我在我的活动中膨胀了这样的布局：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:baselineAligned="false"
android:orientation="horizontal" >
<FrameLayout
android:id="@+id/category_fragment"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1" />
<FrameLayout
android:id="@+id/sub_category_fragment"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1" />
<FrameLayout
android:id="@+id/sub_sub_category_fragment"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_weight="1" />
</LinearLayout>
这是我的活动AsyncTask。问题是 - 在执行 Asynctask 之后，活动布局没有更新。它保持空白。
package me.kaidul.uhunt;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import me.kaidul.uhunt.ChaptersListFragment.OnChapterSelectListener;
import me.kaidul.uhunt.SubChaptersListFragment.OnSubChapterSelectListener;
import com.actionbarsherlock.app.SherlockFragmentActivity;
import com.google.gson.stream.JsonReader;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
public class CompetitiveProgrammingActivity extends SherlockFragmentActivity
implements OnChapterSelectListener, OnSubChapterSelectListener {
public static List<Chapter> chapterList = new ArrayList<Chapter>();
private ProcessTask processTask = null;
Fragment chapterFragment = new ChaptersListFragment();
Fragment subChapterFragment = new SubChaptersListFragment();
Fragment subSubChapterFragment = new SubSubChaptersListFragment();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
processTask = new ProcessTask(this);
processTask.execute();
}
protected class ProcessTask extends AsyncTask<Void, Void, Void> {
private CompetitiveProgrammingActivity activity;
public ProcessTask(CompetitiveProgrammingActivity activity) {
this.activity = activity;
}
@Override
protected Void doInBackground(Void... params) {
InputStream inputStream = null;
try {
inputStream = getAssets().open(
CommonUtils.FILE_COMPETITIVE_PROGRAMMING_3);
JsonReader reader = new JsonReader(new InputStreamReader(
inputStream));
reader.beginArray(); // array #1
while (reader.hasNext()) {
String chapterTitle = null;
List<SubChapter> subList = new ArrayList<SubChapter>();
reader.beginObject(); // object #2
while (reader.hasNext()) {
reader.skipValue();
chapterTitle = reader.nextString();
reader.skipValue();
reader.beginArray(); // array #3
while (reader.hasNext()) {
String subChapterTitle = null;
List<SubSubChapter> subSubList = new ArrayList<SubSubChapter>();
reader.beginObject(); // object #4
while (reader.hasNext()) {
reader.skipValue();
subChapterTitle = reader.nextString();
reader.skipValue();
reader.beginArray(); // array #5
while (reader.hasNext()) {
reader.beginArray(); // array #6
String subSubChapterTitle = reader
.nextString(); // sub-sub-category
// title
List<ProblemList> problemsList = new ArrayList<ProblemList>();
while (reader.hasNext()) {
int signedProblemID = reader.nextInt(); // problemNo
String title = reader.nextString();
if (signedProblemID < 0)
problemsList.add(new ProblemList(
Math.abs(signedProblemID),
title, true));
else
problemsList.add(new ProblemList(
signedProblemID, title,
false));
}
reader.endArray(); // array #6
subSubList.add(new SubSubChapter(
subSubChapterTitle, problemsList));
}
reader.endArray(); // array #5
}
reader.endObject(); // object #4
subList.add(new SubChapter(subChapterTitle,
subSubList));
}
reader.endArray(); // array #3
}
reader.endObject(); // object #2
chapterList.add(new Chapter(chapterTitle, subList));
}
reader.endArray(); // array #1
reader.close();
} catch (IOException e) {
// nothing
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
// nothing
}
}
}
return null;
}
@Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
activity.setContentView(R.layout.competitive_programming_exercise);
FragmentTransaction transaction = activity.getSupportFragmentManager()
.beginTransaction();
if (activity.findViewById(R.id.fragment_container) != null) {
transaction.replace(R.id.fragment_container,
chapterFragment);
} else {
// these fragments are not upated
transaction.replace(R.id.category_fragment, chapterFragment);
transaction.replace(R.id.sub_category_fragment,
subChapterFragment);
transaction.replace(R.id.sub_sub_category_fragment,
subSubChapterFragment);
}
transaction.commit();
}
}
static protected class Chapter {
String chapterTitle;
List<SubChapter> subchapterList;
public Chapter(String chapterTitle, List<SubChapter> subchapterList) {
this.chapterTitle = chapterTitle;
this.subchapterList = subchapterList;
}
}
static protected class SubChapter {
String subChapterTitle;
List<SubSubChapter> subsubchapterList;
public SubChapter(String subChapterTitle,
List<SubSubChapter> subsubchapterList) {
this.subChapterTitle = subChapterTitle;
this.subsubchapterList = subsubchapterList;
}
}
static protected class SubSubChapter {
String subSubChapterTitle;
List<ProblemList> problemList;
public SubSubChapter(String subSubChapterTitle,
List<ProblemList> problemList) {
this.subSubChapterTitle = subSubChapterTitle;
this.problemList = problemList;
}
}
static public class ProblemList {
Integer problemNo;
String problemTitle;
boolean isStarred;
public ProblemList(Integer problemNo, String problemTitle,
boolean isStarred) {
this.problemNo = problemNo;
this.isStarred = isStarred;
this.problemTitle = problemTitle;
}
}
@Override
public void onChapterSelected(int position) {
SubChaptersListFragment subChaptersListFrag = (SubChaptersListFragment) getSupportFragmentManager()
.findFragmentById(R.id.sub_category_fragment);
if (subChaptersListFrag != null) {
subChaptersListFrag.updateList(position);
} else {
subChapterFragment = new SubChaptersListFragment();
Bundle args = new Bundle();
args.putInt(SubChaptersListFragment.CHAPTER_POSITION, position);
subChapterFragment.setArguments(args);
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
transaction.replace(R.id.fragment_container, subChapterFragment);
transaction.commit();
}
}
@Override
public void onSubChapterSelected(int prev, int position) {
SubSubChaptersListFragment subSubChaptersListFrag = (SubSubChaptersListFragment) getSupportFragmentManager()
.findFragmentById(R.id.sub_sub_category_fragment);
if (subSubChaptersListFrag != null) {
subSubChaptersListFrag.updateList(prev, position);
} else {
subSubChapterFragment = new SubSubChaptersListFragment();
Bundle args = new Bundle();
args.putIntArray(SubSubChaptersListFragment.POSITIONS, new int[] {
prev, position });
subSubChapterFragment.setArguments(args);
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
transaction.replace(R.id.fragment_container, subSubChapterFragment);
transaction.commit();
}
}
@Override
public void onStop() {
super.onStop();
if (processTask != null
&& processTask.getStatus() != AsyncTask.Status.FINISHED) {
processTask.cancel(true);
}
}
}