android.os.NetworkOnMainThreadException

<strong>NetworkOnMainThreadException</strong>: The exception that is thrown when an application attempts to perform a networking operation on its main thread.

 

You should call sendfeedback method on asynctask then only above code will work. As webserver is taking lot of time to response main thread <br>becomes unresponsive. To avoid it you should call it on another thread. Hence asynctask is better.




当在主线程中执行网络操作时，NetworkOnMainThreadException会抛出这个异常；

你应该调用“asynctask”的“sendfeedback”方法来执行网络操作；当Web服务器花费很多时间响应主线程而变成迟钝，为了避免这种情况，使用“asynctask”更好

package com.example.lj.imagedemo;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.os.AsyncTask;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.widget.ImageView;import java.io.IOException;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;public class MainActivity extends AppCompatActivity {    private static final String TAG = "MainActivity";    private ImageView imageView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        try {            imageView = (ImageView) findViewById(R.id.imageView);/*            new Thread(new Runnable() {                @Override                public void run() {                    //图片资源                    String url = "http://s16.sinaimg.cn/orignal/89429f6dhb99b4903ebcf&690";                    //得到可用的图片                    Bitmap bitmap = getHttpBitmap(url);                    if (bitmap == null) {                        Log.i(TAG, "bitmap is null");                    }                    //显示                    imageView.setImageBitmap(bitmap);                }            }).start();*/            new DownloadUrlBitmap().execute("http://192.168.118.120:8888/img/dn1.jpg");        } catch (Exception e) {            e.printStackTrace();        }    }    private class DownloadUrlBitmap extends AsyncTask<String, Void, Bitmap> {        @Override        protected Bitmap doInBackground(String... params) {            return loadImageFromNetwork(params[0]);        }        @Override        protected void onPostExecute(Bitmap bitmap) {            imageView.setImageBitmap(bitmap);        }    }    private Bitmap loadImageFromNetwork(String url) {        //得到可用的图片        Bitmap bitmap = simpleNetworkImage(url);        if (bitmap == null) {            Log.i(TAG, "bitmap is null");        }        return bitmap;    }    public Bitmap simpleNetworkImage(String url) {        Bitmap pngBM = null;        try {            URL picUrl = new URL(url);            pngBM = BitmapFactory.decodeStream(picUrl.openStream());        } catch (IOException e) {            e.printStackTrace();        }        return pngBM;    }    /**     * 获取网落图片资源     *     * @param url     * @return     */    public Bitmap getHttpBitmap(String url) {        URL myFileURL;        Bitmap bitmap = null;        try {            myFileURL = new URL(url);            //获得连接            HttpURLConnection conn = (HttpURLConnection) myFileURL.openConnection();            //设置超时时间为6000毫秒，conn.setConnectionTiem(0);表示没有时间限制            conn.setConnectTimeout(6000);            //连接设置获得数据流            conn.setDoInput(true);            //不使用缓存            conn.setUseCaches(false);            //这句可有可无，没有影响            //conn.connect();            //得到数据流            InputStream is = conn.getInputStream();            //解析得到图片            bitmap = BitmapFactory.decodeStream(is);            //关闭数据流            is.close();        } catch (Exception e) {            e.printStackTrace();        }        return bitmap;    }}