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RecyclerView 局部刷新的坑，34岁程序员年薪50w

2022-03-01 14:31:19 作者：互联网

@param position 下标
@param packageName 要替换的文本名
*/
public void updateItem(int position, String packageName) {
if (position >= 0 && position < data.size()) {
data.get(position).setPackageName(packageName);
}
notifyDataSetChanged();
}

踩坑

而我们要做的是一个下载列表，在下载的callback里面我们要去更新列表的progressBar还有Button的文本：

Activity中获取到下载的callback：

@Override
public void onProgress(long finished, long total, int progress) {
XLog.e(mInfoBean.getDownLoadUrl() + “-----------||||||” + progress);
String downloadPerSize = Kits.File.getDownloadPerSize(finished, total);
mInfoBean.setDownLoadStatus(STATUS_DOWNLOADING);
mInfoBean.setDownloadPerSize(downloadPerSize);
mInfoBean.setProgress(progress);
if (isCurrentListViewItemVisible(mPosition)) {
mTestDownLoadAdapter.setProgress(progress, mPosition, downloadPerSize);
}
}

适配器中暴露的用于更新progressBar进度的方法

/**

暴露用于修改进度值的方法
@param progress
@param position
@param progressStr
*/
public void setProgress(int progress, int position, String progressStr) {
data.get(position).setProgress(progress);
data.get(position).setDownloadPerSize(progressStr);
notifyItemChanged(position);
}

适配器的onBindViewHolder()中处理数据结果

@Override
public void onBindViewHolder(final TestDownLoadHolder holder, final int position) {
final AppInfoBean appInfoBean = data.get(position);
if (appInfoBean != null) {
ILFactory.getLoader().loadNet(holder.mIvDownPic, appInfoBean.getDownLoadPic(), ImgOptions.getDefImaOptions());
holder.mPbDownProgress.setProgress(appInfoBean.getProgress());
holder.mBtDownLoad.setText(appInfoBean.getDownloadPerSize());
holder.mBtDownLoad.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (getRecItemClick() != null) {
getRecItemClick().onItemClick(position, appInfoBean, 0, holder);
}
}
});
}

}

这里我们使用的是notifyItemChanged局部刷新而不是notifyDataSetChanged。讲道理我们到了这一步就已经可以满足需求了，然而…事实不讲道理：

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-D02S7a5j-1646116102674)(https://user-gold-cdn.xitu.io/2017/10/27/72395e18c6486bb49278862724e630b4?imageView2/0/w/1280/h/960/ignore-error/1)]

一闪一闪亮晶晶

额…原谅demo画得太丑了。这里我们可以发现…为毛我的图片…一闪一闪的，亮瞎我的狗眼了。
至于为什么会闪动？
猜测：

ImageView的宽高问题，重新计算导致了闪动
更新到了ImageView，然后glide又重新加载了一次图片。
刷新到了ImageView，这个item渲染了一次。

解疑：

采用了写死宽高的方法，但是！页面还是会闪动…gif就不传了，录制好麻烦。猜测1已经否决了。

ILFactory.getLoader().loadNet(holder.mIvDownPic, appInfoBean.getDownLoadPic(), ImgOptions.getDefImaOptions());

android:src="@mipmap/ic_launcher"

重新理下，我们需要更新的是Button和progressBar，其实ImageView我们是不需要额外去更新的。

那我们的问题就聚焦在如何只更新一部分控件，其他控件不动

解决

至于怎么解决呢…扒源码：

/**

Notify any registered observers that the item at position has changed.
Equivalent to calling notifyItemChanged(position, null);.
This is an item change event, not a structural change event. It indicates that any
reflection of the data at position is out of date and should be updated.
The item at position retains the same identity.
@param position Position of the item that has changed
@see #notifyItemRangeChanged(int, int)
*/
public final void notifyItemChanged(int position) {
mObservable.notifyItemRangeChanged(position, 1);
}

/**

Notify any registered observers that the item at position has changed with an
optional payload object.
This is an item change event, not a structural change event. It indicates that any
reflection of the data at position is out of date and should be updated.
The item at position retains the same identity.
Client can optionally pass a payload for partial change. These payloads will be merged
and may be passed to adapter’s {@link #onBindViewHolder(ViewHolder, int, List)} if the
item is already represented by a ViewHolder and it will be rebound to the same
ViewHolder. A notifyItemRangeChanged() with null payload will clear all existing
payloads on that item and prevent future payload until
{@link #onBindViewHolder(ViewHolder, int, List)} is called. Adapter should not assume
that the payload will always be passed to onBindViewHolder(), e.g. when the view is not
attached, the payload will be simply dropped.
@param position Position of the item that has changed
@param payload Optional parameter, use null to identify a “full” update
@see #notifyItemRangeChanged(int, int)
*/
public final void notifyItemChanged(int position, Object payload) {
mObservable.notifyItemRangeChanged(position, 1, payload);
}

在这里我们看到一句话：

@param payload Optional parameter, use null to identify a “full” update

传入“null”就是更新全部！那我们调用的时候是传入什么呢！看下：

public final void notifyItemChanged(int position) {
mObservable.notifyItemRangeChanged(position, 1);
}

继而调用：

public void notifyItemRangeChanged(int positionStart, int itemCount) {
notifyItemRangeChanged(positionStart, itemCount, null);
}

继而调用：

public void notifyItemRangeChanged(int positionStart, int itemCount, Object payload) {
// since onItemRangeChanged() is implemented by the app, it could do anything, including
// removing itself from {@link mObservers} - and that could cause problems if
// an iterator is used on the ArrayList {@link mObservers}.
// to avoid such problems, just march thru the list in the reverse order.
for (int i = mObservers.size() - 1; i >= 0; i–) {
mObservers.get(i).onItemRangeChanged(positionStart, itemCount, payload);
}
}

[捂脸] 一个大写的null…

OK，那我们修改下我们的调用方法：

/**

暴露用于修改进度值的方法
@param progress
@param position
@param progressStr
*/
public void setProgress(int progress, int position, String progressStr) {
data.get(position).setProgress(progress);
data.get(position).setDownloadPerSize(progressStr);
notifyItemChanged(position, 1);
}

/**

暴露用于修改按钮文字值的方法
@param position
@param buttonStr
*/
public void setButtonStatus(int position, String buttonStr) {
data.get(position).setDownloadPerSize(buttonStr);
notifyItemChanged(position, 1);
}

这里我们传入了一个 “1”,这个1是随意传入的，其他值也可以。

继而我们需要重写onBindViewHolder方法如下：

@Override
public void onBindViewHolder(TestDownLoadHolder holder, int position, List payloads) {
XLog.e("--------------------------has payloads");
if (payloads.isEmpty()) {
XLog.e("--------------------------no payloads");
onBindViewHolder(holder, position);
} else {
XLog.e("--------------------------false payloads");
final AppInfoBean appInfoBean = data.get(position);
if (appInfoBean != null) {
holder.mPbDownProgress.setProgress(appInfoBean.getProgress());
holder.mBtDownLoad.setText(appInfoBean.getDownloadPerSize());
}
}
}

}
getDownloadPerSize());
holder.mBtDownLoad.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (getRecItemClick() != null) {
getRecItemClick().onItemClick(position, appInfoBean, 0, holder);
}
}
});
}

}

标签：int,holder,void,34,appInfoBean,position,50w,RecyclerView,public
来源： https://blog.csdn.net/m0_66685346/article/details/123205254