android：ListView的局部刷新

1.简介

对于android中的ListView刷新机制，大多数的程序员都是很熟悉的，修改或者添加adapter中的数据源之后，然后调用notifyDataSetChanged()刷新ListView。在这种模式下，我们会在getView中，根据不同的数据源，让控件显示不同的内容。这种模式是最常见的刷新模式，当我们来回滑动ListView的时候，调用adapter的getView方法，然后listview对adapter返回的View进行绘制。这种模式下，View的显示内容或状态都记录在adapter里面的数据源中，listview的更新频率不频繁，它随着数据源的变化而更新。

->ListView局部刷新问题的引入：

假设我们的ListView的Item中有一个进度条（ProgressBar）和一个按钮，当我们点击一下按钮，进度条就会从0到100进行刷新，而且一般都需要在1s以内完成刷新过程，也就是说：在ListView的任一个Item中，触发了Button的事件之后，在1s以内，或者更短的时间，ProgressBar需要刷新100次。显然，如果我们使用修改数据源，调用notifyDataSetChanged()进行刷新的机制明显是不恰当的，效率极低，而且不一定凑效。那么，我们自然想到当点击的时候，希望能够获取到点击后的View内部的ProgressBar控件的对象，然后直接调用progressBar的setProgress就可以了，本以为这样就大功告成了。忽然，你会发现，当progressBar正在更新的时候，此时，往下滑listview，突然发现下面的某个进度条也在更新。仔细一分析，还真有道理，因为ListView中的View是复用的，当你向下滑动listview的时候，你此时操作的progressBar对象，已经不是刚才点击的那个Item了，因为很多Item复用一个View。那么如何解决这个问题呢？

2.解决方案

记录点击的Item的position，然后在更新过程中，不断的判断，该position是不是介于可见的Item之间，如果是，则更新，否者，不更新。

private void updateProgressPartly(int progress,int position){
int firstVisiblePosition = listview.getFirstVisiblePosition();
int lastVisiblePosition = listview.getLastVisiblePosition();
if(position>=firstVisiblePosition && position<=lastVisiblePosition){
View view = listview.getChildAt(position - firstVisiblePosition);
if(view.getTag() instanceof ViewHolder){
ViewHolder vh = (ViewHolder)view.getTag();
vh.pb.setProgress(progress);
}
}
}

其他相关代码：

ListAdapter

/*
* $filename: ListAdapter.java,v $
* $Date: 2014-9-19  $
* Copyright (C) ZhengHaibo, Inc. All rights reserved.
* This software is Made by Zhenghaibo.
*/
package net.mobctrl.listviewdemo;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ProgressBar;

/*
*@author: ZhengHaibo
*blog:     http://blog.csdn.net/nuptboyzhb *mail:    zhb931706659@126.com
*web:     http://www.mobctrl.net *2014-9-19  Nanjing,njupt,China
*/
public class ListAdapter extends BaseAdapter {

private List<model> datas;
private Context context;

private UpdateCallback updateCallback;

public UpdateCallback getUpdateCallback() {
return updateCallback;
}

public void setUpdateCallback(UpdateCallback updateCallback) {
this.updateCallback = updateCallback;
}

public ListAdapter(Context context) {
datas = new ArrayList<model>();
this.context = context;
}

public void addData(Model model) {
datas.add(model);
notifyDataSetChanged();
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return datas.size();
}

@Override
public Object getItem(int pos) {
// TODO Auto-generated method stub
return datas.get(pos);
}

@Override
public long getItemId(int arg0) {
// TODO Auto-generated method stub
return 0;
}

@Override
public View getView(final int pos, View convertView, ViewGroup viewGroup) {
final Model model = datas.get(pos);
ViewHolder viewHolder = null;
if (null == convertView) {
viewHolder = new ViewHolder();
convertView = LayoutInflater.from(context).inflate(
R.layout.list_item_layout, null);
viewHolder.pb = (ProgressBar) convertView
.findViewById(R.id.pb_show);
viewHolder.btn = (Button) convertView.findViewById(R.id.btn);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
convertView.setTag(viewHolder);
}
viewHolder.btn.setText(model.getName());
viewHolder.btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if(null != updateCallback){
updateCallback.startProgress(model,pos);
}
}
});
viewHolder.pb.setProgress(0);
// cache the view
return convertView;
}

public static class ViewHolder {
ProgressBar pb;
Button btn;
}

}

Activity

/*
* $filename: ListAdapter.java,v $
* $Date: 2014-9-19  $
* Copyright (C) ZhengHaibo, Inc. All rights reserved.
* This software is Made by Zhenghaibo.
*/
package net.mobctrl.listviewdemo;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ProgressBar;

/*
*@author: ZhengHaibo
*blog:     http://blog.csdn.net/nuptboyzhb *mail:    zhb931706659@126.com
*web:     http://www.mobctrl.net *2014-9-19  Nanjing,njupt,China
*/
public class ListAdapter extends BaseAdapter {

private List<model> datas;
private Context context;

private UpdateCallback updateCallback;

public UpdateCallback getUpdateCallback() {
return updateCallback;
}

public void setUpdateCallback(UpdateCallback updateCallback) {
this.updateCallback = updateCallback;
}

public ListAdapter(Context context) {
datas = new ArrayList<model>();
this.context = context;
}

public void addData(Model model) {
datas.add(model);
notifyDataSetChanged();
}

@Override
public int getCount() {
// TODO Auto-generated method stub
return datas.size();
}

@Override
public Object getItem(int pos) {
// TODO Auto-generated method stub
return datas.get(pos);
}

@Override
public long getItemId(int arg0) {
// TODO Auto-generated method stub
return 0;
}

@Override
public View getView(final int pos, View convertView, ViewGroup viewGroup) {
final Model model = datas.get(pos);
ViewHolder viewHolder = null;
if (null == convertView) {
viewHolder = new ViewHolder();
convertView = LayoutInflater.from(context).inflate(
R.layout.list_item_layout, null);
viewHolder.pb = (ProgressBar) convertView
.findViewById(R.id.pb_show);
viewHolder.btn = (Button) convertView.findViewById(R.id.btn);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
convertView.setTag(viewHolder);
}
viewHolder.btn.setText(model.getName());
viewHolder.btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if(null != updateCallback){
updateCallback.startProgress(model,pos);
}
}
});
viewHolder.pb.setProgress(0);
// cache the view
return convertView;
}

public static class ViewHolder {
ProgressBar pb;
Button btn;
}

}
</model></model>

Activity

?
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package net.mobctrl.listviewdemo;

import net.mobctrl.listviewdemo.ListAdapter.ViewHolder;

import org.androidannotations.annotations.AfterViews;
import org.androidannotations.annotations.EActivity;
import org.androidannotations.annotations.UiThread;
import org.androidannotations.annotations.ViewById;

import android.app.Activity;
import android.view.View;
import android.widget.ListView;
/**
* @author 郑海波
* @webset http://www.mobctrl.net * ListView的局部刷新
*/
@EActivity(R.layout.activity_main)
public class MainActivity extends Activity implements UpdateCallback{

@ViewById
ListView listview;

private ListAdapter adapter;

@AfterViews
void afterViews() {
adapter = new ListAdapter(this);
adapter.setUpdateCallback(this);
listview.setAdapter(adapter);
initDatas();
}

private void initDatas() {
for(int i = 0;i<100;i++){
Model model = new Model(i, <click> --> );
adapter.addData(model);
}
}

@Override
public void startProgress(final Model model,final int position) {
/** start the Thread to update the Progress*/
new Thread(new Runnable() {

@Override
public void run() {
for(int i = 0;i<=100;i++){
updateProgressInUiThread(model, i,position);
try {
Thread.sleep(50);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}).start();
}

@UiThread
void updateProgressInUiThread(Model model,int progress,int position){
updateProgressPartly(progress,position);
}

private void updateProgressPartly(int progress,int position){
int firstVisiblePosition = listview.getFirstVisiblePosition();
int lastVisiblePosition = listview.getLastVisiblePosition();
if(position>=firstVisiblePosition && position<=lastVisiblePosition){
View view = listview.getChildAt(position - firstVisiblePosition);
if(view.getTag() instanceof ViewHolder){
ViewHolder vh = (ViewHolder)view.getTag();
vh.pb.setProgress(progress);
}
}
}

}

布局：

整个项目的源代码：https://github.com/nuptboyzhb/ListViewPartRefreash

效果为：