android-gif-drawable(https://github.com/koral–/android-gif-drawable/releases)开源项目—是一个蛮不错的android gif显示实现.本文在android-gif-drawable基础上介绍如何实现TextView、EditText上展示Gif动态图。
网上有蛮多介绍这个框架使用的文章，比如。
核心类GifDrawable间隔一定时间读取下一帧数据，然后执行invalidateSelf()—-》CallBack::invalidateDrawable()—》View::verifyDrawable()和View::invalidate()，该帧数据刷新流程就执行结束。
而android-gif-drawable框架目前已支持GifImageView、GifImageButton、GifTextView三个android widget，且GifImageView、GifImageButton支持对src和backgroud设置Gif，而GifTextView对支持backgroud和CompoundDrawables设置Gif。
现在很多app都支持Gif表情，但貌似还没有一个app对输入框(等)支持GIF。而基本所有的表情图片(包括Emoji)都是使用ImageSpan实现的。但默认的ImageSpan是无法支持GIF的。
参考android-gif-drawable框架中gif帧数据刷新流程，要支持GIF需要考虑并完成下面三个操作：
1)对ImageSpan中的GifDrawable，何时设置其Callback，又何时清空该Callback，目前TextView、ImageSpan和Spaned都没有设置Callback的地方，我们需要找一个合适的地方将TextView设置为GifDrawable的Callback；
2)在TextView::invalidateDrawable()中实现对GifDrawable的校验，即验证该GifDrawable是TextView的内容，需要刷新；
3)在TextView::invalidateDrawable()中实现如何刷新TextView显示；
首先对于1)，我们参考下ImageView和TextView实现。ImageView的src drawable对应实现如下：
/*** Sets a drawable as the content of this ImageView.** @param drawable The drawable to set*/public void setImageDrawable(Drawable drawable) {if (mDrawable != drawable) {…updateDrawable(drawable);…}}private void updateDrawable(Drawable d) {if (mDrawable != null) {mDrawable.setCallback(null);unscheduleDrawable(mDrawable);}mDrawable = d;if (d != null) {d.setCallback(this);if (d.isStateful()) {d.setState(getDrawableState());}d.setLevel(mLevel);d.setLayoutDirection(getLayoutDirection());d.setVisible(getVisibility() == VISIBLE, true);mDrawableWidth = d.getIntrinsicWidth();mDrawableHeight = d.getIntrinsicHeight();applyColorMod();configureBounds();} else {mDrawableWidth = mDrawableHeight = -1;}}也就是说，ImageView在设置其src时，清空旧mDrawable的callback，然后将新设置的src drawable的callback设置为ImageView本身。
同理，TextView对于CompoundDrawables的callback处理也是在setCompoundDrawables()时。
而ImageSpan需要在什么时机设置GifDrawable的callback呢，
public class GifImageSpan extends ImageSpan{private Drawable mDrawable = null;public GifImageSpan(Drawable d) {super(d);mDrawable = d;}public GifImageSpan(Drawable d, int verticalAlignment) {super(d, verticalAlignment);mDrawable = d;}@Overridepublic Drawable getDrawable() {return mDrawable;}}public class GifEditText extends EditText {private GifSpanChangeWatcher mGifSpanChangeWatcher;public GifEditText(Context context) {super(context);initGifSpanChangeWatcher();}public GifEditText(Context context, AttributeSet attrs) {super(context, attrs);initGifSpanChangeWatcher();}public GifEditText(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);initGifSpanChangeWatcher();}private void initGifSpanChangeWatcher() {mGifSpanChangeWatcher = new GifSpanChangeWatcher(this);addTextChangedListener(mGifSpanChangeWatcher);}@Overridepublic void setText(CharSequence text, BufferType type) {CharSequence oldText = null;try {//EditText的默认mText为""，是一个String，但getText()强转为Editable，尼玛，只能try/catch了oldText = getText();//首先清空所有旧GifImageSpan的callback和oldText上的GifSpanChangeWatcherif (!TextUtils.isEmpty(oldText) && oldText instanceof Spannable) {Spannable sp = (Spannable) oldText;final GifImageSpan[] spans = sp.getSpans(0, sp.length(), GifImageSpan.class);final int count = spans.length;for (int i = 0; i < count; i++) {spans[i].getDrawable().setCallback(null);}final GifSpanChangeWatcher[] watchers = sp.getSpans(0, sp.length(), GifSpanChangeWatcher.class);final int count1 = watchers.length;for (int i = 0; i < count1; i++) {sp.removeSpan(watchers[i]);}}} catch (Exception e) {}if (!TextUtils.isEmpty(text)) {if (!(text instanceof Editable)) {text = new SpannableStringBuilder(text);}}if (!TextUtils.isEmpty(text) && text instanceof Spannable) {Spannable sp = (Spannable) text;//设置新text中所有GifImageSpan的callback为当前EditTextfinal GifImageSpan[] spans = sp.getSpans(0, sp.length(), GifImageSpan.class);final int count = spans.length;for (int i = 0; i < count; i++) {spans[i].getDrawable().setCallback(this);}//清空新text上的GifSpanChangeWatcherfinal GifSpanChangeWatcher[] watchers = sp.getSpans(0, sp.length(), GifSpanChangeWatcher.class);final int count1 = watchers.length;for (int i = 0; i < count1; i++) {sp.removeSpan(watchers[i]);}if (mGifSpanChangeWatcher == null) {mGifSpanChangeWatcher = new GifSpanChangeWatcher(this);}//设置新text上的GifSpanChangeWatchersp.setSpan(mGifSpanChangeWatcher, 0, text.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE | (100 << Spanned.SPAN_PRIORITY_SHIFT));}super.setText(text, type);}}
昨晚多几分钟的准备，今天少几小时的麻烦。
