异步任务下载网络图片

偏执的太偏执、 2021-09-26 00:56 309阅读 0赞

package com.example.mydouban;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.net.HttpURLConnection;
    import java.net.MalformedURLException;
    import java.net.URL;
    
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.os.AsyncTask;
    
    public class LoadImageAsynTask extends AsyncTask<String, Void, Bitmap>{
    
        LoadImageAsynTaskCallBack loadImageAsynTaskCallBack;
    
        public LoadImageAsynTask(LoadImageAsynTaskCallBack loadImageAsynTaskCallBack){
    
            this.loadImageAsynTaskCallBack=loadImageAsynTaskCallBack;
    
        }
    
        //设置回调接口
        public interface LoadImageAsynTaskCallBack{
    
            public void beforeLoadImage();
            public void afterLoadImage();
        }
    
    
        /* * 异步任务执行之前调用 */
        @Override
        protected void onPreExecute() {
            //具体执行什么操作LoadImageAsynTask不知道
            //让调用LoadImageAsynTask的人去实现
            loadImageAsynTaskCallBack.beforeLoadImage();
    
            super.onPreExecute();
        }
    
        /* * 异步任务执行之后调用 */
    
        @Override
        protected void onPostExecute(Bitmap result) {
            // TODO Auto-generated method stub
            loadImageAsynTaskCallBack.afterLoadImage();
            super.onPostExecute(result);
        }
    
        /* * 后台子线程运行的异步任务 */
    
        @Override
        protected Bitmap doInBackground(String... params) {
    
    
            try {
                String path=params[0];
                URL url=new URL(path);
                HttpURLConnection conn=(HttpURLConnection) url.openConnection();
                InputStream is=conn.getInputStream();
                return BitmapFactory.decodeStream(is);
    
            } catch (MalformedURLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
                return null;
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
                return null;
            }
    
    
        }
    
    
    // 调用这个异步任务并且sd卡缓存图片
    //加入两个sd卡的权限 WRITE_EXTERNAL_STORAGE MOUNT_NUMOUNT_FILESYSTEM
    
        //获取图片的名称
        String iconurl=url;
        String iconName=iconurl.substring(iconurl.lastIndexOf("/")+1, iconurl.length());
    
        File file=new File("/sdcard/"+iconName);
        if(file.exists()){
            iv_icon.setImageURI(Uri.fromFile(file));
        }else{
    
        LoadImageAsynTask task=new LoadImageAsynTask(new LoadImageAsynTaskCallBack() {
    
            @Override
            public void beforeLoadImage() {
                // TODO Auto-generated method stub
                iv_icon.setImageResource();
    
            }
    
            @Override
            public void afterLoadImage(Bitmap bitmap) {
                // TODO Auto-generated method stub
                if(bitmap!=null){
                    iv_icon.setImageBitmap(bitmap);
                    //把图片保存到sd卡上
                    File file=new File("/sdcard/"+iconName);
                    FileOutputStream stream=new FileOutputStream(file);
                    bitmap.compress(CompressFormat.JPEG, 100, stream);
                }
                else{
                    iv_icon.setImageResource();
                }
            }
        });
        task.execute(url);
    
        }
    }