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 ;
    }

    @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();
        // 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 ;
    }

    @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();
        // cache the view
        return convertView;
    }

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

}
</model></model>

Activity

?

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 = ;i<;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 = ;i<=;i++){
                    updateProgressInUiThread(model, i,position);
                    try {
                        Thread.sleep();
                    } 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：