢出菜单了，至于代码实现如何，一会再进行分析；
- onForwardingStopped()表示当溢出菜单仍然显示，再次触摸溢出菜单按钮时回调该方法，这里首先判断mPostOpenRunnable是否为空，也即是否采用了Post Runnable的处理方式，如果没有则执行hideOverflowMenu()方法，按照字面的意思就是隐藏溢出菜单，至于代码实现如何，一会再进行分析；
- getPopup()表示获取弹出菜单窗口，也即指定需要控制的弹出窗口，这里设置为溢出菜单按钮关联的PopupWindow
类OverflowMenuButton也重写了View的performClick()方法，代码如下：
@Override
public boolean performClick() {
if (super.performClick()) {
return true;
}
playSoundEffect(SoundEffectConstants.CLICK);
showOverflowMenu();
return true;
}
从上面分析可以看出，showOverflowMenu()方法是咱们分析溢出菜单显示的关键，那我们就来看一下这个方法的实现逻辑吧
public boolean showOverflowMenu() {
if (mReserveOverflow && !isOverflowMenuShowing() && mMenu != null && mMenuView != null &&
mPostedOpenRunnable == null && !mMenu.getNonActionItems().isEmpty()) {
OverflowPopup popup = new OverflowPopup(mContext, mMenu, mOverflowButton, true);
mPostedOpenRunnable = new OpenOverflowRunnable(popup);
// Post this for later; we might still need a layout for the anchor to be right.
((View) mMenuView).post(mPostedOpenRunnable);
// ActionMenuPresenter uses null as a callback argument here
// to indicate overflow is opening.
super.onSubMenuSelected(null);
return true;
}
return false;
} private class OpenOverflowRunnable implements Runnable {
private OverflowPopup mPopup;
public OpenOverflowRunnable(OverflowPopup popup) {
mPopup = popup;
}
public void run() {
mMenu.changeMenuMode();
final View menuView = (View) mMenuView;
if (menuView != null && menuView.getWindowToken() != null && mPopup.tryShow()) {
mOverflowPopup = mPopup;
}
mPostedOpenRunnable = null;
}
}
OverflowPopup.tryShow()方法又是如何显示溢出菜单窗体的呢？查找类OverflowPopup并没有tryShow()方法，那么调用的应该就是父类（MenuPopupHelper）的tryShow()方法了，代码如下：
public boolean tryShow() {
mPopup = new ListPopupWindow(mContext, null, com.android.internal.R.attr.popupMenuStyle);
mPopup.setOnDismissListener(this);
mPopup.setOnItemClickListener(this);
mPopup.setAdapter(mAdapter);
mPopup.setModal(true);
View anchor = mAnchorView;
if (anchor != null) {
final boolean addGlobalListener = mTreeObserver == null;
mTreeObserver = anchor.getViewTreeObserver(); // Refresh to latest
if (addGlobalListener) mTreeObserver.addOnGlobalLayoutListener(this);
anchor.addOnAttachStateChangeListener(this);
mPopup.setAnchorView(anchor);
mPopup.setDropDownGravity(mDropDownGravity);
} else {
return false;
}
if (!mHasContentWidth) {
mContentWidth = measureContentWidth();
mHasContentWidth = true;
}
mPopup.setContentWidth(mContentWidth);
mPopup.setInputMethodMode(PopupWindow.INPUT_METHOD_NOT_NEEDED);
mPopup.show();
mPopup.getListView().setOnKeyListener(this);
return true;
}- setDismissListener() 负责侦听弹出窗体关闭的事件；这里把this传入，也就是说OverflowPopup的父类MenuPopupHelper是实现了接口PopupWindow.OnDismissListener的，也即实现了接口方法onDismiss()的，关于onDismiss()方法，稍后在分析溢出菜单隐藏时再进行介绍；
- setOnItemClickListener() 负责侦听弹出窗体的菜单项点击事件；这里把this传入，也就是说OverflowPopup的父类MenuPopupHelper是实现了接口AdapterView.OnItemClickListener的，也就是实现了接口方法onItemClick()的，在这个方法中，会调用MenuBuilder的performItemAction()方法，这个方法在上一章已经进行过介绍，有兴趣的朋友可以看android中ActionBar的源代码分析（三）
- setAdapter() 这个就是设置ListView的数据适配类；这里传入的是mAdapter，其实现类为MenuPopupHelper.MenuAdapter，实现代码如下：
private class MenuAdapter extends BaseAdapter {
private MenuBuilder mAdapterMenu;
private int mExpandedIndex = -1;
public MenuAdapter(MenuBuilder menu) {
mAdapterMenu = menu;
findExpandedIndex();
}
public int getCount() {
ArrayList<MenuItemImpl> items = mOverflowOnly ?
mAdapterMenu.getNonActionItems() : mAdapterMenu.getVisibleItems();
if (mExpandedIndex < 0) {
return items.size();
}
return items.size() - 1;
}
public MenuItemImpl getItem(int position) {
ArrayList<MenuItemImpl> items = mOverflowOnly ?
mAdapterMenu.getNonActionItems() : mAdapterMenu.getVisibleItems();
if (mExpandedIndex >= 0 && position >= mExpandedIndex) {
position++;
}
return items.get(position);
}
public long getItemId(int position) {
// Since a menu item's ID is optional, we'll use the position as an
// ID for the item in the AdapterView
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = mInflater.inflate(ITEM_LAYOUT, parent, false);
}
MenuView.ItemView itemView = (MenuView.ItemView) convertView;
if (mForceShowIcon) {
((ListMenuItemView) convertView).setForceShowIcon(true);
}
itemView.initialize(getItem(position), 0);
return convertView;
}
void findExpandedIndex() {
final MenuItemImpl expandedItem = mMenu.getExpandedItem();
if (expandedItem != null) {
final ArrayList<MenuItemImpl> items = mMenu.getNonActionItems();
final int count = items.size();
for (int i = 0; i < count; i++) {
final MenuItemImpl item = items.get(i);
if (item == expandedItem) {
mExpandedIndex = i;
return;
}
}
}
mExpandedIndex = -1;
}
@Override
public void notifyDataSetChanged() {
findExpandedIndex();
super.notifyDataSetChanged();
}
}<com.android.internal.view.menu.ListMenuItemView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="?android:attr/dropdownListPreferredItemHeight"
android:minWidth="196dip"
android:paddingEnd="16dip">
<!-- Icon will be inserted here. -->
<!-- The title and summary have some gap between them, and this 'group' should be centered vertically. -->
<RelativeLayout
android:layout_width="0dip"
android:layout_weight="1"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:layout_marginStart="16dip"
android:duplicateParentState="true">
<TextView
android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:textAppearance="?android:attr/textAppearanceLargePopupMenu"
android:singleLine="true"
android:duplicateParentState="true"
android:ellipsize="marquee"
android:fadingEdge="horizontal"
android:textAlignment="viewStart" />
<TextView
android:id="@+id/shortcut"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/title"
android:layout_alignParentStart="true"
android:textAppearance="?android:attr/textAppearanceSmallPopupMenu"
android:singleLine="true"
android:duplicateParentState="true"
android:textAlignment="viewStart" />
</RelativeLayout>
<!-- Checkbox, and/or radio button will be inserted here. -->
</com.android.internal.view.menu.ListMenuItemView> public void setIcon(Drawable icon) {
<span style="white-space:pre"> </span>//判断图标是否需要显示
final boolean showIcon = mItemData.shouldShowIcon() || mForceShowIcon;
if (!showIcon && !mPreserveIconSpacing) {
return;
}
if (mIconView == null && icon == null && !mPreserveIconSpacing) {
return;
}
//如果需要显示图标，则创建控件并添加进来
if (mIconView == null) {
insertIconView();
}
//设置可见性
if (icon != null || mPreserveIconSpacing) {
mIconView.setImageDrawable(showIcon ? icon : null);
if (mIconView.getVisibility() != VISIBLE) {
mIconView.setVisibility(VISIBLE);
}
} else {
mIconView.setVisibility(GONE);
}
}
在setIcon()方法中，首先判断图标是否需要显示，如果不需要显示则直接退出，否则就创建ImageView来显示图标，最后设置ImageView的可见性，这里我们注意到，菜单图标的可见性受mItemData.shouldShowIcon()的控制，这里的mItemData的实现类为MenuItemImpl，我们看一下MenuItemImpl.shouldShowIcon()的实现代码：
public boolean shouldShowIcon() {
return mMenu.getOptionalIconsVisible();
}溢出菜单隐藏执行过程分析
上面提到ListPopupWindow是一个包含ListView的PopupWindow，OverflowPopup在创建ListPopupWindow时，调用ListPopupWindow.setDismiss()去侦听弹出窗体关闭的事件，而传入参数为this，也就是OverflowPopup的父类MenuPopupHelper是实现了接口PopupWindow.OnDismissListener的，也即实现了接口方法onDismiss()的，onDismiss()方法的代码如下： public void onDismiss() {
mPopup = null;
mMenu.close();
if (mTreeObserver != null) {
if (!mTreeObserver.isAlive()) mTreeObserver = mAnchorView.getViewTreeObserver();
mTreeObserver.removeGlobalOnLayoutListener(this);
mTreeObserver = null;
}
mAnchorView.removeOnAttachStateChangeListener(this);
} public void close() {
close(true);
}
final void close(boolean allMenusAreClosing) {
if (mIsClosing) return;
mIsClosing = true;
for (WeakReference<MenuPresenter> ref : mPresenters) {
final MenuPresenter presenter = ref.get();
if (presenter == null) {
mPresenters.remove(ref);
} else {
presenter.onCloseMenu(this, allMenusAreClosing);
}
}
mIsClosing = false;
} public void onCloseMenu(MenuBuilder menu, boolean allMenusAreClosing) {
dismissPopupMenus();
super.onCloseMenu(menu, allMenusAreClosing);
}
public boolean dismissPopupMenus() {
boolean result = hideOverflowMenu();
result |= hideSubMenus();
return result;
} public boolean hideOverflowMenu() {
if (mPostedOpenRunnable != null && mMenuView != null) {
((View) mMenuView).removeCallbacks(mPostedOpenRunnable);
mPostedOpenRunnable = null;
return true;
}
MenuPopupHelper popup = mOverflowPopup;
if (popup != null) {
popup.dismiss();
return true;
}
return false;
}hideOverflowMenu()方法实现逻辑很简单，其实就是调用了PopupWindow的dismiss方法进行的。
关于ActionBar的OverflowMenu的执行过程分析到此为止，如有需要交流，欢迎留言！
3495
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
