简介:
Picasso是Square公司开源的一个Android图形缓存库。可以实现图片下载和缓存功能。
特点:
1.加载载网络或本地图片并自动缓存处理;
2.链式调用;
3.图形转换操作,如变换大小,旋转等,提供了接口来让用户可以自定义转换操作;
4.在Adapter中回收和取消当前的下载功能;
与Universal-ImageLoader库对比:
1.都有高效的网络图片下载和缓存性能;
2.Universal-ImageLoader功能多,灵活使用配置;
3.Picasso使用复杂的图片压缩转换来尽可能的减少内存消耗;
4.在Adapter中需要取消已经不在视野范围的ImageView图片资源的加载,否则会导致图片错位,Picasso已经解决了这个问题;
用法:
1.图片转换:转换图片以适应布局大小并减少内存占用
Picasso.with(context).load(url).resize(50, 50) .centerCrop() .into(imageView);
2.Adapter 中的下载:Adapter的重用会被自动检测到,Picasso会取消上次的加载;
3.空白或者错误占位图片设置方法及本地资源文件的加载方法;
4.Picasso采用链式调用加载和处理图片方式;
5.除了加载网络图片,picasso还支持加载Resources, assets, files, content providers中的本地资源文件;
下面实现一个ListView显示网络图片:
这里找了四张网络菜谱图片,在代码中新添加一个菜类:
//表示菜类(经过烹调的蔬菜、蛋品、肉类等) public class Dish { private String imgUrl; // 图片地址 private String name; // 菜名 private String price; // 菜价 public Dish(String imgUrl, String name, String price) { this.imgUrl = imgUrl; this.name = name; this.price = price; } public String getImgUrl() { return imgUrl; } public void setImgUrl(String imgUrl) { this.imgUrl = imgUrl; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPrice() { return price; } public void setPrice(String price) { this.price = price; } }
import java.util.ArrayList; import android.app.Activity; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ImageView; import android.widget.ListView; import android.widget.TextView; import com.squareup.picasso.Picasso; public class MainActivity extends Activity { private static final String BASE_URL = "http://img1.3lian.com/img2011/w1/106/85/"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ArrayList<Dish> dishList = new ArrayList<Dish>(); dishList.add(new Dish(BASE_URL + "42.jpg", "水煮鱼片", "38.00")); dishList.add(new Dish(BASE_URL + "34.jpg", "小炒肉", "18.00")); dishList.add(new Dish(BASE_URL + "37.jpg", "清炒时蔬", "15.00")); dishList.add(new Dish(BASE_URL + "11.jpg", "金牌烤鸭", "36.00")); dishList.add(new Dish(BASE_URL + "12.jpg", "粉丝肉煲", "20.00")); ListView mListView = (ListView) this.findViewById(R.id.listview); MainListViewAdapter adapter = new MainListViewAdapter(dishList); mListView.setAdapter(adapter); } // ListView适配器 private class MainListViewAdapter extends BaseAdapter { private ArrayList<Dish> dishList; public MainListViewAdapter(ArrayList<Dish> list) { this.dishList = list; } @Override public int getCount() { return dishList.size(); } @Override public Object getItem(int position) { return dishList.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { ListViewItemHolder item = null; if (convertView == null) { convertView = LayoutInflater.from(MainActivity.this).inflate( R.layout.main_listview_item, null); item = new ListViewItemHolder(); item.img_iv = (ImageView) convertView .findViewById(R.id.imageView1); item.name_textview = (TextView) convertView .findViewById(R.id.textView1); item.price_textview = (TextView) convertView .findViewById(R.id.textView2); convertView.setTag(item); } else { item = (ListViewItemHolder) convertView.getTag(); } Dish dish = dishList.get(position); //这里就是异步加载网络图片的地方 Picasso.with(MainActivity.this).load(dish.getImgUrl()) .into(item.img_iv); item.name_textview.setText(dish.getName()); item.price_textview.setText(dish.getPrice() + "元"); return convertView; } } // ListView的Item组件类 private class ListViewItemHolder { ImageView img_iv; TextView name_textview; TextView price_textview; } }
原文地址:http://blog.csdn.net/bear_huangzhen/article/details/45868755