为什么ical4j这么久建？ [英] Why is ical4j taking so long to build?
问题描述
我试图解析在Android中使用ical4j谷歌日历的iCal（的.ics）文件。但它接管40秒打造从输入流的日历。
I am trying to parse a google calendar ical (.ics) file using ical4j in android. But its taking over 40 seconds to build the calendar from the input stream.
calendar = builder.build(fis);
该iCal文件仅在大小150KB。
此外，当我使用相同的code和在PC上运行它，日历的建设发生在不到一秒钟。
我也注意到在LogCat中大量垃圾收集。
任何一个能帮助我吗？
The ical file is only 150KB in size. Also, When I use the same code and run it in PC, the building of calendar takes place in less than a second. I have also noticed huge amounts of Garbage Collection in the LogCat. Can Any one help me?
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView = (TextView)findViewById(R.id.Hello_World);
new Download().execute();
}
final class Download extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute(){
TextView.setText("Downloading");
}
@Override
protected Void doInBackground(Void... arg0) {
try {
URL url = new URL(URL);
HttpURLConnection c = (HttpURLConnection) url.openConnection();
c.setRequestMethod("GET");
c.connect();
FileOutputStream fos = openFileOutput(fileName, MainActivity.MODE_PRIVATE);
InputStream is = c.getInputStream();
byte[] buffer = new byte[1024];
int length = 0;
while ((length = is.read(buffer)) != -1) {
fos.write(buffer, 0, length);
}
fos.close();
is.close();
} catch (IOException e) {
Log.d("log_tag", "Error: " + e);
}
return null;
}
@Override
protected void onPostExecute(Void Result) {
TextView.setText("Saved...Loading Data");
new Loadicaldata().execute();
}
}
final class Loadicaldata extends AsyncTask<Void, Void, Void> {
String Summary = null;
@Override
protected Void doInBackground(Void... arg0) {
FileInputStream fis = null;
try {
fis = openFileInput(fileName);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
CompatibilityHints.setHintEnabled(CompatibilityHints.KEY_RELAXED_UNFOLDING, true);
CompatibilityHints.setHintEnabled(CompatibilityHints.KEY_RELAXED_VALIDATION, true);
CalendarBuilder builder = new CalendarBuilder();
Calendar calendar = null;
try {
calendar = builder.build(fis);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ParserException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
b.append(calendar.getProperty("X-WR-CALNAME").getValue());
ComponentList events = calendar.getComponents(Component.VEVENT);
VEvent Event = (VEvent) events.get(0);
Summary = Event.getDescription().getValue();
/*
for (Object event : calendar.getComponents(Component.VEVENT)) {
if (((VEvent) event).getSummary() != null) {
b.append("\n\n");
b.append(((VEvent) event).getSummary().getValue());
b.append(": ");
b.append(((VEvent) event).getStartDate().getDate());
}
}
*/
return null;
}
@Override
protected void onPostExecute(Void Result) {
TextView.setText(Summary);
}
}
LogCat中：
http://dl.dropbox.com/u/35866688/LogCat.txt
另外，我可以肯定地排除IO错误的可能性，因为Calendar.load方法采用长为好。
Also, I can safely rule out the possibility of IO error, as Calendar.load method takes that long as well.
这是iCal文件，如果有人有兴趣。
<一href=\"https://www.google.com/calendar/ical/m0es4hhj4g9d69ibak88tvoup0%40group.calendar.google.com/public/basic.ics\" rel=\"nofollow\">https://www.google.com/calendar/ical/m0es4hhj4g9d69ibak88tvoup0%40group.calendar.google.com/public/basic.ics
This is the ical file if anyone is interested. https://www.google.com/calendar/ical/m0es4hhj4g9d69ibak88tvoup0%40group.calendar.google.com/public/basic.ics
推荐答案
一种可能性是，你是从 doInBackground 法无缓冲输入流中读取。如果 CalendarBuilder.build（...）方法一次读取一个字节，这会产生大量的系统调用，而放慢改革的步伐显著。
One possibility is that you are reading from an unbuffered input stream in the doInBackground method. If the CalendarBuilder.build(...) method reads one byte at a time, this will generate a lot of system calls, and slow things down significantly.
一个第二个可能性是，该问题是由垃圾收集引起的。有没有很多可以做的，但增加堆大小可能的可能的帮助。 （过度GC开销的原因之一是关闭不好，如果他们不能在每个GC循环回收的内存运行与堆是接近满。地方选区尾部的效率...）
A second possibility is that the problem is caused by garbage collection. There's not a lot you can do about that, but increasing the heap size might might help. (One cause of excessive GC overheads is running with a heap that is close to full. The efficiency of GCs tail off badly if they are unable to reclaim much memory in each GC cycle ... )
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