源码如下所示，关于重点的逻辑，我在这里只是简单的注释了一下。
public void show() {
//首先判断对话框是否显示
if (mShowing) {
if (mDecor != null) {
if (mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {
mWindow.invalidatePanelMenu(Window.FEATURE_ACTION_BAR);
}
mDecor.setVisibility(View.VISIBLE);
}
return;
}
mCanceled = false;
/* 判断对话框是否创建过，如果没有创建过
* 在dispatchOnCreate里面就会回调onCreate函数
*/
if (!mCreated) {
dispatchOnCreate(null);
}
//回调onStart函数
onStart();
//获取Window对象总的DecorView，如果调用了setContentView就会创建DecorView
mDecor = mWindow.getDecorView();
//下面就会获取布局的一些属性
if (mActionBar == null && mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {
final ApplicationInfo info = mContext.getApplicationInfo();
mWindow.setDefaultIcon(info.icon);
mWindow.setDefaultLogo(info.logo);
mActionBar = new WindowDecorActionBar(this);
}
WindowManager.LayoutParams l = mWindow.getAttributes();
if ((l.softInputMode
& WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) == 0) {
WindowManager.LayoutParams nl = new WindowManager.LayoutParams();
nl.copyFrom(l);
nl.softInputMode |=
WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
l = nl;
}
try {
//将DecorView添加到WindowManager中，这些就会显示了
mWindowManager.addView(mDecor, l);
//将mShowing置为true
mShowing = true;
sendShowMessage();
} finally {
}
}
- 方法体的内容比较多，由于一开始mShowing变量用于表示当前dialog是否正在显示，由于我们刚刚开始调用执行show方法，所以这里的mShowing变量的值为false，所以if分支的内容不会被执行，继续往下看：
if (!mCreated) {
dispatchOnCreate(null);
}
- mCreated这个控制变量控制dispatchOnCreate方法只被执行一次，由于是第一次执行，所以这里会执行dispatchOnCreate方法，好吧，看一下dispatchOnCreate方法的执行逻辑：
- 调用了onStart方法，这个方法主要用于设置ActionBar，这里不做过多的说明，然后初始化WindowManager.LayoutParams对象，并最终调用我们的mWindowManager.addView()方法。
protected void onStart() {
if (mActionBar != null) mActionBar.setShowHideAnimationEnabled(true);
}
- 最后调用了sendShowMessage方法，可以看一下这个方法的实现：
- 这里会发送一个Dialog已经显示的异步消息，该消息最终会在ListenersHandler中的handleMessage方法中被执行：
private static final class ListenersHandler extends Handler {
private WeakReference mDialog;
public ListenersHandler(Dialog dialog) {
mDialog = new WeakReference(dialog);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case DISMISS:
((OnDismissListener) msg.obj).onDismiss(mDialog.get());
break;
case CANCEL:
((OnCancelListener) msg.obj).onCancel(mDialog.get());
break;
case SHOW:
((OnShowListener) msg.obj).onShow(mDialog.get());
break;
}
}
}
由于我们的msg.what = SHOW,所以会执行OnShowListener.onShow方法，那么这个OnShowListener是何时赋值的呢？还记得我们构造AlertDialog.Builder么？
alertDialog.setOnShowListener(new DialogInterface.OnShowListener() {
@Override
public void onShow(DialogInterface dialog) {
}
});
- 这样就为我们的AlertDialog.Builder设置了OnShowListener，可以看一下setOnShowListener方法的具体实现：
所以无论执行的cancel方法还是dismiss方法，无论方法是在主线程执行还是子线程中执行，最终调用的都是dismissDialog方法，那么就看一下dismissDialog是怎么个执行逻辑。
- 首先判断当前的mDector是否为空，或者当前Dialog是否在显示，若为空或者没有在显示，则直接return掉，也就是说当前我们的dialog已经不再显示了，则不需要往下在执行。然后调用了mWindow.isDestroyed()方法，判断Window对象是否已经被销毁，若已经被销毁，则直接return，并打印错误日志。
然后再调用了mWindowManager.removeViewImmediate(mDector)，这里的mDector是Dialog窗口的根布局，看这个方法的名字应该就是Dialog去除根布局的操作了，可以看一下这个方法的具体实现。
void dismissDialog() {
if (mDecor == null || !mShowing) {
return;
}
if (mWindow.isDestroyed()) {
Log.e(TAG, "Tried to dismissDialog() but the Dialog's window was already destroyed!");
return;
}
try {
mWindowManager.removeViewImmediate(mDecor);
} finally {
if (mActionMode != null) {
mActionMode.finish();
}
mDecor = null;
mWindow.closeAllPanels();
onStop();
mShowing = false;
sendDismissMessage();
}
}
- mWindowManager其实是WindowManagerImpl的实例，所以这里的removeViewImmediate方法应该是WindowManagerImpl中的方法，看一下它的具体实现：
@Override
public void removeViewImmediate(View view) {
mGlobal.removeView(view, true);
}
可以发现，这里它调用了mGlobal.removeView方法，而这里的mGlobal是WindowManagerGlobal的实例，所以再看一下WIndowManagerGlobal中removeView的实现逻辑:
public void removeView(View view, boolean immediate) {
if (view == null) {
throw new IllegalArgumentException("view must not be null");
}
synchronized (mLock) {
int index = findViewLocked(view, true);
View curView = mRoots.get(index).getView();
removeViewLocked(index, immediate);
if (curView == view) {
return;
}
throw new IllegalStateException("Calling with view " + view
+ " but the ViewAncestor is attached to " + curView);
}
}
可以发现，这里在获取了保存的mDector组件之后，又调用了removeViewLocked方法，在看一下这个方法的具体实现逻辑：
private void removeViewLocked(int index, boolean immediate) {
ViewRootImpl root = mRoots.get(index);
View view = root.getView();
if (view != null) {
InputMethodManager imm = InputMethodManager.getInstance();
if (imm != null) {
imm.windowDismissed(mViews.get(index).getWindowToken());
}
}
boolean deferred = root.die(immediate);
if (view != null) {
view.assignParent(null);
if (deferred) {
mDyingViews.add(view);
}
}
}
看到了么，我们获取了mDector组件的ViewRootImpl，然后调用了其的die方法，通过这个方法实现Window组件的销毁流程。
boolean die(boolean immediate) {
// Make sure we do execute immediately if we are in the middle of a traversal or the damage
// done by dispatchDetachedFromWindow will cause havoc on return.
if (immediate && !mIsInTraversal) {
doDie();
return false;
}
if (!mIsDrawing) {
destroyHardwareRenderer();
} else {
Log.e(TAG, "Attempting to destroy the window while drawing!\n" +
" window=" + this + ", title=" + mWindowAttributes.getTitle());
}
mHandler.sendEmptyMessage(MSG_DIE);
return true;
}
可以看到在方法体中有调用了doDie方法，看名字应该就是真正执行window销毁工作的方法了，我们在看一下doDie方法的具体实现：
void doDie() {
checkThread();
if (LOCAL_LOGV) Log.v(TAG, "DIE in " + this + " of " + mSurface);
synchronized (this) {
if (mRemoved) {
return;
}
mRemoved = true;
if (mAdded) {
dispatchDetachedFromWindow();
}
if (mAdded && !mFirst) {
destroyHardwareRenderer();
if (mView != null) {
int viewVisibility = mView.getVisibility();
boolean viewVisibilityChanged = mViewVisibility != viewVisibility;
if (mWindowAttributesChanged || viewVisibilityChanged) {
// If layout params have been changed, first give them
// to the window manager to make sure it has the correct
// animation info.
try {
if ((relayoutWindow(mWindowAttributes, viewVisibility, false)
& WindowManagerGlobal.RELAYOUT_RES_FIRST_TIME) != 0) {
mWindowSession.finishDrawing(mWindow);
}
} catch (RemoteException e) {
}
}
mSurface.release();
}
}
mAdded = false;
}
WindowManagerGlobal.getInstance().doRemoveView(this);
}
- 可以看到方法体中，首先调用了checkThread方法，判断当前执行代码的线程，若不是主线程，则抛出异常：
void checkThread() {
if (mThread != Thread.currentThread()) {
throw new CalledFromWrongThreadException(
"Only the original thread that created a view hierarchy can touch its views.");
}
}
顺着doDie的方法往下看，又调用了dispatchDetachedFromWindow()方法，这个方法主要是销毁Window中的各中成员变量，临时变量等
void dispatchDetachedFromWindow() {
if (mView != null && mView.mAttachInfo != null) {
mAttachInfo.mTreeObserver.dispatchOnWindowAttachedChange(false);
mView.dispatchDetachedFromWindow();
}
mAccessibilityInteractionConnectionManager.ensureNoConnection();
mAccessibilityManager.removeAccessibilityStateChangeListener(
mAccessibilityInteractionConnectionManager);
mAccessibilityManager.removeHighTextContrastStateChangeListener(
mHighContrastTextManager);
removeSendWindowContentChangedCallback();
destroyHardwareRenderer();
setAccessibilityFocus(null, null);
mView.assignParent(null);
mView = null;
mAttachInfo.mRootView = null;
mSurface.release();
if (mInputQueueCallback != null && mInputQueue != null) {
mInputQueueCallback.onInputQueueDestroyed(mInputQueue);
mInputQueue.dispose();
mInputQueueCallback = null;
mInputQueue = null;
}
if (mInputEventReceiver != null) {
mInputEventReceiver.dispose();
mInputEventReceiver = null;
}
try {
mWindowSession.remove(mWindow);
} catch (RemoteException e) {
}
// Dispose the input channel after removing the window so the Window Manager
// doesn't interpret the input channel being closed as an abnormal termination.
if (mInputChannel != null) {
mInputChannel.dispose();
mInputChannel = null;
}
mDisplayManager.unregisterDisplayListener(mDisplayListener);
unscheduleTraversals();
}
可以看到在方法中调用了mView.dispatchDetachedFromWindow方法，这个方法的作用就是将mView从Window中detach出来，可以看一下这个方法的具体实现：
void dispatchDetachedFromWindow() {
AttachInfo info = mAttachInfo;
if (info != null) {
int vis = info.mWindowVisibility;
if (vis != GONE) {
onWindowVisibilityChanged(GONE);
}
}
onDetachedFromWindow();
onDetachedFromWindowInternal();
InputMethodManager imm = InputMethodManager.peekInstance();
if (imm != null) {
imm.onViewDetachedFromWindow(this);
}
ListenerInfo li = mListenerInfo;
final CopyOnWriteArrayList listeners =
li != null ? li.mOnAttachStateChangeListeners : null;
if (listeners != null && listeners.size() > 0) {
// NOTE: because of the use of CopyOnWriteArrayList, we *must* use an iterator to
// perform the dispatching. The iterator is a safe guard against listeners that
// could mutate the list by calling the various add/remove methods. This prevents
// the array from being modified while we iterate it.
for (OnAttachStateChangeListener listener : listeners) {
listener.onViewDetachedFromWindow(this);
}
}
if ((mPrivateFlags & PFLAG_SCROLL_CONTAINER_ADDED) != 0) {
mAttachInfo.mScrollContainers.remove(this);
mPrivateFlags &= ~PFLAG_SCROLL_CONTAINER_ADDED;
}
mAttachInfo = null;
if (mOverlay != null) {
mOverlay.getOverlayView().dispatchDetachedFromWindow();
}
}
其中onDetachedFromWindow方法是一个空的回调方法，这里重点看一下onDetachedFromWindowInternal方法：
protected void onDetachedFromWindowInternal() {
mPrivateFlags &= ~PFLAG_CANCEL_NEXT_UP_EVENT;
mPrivateFlags3 &= ~PFLAG3_IS_LAID_OUT;
removeUnsetPressCallback();
removeLongPressCallback();
removePerformClickCallback();
removeSendViewScrolledAccessibilityEventCallback();
stopNestedScroll();
// Anything that started animating right before detach should already
// be in its final state when re-attached.
jumpDrawablesToCurrentState();
destroyDrawingCache();
cleanupDraw();
mCurrentAnimation = null;
}
- onDetachedFromWindowInternal方法的方法体也不是特别长，都是一些调用函数，这里看一下destropDrawingCache方法，这个方法主要是销毁View的缓存Drawing，我们来看一下具体实现：
