以下是我从网络下载数据的编码，在执行后我将其保存到数据库，然后更新用于 GUI 的 ListAdapter。
问题是当保存到数据库时，屏幕在保存到数据库时冻结，对于 600 条记录，大约需要 20 秒。
请让我知道，我怎样才能改变它，这样 UI 就不会冻结。
private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
public DownloadWebPageTask() {
}
@Override
protected void onPreExecute() {
super.onPreExecute();
progressDialog = ProgressDialog.show(getActivity(),
"Please wait...", "Retrieving data ...", true);
progressDialog.setCancelable(true);
}
}
}
@Override
protected String doInBackground(String... urls) {
String response = "";
for (String url : urls) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
InputStream content = client.execute(httpGet).getEntity()
.getContent();
BufferedReader buffer = new BufferedReader(
new InputStreamReader(content));
String s = "";
while ((s = buffer.readLine()) != null) {
response += s;
}
} catch (Exception e) {
e.printStackTrace();
}
}
return response;
}
@SuppressLint("NewApi")
@Override
protected void onPostExecute(String result) {
try {
if (type.equalsIgnoreCase("ALL COURSES")) {
dbList = db.getAllCourseDBs(type);
if (dbList.isEmpty())
{
progressDialog.dismiss();
}
if((result==null)|| result.isEmpty())
{
}
else
{
if (type.equalsIgnoreCase("ALL COURSES")) {
db.deleteAllCourseByTypeDB(type);
}
else
{
db.deleteAllCourseByCategoryIdDB(category_id);
}
JSONArray jArray = new JSONArray(result);
for (int i = 0; i < jArray.length(); i++)
{
JSONObject json_data_one = jArray.getJSONObject(i);
db.deleteAllCourseCategoryByTypeDB(type);
for (int j = 0; i < jArray.length(); i++)
{
CourseDB nbnt = new CourseDB();
long insideStart = System.currentTimeMillis();
JSONObject json_data = jArray.getJSONObject(i);
String crsCd=null, crsTitle=null;
if (type.equalsIgnoreCase("Area of Training")) {
crsCd = json_data.getString("courseCd");
crsTitle = json_data.getString("courseTitle");
}
else{
crsCd = (json_data.getString("crsCd"));
crsTitle = (json_data.getString("crsTitle"));
}
nbnt.setcourse_crs(crsCd);
nbnt.setcategory_course_type(type);
nbnt.setcourse_name(crsTitle);
nbnt.setcat_foreign_id(category_id);
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd_HHmmss");
String currentDateandTime = sdf.format(new Date());
System.out.println("date to be inseted in DB"+currentDateandTime);
nbnt.setcourse_time(currentDateandTime);
arrayofWebData.add(nbnt);
db.beginTransaction();
SQLiteDatabase sqlDB = db.getWritableDatabase();
long startTime = System.currentTimeMillis();
db.addcourseByType(nbnt, sqlDB);
db.setTransactionSuccessful();
db.endTransaction();
db.close();
long endTime = System.currentTimeMillis();
readWebpagerating();
Collections.sort(arrayofWebData, new CourseDBComparator ());
listAdapter = new SelectArralAdapter(getActivity(),
arrayofWebData);
lv123.setAdapter(listAdapter);
lv123.setFastScrollEnabled(true);
lv123.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
CourseDB planet = listAdapter.getItem(position);
String key = planet.getcourse_crs();
String KEY_ID_NOTEBOOK = db.CourseDB(key);
System.out.println("value if key_id" + KEY_ID_NOTEBOOK);
Intent intent25 = new Intent(getActivity(),
CourseDetailsActivity.class);
intent25.putExtra("course_id", key);
intent25.putExtra("category_id", category_id);
intent25.putExtra("type", type);
intent25.putExtra("category_name", category_name);
startActivity(intent25);
getActivity().finish();
}
});
}
}
}
}
catch (JSONException e) {
Log.e("log tag", "Error parsing data" + e.toString());
}
}
}
按照建议更改了代码，屏幕现在不会冻结，但如果我移动到另一个屏幕，它会在执行后崩溃。
private class DownloadWebPageTask extends AsyncTask<String, Void, String> {
public DownloadWebPageTask() {
}
@Override
protected void onPreExecute() {
super.onPreExecute();
if (type.equalsIgnoreCase("ALL COURSES")) {
dbList = db.getAllCourseDBs(type);
if (dbList.isEmpty())
{
progressDialog = ProgressDialog.show(getActivity(),
"Please wait...", "Retrieving data ...", true);
progressDialog.setCancelable(true);
}
}else if(type.equalsIgnoreCase("SEARCH")){
// DO NOTHING
}
else
{
dbList = db.getAllCourseDBByTypes(category_id, type);
if (dbList.isEmpty())
{
System.out.println("the value of the dbList inside all coursestypes"+dbList.size());
progressDialog = ProgressDialog.show(getActivity(),
"Please wait...", "Retrieving data ...", true);
progressDialog.setCancelable(true);
}
}
}
@Override
protected String doInBackground(String... urls) {
String response = "";
for (String url : urls) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
InputStream content = client.execute(httpGet).getEntity()
.getContent();
BufferedReader buffer = new BufferedReader(
new InputStreamReader(content));
String s = "";
while ((s = buffer.readLine()) != null) {
response += s;
}
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("value of the response"+response);
//adding new */
if((response==null)|| response.isEmpty())
{
}
else
{
if (type.equalsIgnoreCase("ALL COURSES")) {
db.deleteAllCourseByTypeDB(type);
}else if(type.equalsIgnoreCase("SEARCH")){
// DO NOTHING
}
else
{
db.deleteAllCourseByCategoryIdDB(category_id);
}
JSONArray jArray;
try {
jArray = new JSONArray(response);
for (int i = 0; i < jArray.length(); i++)
{
JSONObject json_data_one = jArray.getJSONObject(i);
System.out.println("All the not empty");
db.deleteAllCourseCategoryByTypeDB(type);
for (int j = 0; i < jArray.length(); i++)
{
CourseDB nbnt = new CourseDB();
long insideStart = System.currentTimeMillis();
JSONObject json_data = jArray.getJSONObject(i);
String crsCd=null, crsTitle=null;
if (type.equalsIgnoreCase("Area of Training")) {
System.out.println("im area of tarinin");
crsCd = json_data.getString("courseCd");
crsTitle = json_data.getString("courseTitle");
}
else{
crsCd = (json_data.getString("crsCd"));
crsTitle = (json_data.getString("crsTitle"));
}
System.out.println("Time for one JSON parsing "
+ (System.currentTimeMillis() - insideStart));
nbnt.setcourse_crs(crsCd);
nbnt.setcategory_course_type(type);
nbnt.setcourse_name(crsTitle);
nbnt.setcat_foreign_id(category_id);
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd_HHmmss");
String currentDateandTime = sdf.format(new Date());
System.out.println("date to be inseted in DB"+currentDateandTime);
nbnt.setcourse_time(currentDateandTime);
arrayofWebData.add(nbnt);
db.beginTransaction();
SQLiteDatabase sqlDB = db.getWritableDatabase();
long startTime = System.currentTimeMillis();
db.addcourseByType(nbnt, sqlDB);
db.setTransactionSuccessful();
db.endTransaction();
db.close();
}
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return response;
}
@SuppressLint("NewApi")
@Override
protected void onPostExecute(String result) {
if (type.equalsIgnoreCase("ALL COURSES")) {
dbList = db.getAllCourseDBs(type);
if (dbList.isEmpty())
{
progressDialog.dismiss();
}
}else if(type.equalsIgnoreCase("SEARCH")){
// DO NOTHING
}
else
{
dbList = db.getAllCourseDBByTypes(category_id, type);
if (dbList.isEmpty())
{
System.out.println("the value of the dbList inside all coursestypes"+dbList.size());
progressDialog.dismiss();
}
}
readWebpagerating();
Collections.sort(arrayofWebData, new CourseDBComparator ());
listAdapter = new SelectArralAdapter(getActivity(),
arrayofWebData);
lv123.setAdapter(listAdapter);
lv123.setFastScrollEnabled(true);
lv123.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
CourseDB planet = listAdapter.getItem(position);
String key = planet.getcourse_crs();
String KEY_ID_NOTEBOOK = db.CourseDB(key);
System.out.println("value if key_id" + KEY_ID_NOTEBOOK);
System.out.println("category id on lcick listnere inside the post ecexute" + category_id);
Intent intent25 = new Intent(getActivity(),
CourseDetailsActivity.class);
intent25.putExtra("course_id", key);
intent25.putExtra("category_id", category_id);
intent25.putExtra("type", type);
intent25.putExtra("category_name", category_name);
startActivity(intent25);
getActivity().finish();
}
});
}
}