AbstractDraweeController.submitRequest()源碼分析 續
這部分的邏輯之前已經分析了一部分,在此我們分析一下關於回調處理的部分
……
1. 獲取到數據源
2. 註冊數據源的觀察者(這裏使用的回調是mUiThreadImmediateExecutor–>ui的線程池,關於這個線程池標記爲Q8,這個是很好的一個封裝,將UI線程封裝爲了線程池)
3. 對於返回的數據結果的處理體現在接口中DataSubscriber
protected void submitRequest() {
mEventTracker.recordEvent(Event.ON_DATASOURCE_SUBMIT);
getControllerListener().onSubmit(mId, mCallerContext);
mSettableDraweeHierarchy.setProgress(0, true);
mIsRequestSubmitted = true;
mHasFetchFailed = false;
mDataSource = getDataSource();
if (FLog.isLoggable(FLog.VERBOSE)) {
FLog.v(
TAG,
"controller %x %s: submitRequest: dataSource: %x",
System.identityHashCode(this),
mId,
System.identityHashCode(mDataSource));
}
final String id = mId;
final boolean wasImmediate = mDataSource.hasResult();
final DataSubscriber<T> dataSubscriber =
new BaseDataSubscriber<T>() {
@Override
public void onNewResultImpl(DataSource<T> dataSource) {
// isFinished must be obtained before image, otherwise we might set intermediate result
// as final image.
boolean isFinished = dataSource.isFinished();
float progress = dataSource.getProgress();
T image = dataSource.getResult();
if (image != null) {
onNewResultInternal(id, dataSource, image, progress, isFinished, wasImmediate);
} else if (isFinished) {
onFailureInternal(id, dataSource, new NullPointerException(), /* isFinished */ true);
}
}
@Override
public void onFailureImpl(DataSource<T> dataSource) {
onFailureInternal(id, dataSource, dataSource.getFailureCause(), /* isFinished */ true);
}
@Override
public void onProgressUpdate(DataSource<T> dataSource) {
boolean isFinished = dataSource.isFinished();
float progress = dataSource.getProgress();
onProgressUpdateInternal(id, dataSource, progress, isFinished);
}
};
mDataSource.subscribe(dataSubscriber, mUiThreadImmediateExecutor);
}
再看回調的相關方法之前,先看看BaseDataSubscriber的相關類的繼承體系
這個的設計方式與Consumer的設計模式類似,都是先是一個接口,然後抽象的一個實現Abstract***類中實現這些接口,然後暴露出相關的實現方法impl,這種設計的方式有很多好處,很值得我們借鑑,實現了面向接口的編程,同時,通用的邏輯又在抽象類中得以實現,接口相關的內容供外界調用,Impl的相關方法供內部實現.
BaseDataSubscriber類的源碼
@Override
public void onNewResult(DataSource<T> dataSource) {
try {
onNewResultImpl(dataSource);
} finally {
if (dataSource.isFinished()) {
dataSource.close();
}
}
}
@Override
public void onFailure(DataSource<T> dataSource) {
try {
onFailureImpl(dataSource);
} finally {
dataSource.close();
}
}
@Override
public void onCancellation(DataSource<T> dataSource) {
}
@Override
public void onProgressUpdate(DataSource<T> dataSource) {
}
protected abstract void onNewResultImpl(DataSource<T> dataSource);
protected abstract void onFailureImpl(DataSource<T> dataSource);
回到我們的正題,查看AbstractDraweeController的匿名BaseDataSubscriber實現類
* 匿名BaseDataSubscriber實現類相關源碼*
還是以處理成功爲例,這裏會調用AbstractDraweeController的onNewResultInternal方法
new BaseDataSubscriber<T>() {
@Override
public void onNewResultImpl(DataSource<T> dataSource) {
// isFinished must be obtained before image, otherwise we might set intermediate result
// as final image.
boolean isFinished = dataSource.isFinished();
float progress = dataSource.getProgress();
T image = dataSource.getResult();
if (image != null) {
onNewResultInternal(id, dataSource, image, progress, isFinished, wasImmediate);
} else if (isFinished) {
onFailureInternal(id, dataSource, new NullPointerException(), /* isFinished */ true);
}
}
@Override
public void onFailureImpl(DataSource<T> dataSource) {
onFailureInternal(id, dataSource, dataSource.getFailureCause(), /* isFinished */ true);
}
@Override
public void onProgressUpdate(DataSource<T> dataSource) {
boolean isFinished = dataSource.isFinished();
float progress = dataSource.getProgress();
onProgressUpdateInternal(id, dataSource, progress, isFinished);
}
AbstractDraweeController.onNewResultInternal() 源碼分析
邏輯如下:
1. 檢查是否是自己想要的結果,如果不是,直接釋放資源(感覺這塊像是在fix bug 一樣,沒有注意到這塊爲何會如此處理,查看代碼說是因爲後續還是會返回之前的一些結果,所以這裏做了這樣的判斷)
2. 根據返回的image信息,生成drawable
3. 如果是已經請求完成的信息,便直接將mDataSource設置爲null(個人有點疑惑,命名在release的時候,會釋放dataSource的信息,這裏卻直接設置爲空,可能是爲了第一步的資源檢查或者說單純的釋放引用,讓內存及時回收,如果有理解的請留言回覆我,感謝)
4. 將drawable對象交給hierarchy來處理
5. 釋放drawable的相關信息(這裏指的是緩存之類的信息,爲了節省內存空間,而沒有釋放drawble)
private void onNewResultInternal(
String id,
DataSource<T> dataSource,
@Nullable T image,
float progress,
boolean isFinished,
boolean wasImmediate) {
// ignore late callbacks (data source that returned the new result is not the one we expected)
if (!isExpectedDataSource(id, dataSource)) {
logMessageAndImage("ignore_old_datasource @ onNewResult", image);
releaseImage(image);
dataSource.close();
return;
}
mEventTracker.recordEvent(
isFinished ? Event.ON_DATASOURCE_RESULT : Event.ON_DATASOURCE_RESULT_INT);
// create drawable
Drawable drawable;
try {
drawable = createDrawable(image);
} catch (Exception exception) {
logMessageAndImage("drawable_failed @ onNewResult", image);
releaseImage(image);
onFailureInternal(id, dataSource, exception, isFinished);
return;
}
T previousImage = mFetchedImage;
Drawable previousDrawable = mDrawable;
mFetchedImage = image;
mDrawable = drawable;
try {
// set the new image
if (isFinished) {
logMessageAndImage("set_final_result @ onNewResult", image);
mDataSource = null;
mSettableDraweeHierarchy.setImage(drawable, 1f, wasImmediate);
getControllerListener().onFinalImageSet(id, getImageInfo(image), getAnimatable());
// IMPORTANT: do not execute any instance-specific code after this point
} else {
logMessageAndImage("set_intermediate_result @ onNewResult", image);
mSettableDraweeHierarchy.setImage(drawable, progress, wasImmediate);
getControllerListener().onIntermediateImageSet(id, getImageInfo(image));
// IMPORTANT: do not execute any instance-specific code after this point
}
} finally {
if (previousDrawable != null && previousDrawable != drawable) {
releaseDrawable(previousDrawable);
}
if (previousImage != null && previousImage != image) {
logMessageAndImage("release_previous_result @ onNewResult", previousImage);
releaseImage(previousImage);
}
}
}
在這裏我們最關心的就是drawable交給hierarchy後是如何處理的
那就繼續跟蹤,
GenericDraweeHierarchy.setImage()
@Override
public void setImage(Drawable drawable, float progress, boolean immediate) {
drawable = maybeApplyRoundingBitmapOnly(mRoundingParams, mResources, drawable);
drawable.mutate();
mActualImageSettableDrawable.setDrawable(drawable);
mFadeDrawable.beginBatchMode();
fadeOutBranches();
fadeInLayer(mActualImageIndex);
setProgress(progress);
if (immediate) {
mFadeDrawable.finishTransitionImmediately();
}
mFadeDrawable.endBatchMode();
}
其實在這裏面完成了圖像的展示,但是單純的如此查看這段邏輯,我們還是會感覺到有點迷惑,只是發現了drawable的一些變化,然後就沒有了,那麼處理的邏輯在哪裏呢?其實這個是drawable的強大之處(爲什麼強大,大家可以先看看google android的官方網站上關於drawable的介紹以及再看看鴻洋大神關於drawable的一些案例介紹http://blog.csdn.net/lmj623565791/article/details/43752383),fresco自己又實現了一套drawable的繼承體系,專門來處理ui上的一些變化效果,,接下來我也會提及一部分這方面的知識,便於大家理解.drawable的部分插敘完成後,我們繼續分析Hierachy的相關知識
下篇鏈接:Fresco 源碼分析(四) 後臺數據返回到前臺的處理 - Drawable體系的介紹(1)(http://blog.csdn.net/IEYUDEYINJI/article/details/48879647)
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