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基础上介绍怎样实现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，比方http://www.open-open.com/lib/view/open1404888098200.html。
核心类GifDrawable间隔一定时间读取下一帧数据，然后运行invalidateSelf()----》CallBack::invalidateDrawable()---》View::verifyDrawable()和View::invalidate()，该帧数据刷新流程就运行结束。
而android-gif-drawable框架眼下已支持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。
如今非常多app都支持Gif表情。但貌似还没有一个app对输入框(等)支持GIF。而基本全部的表情图片(包含Emoji)都是使用ImageSpan实现的。但默认的ImageSpan是无法支持GIF的。
參考android-gif-drawable框架中gif帧数据刷新流程，要支持GIF须要考虑并完毕以下三个操作：
1)对ImageSpan中的GifDrawable，何时设置其Callback，又何时清空该Callback，眼下TextView、ImageSpan和Spaned都没有设置Callback的地方。我们须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，须要刷新；
3)在TextView::invalidateDrawable()中实现怎样刷新TextView显示；
首先对于1)。我们參考下ImageView和TextView实现。ImageView的src drawable相应实现例如以下：
/**
* 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须要在什么时机设置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;
}
@Override
public 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);
}
@Override
public 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。仅仅能try/catch了
oldText = getText();
//首先清空全部旧GifImageSpan的callback和oldText上的GifSpanChangeWatcher
if (!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中全部GifImageSpan的callback为当前EditText
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(this);
}
//清空新text上的GifSpanChangeWatcher
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]);
}
if (mGifSpanChangeWatcher == null) {
mGifSpanChangeWatcher = new GifSpanChangeWatcher(this);
}
//设置新text上的GifSpanChangeWatcher
sp.setSpan(mGifSpanChangeWatcher, 0, text.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE | (100 << Spanned.SPAN_PRIORITY_SHIFT));
}
super.setText(text, type);
}
}
public class GifSpanChangeWatcher implements SpanWatcher, TextWatcher{
private Drawable.Callback mCallback;
public GifSpanChangeWatcher(Drawable.Callback callback) {
mCallback = callback;
}
public void onSpanChanged(Spannable buf, Object what, int s, int e, int st, int en) {
//do nothing
}
public void onSpanAdded(Spannable buf, Object what, int s, int e) {
//设置callback
if (what instanceof GifImageSpan) {
((GifImageSpan)what).getDrawable().setCallback(mCallback);
}
}
public void onSpanRemoved(Spannable buf, Object what, int s, int e) {
//清空callback
if (what instanceof GifImageSpan) {
((GifImageSpan)what).getDrawable().setCallback(null);
}
}
@Override
public void afterTextChanged(Editable s) {
if (s != null) {
s.setSpan(this, 0, s.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE | (100 << Spanned.SPAN_PRIORITY_SHIFT));
}
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
// TODO Auto-generated method stub
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
// TODO Auto-generated method stub
}
}也就是，在setText()和onSpanAdded()、onSpanRemoved()中运行操作(1)
然后，对于2)，相同參考ImageView和TextView
@Override
protected boolean verifyDrawable(Drawable dr) {
return mDrawable == dr || super.verifyDrawable(dr);
}@Override
protected boolean verifyDrawable(Drawable who) {
final boolean verified = super.verifyDrawable(who);
if (!verified && mDrawables != null) {
return who == mDrawables.mDrawableLeft || who == mDrawables.mDrawableTop ||
who == mDrawables.mDrawableRight || who == mDrawables.mDrawableBottom ||
who == mDrawables.mDrawableStart || who == mDrawables.mDrawableEnd;
}
return verified;
} 直接上代码public class GifEditText extends EditText {
private GifImageSpan getImageSpan(Drawable drawable) {
GifImageSpan imageSpan = null;
CharSequence text = getText();
if (!TextUtils.isEmpty(text)) {
if (text instanceof Spanned) {
Spanned spanned = (Spanned) text;
GifImageSpan[] spans = spanned.getSpans(0, text.length(), GifImageSpan.class);
if (spans != null && spans.length > 0) {
for (GifImageSpan span : spans) {
if (drawable == span.getDrawable()) {
imageSpan = span;
}
}
}
}
}
return imageSpan;
}
}getImageSpan()方法通过getSpans()获取全部的GifImageSpan。然后对照drawable，返回对应的GifImageSpan。最后。操作3）更新View显示。相同參考下TextView
@Override
public void invalidateDrawable(Drawable drawable) {
if (verifyDrawable(drawable)) {
final Rect dirty = drawable.getBounds();
int scrollX = mScrollX;
int scrollY = mScrollY;
// IMPORTANT: The coordinates below are based on the coordinates computed
// for each compound drawable in onDraw(). Make sure to update each section
// accordingly.
final TextView.Drawables drawables = mDrawables;
if (drawables != null) {
if (drawable == drawables.mDrawableLeft) {
final int compoundPaddingTop = getCompoundPaddingTop();
final int compoundPaddingBottom = getCompoundPaddingBottom();
final int vspace = mBottom - mTop - compoundPaddingBottom - compoundPaddingTop;
scrollX += mPaddingLeft;
scrollY += compoundPaddingTop + (vspace - drawables.mDrawableHeightLeft) / 2;
} else if (drawable == drawables.mDrawableRight) {
final int compoundPaddingTop = getCompoundPaddingTop();
final int compoundPaddingBottom = getCompoundPaddingBottom();
final int vspace = mBottom - mTop - compoundPaddingBottom - compoundPaddingTop;
scrollX += (mRight - mLeft - mPaddingRight - drawables.mDrawableSizeRight);
scrollY += compoundPaddingTop + (vspace - drawables.mDrawableHeightRight) / 2;
} else if (drawable == drawables.mDrawableTop) {
final int compoundPaddingLeft = getCompoundPaddingLeft();
final int compoundPaddingRight = getCompoundPaddingRight();
final int hspace = mRight - mLeft - compoundPaddingRight - compoundPaddingLeft;
scrollX += compoundPaddingLeft + (hspace - drawables.mDrawableWidthTop) / 2;
scrollY += mPaddingTop;
} else if (drawable == drawables.mDrawableBottom) {
final int compoundPaddingLeft = getCompoundPaddingLeft();
final int compoundPaddingRight = getCompoundPaddingRight();
final int hspace = mRight - mLeft - compoundPaddingRight - compoundPaddingLeft;
scrollX += compoundPaddingLeft + (hspace - drawables.mDrawableWidthBottom) / 2;
scrollY += (mBottom - mTop - mPaddingBottom - drawables.mDrawableSizeBottom);
}
}
invalidate(dirty.left + scrollX, dirty.top + scrollY,
dirty.right + scrollX, dirty.bottom + scrollY);
}
}计算compoundDrawable位置栏，然后运行invalidate。对于GifEditText貌似也能够类似操作，依据GifImageSpan的start、end计算其位置栏，然后运行invalidate()。只是计算过程太过复杂了。只是android4.4的TextView提供这种方法void invalidateRegion(int start, int end, boolean invalidateCursor) 方法用于刷新start和end之间的区域，但还是蛮复杂的看的人眼花缭乱。研究了下这种方法终于是由谁调用的。
invalidateRegion()<<---invalidateCursor()<<---spanChange()<<---ChangeWatcher::onSpanChanged()、ChangeWatcher::onSpanAdded()、ChangeWatcher::onSpanRemoved()
也就是说，仅仅要TextView内容中span发生变化都会触发invalidateRegion()来刷新相应区域和cursor。
@Override
public void invalidateDrawable(Drawable drawable) {
GifImageSpan imageSpan = getImageSpan(drawable);
Log.e("", "invalidateDrawable imageSpan:" + imageSpan);
if (imageSpan != null) {
CharSequence text = getText();
if (!TextUtils.isEmpty(text)) {
if (text instanceof Editable) {
Log.e("", "invalidateDrawable Editable:");
Editable editable = (Editable)text;
int start = editable.getSpanStart(imageSpan);
int end = editable.getSpanEnd(imageSpan);
int flags = editable.getSpanFlags(imageSpan);
editable.setSpan(imageSpan, start, end, flags);
}
}
} else {
super.invalidateDrawable(drawable);
}
}直接又一次设置该ImageSpan就可以触发ChangeWatcher::onSpanChanged()回调。也就会马上刷新其区域和cursor。大功告成。执行ok。
上面是对EditText的实现，针对TextView实现略微有点差别
public class GifSpanTextView extends GifTextView {
private GifSpanChangeWatcher mGifSpanChangeWatcher;
public GifSpanTextView(Context context) {
super(context);
initGifSpanChangeWatcher();
}
public GifSpanTextView(Context context, AttributeSet attrs) {
super(context, attrs);
initGifSpanChangeWatcher();
}
public GifSpanTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initGifSpanChangeWatcher();
}
private void initGifSpanChangeWatcher() {
mGifSpanChangeWatcher = new GifSpanChangeWatcher(this);
addTextChangedListener(mGifSpanChangeWatcher);
}
@Override
public void setText(CharSequence text, BufferType type) {
type = BufferType.EDITABLE;
CharSequence oldText = getText();
if (!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]);
}
}
if (!TextUtils.isEmpty(text) && text instanceof Spannable) {
Spannable sp = (Spannable) text;
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(this);
}
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]);
}
if (mGifSpanChangeWatcher == null) {
mGifSpanChangeWatcher = new GifSpanChangeWatcher(this);;
}
sp.setSpan(mGifSpanChangeWatcher, 0, text.length(), Spanned.SPAN_INCLUSIVE_INCLUSIVE | (100 << Spanned.SPAN_PRIORITY_SHIFT));
}
super.setText(text, type);
}
private GifImageSpan getImageSpan(Drawable drawable) {
GifImageSpan imageSpan = null;
CharSequence text = getText();
if (!TextUtils.isEmpty(text)) {
if (text instanceof Spanned) {
Spanned spanned = (Spanned) text;
GifImageSpan[] spans = spanned.getSpans(0, text.length(), GifImageSpan.class);
if (spans != null && spans.length > 0) {
for (GifImageSpan span : spans) {
if (drawable == span.getDrawable()) {
imageSpan = span;
}
}
}
}
}
return imageSpan;
}
@Override
public void invalidateDrawable(Drawable drawable) {
GifImageSpan imageSpan = getImageSpan(drawable);
if (imageSpan != null) {
CharSequence text = getText();
if (!TextUtils.isEmpty(text)) {
if (text instanceof Editable) {
Editable editable = (Editable)text;
int start = editable.getSpanStart(imageSpan);
int end = editable.getSpanEnd(imageSpan);
int flags = editable.getSpanFlags(imageSpan);
editable.removeSpan(imageSpan);
editable.setSpan(imageSpan, start, end, flags);
}
}
} else {
super.invalidateDrawable(drawable);
}
}
}设置其android:editable="true"或正上方setText(CharSequence text, BufferType type)将type设置BufferType.EDITABLE。