我正在开发一个Android应用程序，但Asynctask和Looper给我带来了更多问题，我不明白如何解决这个问题... 这是我的主要活动：
@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public class MainActivity extends Activity {
private ProgressDialog progress = null;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Check if the connectivity is available
CheckConnectivity check = new CheckConnectivity();
Boolean conn = check.checkNow(this.getApplicationContext());
//if connectivity is available
if(conn == true){
//Create the action bar
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
ActionBar actionBar = getActionBar();
actionBar.setDisplayShowTitleEnabled(true);
actionBar.setDisplayHomeAsUpEnabled(false);
actionBar.setHomeButtonEnabled(false);
actionBar.setBackgroundDrawable(new ColorDrawable(Color.parseColor("#0170a5")));
}
setContentView(R.layout.activity_main);
GetNews getNews = new GetNews();
getNews.execute();
}else{
connectivityMessage("Nessuna connessione presente, assicurati di avere il traffico dati oppure il Wi-Fi attivato e riprova.");
}
}
/******************************************************************************************************/
private class GetNews extends AsyncTask<Void, Void, String>{
@Override
protected String doInBackground(Void... params) {
Looper.prepare();
ReadServer read = new ReadServer();
String result = read.readserver("list_news","homepage");
return result;
}
@Override
protected void onCancelled() {
super.onCancelled();
}
@Override
protected void onPreExecute() {
progress = ProgressDialog.show(
MainActivity.this, null, "Caricamento notizie...");
super.onPreExecute();
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try {
String url_img = null;
String path = "http://www.MYPATH.it";
TableLayout MainTable = (TableLayout) findViewById(R.id.main_table);
JSONArray Jobj = new JSONArray(result);
for (int i = 0; i < Jobj.length(); i++) {
TableRow row = new TableRow(getApplicationContext());
row.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT, TableRow.LayoutParams.WRAP_CONTENT));
JSONObject news_preview = Jobj.getJSONObject(i);
Integer news_id = news_preview.getInt("id_articolo");
String news_title = news_preview.getString("titolo");
String news_image = news_preview.getString("immagine");
// Check if image url is relative or absolute
Pattern p = Pattern.compile("^(https?|ftp|file)://[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]");
Matcher m = p.matcher(news_image);
if (m.matches() == false) {
url_img = path + news_image;
} else if (m.matches() == true) {
url_img = news_image;
}
// Call Html Parser to parse text
HtmlParser parsed_string = new HtmlParser();
Spanned title_nohtml = parsed_string.htmlparser(news_title);
final ImageView img = new ImageView(getApplicationContext());
final TextView txt = new TextView(getApplicationContext());
LayoutParams params = new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
img.setAdjustViewBounds(true);
Bitmap bitmap = BitmapFactory.decodeStream((InputStream) new URL(url_img).getContent());
Bitmap resized = null;
int screenLayout = getApplicationContext().getResources().getConfiguration().screenLayout;
screenLayout &= Configuration.SCREENLAYOUT_SIZE_MASK;
switch (screenLayout) {
case Configuration.SCREENLAYOUT_SIZE_SMALL:
row.setPadding(0, 7, 2, 7);
resized = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
txt.setTextSize(18);
break;
case Configuration.SCREENLAYOUT_SIZE_NORMAL:
row.setPadding(0, 14, 2, 14);
resized = Bitmap.createScaledBitmap(bitmap, 140, 140, true);
txt.setTextSize(18);
break;
case Configuration.SCREENLAYOUT_SIZE_LARGE:
row.setPadding(0, 14, 2, 14);
resized = Bitmap.createScaledBitmap(bitmap, 200, 200, true);
txt.setTextSize(24);
break;
case Configuration.SCREENLAYOUT_SIZE_XLARGE:
row.setPadding(0, 14, 2, 14);
resized = Bitmap.createScaledBitmap(bitmap, 200, 200, true);
txt.setTextSize(24);
break;
default:
break;
}
img.setImageBitmap(resized);
txt.setGravity(Gravity.LEFT | Gravity.CENTER_HORIZONTAL | Gravity.CENTER_VERTICAL);
txt.setLayoutParams(params);
txt.setBackgroundColor(Color.WHITE);
txt.setTypeface(null, Typeface.BOLD);
txt.setTextColor(Color.BLACK);
txt.setId(news_id);
txt.setText(title_nohtml);
txt.setClickable(true);
row.addView(img);
row.addView(txt);
MainTable.addView(row);
txt.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, NewsDetail.class);
Bundle extras = new Bundle();
extras.putInt("id_news", txt.getId());
intent.putExtras(extras);
startActivity(intent);
}
});
}
}catch (Exception e) {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(MainActivity.this);
alertDialog.setTitle("Si è verificato un errore");
alertDialog.setMessage("Errore 001" + "\n" + "Non è stato possibile soddisfare la tua richiesta, riprova più tardi.");
alertDialog.show();
}
progress.dismiss();
Looper.loop();
Looper.getMainLooper().quitSafely();
change();
}
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
}
/******************************************************************************************************/
@Override
public void onStart() {
super.onStart();
Tracker tracker = GoogleAnalytics.getInstance(this).getTracker("UA-49974758-1");
tracker.set(Fields.SCREEN_NAME, "Visualizzazione prima pagina");
tracker.send(MapBuilder.createAppView().set(Fields.customDimension(1), "Premium").build());
}
/******************************************************************************************************/
public void change(){
ChangeLog cl = new ChangeLog(this);
if (cl.firstRun())
cl.getLogDialog().show();
}
/******************************************************************************************************/
@Override
public void onDestroy() {
super.onDestroy();
if ( progress!=null && progress.isShowing() ){
progress.cancel();
}
}
/******************************************************************************************************/
@Override
public void onPause() {
super.onPause();
if ( progress!=null && progress.isShowing() ){
progress.cancel();
}
}
*****编辑*****
视频库代码：
@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public class VideoGallery extends Activity {
private ProgressDialog progress = null;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Check if the connectivity is available
CheckConnectivity check = new CheckConnectivity();
Boolean conn = check.checkNow(this.getApplicationContext());
//if connectivity is available
if(conn == true){
//Create the action bar
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
ActionBar actionBar = getActionBar();
actionBar.setDisplayShowTitleEnabled(true);
actionBar.setDisplayHomeAsUpEnabled(false);
actionBar.setHomeButtonEnabled(false);
actionBar.setBackgroundDrawable(new ColorDrawable(Color.parseColor("#0170a5")));
}
setContentView(R.layout.activity_main);
GetVideo getVideo = new GetVideo();
getVideo.execute();
}else{
connectivityMessage("Nessuna connessione presente, assicurati di avere il traffico dati oppure il Wi-Fi attivato e riprova.");
}
}
/************************************************************************/
private class GetVideo extends AsyncTask<Void, Void, String>{
@Override
protected String doInBackground(Void... params) {
Looper.prepare(); <---- LINE 86
ReadServer read = new ReadServer();
String result = read.readserver("id_gallery", "gall_video");
return result;
}
@Override
protected void onCancelled() {
super.onCancelled();
}
@Override
protected void onPreExecute() {
progress = ProgressDialog.show(
VideoGallery.this, null, "Caricamento video...");
super.onPreExecute();
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try{
TableLayout MainTable = (TableLayout)findViewById(R.id.main_table);
JSONArray Jobj = new JSONArray(result);
String url_img = null;
String url_video = null;
for (int i = 0; i < Jobj.length(); i++){
TableRow row = new TableRow(getApplicationContext());
row.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT, TableRow.LayoutParams.WRAP_CONTENT));
JSONObject list_video = Jobj.getJSONObject(i);
Integer video_id = list_video.getInt("id_video");
String video_title = list_video.getString("nome_video");
String video_image = list_video.getString("video_img");
String video_url = list_video.getString("url_video");
Pattern p = Pattern.compile("^(https?|ftp|file)://[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]");
Matcher m = p.matcher(video_image);
Pattern v = Pattern.compile("^/video/[-a-zA-Z0-9+&@#/%?=~_|!:,.;]*[-a-zA-Z0-9+&@#/%=~_|]");
Matcher vm = v.matcher(video_url);
//Path video
if(vm.matches() == false){
url_video = path_youtube+video_url;
}else if(vm.matches() == true){
url_video = path_an_tv+video_url;
}
//Path image
if(m.matches() == false){
url_img = path+video_image;
}else if(m.matches() == true){
url_img = video_image;
}
final ImageView img = new ImageView(getApplicationContext());
final TextView txt = new TextView(getApplicationContext());
LayoutParams params;
img.setAdjustViewBounds(true);
img.setScaleType(ImageView.ScaleType.CENTER_CROP);
txt.setGravity(Gravity.LEFT | Gravity.CENTER_HORIZONTAL | Gravity.CENTER_VERTICAL );
Bitmap bitmap = BitmapFactory.decodeStream((InputStream)new URL(url_img).getContent());
Bitmap resized = null;
int screenLayout = getApplicationContext().getResources().getConfiguration().screenLayout;
screenLayout &= Configuration.SCREENLAYOUT_SIZE_MASK;
switch (screenLayout) {
case Configuration.SCREENLAYOUT_SIZE_SMALL:
row.setPadding(0, 7, 0, 7);
resized = Bitmap.createScaledBitmap(bitmap, 70, 70, true);
params = new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, 70);
txt.setLayoutParams(params);
txt.setTextSize(18);
break;
case Configuration.SCREENLAYOUT_SIZE_NORMAL:
row.setPadding(0, 14, 0, 14);
resized = Bitmap.createScaledBitmap(bitmap, 140, 140, true);
params = new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, 140);
txt.setLayoutParams(params);
txt.setTextSize(18);
break;
case Configuration.SCREENLAYOUT_SIZE_LARGE:
row.setPadding(0, 14, 0, 14);
resized = Bitmap.createScaledBitmap(bitmap, 200, 200, true);
params = new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, 200);
txt.setLayoutParams(params);
txt.setTextSize(24);
break;
case Configuration.SCREENLAYOUT_SIZE_XLARGE:
row.setPadding(0, 14, 0, 14);
resized = Bitmap.createScaledBitmap(bitmap, 200, 200, true);
params = new TableRow.LayoutParams(LayoutParams.MATCH_PARENT, 200);
txt.setLayoutParams(params);
txt.setTextSize(24);
break;
default:
break;
}
txt.setBackgroundColor(Color.WHITE);
txt.setTypeface(null, Typeface.BOLD);
txt.setTextColor(Color.BLACK);
txt.setId(video_id);
txt.setTag(url_video);
txt.setText(video_title);
txt.setClickable(true);
img.setImageBitmap(resized);
row.addView(img);
row.addView(txt);
MainTable.addView(row);
txt.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
startActivity(new Intent(Intent.ACTION_VIEW,Uri.parse((String) txt.getTag())));
}
});
}
}catch(Exception e){
AlertDialog.Builder alertDialog = new AlertDialog.Builder(VideoGallery.this);
alertDialog.setTitle("Si è verificato un errore");
alertDialog.setMessage("Errore 001" +"\n"+"Non è stato possibile soddisfare la tua richiesta, riprova più tardi.");
alertDialog.show();
}
progress.dismiss();
Looper.loop();
Looper.getMainLooper().quitSafely();
}
@Override
protected void onProgressUpdate(Void... values) {
super.onProgressUpdate(values);
}
}
/******************************************************************************************************/
@Override
public void onStart() {
super.onStart();
Tracker tracker = GoogleAnalytics.getInstance(this).getTracker("UA-49974758-1");
tracker.set(Fields.SCREEN_NAME, "Visualizzazione video");
tracker.send(MapBuilder.createAppView().set(Fields.customDimension(1), "Premium").build());
}
/******************************************************************************************************/
@Override
public void onDestroy() {
super.onDestroy();
if ( progress!=null && progress.isShowing() ){
progress.cancel();
}
}
/******************************************************************************************************/
@Override
public void onPause() {
super.onPause();
if ( progress!=null && progress.isShowing() ){
progress.cancel();
}
}
当我将活动更改为另一个再次包含asynctask的活动时，发生了错误：
11-14 11:49:18.196: E/AndroidRuntime(18749): FATAL EXCEPTION: AsyncTask #1
11-14 11:49:18.196: E/AndroidRuntime(18749): java.lang.RuntimeException: An error occured while executing doInBackground()
11-14 11:49:18.196: E/AndroidRuntime(18749): at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-14 11:49:18.196: E/AndroidRuntime(18749): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
11-14 11:49:18.196: E/AndroidRuntime(18749): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
11-14 11:49:18.196: E/AndroidRuntime(18749): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
11-14 11:49:18.196: E/AndroidRuntime(18749): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-14 11:49:18.196: E/AndroidRuntime(18749): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
11-14 11:49:18.196: E/AndroidRuntime(18749): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
11-14 11:49:18.196: E/AndroidRuntime(18749): at java.lang.Thread.run(Thread.java:841)
11-14 11:49:18.196: E/AndroidRuntime(18749): Caused by: java.lang.RuntimeException: Only one Looper may be created per thread
11-14 11:49:18.196: E/AndroidRuntime(18749): at android.os.Looper.prepare(Looper.java:78)
11-14 11:49:18.196: E/AndroidRuntime(18749): at android.os.Looper.prepare(Looper.java:73)
11-14 11:49:18.196: E/AndroidRuntime(18749): at com.miaapplicazione.VideoGallery$GetVideo.doInBackground(VideoGallery.java:86)
11-14 11:49:18.196: E/AndroidRuntime(18749): at com.miaapplicazione.VideoGallery$GetVideo.doInBackground(VideoGallery.java:1)
****编辑2 ****
如果我删除Looper.prepare（）;在视频库中发生了另一个错误：
11-14 12:01:48.357: E/AndroidRuntime(20476): FATAL EXCEPTION: AsyncTask #2
11-14 12:01:48.357: E/AndroidRuntime(20476): java.lang.RuntimeException: An error occured while executing doInBackground()
11-14 12:01:48.357: E/AndroidRuntime(20476): at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-14 12:01:48.357: E/AndroidRuntime(20476): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
11-14 12:01:48.357: E/AndroidRuntime(20476): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
11-14 12:01:48.357: E/AndroidRuntime(20476): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
11-14 12:01:48.357: E/AndroidRuntime(20476): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-14 12:01:48.357: E/AndroidRuntime(20476): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
11-14 12:01:48.357: E/AndroidRuntime(20476): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
11-14 12:01:48.357: E/AndroidRuntime(20476): at java.lang.Thread.run(Thread.java:841)
11-14 12:01:48.357: E/AndroidRuntime(20476): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
11-14 12:01:48.357: E/AndroidRuntime(20476): at android.os.Handler.<init>(Handler.java:197)
11-14 12:01:48.357: E/AndroidRuntime(20476): at android.os.Handler.<init>(Handler.java:111)
11-14 12:01:48.357: E/AndroidRuntime(20476): at android.app.Activity.<init>(Activity.java:759)
11-14 12:01:48.357: E/AndroidRuntime(20476): at com.alessandrianews.ReadServer.<init>(ReadServer.java:17)
11-14 12:01:48.357: E/AndroidRuntime(20476): at com.alessandrianews.VideoGallery$GetVideo.doInBackground(VideoGallery.java:86)
11-14 12:01:48.357: E/AndroidRuntime(20476): at com.alessandrianews.VideoGallery$GetVideo.doInBackground(VideoGallery.java:1)
11-14 12:01:48.357: E/AndroidRuntime(20476): at android.os.AsyncTask$2.call(AsyncTask.java:287)
11-14 12:01:48.357: E/AndroidRuntime(20476): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
11-14 12:01:48.357: E/AndroidRuntime(20476): ... 4 more
我怎么能解决这个问题？我读了所有其他问题，但解决方案对我没有帮助。
答案 0 :(得分：0)
如果你想使用AsyncTask所以使用它，你不应该把它与Lopper混合......
protected Integer doInBackground(Void... params) {}
已经在后台线程上工作了，没有理由为Lopper打电话，为什么？
如果您的应用程序需要进行某种长时间的计算，那么AsyncTask是非常好的工具，因为它提供了处理UI线程的方法，并允许更新UI以及一些工作进度，因为每个将使用您的应用程序的用户都应该知道该应用程序“做某事”（当需要超过2-5秒时）。
它也是通用的，并提供一些好处。
如果您不需要更新UI，只需使用例如Handler。
删除Looper.prepare();
答案 1 :(得分：0)
尝试添加：
if (Looper.myLooper() == null) Looper.prepare;
它对我有用