多个AsyncTask，ConcurrentModificationException。救命！ - Android

时间：2014-04-15 22:55:15

标签： java android image bitmap android-asynctask

我正在为Android制作照片流媒体应用。为了避免内存问题，我运行了两个AsyncTasks来下载数据。获取并将JSON对象解析为自定义对象（此处显示为:) 

    package edu.iastate.its.webdev.training.photostream;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;

import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.os.AsyncTask;
import android.util.JsonReader;

public class StringAsync extends AsyncTask<String, Integer, String>
{


    @Override
    protected String doInBackground(String...urls) 
    {

        InputStream content = null;
        DefaultHttpClient temp = new DefaultHttpClient();

        HttpGet temp2 = new HttpGet(urls[0]);

        try {
            HttpResponse temp3 = temp.execute(temp2);
            content = temp3.getEntity().getContent();
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        Reader reader = null;

        try {
            reader = new InputStreamReader(content, "UTF-8");
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


        char[] buffer = new char[Integer.MAX_VALUE/200];
        try {
            reader.read(buffer);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return new String(buffer);
    }


    @Override
    protected void onPostExecute(String result) 
    {
        if(result == null) throw new IllegalStateException("No result");
        if(result.substring(0, 3).equals("null")) result = result.substring(4, result.length()-1);

        super.onPostExecute(result);



        JsonReader temp = new JsonReader(new StringReader(result));
        try {
            temp.beginArray();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


        temp.setLenient(true);
        try {
            while(temp.hasNext())
            {
                PhotoItem tempItem = new PhotoItem("null", 0, 0, "null", "null", "null");
                temp.beginObject();
                temp.skipValue();

                tempItem.setId(temp.nextInt());
                temp.skipValue();

                tempItem.setName(temp.nextString());
                temp.skipValue();

                tempItem.setDescription(temp.nextString());
                temp.skipValue();

                temp.skipValue();
                temp.skipValue();

                temp.skipValue();
                temp.skipValue();

                temp.skipValue();
                temp.skipValue();

                tempItem.setThumbImageURL(temp.nextString());
                temp.skipValue();

                temp.skipValue();
                temp.skipValue();

                tempItem.setFullImageURL(temp.nextString());
                temp.skipValue();

                tempItem.setViewsNumber(temp.nextInt());
                temp.skipValue();

                temp.skipValue();
                temp.skipValue();

                temp.skipValue();
                //temp.skipValue();

                temp.endObject();
                MainActivity.photos.add(tempItem);
            }
            //temp.endArray();
            temp.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

另一个从JSON中的URL下拉图像：

package edu.iastate.its.webdev.training.photostream;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.util.ArrayList;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;

public class PhotoAsync extends AsyncTask<ArrayList<PhotoItem>, Integer, Bitmap>
{

    private ArrayList<PhotoItem> temp = null;
    @Override
    protected synchronized Bitmap doInBackground(ArrayList<PhotoItem>...idArg) 
    {



        temp = idArg[0];
        String tempURL = "null";

        for(PhotoItem p : temp)
        {
            p.setThumbImageBM(getBitmapFromURL(p.getThumbURL()));
            p.setFullImageBM(getBitmapFromURL(p.getFullURL()));
        }

        if(temp.size() > 0)
        return temp.get(0).getLargeImage();
        else
        return null;
    }

    @Override
    protected synchronized void onPostExecute(Bitmap result)
    {

    }

    private Bitmap getBitmapFromURL(String src) 
    {
        try {
            java.net.URL url = new java.net.URL(src);
            HttpURLConnection connection = (HttpURLConnection) url
                    .openConnection();
            connection.setDoInput(true);
            connection.connect();
            InputStream input = connection.getInputStream();

            BitmapFactory.Options option = new BitmapFactory.Options();
            option.inSampleSize = 8;

            Bitmap myBitmap = BitmapFactory.decodeStream(input);
            return myBitmap;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }
}

我一直收到这个错误：

04-15 17:52:04.539: W/dalvikvm(23235): threadid=14: thread exiting with uncaught exception (group=0x417c0da0)
04-15 17:52:04.539: E/AndroidRuntime(23235): FATAL EXCEPTION: AsyncTask #4
04-15 17:52:04.539: E/AndroidRuntime(23235): Process: edu.iastate.its.webdev.training.photostream, PID: 23235
04-15 17:52:04.539: E/AndroidRuntime(23235): java.lang.RuntimeException: An error occured while executing doInBackground()
04-15 17:52:04.539: E/AndroidRuntime(23235):    at android.os.AsyncTask$3.done(AsyncTask.java:300)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at java.util.concurrent.FutureTask.run(FutureTask.java:242)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at java.lang.Thread.run(Thread.java:841)
04-15 17:52:04.539: E/AndroidRuntime(23235): Caused by: java.util.ConcurrentModificationException
04-15 17:52:04.539: E/AndroidRuntime(23235):    at java.util.ArrayList$ArrayListIterator.next(ArrayList.java:573)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at edu.iastate.its.webdev.training.photostream.PhotoAsync.doInBackground(PhotoAsync.java:25)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at edu.iastate.its.webdev.training.photostream.PhotoAsync.doInBackground(PhotoAsync.java:1)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at android.os.AsyncTask$2.call(AsyncTask.java:288)
04-15 17:52:04.539: E/AndroidRuntime(23235):    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
04-15 17:52:04.539: E/AndroidRuntime(23235):    ... 4 more

我是网络代码的新手，也是JSON的新手。任何帮助表示赞赏！

1 个答案:

答案 0 :(得分：1)

在Java中，不允许使用foreach循环原样修改List。这就是调用ConcurrentModificationException的原因。有关详细信息，请参阅http://docs.oracle.com/javase/6/docs/api/java/util/ConcurrentModificationException.html。

您可以使用普通的for循环并以这种方式迭代/修改。

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