繼上文講述了dialog的創(chuàng)建流程之后，接下來(lái)講一下popwindow的創(chuàng)建以及和dialog的不同之處
首先看任何代碼都要帶著疑問(wèn)去看览露，不然很容易一頭霧水觉义，先說(shuō)幾個(gè)問(wèn)題
1.popwindow的顯示分2種黑毅，一種是showAsDropDown和showAtLocation
其各自實(shí)現(xiàn)的原理
2.popwindow的動(dòng)畫(huà)是和dialog一樣是window的動(dòng)畫(huà)么
3.popwindow的點(diǎn)擊是如何處理的暑中？
4.popwindow中和dialog一樣新建了一個(gè)phonewindow，同時(shí)又用附屬的activity的windowManager添加的么其障？
首先簡(jiǎn)單看下顯示的代碼

View mPopView = getLayoutInflater().inflate(R.layout.popwindow_layout, null);
                // 將轉(zhuǎn)換的View放置到 新建一個(gè)popuwindow對(duì)象中
                mPopupWindow = new PopupWindow(mPopView,
                        WindowManager.LayoutParams.WRAP_CONTENT,
                        WindowManager.LayoutParams.WRAP_CONTENT);
                // 點(diǎn)擊popuwindow外讓其消失
                mPopupWindow.setOutsideTouchable(true);

                 mPopupWindow.showAsDropDown(mCenterTx, Gravity.CENTER, 0, 0);

可以看到用法和dialog如出一轍银室，主要看下其構(gòu)造和show的邏輯吧

  public PopupWindow(View contentView, int width, int height, boolean focusable) {
        if (contentView != null) {
            mContext = contentView.getContext();
            mWindowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
        }

        setContentView(contentView);
        setWidth(width);
        setHeight(height);
        setFocusable(focusable);
    }

可以看到用的還是依附的activity的windowManager，然后設(shè)置了幾個(gè)屬性励翼。
接下來(lái)看下關(guān)鍵的showAsDropDown方法

public void showAsDropDown(View anchor, int xoff, int yoff, int gravity) {
        if (isShowing() || mContentView == null) {
            return;
        }

        TransitionManager.endTransitions(mDecorView);

        registerForScrollChanged(anchor, xoff, yoff, gravity);

        mIsShowing = true;
        mIsDropdown = true;
//關(guān)鍵點(diǎn)一
        final WindowManager.LayoutParams p = createPopupLayoutParams(anchor.getWindowToken());
        preparePopup(p);關(guān)鍵點(diǎn)一

        final boolean aboveAnchor = findDropDownPosition(anchor, p, xoff, yoff, gravity);
        updateAboveAnchor(aboveAnchor);
//關(guān)鍵點(diǎn)二
        invokePopup(p);
    }

關(guān)鍵點(diǎn)一：

 public IBinder getWindowToken() {
        return mAttachInfo != null ? mAttachInfo.mWindowToken : null;
    }

無(wú)論是popwindow還是dialog時(shí)蜈敢，show的時(shí)候都要綁定所屬activity的token，而mAttachInfo這個(gè)對(duì)象是viewRootImp初始化的時(shí)候新建的
而初始化的時(shí)機(jī)就是WindowManagerGlobal.addview時(shí)候所創(chuàng)建的
所以這個(gè)token是為null的汽抚，在onCreate時(shí)候
接下來(lái)看下createPopupLayoutParams方法

private WindowManager.LayoutParams createPopupLayoutParams(IBinder token) {
        final WindowManager.LayoutParams p = new WindowManager.LayoutParams();

        // These gravity settings put the view at the top left corner of the
        // screen. The view is then positioned to the appropriate location by
        // setting the x and y offsets to match the anchor's bottom-left
        // corner.
        p.gravity = Gravity.START | Gravity.TOP;
        p.flags = computeFlags(p.flags);
        p.type = mWindowLayoutType;
        p.token = token;
        p.softInputMode = mSoftInputMode;
        p.windowAnimations = computeAnimationResource();

        if (mBackground != null) {
            p.format = mBackground.getOpacity();
        } else {
            p.format = PixelFormat.TRANSLUCENT;
        }

        if (mHeightMode < 0) {
            p.height = mLastHeight = mHeightMode;
        } else {
            p.height = mLastHeight = mHeight;
        }

        if (mWidthMode < 0) {
            p.width = mLastWidth = mWidthMode;
        } else {
            p.width = mLastWidth = mWidth;
        }

        // Used for debugging.
        p.setTitle("PopupWindow:" + Integer.toHexString(hashCode()));

        return p;
    }

很顯然抓狭，用的動(dòng)畫(huà)也是windowManger里屬性的動(dòng)畫(huà)

來(lái)看下關(guān)鍵點(diǎn)二

private void preparePopup(WindowManager.LayoutParams p) {
        if (mContentView == null || mContext == null || mWindowManager == null) {
            throw new IllegalStateException("You must specify a valid content view by "
                    + "calling setContentView() before attempting to show the popup.");
        }

        // The old decor view may be transitioning out. Make sure it finishes
        // and cleans up before we try to create another one.
        if (mDecorView != null) {
            mDecorView.cancelTransitions();
        }

        // When a background is available, we embed the content view within
        // another view that owns the background drawable.
        if (mBackground != null) {
            mBackgroundView = createBackgroundView(mContentView);
            mBackgroundView.setBackground(mBackground);
        } else {
            mBackgroundView = mContentView;
        }

        mDecorView = createDecorView(mBackgroundView);

        // The background owner should be elevated so that it casts a shadow.
        mBackgroundView.setElevation(mElevation);

        // We may wrap that in another view, so we'll need to manually specify
        // the surface insets.
        final int surfaceInset = (int) Math.ceil(mBackgroundView.getZ() * 2);
        p.surfaceInsets.set(surfaceInset, surfaceInset, surfaceInset, surfaceInset);
        p.hasManualSurfaceInsets = true;

        mPopupViewInitialLayoutDirectionInherited =
                (mContentView.getRawLayoutDirection() == View.LAYOUT_DIRECTION_INHERIT);
        mPopupWidth = p.width;
        mPopupHeight = p.height;
    }

可以看到popwindow并沒(méi)有像dialog一樣，新建了一個(gè)phonewindow,那它是window么造烁？肯定是辐宾，只不過(guò)它的windowManager.layoutParams的屬性要自己配置狱从，而且它也沒(méi)有常規(guī)setContentView的這么多的嵌套
那既然沒(méi)有新建phonewindow,那它的點(diǎn)擊事件的回掉又從那里來(lái)呢膨蛮？

 private class PopupDecorView extends FrameLayout {
        private TransitionListenerAdapter mPendingExitListener;

        public PopupDecorView(Context context) {
            super(context);
        }

        @Override
        public boolean dispatchKeyEvent(KeyEvent event) {
            if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
                if (getKeyDispatcherState() == null) {
                    return super.dispatchKeyEvent(event);
                }

                if (event.getAction() == KeyEvent.ACTION_DOWN && event.getRepeatCount() == 0) {
                    final KeyEvent.DispatcherState state = getKeyDispatcherState();
                    if (state != null) {
                        state.startTracking(event, this);
                    }
                    return true;
                } else if (event.getAction() == KeyEvent.ACTION_UP) {
                    final KeyEvent.DispatcherState state = getKeyDispatcherState();
                    if (state != null && state.isTracking(event) && !event.isCanceled()) {
                        dismiss();
                        return true;
                    }
                }
                return super.dispatchKeyEvent(event);
            } else {
                return super.dispatchKeyEvent(event);
            }
        }
....

可以看到它的點(diǎn)擊事件全部有自己的PopupDecorView重寫(xiě)了叠纹，并沒(méi)有遵循傳統(tǒng)的decorview的事件的傳遞方式，所以也沒(méi)有了回掉
關(guān)鍵點(diǎn)三

 private void invokePopup(WindowManager.LayoutParams p) {
        if (mContext != null) {
            p.packageName = mContext.getPackageName();
        }

        final PopupDecorView decorView = mDecorView;
        decorView.setFitsSystemWindows(mLayoutInsetDecor);

        setLayoutDirectionFromAnchor();

        mWindowManager.addView(decorView, p);

        if (mEnterTransition != null) {
            decorView.requestEnterTransition(mEnterTransition);
        }
    }

這里還是用activity的windowManager添加的敞葛，后續(xù)的操作和dialog的顯示是一樣的誉察，這里就不再特別分析了，有個(gè)關(guān)于token的地方要著重說(shuō)下
window的adjustLayoutParamsForSubWindow方法

void adjustLayoutParamsForSubWindow(WindowManager.LayoutParams wp) {
        CharSequence curTitle = wp.getTitle();
        if (wp.type >= WindowManager.LayoutParams.FIRST_SUB_WINDOW &&
            wp.type <= WindowManager.LayoutParams.LAST_SUB_WINDOW) {
            if (wp.token == null) {
                View decor = peekDecorView();
                if (decor != null) {
                    wp.token = decor.getWindowToken();
                }
            }
            if (curTitle == null || curTitle.length() == 0) {
                String title;
                if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_MEDIA) {
                    title="Media";
                } else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_MEDIA_OVERLAY) {
                    title="MediaOvr";
                } else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_PANEL) {
                    title="Panel";
                } else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_SUB_PANEL) {
                    title="SubPanel";
                } else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_ABOVE_SUB_PANEL) {
                    title="AboveSubPanel";
                } else if (wp.type == WindowManager.LayoutParams.TYPE_APPLICATION_ATTACHED_DIALOG) {
                    title="AtchDlg";
                } else {
                    title=Integer.toString(wp.type);
                }
                if (mAppName != null) {
                    title += ":" + mAppName;
                }
                wp.setTitle(title);
            }
        } else {
            if (wp.token == null) {
                wp.token = mContainer == null ? mAppToken : mContainer.mAppToken;
            }
            if ((curTitle == null || curTitle.length() == 0)
                    && mAppName != null) {
                wp.setTitle(mAppName);
            }
        }
        if (wp.packageName == null) {
            wp.packageName = mContext.getPackageName();
        }
        if (mHardwareAccelerated) {
            wp.flags |= WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED;
        }
    }

可以看到由于popwindow是子窗口類(lèi)型惹谐，token為null的情況下會(huì)調(diào)用activity的decorview的token持偏，當(dāng)然在oncreate時(shí)也為null了，而dialog就不同了氨肌，默認(rèn)給到的就是null鸿秆，走了else的邏輯直接把mApptoken也就是activity的token給到了，這也是為何popwindow不能再oncreate顯示而dialog可以的最根本原因

總結(jié)

先來(lái)說(shuō)下幾個(gè)問(wèn)題
1.顯示的位置其實(shí)和WindowManager.layoutParams有關(guān)showAsDropDown其實(shí)就是算出錨地的位置然后放到其下方怎囚，而showAtLocation沒(méi)有此段邏輯
2.動(dòng)畫(huà)的顯示卿叽，其實(shí)也是依靠WindowManager.layoutParam的屬性，可以說(shuō)一樣的
3.點(diǎn)擊區(qū)域的處理恳守，這個(gè)和dialog有所不同考婴，由于不是系統(tǒng)的decorview，所以重寫(xiě)了分發(fā)的方法催烘。
4.源碼中表明了都是windowManager添加的沥阱，但是popwindow并沒(méi)有新建phonewinow,其實(shí)新建一個(gè)子window只要windowManager和decorview就能新建，新建了phonewindow默認(rèn)的屬性就是應(yīng)用類(lèi)型的window而已伊群，這也是兩者最大的不同之處
很多人說(shuō)popwindow比dialog都要“輕”考杉，但是又說(shuō)不出個(gè)所以然來(lái)，其實(shí)無(wú)非就是子window上不能新建子window舰始，而dialog上可以添加子window罷了

注意點(diǎn):

1.popwindow和dialog都會(huì)存在activity的token不存在了崇棠，而不能顯示的情況.要做好基類(lèi)的統(tǒng)一處理
2.popwinow一般用在依靠某個(gè)view顯示的位置情況，dialog則不然