AsyncTask异步类下载图片案例

package com.example.myapplication; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.os.AsyncTask; import android.widget.ImageView; import java.io.BufferedInputStream; import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; public class ImageDownTask extends AsyncTask<String,Void, Bitmap> { private ImageView img; public ImageDownTask(ImageView img) { //通过构造方法进行依赖注入 this.img = img; } //后台处理逻辑（下载图片的功能在此方法中实现） @Override protected Bitmap doInBackground(String... strings) { //形参接受输入的参数（下载图片的地址） Bitmap bmp=null; try { URL url=new URL(strings[0]); //通过URL是客户端与服务器端建立连接 HttpURLConnection coon=(HttpURLConnection) url.openConnection(); //I/O流 InputStream is=coon.getInputStream(); //缓冲流 BufferedInputStream bis=new BufferedInputStream(is); //将缓冲流中数据封装成图片 bmp = BitmapFactory.decodeStream(bis); //下载完成后，关闭I/O管道 bis.close(); is.close(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return bmp; } //更新 @Override protected void onPostExecute(Bitmap bitmap) { super.onPostExecute(bitmap); img.setImageBitmap(bitmap); } }