# Drawable Animation ## 幀動畫使用 ### animalist.xml ``` <?xml version="1.0" encoding="utf-8"?> <animation-list xmlns:android="http://schemas.android.com/apk/res/android" android:oneshot="false"> <item android:drawable="@mipmap/c_1" android:duration="50" /> <item android:drawable="@mipmap/c_2" android:duration="50" /> <!-- 省略... --> <item android:drawable="@mipmap/circle_19" android:duration="50" /> <item android:drawable="@mipmap/circle_20" android:duration="50" /> </animation-list> ``` ### layout.xml ``` <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" tools:context="com.ansen.frameanimation.sample.MainActivity"> <ImageView android:id="@+id/image" android:layout_width="wrap_content" android:layout_height="wrap_content" android:src="@drawable/animlist" /> </LinearLayout> ``` ### java類使用 ``` ImageView image = (ImageView) findViewById(R.id.image); AnimationDrawable animationDrawable = (AnimationDrawable) image.getDrawable(); animationDrawable.start(); ``` ## DrawableAnimation流程圖  ## 幀動畫代碼執行過程 ### start ``` public class AnimationDrawable extends DrawableContainer implements Runnable, Animatable { /***代碼部分省略***/ @Override public void start() { mAnimating = true; if (!isRunning()) { // Start from 0th frame. setFrame(0, false, mAnimationState.getChildCount() > 1 || !mAnimationState.mOneShot); } } //設置當前展示第幾幀 private void setFrame(int frame, boolean unschedule, boolean animate) { if (frame >= mAnimationState.getChildCount()) { return; } mAnimating = animate; mCurFrame = frame; selectDrawable(frame); //如果取消下一幀任務，或者這已經是當前最后一幀，則取消當幀動畫任務 if (unschedule || animate) { unscheduleSelf(this); } if (animate) { // Unscheduling may have clobbered these values; restore them mCurFrame = frame; mRunning = true; scheduleSelf(this, SystemClock.uptimeMillis() + mAnimationState.mDurations[frame]); } } //安排動畫繪制任務 public void scheduleSelf(Runnable what, long when) { //該Callback是當前AnimationDrawable綁定的View final Callback callback = getCallback(); //判斷當前綁定的View是否被銷毀 if (callback != null) { callback.scheduleDrawable(this, what, when); } } } ``` ### scheduleDrawable - [ViewRootImpl的獨白，我不是一個View(布局篇)](https://blog.csdn.net/stven_king/article/details/78775166) - [Android系統的編舞者Choreographer](https://blog.csdn.net/stven_king/article/details/80098845) ``` public class View implements Drawable.Callback, KeyEvent.Callback, AccessibilityEventSource { /***部分代碼省略***/ @Override public void scheduleDrawable(Drawable who, Runnable what, long when) { if (verifyDrawable(who) && what != null) { final long delay = when - SystemClock.uptimeMillis(); if (mAttachInfo != null) { //請求Vsync信號同步 mAttachInfo.mViewRootImpl.mChoreographer.postCallbackDelayed( Choreographer.CALLBACK_ANIMATION, what, who, Choreographer.subtractFrameDelay(delay)); } else { ViewRootImpl.getRunQueue().postDelayed(what, delay); } } } } ``` ### run ``` public class AnimationDrawable extends DrawableContainer implements Runnable, Animatable { /***代碼部分省略***/ //Choreographer的Vsync同步回調 @Override public void run() { nextFrame(false); } //繼續執行下一幀動畫 private void nextFrame(boolean unschedule) { int nextFrame = mCurFrame + 1; final int numFrames = mAnimationState.getChildCount(); final boolean isLastFrame = mAnimationState.mOneShot && nextFrame >= (numFrames - 1); // Loop if necessary. One-shot animations should never hit this case. if (!mAnimationState.mOneShot && nextFrame >= numFrames) { nextFrame = 0; } //新一輪的循環又開始 setFrame(nextFrame, unschedule, !isLastFrame); } } ``` ## 其他 ### CallBack的綁定 ``` public class View implements Drawable.Callback, KeyEvent.Callback, AccessibilityEventSource { /***部分代碼省略***/ @Deprecated public void setBackgroundDrawable(Drawable background) { /***部分代碼省略***/ //清除之前的背景 if (mBackground != null) { mBackground.setCallback(null); unscheduleDrawable(mBackground); } if (background != null) { /***部分代碼省略***/ //Drawable綁定當前的View background.setCallback(this); if (background.isStateful()) { background.setState(getDrawableState()); } background.setVisible(getVisibility() == VISIBLE, false); mBackground = background; applyBackgroundTint(); if ((mPrivateFlags & PFLAG_SKIP_DRAW) != 0) { mPrivateFlags &= ~PFLAG_SKIP_DRAW; requestLayout = true; } } else { /***部分代碼省略***/ } computeOpaqueFlags(); if (requestLayout) { requestLayout(); } mBackgroundSizeChanged = true; invalidate(true); } } ``` ### 內存方面 幀動畫相比較屬性動畫而言可能會出現OOM，因為在家的每一幀的圖片會占用很大的內存空間。 幀動畫不會出現內存泄露的問題： ``` public abstract class Drawable { /***部分代碼省略***/ //持有當前View的弱引用，當View回收之后，沒辦法繼續下一幀的展示 private WeakReference<Callback> mCallback = null; public Callback getCallback() { if (mCallback != null) { return mCallback.get(); } return null; } } ```