前言
相信童鞋們都用過RecyclerView，假設說要我們做一個列表更新Item的功能，相信大部分同學都會這麼寫的：
/**
* 更新列表資料某一項的packageName
*
* @param position 下標
* @param packageName 要替換的文字名
*/
public void updateItem(int position, String packageName) {
if (position >= 0 && position < data.size()) {
data.get(position).setPackageName(packageName);
}
notifyDataSetChanged();
}複製程式碼踩坑
而我們要做的是一個下載列表，在下載的callback裡面我們要去更新列表的progressBar還有Button的文字：
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);
}
}複製程式碼介面卡中暴露的用於更新progressBar進度的方法
/**
* 暴露用於修改進度值的方法
*
* @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);
}複製程式碼介面卡的onBindViewHolder()中處理資料結果
@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);
}
}
});
}
}複製程式碼這裡我們使用的是notifyItemChanged區域性重新整理而不是notifyDataSetChanged。講道理我們到了這一步就已經可以滿足需求了，然而…事實不講道理：
額…原諒demo畫得太醜了。這裡我們可以發現….為毛我的圖片…一閃一閃的，亮瞎我的狗眼了。
至於為什麼會閃動？
猜測：
- ImageView的寬高問題，重新計算導致了閃動
- 更新到了ImageView，然後glide又重新載入了一次圖片。
- 重新整理到了ImageView，這個item渲染了一次。
解疑：
- 採用了寫死寬高的方法，但是！頁面還是會閃動…gif就不傳了，錄製好麻煩。猜測1已經否決了。
- 註釋掉
ILFactory.getLoader().loadNet(holder.mIvDownPic, appInfoBean.getDownLoadPic(), ImgOptions.getDefImaOptions());複製程式碼在xml中寫入
android:src="@mipmap/ic_launcher"複製程式碼測試下，結果還是會閃動…那猜測2又不對了！
- 重新理下，我們需要更新的是Button和progressBar，其實ImageView我們是不需要額外去更新的。
那我們的問題就聚焦在如何只更新一部分控制元件，其他控制元件不動
解決
至於怎麼解決呢…扒原始碼：
/**
* 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);
}複製程式碼 /**
* 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);
}複製程式碼在這裡我們看到一句話：
@param payload Optional parameter, use null to identify a "full" update複製程式碼傳入“null”就是更新全部！那我們呼叫的時候是傳入什麼呢！看下：
public final void notifyItemChanged(int position) {
mObservable.notifyItemRangeChanged(position, 1);
}複製程式碼繼而呼叫：
public void notifyItemRangeChanged(int positionStart, int itemCount) {
notifyItemRangeChanged(positionStart, itemCount, null);
}複製程式碼繼而呼叫：
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);
}
}複製程式碼[捂臉] 一個大寫的null…
OK，那我們修改下我們的呼叫方法：
/**
* 暴露用於修改進度值的方法
*
* @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);
}
/**
* 暴露用於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);
}複製程式碼這裡我們傳入了一個 “1”,這個1是隨意傳入的，其他值也可以。
繼而我們需要重寫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);
}
}
});
}
}複製程式碼可以看到我們這裡有2個onBindViewHolder方法，在第一個OnBindViewHolder裡面我們需要判斷下payloads是否為空，如果為空的話執行預設的OnBindViewHolder方法，如果不為空的話，執行我們自己的區域性重新整理方法
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());
}
}複製程式碼貼下完整的介面卡方法：
/**
* @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);
}
/**
* 更新列表資料某一項的packageName
*
* @param position 下標
* @param packageName 要替換的文字名
*/
public void updateItem(int position, String packageName) {
if (position <= 0 && position < data.size()) {
data.get(position).setPackageName(packageName);
}
notifyDataSetChanged();
}
/**
* 暴露用於修改進度值的方法
*
* @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);
}
/**
* 暴露用於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);
}
}
});
}
}
/**
* 開啟下載
*
* @param position
*/
public void doStartDownLoad(int position) {
}
/**
* 開啟安裝
*
* @param position
*/
public void doInstall(int position) {
}
/**
* 開啟停止下載
*
* @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);
}
}
}複製程式碼Ok，執行，跑下效果為：
確實是解決了。