ListView局部刷新的问题

来源：互联网发布：黄耀明和林夕知乎编辑：程序博客网时间：2024/06/05 00:24

有时候，我们需要更改ListView中某一个Item样式，假如这个时候使用notifydatasetChanged去刷新整个界面是没有必要的，今天我们看看如何只刷新指定条目的Item.
这里写图片描述

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;    }}

public class MainActivity extends Activity implements UpdateCallback{    ListView listview;    private ListAdapter adapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        listview = (ListView) findViewById(R.id.listview);        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();    }    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();        //在看见范围内才更新进度条        if(position>=firstVisiblePosition && position<=lastVisiblePosition){            //获取指定位置view对象            View view = listview.getChildAt(position - firstVisiblePosition);            if(view.getTag() instanceof ListAdapter.ViewHolder){                //获取指定view对应的ViewHolder                ListAdapter.ViewHolder vh = (ListAdapter.ViewHolder)view.getTag();                vh.pb.setProgress(progress);            }        }    }}

总结一下ListView局部刷新如何实现：
1.获取到当前可见的第一个条目和最后一个条目的位置
2.判断我们要更新的条目的位置是不是在这个范围内，这么做是为了防止ListView的复用问题
3.通过getChildAt方法获取ListView指定位置的条目View对象
4.通过这个view对象的getTag方法获取ViewHolder对象
5.更新数据

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