Bitmap猎人
这个名字起哦真是形象：专为搜寻Bitmap的猎人。
Paste_Image.png
BitmapHunter 从哪里来？
还记得action被分发，被执行的地方么？
void performSubmit(Action action, boolean dismissFailed) {
------
hunter = forRequest(action.getPicasso(), this, cache, stats, action);// create
hunter.future = service.submit(hunter);// 执行
hunterMap.put(action.getKey(), hunter);// 该搜寻任务，记录在案！
-----
}
hunter的构造：
Paste_Image.png
只要Picasso中有一个RequestHandler能处理 该request的，就利用该handler来构建 BitmapHunter！
Picasso提供的RequestHandler：
Paste_Image.png
RequestHandler这个抽象类
Paste_Image.png
它的一些实现类：
Paste_Image.png
一些RequestHandler具体的 对请求能否处理的实现：
能否处理这个请求：注意根据请求的uri所采用的协议来实现的。
- NetworkRequestHandler
@Override public boolean canHandleRequest(Request data) {
String scheme = data.uri.getScheme();
return (SCHEME_HTTP.equals(scheme) || SCHEME_HTTPS.equals(scheme));
}
- FileRequestHandler
@Override public boolean canHandleRequest(Request data) {
return SCHEME_FILE.equals(data.uri.getScheme());
}
- AssetRequestHandler
@Override public boolean canHandleRequest(Request data) {
Uri uri = data.uri;
return (SCHEME_FILE.equals(uri.getScheme())
&& !uri.getPathSegments().isEmpty() && ANDROID_ASSET.equals(uri.getPathSegments().get(0)));
}
一些RequestHandler具体的 对请求的资源加载的实现：
- NetworkRequestHandler
Paste_Image.png
- FileRequestHandler
Paste_Image.png
- AssetRequestHandler
Paste_Image.png
有意思的是：对网络图片的加载 Picasso抽象了一个Downloader
具体的加载由OkHttp来实现的：
Paste_Image.png
他是一个Runnable
直接 run
Paste_Image.png
hunt():
Bitmap hunt() throws IOException {
Bitmap bitmap = null;
// 1. load bitmap from memery
if (shouldReadFromMemoryCache(memoryPolicy)) {
bitmap = cache.get(key);
if (bitmap != null) {
stats.dispatchCacheHit();
loadedFrom = MEMORY;
if (picasso.loggingEnabled) {
log(OWNER_HUNTER, VERB_DECODED, data.logId(), "from cache");
}
return bitmap;
}
}
// 2. load from requestHandler
data.networkPolicy = retryCount == 0 ? NetworkPolicy.OFFLINE.index : networkPolicy;
RequestHandler.Result result = requestHandler.load(data, networkPolicy);
if (result != null) {
loadedFrom = result.getLoadedFrom();
exifOrientation = result.getExifOrientation();
bitmap = result.getBitmap();
// If there was no Bitmap then we need to decode it from the stream.
if (bitmap == null) {
InputStream is = result.getStream();
try {
bitmap = decodeStream(is, data);
} finally {
Utils.closeQuietly(is);
}
}
}
if (bitmap != null) {
if (picasso.loggingEnabled) {
log(OWNER_HUNTER, VERB_DECODED, data.logId());
}
stats.dispatchBitmapDecoded(bitmap);
if (data.needsTransformation() || exifOrientation != 0) {
synchronized (DECODE_LOCK) {
if (data.needsMatrixTransform() || exifOrientation != 0) {
bitmap = transformResult(data, bitmap, exifOrientation);
if (picasso.loggingEnabled) {
log(OWNER_HUNTER, VERB_TRANSFORMED, data.logId());
}
}
if (data.hasCustomTransformations()) {
bitmap = applyCustomTransformations(data.transformations, bitmap);
if (picasso.loggingEnabled) {
log(OWNER_HUNTER, VERB_TRANSFORMED, data.logId(), "from custom transformations");
}
}
}
if (bitmap != null) {
stats.dispatchBitmapTransformed(bitmap);
}
}
}
return bitmap;
}
requestHandler 是什么？
