1.新建Android工程AsyncLoadPicture

新建布局文件activity_main.xml主界面为一个GridView，还有其子项布局文件gridview_item.xml

2.功能主界面MainActivity.java,主代码如下

package com.example.asyncloadpicture; import java.util.ArrayList; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.AsyncTask; import android.os.Bundle; import android.widget.GridView; /** * @author ymw * @data -- */ public class MainActivity extends Activity { private GridView gridViewImg; private ArrayList<ImageEntity> imageList = new ArrayList<ImageEntity>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); gridViewImg = (GridView) findViewById(R.id.gridViewImg); initData(); } private void initData() { for (int i = ; i < ; i++) { ImageEntity b = new ImageEntity(); b.setImage(BitmapFactory.decodeResource(getResources(), R.drawable.nopicture)); imageList.add(b); } ImageAdapter adapter = new ImageAdapter(getApplicationContext(), imageList); gridViewImg.setAdapter(adapter); String[] params = { "http://images.cnitblog.com/i///.png", "p" }; new ImageLoadTask(getApplicationContext(), adapter).execute(params); } /** 图片异步加载类 */ public class ImageLoadTask extends AsyncTask<String, Void, Void> { private ImageAdapter adapter; public ImageLoadTask(Context context, ImageAdapter adapter) { this.adapter = adapter; } @Override protected Void doInBackground(String... params) { String url = params[];// 获取传来的参数，图片uri地址 String p = params[]; for (int i = ; i < adapter.getCount(); i++) { ImageEntity bean = (ImageEntity) adapter.getItem(i); Bitmap bitmap = BitmapFactory.decodeStream(Request .HandlerData(url)); bean.setImage(bitmap); publishProgress(); // 通知去更新UI } return null; } public void onProgressUpdate(Void... voids) { if (isCancelled()) return; // 更新UI adapter.notifyDataSetChanged(); } } /** 图片实体 */ public class ImageEntity { private Bitmap image; public Bitmap getImage() { return image; } public void setImage(Bitmap image) { this.image = image; } } }

3.GridView列表图片适配器代码ImageAdapter.java

package com.example.asyncloadpicture; import java.util.ArrayList; import android.content.Context; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.ImageView; import com.example.asyncloadpicture.MainActivity.ImageEntity; /** * * @author ymw * @data -- 图片适配器 */ public class ImageAdapter extends BaseAdapter { private Context _context; private ArrayList<ImageEntity> _list; public ImageAdapter(Context context, ArrayList<ImageEntity> imageList) { this._context = context; this._list = imageList; } @Override public int getCount() { return _list.size(); } @Override public Object getItem(int position) { return _list.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { LayoutInflater inflater = LayoutInflater.from(_context); convertView = inflater.inflate(R.layout.gridview_item, null); ImageView imgView = (ImageView) convertView.findViewById(R.id.imgView); ImageEntity b = _list.get(position); // 如果有图片则读取，没有则跳过 if (b.getImage() != null) { imgView.setImageBitmap(b.getImage()); } return convertView; } }

4.请求网络读取图片的类Request.java

package com.example.asyncloadpicture; import java.io.IOException; import java.io.InputStream; import java.net.URL; import java.net.URLConnection; import android.graphics.drawable.Drawable; import android.util.Log; /** * 工具类，主要根据url读取图片返回流的方法 * * @author ymw * */ public class Request { public static InputStream HandlerData(String url) { InputStream inStream = null; try { URL feedUrl = new URL(url); URLConnection conn = feedUrl.openConnection(); conn.setConnectTimeout( * ); inStream = conn.getInputStream(); } catch (Exception e) { e.printStackTrace(); } return inStream; } /** 直接返回Drawable对象设置图片 */ public static Drawable loadImageFromNetwork(String imageUrl) { Drawable drawable = null; try { // 可以在这里通过文件名来判断，是否本地有此图片 drawable = Drawable.createFromStream( new URL(imageUrl).openStream(), "image.jpg"); } catch (IOException e) { Log.d("test", e.getMessage()); } if (drawable == null) { Log.d("test", "null drawable"); } else { Log.d("test", "not null drawable"); } return drawable; } }

以上内容给大家介绍了Android 中使用 AsyncTask 异步读取网络图片的相关知识，希望对大家有所帮助！

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