自Android L系统发布后，Activity相关的动画API增加了好多，包括Explode, Slide等，这些动画都是在Transition框架之上运行的。
Activity的PerformCreate函数
final void performCreate(Bundle icicle) {
onCreate(icicle);
mActivityTransitionState.readState(icicle);
performCreateCommon();
}
final void performCreateCommon() {
mVisibleFromClient = !mWindow.getWindowStyle().getBoolean(
com.android.internal.R.styleable.Window_windowNoDisplay, false);
mFragments.dispatchActivityCreated();
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
}
setEnterActivityOptions(Activity activity, ActivityOptions options)方法1
public void setEnterActivityOptions(Activity activity, ActivityOptions options) {
if (activity.getWindow().hasFeature(Window.FEATURE_ACTIVITY_TRANSITIONS)
&& options != null && mEnterActivityOptions == null
&& mEnterTransitionCoordinator == null
&& options.getAnimationType() == ActivityOptions.ANIM_SCENE_TRANSITION) {
mEnterActivityOptions = options;
mIsEnterTriggered = false;
if (mEnterActivityOptions.isReturning()) {
restoreExitedViews();
int result = mEnterActivityOptions.getResultCode();
if (result != 0) {
activity.onActivityReenter(result, mEnterActivityOptions.getResultData());
}
}
}
}
framework/base/core/java/android/app/ActivityTransitionState.java
Activity.performStart()1
final void performStart() {
mActivityTransitionState.setEnterActivityOptions(this, getActivityOptions());
mFragments.noteStateNotSaved();
mCalled = false;
mFragments.execPendingActions();
mInstrumentation.callActivityOnStart(this);
if (!mCalled) {
throw new SuperNotCalledException(
"Activity " + mComponent.toShortString() +
" did not call through to super.onStart()");
}
mFragments.dispatchStart();
mFragments.reportLoaderStart();
mActivityTransitionState.enterReady(this);
}
framework/base/core/java/android/app/Activity.java
进入ActivityTransitionState.enterReady(Activity activity)1
public void enterReady(Activity activity) {
if (mEnterActivityOptions == null || mIsEnterTriggered) {
return;
}
mIsEnterTriggered = true;
mHasExited = false;
ArrayList<String> sharedElementNames = mEnterActivityOptions.getSharedElementNames();
ResultReceiver resultReceiver = mEnterActivityOptions.getResultReceiver();
if (mEnterActivityOptions.isReturning()) {
restoreExitedViews();
activity.getWindow().getDecorView().setVisibility(View.VISIBLE);
}
mEnterTransitionCoordinator = new EnterTransitionCoordinator(activity,
resultReceiver, sharedElementNames, mEnterActivityOptions.isReturning());
if (!mIsEnterPostponed) {
startEnter();
}
}
如果动画没有postponed,执行startEnter()方法
1 | private void startEnter() { if (mEnterActivityOptions.isReturning()) { if (mExitingToView != null) { mEnterTransitionCoordinator.viewInstancesReady(mExitingFrom, mExitingTo, mExitingToView); } else { mEnterTransitionCoordinator.namedViewsReady(mExitingFrom, mExitingTo); } } else { mEnterTransitionCoordinator.namedViewsReady(null, null); mEnteringNames = mEnterTransitionCoordinator.getAllSharedElementNames(); } mExitingFrom = null; mExitingTo = null; mExitingToView = null; mEnterActivityOptions = null; } |
新启动的Activity, mEnterActivityOptions.isReturning()为false ,进入else。1
public void namedViewsReady(ArrayList<String> accepted, ArrayList<String> localNames) {
triggerViewsReady(mapNamedElements(accepted, localNames));
}
private void triggerViewsReady(final ArrayMap<String, View> sharedElements) {
if (mAreViewsReady) {
return;
}
mAreViewsReady = true;
final ViewGroup decor = getDecor();
// Ensure the views have been laid out before capturing the views -- we need the epicenter.
if (decor == null || (decor.isAttachedToWindow() &&
(sharedElements.isEmpty() || !sharedElements.valueAt(0).isLayoutRequested()))) {
viewsReady(sharedElements);
} else {
decor.getViewTreeObserver()
.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
@Override
public boolean onPreDraw() {
decor.getViewTreeObserver().removeOnPreDrawListener(this);
viewsReady(sharedElements);
return true;
}
});
}
}
1 | protected void viewsReady(ArrayMap<String, View> sharedElements) { super.viewsReady(sharedElements); mIsReadyForTransition = true; hideViews(mSharedElements); if (getViewsTransition() != null && mTransitioningViews != null) { hideViews(mTransitioningViews); } if (mIsReturning) { sendSharedElementDestination(); } else { moveSharedElementsToOverlay(); } if (mSharedElementsBundle != null) { onTakeSharedElements(); } } |
上面这段代码主要有三个步骤：
hideView. 将mSharedElements中的view的alpha值设为0.
1
protected void hideViews(ArrayList<View> views) { int count = views.size(); for (int i = 0; i < count; i++) { View view = views.get(i); if (!mOriginalAlphas.containsKey(view)) { mOriginalAlphas.put(view, view.getAlpha()); } view.setAlpha(0f); } }
moveSharedElementsToOverlay. 将mSharedElements的view添加到ViewOverlay。
1
protected void moveSharedElementsToOverlay() { if (mWindow == null || !mWindow.getSharedElementsUseOverlay()) { return; } setSharedElementMatrices(); int numSharedElements = mSharedElements.size(); ViewGroup decor = getDecor(); if (decor != null) { boolean moveWithParent = moveSharedElementWithParent(); Matrix tempMatrix = new Matrix(); for (int i = 0; i < numSharedElements; i++) { View view = mSharedElements.get(i); tempMatrix.reset(); mSharedElementParentMatrices.get(i).invert(tempMatrix); GhostView.addGhost(view, decor, tempMatrix); ViewGroup parent = (ViewGroup) view.getParent(); if (moveWithParent && !isInTransitionGroup(parent, decor)) { GhostViewListeners listener = new GhostViewListeners(view, parent, decor); parent.getViewTreeObserver().addOnPreDrawListener(listener); mGhostViewListeners.add(listener); } } } }
onTakeSharedElements. 开始Transition动画。
1
private void onTakeSharedElements() { if (!mIsReadyForTransition || mSharedElementsBundle == null) { return; } final Bundle sharedElementState = mSharedElementsBundle; mSharedElementsBundle = null; OnSharedElementsReadyListener listener = new OnSharedElementsReadyListener() { @Override public void onSharedElementsReady() { final View decorView = getDecor(); if (decorView != null) { decorView.getViewTreeObserver() .addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() { @Override public boolean onPreDraw() { decorView.getViewTreeObserver().removeOnPreDrawListener(this); startTransition(new Runnable() { @Override public void run() { startSharedElementTransition(sharedElementState); } }); return false; } }); decorView.invalidate(); } } }; if (mListener == null) { listener.onSharedElementsReady(); } else { mListener.onSharedElementsArrived(mSharedElementNames, mSharedElements, listener); } }
开始执行动画1
private void startSharedElementTransition(Bundle sharedElementState) {
ViewGroup decorView = getDecor();
if (decorView == null) {
return;
}
// Remove rejected shared elements
ArrayList<String> rejectedNames = new ArrayList<String>(mAllSharedElementNames);
rejectedNames.removeAll(mSharedElementNames);
ArrayList<View> rejectedSnapshots = createSnapshots(sharedElementState, rejectedNames);
if (mListener != null) {
mListener.onRejectSharedElements(rejectedSnapshots);
}
removeNullViews(rejectedSnapshots);
startRejectedAnimations(rejectedSnapshots);
// Now start shared element transition
ArrayList<View> sharedElementSnapshots = createSnapshots(sharedElementState,
mSharedElementNames);
showViews(mSharedElements, true);
scheduleSetSharedElementEnd(sharedElementSnapshots);
ArrayList<SharedElementOriginalState> originalImageViewState =
setSharedElementState(sharedElementState, sharedElementSnapshots);
requestLayoutForSharedElements();
boolean startEnterTransition = allowOverlappingTransitions() && !mIsReturning;
boolean startSharedElementTransition = true;
setGhostVisibility(View.INVISIBLE);
scheduleGhostVisibilityChange(View.INVISIBLE);
pauseInput();
Transition transition = beginTransition(decorView, startEnterTransition,
startSharedElementTransition);
scheduleGhostVisibilityChange(View.VISIBLE);
setGhostVisibility(View.VISIBLE);
if (startEnterTransition) {
startEnterTransition(transition);
}
setOriginalSharedElementState(mSharedElements, originalImageViewState);
if (mResultReceiver != null) {
// We can't trust that the view will disappear on the same frame that the shared
// element appears here. Assure that we get at least 2 frames for double-buffering.
decorView.postOnAnimation(new Runnable() {
int mAnimations;
@Override
public void run() {
if (mAnimations++ < MIN_ANIMATION_FRAMES) {
View decorView = getDecor();
if (decorView != null) {
decorView.postOnAnimation(this);
}
} else if (mResultReceiver != null) {
mResultReceiver.send(MSG_HIDE_SHARED_ELEMENTS, null);
mResultReceiver = null; // all done sending messages.
}
}
});
}
}