前言
相信童鞋们都用过RecyclerView，假设说要我们做一个列表更新Item的功能，相信大部分同学都会这么写的：
/**
* 更新列表数据某一项的packageName
*
* @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：
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。
- 注释掉
在xml中写入ILFactory.getLoader().loadNet(holder.mIvDownPic, appInfoBean.getDownLoadPic(), ImgOptions.getDefImaOptions());
测试下，结果还是会闪动...那猜测2又不对了！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 <code>position</code> has changed.
* Equivalent to calling <code>notifyItemChanged(position, null);</code>.
*
* <p>This is an item change event, not a structural change event. It indicates that any
* reflection of the data at <code>position</code> is out of date and should be updated.
* The item at <code>position</code> retains the same identity.</p>
*
* @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 <code>position</code> has changed with an
* optional payload object.
*
* <p>This is an item change event, not a structural change event. It indicates that any
* reflection of the data at <code>position</code> is out of date and should be updated.
* The item at <code>position</code> retains the same identity.
* </p>
*
* <p>
* 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<Object> 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());
}
}
}
@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);
}
}
});
}
}可以看到我们这里有2个onBindViewHolder方法，在第一个OnBindViewHolder里面我们需要判断下payloads是否为空，如果为空的话执行默认的OnBindViewHolder方法，如果不为空的话，执行我们自己的局部刷新方法
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());
}
}贴下完整的适配器方法：
/**
* @author Ly
* @date 2017/10/26
*/
public class TestDownLoadAdapter extends SimpleRecAdapter<AppInfoBean, TestDownLoadAdapter.TestDownLoadHolder> {
public TestDownLoadAdapter(Context context) {
super(context);
}
@Override
public TestDownLoadHolder newViewHolder(View itemView) {
return new TestDownLoadHolder(itemView);
}
/**
* 更新列表数据某一项的packageName
*
* @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();
}
/**
* 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);
}
@Override
public int getLayoutId() {
return R.layout.item_test_down;
}
@Override
public void onBindViewHolder(TestDownLoadHolder holder, int position, List<Object> 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());
}
}
}
@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);
}
}
});
}
}
/**
* 开启下载
*
* @param position
*/
public void doStartDownLoad(int position) {
}
/**
* 开启安装
*
* @param position
*/
public void doInstall(int position) {
}
/**
* 开启停止下载
*
* @param position
*/
public void doPauseDownLoad(int position) {
}
public static class TestDownLoadHolder extends RecyclerView.ViewHolder {
@BindView(R.id.iv_down_pic)
public ImageView mIvDownPic;
@BindView(R.id.pb_down_progress)
public ProgressBar mPbDownProgress;
@BindView(R.id.bt_down_load)
public Button mBtDownLoad;
TestDownLoadHolder(View view) {
super(view);
ButterKnife.bind(this, view);
}
}
}Ok，运行，跑下效果为：
确实是解决了。
