android实现ListView或GridView中item的倒数功能

有时在开发中可能会遇到当未到某个时间时需要让ListView或GridView中的相应item进行倒数的需求，此时，如果还是按照常见的ListView或GridView的Adapter的写法+计时功能来实现的话，则当滚动ListView或GridView的时候，item就可能会出现复用问题（即不需要进行倒数或当前item的倒数已经结束了，却还会出现倒数的现象），因此，为了解决这种问题，需要进行倒数时，重新遍历当前对象的集合，然后让每个对象的相应时间值减1，最后再通过Adapter的notifyDataSetChanged方法静态的刷新界面。

  效果如下所示：



MainActivity的代码如下所示：

<span style="font-size:14px;">package com.abner.countdownforlistview;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.widget.ListView;

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

public class MainActivity extends AppCompatActivity {

private ListView lv_goods;
private GoodsAdapter adapter;

private int result = -1;
private Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if (msg.what == 1) {
result = adapter.countDownTime();
if (result == 0) {
handler.removeMessages(1);
return;
} else {
adapter.notifyDataSetChanged();
handler.sendEmptyMessageDelayed(1, 1000);
}
}
}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv_goods = (ListView) findViewById(R.id.lv_goods);
initData();
}

private void initData() {
List<Goods> goodsList = new ArrayList<>();
for (int i = 0; i < 15; i++) {
Goods goods = new Goods();
goods.setGoodsName("这是商品名称：" + i);
goods.setPrice(i * 26);
goods.setTime(i % 3 == 0 ? i * 8 + 62 : 0);
goodsList.add(goods);
}
adapter = new GoodsAdapter(this, goodsList);
lv_goods.setAdapter(adapter);
handler.sendEmptyMessageDelayed(1, 1000);
}
}
</span>

在这个MainActivity中，可以看到通过Handler实现了倒数功能，在为ListView设置完Adapter后即通过handler的sendEmptyMessageDelayed方法发送了一条消息，然后在handler的handleMessage方法中通过调用在adapter中声明的countDownTime方法对相应的对象集合进行遍历再设置相应的值，最后通过返回的result进行判断倒数是否已经结束，如果已经结束则移除消息，否则继续发送消息进行倒数操作。

ListView的GoodsAdapter的代码如下所示：

<span style="font-size:14px;">package com.abner.countdownforlistview;

import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

import java.util.List;

import static com.abner.countdownforlistview.R.id.tv_price;

/**
* Created by abner on 2016/5/6.
*/
public class GoodsAdapter extends BaseAdapter {
private Context context;
private List<Goods> goodsList;

public GoodsAdapter(Context context, List<Goods> goodsList) {
this.context = context;
this.goodsList = goodsList;
}

@Override
public int getCount() {
return goodsList == null ? 0 : goodsList.size();
}

@Override
public Object getItem(int position) {
return goodsList.get(position);
}

@Override
public long getItemId(int position) {
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
final ViewHolder holder;
if (convertView == null) {
holder = new ViewHolder();
convertView = LayoutInflater.from(context).inflate(R.layout.lv_goods_item, null);
holder.tv_goodsName = (TextView) convertView.findViewById(R.id.tv_goodsName);
holder.tv_price = (TextView) convertView.findViewById(tv_price);
holder.tv_time = (TextView) convertView.findViewById(R.id.tv_time);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}

final Goods goods = goodsList.get(position);
holder.tv_goodsName.setText(goods.getGoodsName());
holder.tv_price.setText("￥" + goods.getPrice());

final int time = goods.getTime();
if (time > 0) {
holder.tv_time.setText(getTimeStr(time) + "后开始");
} else {
holder.tv_time.setText("正在进行中...");
}

return convertView;
}

class ViewHolder {
TextView tv_goodsName;
TextView tv_price;
TextView tv_time;
}

private int result = -1;

/**
* 倒数，实时更新每个item的显示时间
*
* @return
*/
public int countDownTime() {
new Thread(new Runnable() {
@Override
public void run() {
try {
Thread.sleep(1000);
//如果goodsList为null或者result等于goodsList.size+1，则表示已经倒数完，此时需要停止倒数
if (goodsList == null || result == goodsList.size() + 1) {
result = 0;
return;
}
result = 1;
for (Goods goods : goodsList) {
if (goods.getTime() == 0) {
goods.setTime(0);
result++; //每当一个对象倒数完或者当前对象已经处于进行中，则让result加1，用于后续所有对象倒数完后，停止倒数
} else {
goods.setTime(goods.getTime() - 1);
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
return result;
}

/**
* 格式化时间显示，格式为：XX分XX秒
*
* @param timeDiff
* @return
*/
public static String getTimeStr(int timeDiff) {
int min = timeDiff / 60;
int sec = timeDiff - min * 60;

String result = "";
if (min == 0) {
result = sec + "秒";
} else {
result = min + "分" + sec + "秒";
}

return result;
}
}</span>
此时，在android中实现ListView或GridView中item的倒数功能就已经完成了。

 源码下载