[英]Async task made my application crashes
但是它们是不同的,我使用Async task
与服务器端进行通信,除了两种情况外,它都可以正常工作:第一种情况是如果服务器由于任何原因导致应用程序崩溃而停止,第二种情况是当我连接到网络但没有互联网时在此访问点上, 我的问题是如何处理此错误以避免崩溃? 这是我的代码
public class news_tab extends Fragment{
ListView newsLIST;
String result_news,result_fav;
String [] Hot_news,newsName1,newsText1 ,agentName;
int [] Hot_news_id,agent_id;
int [] fav_id;
private Context context;
ArrayList<String> newsName,newsText,agentNamelist;
public news_tab()
{
}
public news_tab (Context context)
{
this.context=context;
newsName=new ArrayList<String>();
newsText=new ArrayList<String>();
agentNamelist=new ArrayList<String>();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.news, container, false);
rootView.setBackground(Drawable.createFromPath("@drawable/back"));
newsLIST=(ListView)rootView.findViewById(R.id.newsLV);
getFavouriteNews();
news();
return rootView;
}
public void getFavouriteNews() {
new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... voids) {
try {
if(isNetworkAvailable()) {
HttpRequestSender http = new HttpRequestSender((Activity) context);
result_fav = http.SEND_POST_get_news_fav("**********/dal/login.asmx/getdata_newsfav");
}
else
{
result_fav="";
Toast.makeText(context,"Check the internet Connection",Toast.LENGTH_SHORT).show();
}
// result = http.SEND_Check("******/Login?email="
// +username.getText().toString()+"&password="+password1.getText().toString());
Log.d("String", result_fav);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(Void aVoid) {
if(result_fav.contains("text_news")) {
// x.cancel();
// Toast.makeText(context, "Welcome Favourite", Toast.LENGTH_SHORT).show();
// JSONObject jb = null;
try {
JSONArray JA = new JSONArray(result_fav);
ArrayList <String> newsName , newsText,agentNamelist,urlList;
fav_id= new int [JA.length()];
for (int i = 0; i < JA.length(); i++) {
JSONObject JO = (JSONObject) JA.get(i);
fav_id[i]= (int) JO.get("news_id");
}
} catch (JSONException e) {
e.printStackTrace();
}
}
else
{
// Toast.makeText(context,"No News",Toast.LENGTH_SHORT).show();
}
super.onPostExecute(aVoid);
}
}.execute();
}
private boolean isNetworkAvailable() {
ConnectivityManager connectivityManager
= (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
return activeNetworkInfo != null;
}
最后我得到了这个错误
03-29 10:15:45.500 24585-24585/com.Offferly.ahmad.hakimi E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.Offferly.ahmad.hakimi, PID: 24585
java.lang.NullPointerException
at com.Offferly.ahmad.hakimi.tab.news_tab$2.onPostExecute(news_tab.java:217)
at com.Offferly.ahmad.hakimi.tab.news_tab$2.onPostExecute(news_tab.java:179)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5692)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)
03-29 10:15:45.540 2952-20003/? E/WakeLock: release without a matched acquire!
您不能在doInBackground()方法内显示Toast。 如果要执行此操作,请使用以下代码。
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(<your class name>.this, "Cool Ha?", Toast.LENGTH_SHORT).show();
}});
尝试这个。
如果服务器由于任何原因导致您在result_fav变量中获得空响应而停止,则需要在onPostExecute()方法中处理null
如果(!TextUtils.isEmpty(result_fav)){
//您的代码
}其他{
//显示吐司无效响应
}
在第二种情况下 :
在doInBackground()方法中删除Toast消息。在doInBackground()方法中无法显示Toast消息
您可以在getFavouriteNews()方法中尝试以下方法:
if(isNetworkAvailable()) {
//then call your async task
}
else
{
//Show Toast no internet
}
更改您的if
条件
if(result_fav.contains("text_news"))
至
if(!TextUtil(result_fav) && result_fav.contains("text_news"))
从doinbackground移除吐司。 您应该在ui thread.code上运行它,如下所示
@Override
protected Void doInBackground(Void... voids) {
try {
if(isNetworkAvailable()) {
HttpRequestSender http = new HttpRequestSender((Activity) context);
result_fav = http.SEND_POST_get_news_fav("**********/dal/login.asmx/getdata_newsfav");
}
else
{
result_fav="";
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(context,"Check the internet Connection",Toast.LENGTH_SHORT).show();
}});
}
// result = http.SEND_Check("******/Login?email="
// +username.getText().toString()+"&password="+password1.getText().toString());
Log.d("String", result_fav);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
在onViewCreated
中而不是onCreateView
运行AsyncTask。
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