我正在使用 asyncTask 通过互联网下载一些文件。这是我写的有效的代码
downloadUrl task = new downloadUrl(url1,"jsonData1","/sdcard/appData/LocalJson/jsonData1",context);
task.execute();
downloadUrl task1 = new downloadUrl(url2,"jsonData2","/sdcard/appData/LocalJson/jsonData2",context);
task1.execute();
downloadUrl task2 = new downloadUrl(url3,"jsonData3","/sdcard/appData/LocalJson/jsonData3",context);
task2.execute();
downloadUrl task3 = new downloadUrl(url4,"jsonData4","/sdcard/appData/LocalJson/jsonData4",context);
task3.execute();
现在,考虑到 UI 线程,这些任务并行运行,但它们在彼此之间串行运行,这很耗时。所以相反,我试图在执行程序上执行它们但问题是这样我会丢失一些文件,这意味着当它们序列化运行时,我最终下载了 38 个文件,而在 Executor 上运行我最终得到了 20 .我很确定是这样,因为我在多线程代码中搞砸了一些东西所以我会把它发布到:
@Override
protected String doInBackground(String... args) {
downloadAndStoreJson(url,targetFolder);
JSONObject jsonObj = loadJSONObject(pathForLoad);
try {
processJsonData(jsonObj);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return "done";
}
@Override
protected void onPostExecute(String result) {
s(targetFolder+" Finished!");
++mutex;
progressBar.setProgress(25*mutex);
if(mutex==4){
mutex=0;
progressBar.setProgress(100);
progressBar.dismiss();
s(monuments.size());
Intent intent = new Intent (getApplicationContext(),NextClass.class);
intent.putExtra("monuments", monuments);
startActivity(intent);
}
}
private void downloadAndStoreJson(String url,String tag){
JSONParser jParser = new JSONParser();
JSONObject json = jParser.getJSONFromUrl(url);
String jsonString = json.toString();
byte[] jsonArray = jsonString.getBytes();
File fileToSaveJson = new File("/sdcard/appData/LocalJson/",tag);
BufferedOutputStream bos;
try {
bos = new BufferedOutputStream(new FileOutputStream(fileToSaveJson));
bos.write(jsonArray);
bos.flush();
bos.close();
} catch (FileNotFoundException e4) {
// TODO Auto-generated catch block
e4.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
finally {
jsonArray=null;
jParser=null;
System.gc();
}
}
private JSONObject loadJSONObject(String path){
JSONObject jsonObj = null;
File readFromJson = new File(path);
byte[] lala;
try {
lala= org.apache.commons.io.FileUtils.readFileToByteArray(readFromJson);
s("---------------"+lala.length);
String decoded = new String(lala, "UTF-8");
jsonObj = new JSONObject(decoded);
} catch (IOException e5) {
// TODO Auto-generated catch block
e5.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return jsonObj;
}
processJsonData 是一个长方法,它解析 json 文件,创建对象,然后将它们存储在 ArrayList 中,这就是可能存在问题的地方。