前言
相信童鞋們都用過(guò)RecyclerView，假設(shè)說(shuō)要我們做一個(gè)列表更新Item的功能，相信大部分同學(xué)都會(huì)這么寫(xiě)的：
/**
* 更新列表數(shù)據(jù)某一項(xiàng)的packageName
*
* @param position 下標(biāo)
* @param packageName 要替換的文本名
*/
public void updateItem(int position, String packageName) {
if (position >= 0 && position < data.size()) {
data.get(position).setPackageName(packageName);
}
notifyDataSetChanged();
}
踩坑
而我們要做的是一個(gè)下載列表，在下載的callback里面我們要去更新列表的progressBar還有Button的文本：
Activity中獲取到下載的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);
}
}
適配器中暴露的用于更新progressBar進(jìn)度的方法
/**
* 暴露用于修改進(jìn)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);
}
適配器的onBindViewHolder()中處理數(shù)據(jù)結(jié)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);
}
}
});
}
}
這里我們使用的是notifyItemChanged局部刷新而不是notifyDataSetChanged。講道理我們到了這一步就已經(jīng)可以滿足需求了，然而...事實(shí)不講道理：
一閃一閃亮晶晶
額...原諒demo畫(huà)得太丑了。這里我們可以發(fā)現(xiàn)....為毛我的圖片...一閃一閃的，亮瞎我的狗眼了。
至于為什么會(huì)閃動(dòng)？
猜測(cè)：
- ImageView的寬高問(wèn)題，重新計(jì)算導(dǎo)致了閃動(dòng)
- 更新到了ImageView，然后glide又重新加載了一次圖片。
- 刷新到了ImageView，這個(gè)item渲染了一次。
解疑：
- 采用了寫(xiě)死寬高的方法，但是！頁(yè)面還是會(huì)閃動(dòng)...gif就不傳了，錄制好麻煩。猜測(cè)1已經(jīng)否決了。
- 注釋掉
ILFactory.getLoader().loadNet(holder.mIvDownPic, appInfoBean.getDownLoadPic(), ImgOptions.getDefImaOptions());
在xml中寫(xiě)入
android:src="@mipmap/ic_launcher"
測(cè)試下，結(jié)果還是會(huì)閃動(dòng)...那猜測(cè)2又不對(duì)了！
- 重新理下，我們需要更新的是Button和progressBar，其實(shí)ImageView我們是不需要額外去更新的。
那我們的問(wèn)題就聚焦在如何只更新一部分控件，其他控件不動(dòng)
解決
至于怎么解決呢...扒源碼：
/**
* 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);
}
在這里我們看到一句話：
@param payload Optional parameter, use null to identify a "full" update
傳入“null”就是更新全部！那我們調(diào)用的時(shí)候是傳入什么呢！看下：
public final void notifyItemChanged(int position) {
mObservable.notifyItemRangeChanged(position, 1);
}
繼而調(diào)用：
public void notifyItemRangeChanged(int positionStart, int itemCount) {
notifyItemRangeChanged(positionStart, itemCount, null);
}
繼而調(diào)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);
}
}
[捂臉] 一個(gè)大寫(xiě)的null...
OK，那我們修改下我們的調(diào)用方法：
/**
* 暴露用于修改進(jìn)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);
}
/**
* 暴露用于修改按鈕文字值的方法
*
* @param position
* @param buttonStr
*/
public void setButtonStatus(int position, String buttonStr) {
data.get(position).setDownloadPerSize(buttonStr);
notifyItemChanged(position, 1);
}
這里我們傳入了一個(gè) “1”,這個(gè)1是隨意傳入的，其他值也可以。
繼而我們需要重寫(xiě)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);
}
}
});
}
}
可以看到我們這里有2個(gè)onBindViewHolder方法，在第一個(gè)OnBindViewHolder里面我們需要判斷下payloads是否為空，如果為空的話執(zhí)行默認(rèn)的OnBindViewHolder方法，如果不為空的話，執(zhí)行我們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());
}
}
貼下完整的適配器方法：
/**
* @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);
}
/**
* 更新列表數(shù)據(jù)某一項(xiàng)的packageName
*
* @param position 下標(biāo)
* @param packageName 要替換的文本名
*/
public void updateItem(int position, String packageName) {
if (position <= 0 && position < data.size()) {
data.get(position).setPackageName(packageName);
}
notifyDataSetChanged();
}
/**
* 暴露用于修改進(jìn)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);
}
/**
* 暴露用于修改按鈕文字值的方法
*
* @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);
}
}
});
}
}
/**
* 開(kāi)啟下載
*
* @param position
*/
public void doStartDownLoad(int position) {
}
/**
* 開(kāi)啟安裝
*
* @param position
*/
public void doInstall(int position) {
}
/**
* 開(kāi)啟停止下載
*
* @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，運(yùn)行，跑下效果為：
不會(huì)閃屏.gif
確實(shí)是解決了。
