我正在做的是每隔X秒下载一个带AsyncTask的文件列表：
首先获取视频和图像列表，然后下载每个视频和图像。一切都很完美。
package com.example.tvrplayer;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.content.Context;
import android.os.AsyncTask;
import android.util.Log;
public class updateFiles extends AsyncTask<Object, Integer, Long> {
public PlayerActivity activity;
public updateFiles(PlayerActivity a) { activity = a;}
@Override
protected Long doInBackground(Object... params) {
Context context = (Context) params[0];
String username = (String) params[1];
String linkid = (String) params[2];
String apiurl = (String) params[3];
JSONArray programs = Json.getJson(apiurl + "/rest/program/device/"+ linkid +"/"+ username +"/"+ activity.deviceid, "GET");
File mediadir = context.getDir("tvr", Context.MODE_PRIVATE);
try {
LINE 44- for (int j=0; j < programs.length(); j++) {
JSONObject json_data = programs.getJSONObject(j);
String name = json_data.getString("Name").toLowerCase();
name = name.replace("-", "_");
if (name.contains("mp4") || name.contains("m4v") || name.contains("png") || name.contains("jpg") || name.contains("jpeg")) {
String _name = name.replace("/", "");
File file = new File(mediadir, _name);
Log.i("FILE SIZE", ""+file.length());
if ( file.length() > 0 ) {
Log.i("FILE EXISTS", _name);
} else {
Log.i("START DOWNLOAD", _name);
new Download().execute(context, _name, apiurl + "/rest/transfer/"+ linkid +"/"+ username +"/" + json_data.getString("ID"));
}
Log.i("FILES found", ""+mediadir.listFiles().length);
}
}
} catch (JSONException e) {
Log.e("JSON Exception", e.getMessage());
e.printStackTrace();
}
// activity.filelist = mediadir.listFiles();
return null;
}
@Override
protected void onPostExecute(Long result) {}
}
过了一会儿我收到了这个错误：
02-25 16:19:19.578: E/JSON - 2 -(17470): java.net.SocketException: Socket closed - http://192.168.2.136:8080/rest/program/device/123someasdidFoo123123/email@foo.com/000
02-25 16:19:16.648: W/dalvikvm(17284): threadid=11: thread exiting with uncaught exception (group=0x40bf11f8)
02-25 16:19:16.664: E/AndroidRuntime(17284): FATAL EXCEPTION: AsyncTask #1
02-25 16:19:16.664: E/AndroidRuntime(17284): java.lang.RuntimeException: An error occured while executing doInBackground()
02-25 16:19:16.664: E/AndroidRuntime(17284): at android.os.AsyncTask$3.done(AsyncTask.java:278)
02-25 16:19:16.664: E/AndroidRuntime(17284): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
02-25 16:19:16.664: E/AndroidRuntime(17284): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
02-25 16:19:16.664: E/AndroidRuntime(17284): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
02-25 16:19:16.664: E/AndroidRuntime(17284): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
02-25 16:19:16.664: E/AndroidRuntime(17284): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
02-25 16:19:16.664: E/AndroidRuntime(17284): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
02-25 16:19:16.664: E/AndroidRuntime(17284): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
02-25 16:19:16.664: E/AndroidRuntime(17284): at java.lang.Thread.run(Thread.java:856)
02-25 16:19:16.664: E/AndroidRuntime(17284): Caused by: java.lang.NullPointerException
02-25 16:19:16.664: E/AndroidRuntime(17284): at com.example.tvrplayer.updateFiles.doInBackground(updateFiles.java:44)
02-25 16:19:16.664: E/AndroidRuntime(17284): at com.example.tvrplayer.updateFiles.doInBackground(updateFiles.java:1)
02-25 16:19:16.664: E/AndroidRuntime(17284): at android.os.AsyncTask$2.call(AsyncTask.java:264)
02-25 16:19:16.664: E/AndroidRuntime(17284): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
02-25 16:19:16.664: E/AndroidRuntime(17284): ... 5 more
这是从API获取内容的JSON文件
package com.example.tvrplayer;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
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.os.Handler;
import android.os.Message;
import android.util.Log;
public class Json {
static JSONArray getJson(String url, String method) {
// Log.i("JSON",url);
InputStream is = null;
String result = "";
JSONArray jsonObject = null;
// HTTP
try {
HttpClient httpclient = new DefaultHttpClient(); // for port 80 requests!
if ( method == "GET") {
HttpGet httpget = new HttpGet(url);
HttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
is = entity.getContent();
if (entity != null) {
httpget.abort();
}
} else if (method == "POST") {
HttpPost httppost = new HttpPost(url);
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}
} catch(Exception e) {
Log.e("JSON - 1 -", e.toString());
return null;
}
// Read response to string
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"utf-8"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
// Log.d("JSON result",result);
} catch(Exception e) {
Log.e("JSON - 2 -", e.toString() + " - " + url);
return null;
}
// Convert string to object
try {
jsonObject = new JSONArray(result);
} catch(JSONException e) {
try {
jsonObject = new JSONArray("["+result+"]");
} catch(JSONException e1) {
Log.e("JSON - 3 -", e1.toString());
return null;
}
}
return jsonObject;
}
}
所以我想象的是，当asynctask正忙着下载另一个下载完成并关闭连接？
任何想法是什么或如何解决这个问题？
答案 0 :(得分：1)
您在Null Pointer Exception方法的第44行获得doBackground()。请发布完整的代码，以便我们为您提供进一步的帮助。确保在使用任何对象之前完成所有初始化。在任何情况下，检查第44行，无论你在那里使用哪个对象，都要确保它不是NULL。