Android ListView与RecyclerView局部刷新
一、ListView
之前写过一篇关于ListView局部刷新的博客，这部分对其进行完善
，之前的链接为：Android模拟ListView点击下载和局部刷新
平时在写ListView的时候需要更改某些数据，这种情况我们一般会调用
notifyDataSetChanged()方法进行刷新，调用notifydatasetchange其实会导致adpter的getView方法被多次调用（画面上能显示多少就会被调用多少次），并且在有获取网络图片的情况下会可能造成大量闪动或卡顿，极大的影响用户体验（图片重新加载并闪动在ImageLoader框架中会出现，在glide框架中没有出现）。
所以我们需要做单行刷新来进行优化
这个是Google官方给出的解决方案：
private void updateSingleRow(ListView listView, long id) {
if (listView != null) {
int start = listView.getFirstVisiblePosition();
for (int i = start, j = listView.getLastVisiblePosition(); i <= j; i++)
if (id == ((Messages) listView.getItemAtPosition(i)).getId()) {
View view = listView.getChildAt(i - start);
getView(i, view, listView);
break;
}
}
}
对于这个方法可以参考这个博客：android ListView 单条刷新方法实践及原理解析
可以看出来谷歌的方案是通过listview的getView方法将单行的所有内容都刷新一遍，但是这样如果是有加载网络图片的话可能也会造成闪动重新加载，所以我们需要单独刷新某个item中的某个控件来实现局部刷新
所以我们在Adapter中添加一个局部刷新的方法
/**
* 局部刷新
*
* @param mListView
* @param posi
*/
public void updateSingleRow(ListView mListView, int posi) {
if (mListView != null) {
//获取第一个显示的item
int visiblePos = mListView.getFirstVisiblePosition();
//计算出当前选中的position和第一个的差，也就是当前在屏幕中的item位置
int offset = posi - visiblePos;
int lenth = mListView.getChildCount();
// 只有在可见区域才更新,因为不在可见区域得不到Tag,会出现空指针,所以这是必须有的一个步骤
if ((offset < 0) || (offset >= lenth)) return;
View convertView = mListView.getChildAt(offset);
ViewHolder viewHolder = (ViewHolder) convertView.getTag();
//以下是处理需要处理的控件方法。。。。。
}
}
举个例子，简单的模拟在列表中点击下载并更新列表的demo
1.首先定义一个Bean对象
这里有一个图片url供Glide加载
public class Game {
private String gameName;
private long gameTotalSize;
private long gameDownSize;
private String gameUrl;
private int state;
public Game(String gameName, long gameTotalSize) {
this.gameName = gameName;
this.gameTotalSize = gameTotalSize;
gameUrl = "http://dynamic-image.yesky.com/600x-/uploadImages/upload/20140912/upload/201409/smkxwzdt1n1jpg.jpg";
this.gameDownSize = 0;
}
public String getGameUrl() {
return gameUrl;
}
public String getGameName() {
return gameName;
}
public long getGameTotalSize() {
return gameTotalSize;
}
public long getGameDownSize() {
return gameDownSize;
}
public void setGameDownSize(long gameDownSize) {
this.gameDownSize = gameDownSize;
}
public int getState() {
return state;
}
public void setState(int state) {
this.state = state;
}
}
2.实现一个下载的模拟器（单例类）
public class DownLoadManager {
public interface DownCallBack{
void update(int posi,DownFile downFile);
}
private DownCallBack downCallBack;
public void setDownCallBack(DownCallBack downCallBack) {
this.downCallBack = downCallBack;
}
/**
* 下载文件类，不过在正常的项目中应该有一个ID或者url，
* 用来判断文件，在这个demo中就用列表的position来判断了
*/
public static class DownFile {
public long total;
public long downSize;
public int downState;
public DownFile(long total, long downSize, int downState) {
this.total = total;
this.downSize = downSize;
this.downState = downState;
}
}
public static final int DOWN_WATE = 0X02;
public static final int DOWN_PAUST = 0X03;
public static final int DOWN_FINISH = 0X04;
public static final int DOWN_DOWNLOADING = 0X05;
private ExecutorService executorService;
private SparseArray<DownFile> downFileSparseArray;
private SparseArray<DownTask> downTaskSparseArray;
private static volatile DownLoadManager singleton;
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
int posi = msg.arg1;
DownLoadManager.DownFile downFile = (DownLoadManager.DownFile) msg.obj;
if (downCallBack!=null){
downCallBack.update(posi,downFile);
}
}
};
private DownLoadManager() {
executorService = Executors.newFixedThreadPool(3);
downFileSparseArray = new SparseArray<>();
downTaskSparseArray = new SparseArray<>();
}
public static DownLoadManager getInstance() {
if (singleton == null) {
synchronized (DownLoadManager.class) {
if (singleton == null) {
singleton = new DownLoadManager();
}
}
}
return singleton;
}
public void start(int posi, DownFile downFile) {
if (downFile.downState == DOWN_WATE||downFile.downState == DOWN_FINISH){
return;
}
//首先设置为排队中的状态
downFile.downState = DOWN_WATE;
update(posi, downFile);
downFileSparseArray.put(posi, downFile);
DownTask downTask = new DownTask(posi);
downTaskSparseArray.put(posi, downTask);
executorService.submit(downTask);
}
public void pause(int posi, DownFile downFile) {
downTaskSparseArray.get(posi).stop();
downTaskSparseArray.remove(posi);
downFile.downState = DOWN_PAUST;
update(posi, downFile);
}
public void update(int posi, DownFile downFile) {
Message msg = handler.obtainMessage();
msg.obj = downFile;
msg.arg1 = posi;
msg.sendToTarget();
}
public void stopAll(){
for (int i = 0;i<downTaskSparseArray.size();i++) {
downTaskSparseArray.valueAt(i).stop();
}
downTaskSparseArray.clear();
}
private class DownTask implements Runnable {
private int posi;
private boolean isWorking;
private DownFile downFile;
public DownTask(int posi) {
this.posi = posi;
isWorking = true;
downTaskSparseArray.put(posi, this);
}
public void stop() {
this.isWorking = false;
}
@Override
public void run() {
//一旦成功进入到线程里就变为下载中状态
downFile = downFileSparseArray.get(posi);
downFile.downState = DOWN_DOWNLOADING;
while (isWorking) {
update(posi, downFile);
if (downFile.downSize < downFile.total) {
++downFile.downSize;
} else {
downFile.downState = DOWN_FINISH;
downFileSparseArray.remove(posi);
downTaskSparseArray.remove(posi);
isWorking = false;
break;
}
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
downFile.downState = DOWN_PAUST;
downFileSparseArray.remove(posi);
downTaskSparseArray.remove(posi);
isWorking = false;
}
}
}
}
}
3.创建adapter
public class LvAdapter extends BaseAdapter implements DownLoadManager.DownCallBack{
private Context context;
private List<Game> games;
private LayoutInflater layoutInflater;
private ListView listView;
private DownLoadManager downLoadManager;
public LvAdapter(Context context, ListView listView, List<Game> games) {
this.context = context;
this.games = games;
this.listView = listView;
layoutInflater = LayoutInflater.from(context);
downLoadManager = DownLoadManager.getInstance();
downLoadManager.setDownCallBack(this);
}
@Override
public int getCount() {
return games.size();
}
@Override
public Object getItem(int position) {
return games.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder;
if (convertView == null) {
convertView = layoutInflater.inflate(R.layout.item, parent, false);
viewHolder = new ViewHolder(convertView);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
setItemView(viewHolder, games.get(position), position);
return convertView;
}
private void setItemView(ViewHolder viewHolder, final Game game, final int position) {
viewHolder.itemProgress.setMax((int) game.getGameTotalSize());
viewHolder.itemName.setText(game.getGameName());
viewHolder.itemSize.setText(game.getGameTotalSize() + "");
//加载图片
Glide.with(context).load(game.getGameUrl()).placeholder(R.mipmap.ic_launcher).crossFade(2000).into(viewHolder.itemImg);
viewHolder.itemDownBtn.setText(getGameState(game));
if (game.getGameDownSize() > 0 && game.getGameDownSize() < game.getGameTotalSize()) {
viewHolder.itemProgress.setVisibility(View.VISIBLE);
viewHolder.itemProgress.setProgress((int) game.getGameDownSize());
} else {
viewHolder.itemProgress.setVisibility(View.INVISIBLE);
}
viewHolder.itemDownBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (game.getState() == DownLoadManager.DOWN_DOWNLOADING)
downLoadManager.pause(position, new DownLoadManager.DownFile(game.getGameTotalSize(), game.getGameDownSize(), game.getState()));
else
downLoadManager.start(position, new DownLoadManager.DownFile(game.getGameTotalSize(), game.getGameDownSize(), game.getState()));
}
});
}
private String getGameState(Game game) {
switch (game.getState()) {
case DownLoadManager.DOWN_DOWNLOADING:
return "下载中";
case DownLoadManager.DOWN_FINISH:
return "已完成";
case DownLoadManager.DOWN_PAUST:
return "暂停";
case DownLoadManager.DOWN_WATE:
return "等待中";
}
return "下载";
}
/**
* 局部刷新
*
* @param mListView
* @param posi
*/
public void updateSingleRow(ListView mListView, int posi) {
if (mListView != null) {
//获取第一个显示的item
int visiblePos = mListView.getFirstVisiblePosition();
//计算出当前选中的position和第一个的差，也就是当前在屏幕中的item位置
int offset = posi - visiblePos;
int lenth = mListView.getChildCount();
// 只有在可见区域才更新,因为不在可见区域得不到Tag,会出现空指针,所以这是必须有的一个步骤
if ((offset < 0) || (offset >= lenth)) return;
View convertView = mListView.getChildAt(offset);
ViewHolder viewHolder = (ViewHolder) convertView.getTag();
//以下是处理需要处理的控件
System.out.println("posi = " + posi);
Game game = games.get(posi);
if (game.getGameDownSize() > 0 && game.getGameDownSize() < game.getGameTotalSize()) {
viewHolder.itemProgress.setVisibility(View.VISIBLE);
viewHolder.itemProgress.setProgress((int) game.getGameDownSize());
} else {
viewHolder.itemProgress.setVisibility(View.INVISIBLE);
}
viewHolder.itemDownBtn.setText(getGameState(game));
}
}
@Override
public void update(int posi, DownLoadManager.DownFile downFile) {
Game game = games.get(posi);
game.setGameDownSize(downFile.downSize);
game.setState(downFile.downState);
// notifyDataSetChanged();
updateSingleRow(listView, posi);
}
private class ViewHolder {
TextView itemName, itemSize;
Button itemDownBtn;
ProgressBar itemProgress;
ImageView itemImg;
public ViewHolder(View convertView) {
itemImg = (ImageView) convertView.findViewById(R.id.itemImg);
itemName = (TextView) convertView.findViewById(R.id.itemName);
itemSize = (TextView) convertView.findViewById(R.id.itemSize);
itemDownBtn = (Button) convertView.findViewById(R.id.itemDownBtn);
itemProgress = (ProgressBar) convertView.findViewById(R.id.itemProgress);
}
}
}
基本代码就是这些。
下面是notifyDataSetChanged后刷新的效果：由于不断的刷新界面中所有的item，所以在下载的时候点击按钮没有任何的反应，只有在刷新的间隙时间里点击才可以执行下载
这里写图片描述
可以看到，这里我点击了好多回没有效果，偶尔会成功，这简直没法用了~
局部刷新的效果：
这里写图片描述
一、RecyclerView
看到RecyclerView局部刷新可能大家会说，RecyclerView 中不是有notifyItemChanged（position）么，没错，的确是用这个方法可以刷新一个item，但是这个方法也是有个坑，同样会刷新item中所有东西，并且在不断刷新的时候会执行刷新Item的动画，导致滑动的时候会错开一下，还可能会造成图片重新加载或者不必要的消耗。
下面讲解一下我的方法：
一般我们刷新某个item的方法为
notifyItemChanged(position);
所以我们就从这里入手，
首先查看源码
这里写图片描述
虽然录制的效果不是特别好，但是可以看见明显的浮动错位现象
这个是用这个方法刷新的效果图：
这里写图片描述
这样就恢复正常了
RecyclerView adapter默认的使用我就不在这里多说了。主要是局部刷新。
今天的博客就说到这里，有什么增加的日后再补充~~
源码链接：https://github.com/asd7364645/PartialRefreshDemo
希望喜欢的小伙伴给个屎蛋（star）~~
我是Alex-蜡笔小刘，一个android小白~！
有失误或者错误希望有大神能纠正！也希望与其他“小白”共同进步！
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