This is my code.when I click on button ,it call yourcountry() function then yourcountry() in a thread call location(). I get data from http://192.168.4.1/led/0 with WIFI connection. while-loop runs about 25 times and then it appears Unfortunately app has stopped .I think the problem is in :
runOnUiThread(new Runnable() {
public void run() {
country.setText(show);
}
});
This is my code:
public class MainActivity extends AppCompatActivity {
public Button button;
public TextView country;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = (Button) findViewById(R.id.button);
country=(TextView) findViewById(R.id.country);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
yourcountry();
}
});
} // end of oncreate
public void yourcountry() {
new Thread(new Runnable() {
#Override
public void run() {
location();
}
}).start();
}
private void location() {
// while (true) {
while (true){
try {
URL url = new URL("http://192.168.4.1/led/0");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.connect();
InputStream inputStream = conn.getInputStream();
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "UTF-8");
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String data = "", line = "";
while ((line = bufferedReader.readLine()) != null) {
data += line+"\n" ;
}
show = data;
runOnUiThread(new Runnable() {
public void run() {
country.setText(show);
}
});
sleep(50);
} catch (MalformedURLException e)
{
Log.e("error", e.toString());
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}//end of while
} //end location
}//end of class
Calling a runnable from a new thread doesn't put it in the main thread.
I think you would have better luck wrapping your functions in an AsyncTask. You can do all of your UI work in the
onPostExecute()
Otherwise, you need to wrap your runnable in a handler to ensure you're running it on the UI thread.
Edit::
public class MainActivity extends AppCompatActivity {
public TextView country;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
country=(TextView) findViewById(R.id.country) ;
new MyAsyncTask().execute();
}//on creaate
static boolean shouldRun = true;
class MyAsyncTask extends AsyncTask<Void, Void, String> {
boolean firstRun = true;
#Override
protected String doInBackground(Void... params) {
if (!firstRun) {
try {
Thread.sleep(50);
} catch (InterruptedException e) {
}
} else {
firstRun = false;
}
String data = null;
InputStream inputStream = null;
InputStreamReader inputStreamReader = null;
BufferedReader bufferedReader = null;
try {
URL url = new URL("http://192.168.4.1/led/0");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.connect();
inputStream = conn.getInputStream();
inputStreamReader = new InputStreamReader(inputStream, "UTF-8");
bufferedReader = new BufferedReader(inputStreamReader);
data = "";
String line = "";
while ((line = bufferedReader.readLine()) != null) {
data += line + "\n";
}
} catch (IOException e) {
e.printStackTrace();
data = null;
}
return data;
}
#Override
protected void onPostExecute(String data) {
super.onPostExecute(data);
if (data != null) {
country.setText(data);
}
if (shouldRun) {
new MyAsyncTask().execute();
}
}
}
}
Then you can call:
new MyAsyncTask().execute();
And Permission:
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
Edit::
While(true) isn't good practice, since you have no breaks set. This will run forever (which you don't want).
You can spin off another async task when the first one finishes under some condition.
Related
I'm getting a crash in an Android device which shows an exception about android.os.NetworkOnMainThreadException in AsyncTask. Why do I get this exception? The exception is on line 60 in onPreExecute.
I send context with WeakReference. Please explain the advantage of using WeakReference here.
public class MainActivity extends AppCompatActivity {
RecyclerView recyclerView;
RecyclerView.LayoutManager layoutManager;
RecyclerViewAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = findViewById(R.id.rview);
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setHasFixedSize(true);
MyTask task = new MyTask(this);
task.execute();
}
static class MyTask extends AsyncTask {
BufferedReader reader;
private WeakReference < MainActivity > contextRef;
MyTask(MainActivity mainActivity) {
contextRef = new WeakReference < >(mainActivity);
}
#Override
protected void onPreExecute() {
try {
URL url = new URL("https://api.myjson.com/bins/1fi1zm");
URLConnection connection = url.openConnection();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
} catch(MalformedURLException e) {
e.printStackTrace();
} catch(IOException e) {
e.printStackTrace();
}
}
#Override
protected Object doInBackground(Object[] objects) {
return null;
}
#Override
protected void onPostExecute(Object o) {
MainActivity context = contextRef.get();
if (context != null) {
Gson gson = new Gson();
List < Contact > list;
try {
list = Arrays.asList(gson.fromJson(reader.readLine(), Contact[].class));
context.adapter = new RecyclerViewAdapter(list);
context.recyclerView.setAdapter(context.adapter);
} catch(IOException e) {
e.printStackTrace();
}
}
}
}
}
The issue is for the code in onPreExecute(). It runs on Main Thread and you cannot do background task here. Try this
static class MyTask extends AsyncTask {
BufferedReader reader;
private WeakReference<MainActivity> contextRef;
MyTask(MainActivity mainActivity) {
contextRef = new WeakReference<>(mainActivity);
}
#Override
protected void onPreExecute() {
}
#Override
protected Object doInBackground(Object[] objects) {
try {
URL url = new URL("https://api.myjson.com/bins/1fi1zm");
URLConnection connection = url.openConnection();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(Object o) {
MainActivity context = contextRef.get();
if (context != null) {
Gson gson = new Gson();
List<Contact> list;
try {
list = Arrays.asList(gson.fromJson(reader.readLine(), Contact[].class));
context.adapter = new RecyclerViewAdapter(list);
context.recyclerView.setAdapter(context.adapter);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
Let me know if it solved your issue.
replace your code with this
#Override
protected void onPreExecute() {
}
#Override
protected Object doInBackground(Object[] objects) {
try {
URL url = new URL("https://api.myjson.com/bins/1fi1zm");
URLConnection connection = url.openConnection();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return reader;
}
I try to create synchronized threads, but I always get the following error: android.os.NetworkOnMainThreadException.
I've read more posts, but they don't work for me.
Below I write the code blocks that do not work for me:
1.
final SyncApp syncJob = new SyncApp();
Thread t = new Thread (new Runnable () {
#Override
public void run () {
synchronized (syncJob) {
String s = syncJob.insert (newJobs, GlobalVariables.URL_LOCALHOST + "jobs");
txtState.setText (s);
}}});
}
});
t.Start ();
// t.run ();
2.
myClass.runOnUiThread(new Runnable() {
public void run() {...}
})
3.
Running code in main thread from another thread
SyncApp:
public class SyncApp {
synchronized public String insert(List<Jobs> job, String... params) {
URL url = null;
HttpURLConnection conn = null;
try {
url = new URL(params[0]);
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/json");
conn.setDoInput(true);
conn.setDoOutput(true);
String str = new Gson().toJson(job);
byte[] outputInBytes = str.getBytes();
OutputStream os = conn.getOutputStream();
os.write( outputInBytes );
os.flush();
int responseCode=conn.getResponseCode();
String response = null;
if (responseCode == HttpsURLConnection.HTTP_OK) {
String line;
BufferedReader br=new BufferedReader(new InputStreamReader(conn.getInputStream()));
while ((line=br.readLine()) != null) {
response+=line;
}
}
else {
response=conn.getResponseMessage();
}
return response;
} catch (Exception e) {
e.printStackTrace();
} finally {
conn.disconnect();
}
return null;
}
}
I need to call a thread, wait for the answer and call another thread. Their answers I must use them in the activity
I need to call a thread, wait for the answer and call another thread.
Their answers I must use them in the activity
Example using async tasks to accomplish objective.
In this code, let A be your activity which needs to call a thread,
wait for the answer and call another thread. Customize as needed.
Since you never wait in UI threads, callbacks are used to accomplish synchronization.
Let A be your activity class:
public class A extends Activity {
// some method in activity where you launch a background thread (B)
// which then completes and invokes callback which then creates and launches
// a background thread (C) which then completes and invokes a callback.
//
// In callback C, you are on the UI thread.
protected void someMethod() {
new B(new B.CallbackB() {
public void result(Object o) {
new C(new C.CallbackC() {
public void result(Object o, Object answerFromB) {
// OK - C is now done and we are on UI thread!
// 'o' is answer from C
// 'answerFromB' also provided
}
}, o).execute(new Object());
}
).execute(new Object());
}
}
Define a class B:
public class B extends AsyncTask<Object, Void, Object> {
public static interface CallbackB {
void result(Object o);
}
private CallbackB cb;
public B (CallbackB cb) {
this.cb = cb;
}
protected Object doInBackground(Object... params) {
// do work and return an answer.
return new Object();
}
protected void onPostExecute(Object result) {
if (cb != null) {
cb.result(result);
}
}
}
Define a class C:
public class C extends AsyncTask<Object, Void, Object> {
public static interface CallbackC {
void result(Object o, Object answerFromB);
}
private CallbackC cb;
private Object answerFromB;
public C (CallbackC cb, Object answerFromB) {
this.cb = cb;
this.answerFromB = answerFromB;
}
protected Object doInBackground(Object... params) {
// do work and return an answer.
return new Object();
}
protected void onPostExecute(Object result) {
if (cb != null) {
cb.result(result, answerFromB);
}
}
}
For reference:
https://stackoverflow.com/a/9963705/2711811
My solution is:
public class Sync extends AppCompatActivity {
...
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_sync_server);
dao = new DAO(this);
txtState = findViewById(R.id.txt_log);
btnSincro = findViewById(R.id.btn_sincro);
btnSincro.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
countCall = 0;
callFlow();
}
});
btnHome = findViewById(R.id.btn_home);
btnHome.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(SyncServerActivity.this, MainActivity.class);
startActivity(intent);
}
});
}
private void callFlow() {
switch (countCall) {
case 0:
templates = toTemplate("url");
break;
case 1:
jobs = toJobs("url");
break;
case 2:
job = ... //select item
res = sendJobs(jobs, "url");
break;
default:
runOnUiThread(new Runnable() {
#Override
public void run() {
btnSincro.setEnabled(true);
txtState.append("\n\nEND");
}
});
}
}
private void nextStep() {
setText(txtState, "\nSync \n" + countCall + "/3");
countCall++;
callFlow();
}
private void setText(final TextView text, final String value) {
runOnUiThread(new Runnable() {
#Override
public void run() {
text.setText(value);
}
});
}
public List<Templates> toTemplate(final String... params) {
final List<Templates> list = new ArrayList<>();
Thread t = new Thread(new Runnable() {
#Override
public void run() {
URL url = null;
BufferedReader reader = null;
HttpURLConnection connection = null;
try {
url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
int responseCode = connection.getResponseCode();
String response = null;
if (responseCode == HttpsURLConnection.HTTP_OK) {
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line);
}
String finalJson = buffer.toString();
JSONObject parentObject = new JSONObject(finalJson);
JSONArray parentArray = parentObject.getJSONArray("data");
for (int i = 0; i < parentArray.length(); i++) {
Templates item = new Gson().fromJson(parentArray.get(i).toString(), Templates.class);
list.add(item);
}
} else {
response = connection.getResponseMessage();
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} finally {
if (connection != null)
connection.disconnect();
try {
if (reader != null)
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
nextStep(); //call next Thread
}
}
});
t.start();
return list;
}
public List<Jobs> toJobs(final String... params) {
final List<Jobs> list = new ArrayList<>();
Thread t = new Thread(new Runnable() {
#Override
public void run() {
URL url = null;
BufferedReader reader = null;
HttpURLConnection connection = null;
try {
url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
int responseCode = connection.getResponseCode();
String response = null;
if (responseCode == HttpsURLConnection.HTTP_OK) {
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line);
}
String finalJson = buffer.toString();
JSONObject parentObject = new JSONObject(finalJson);
JSONArray parentArray = parentObject.getJSONArray("data");
for (int i = 0; i < parentArray.length(); i++) {
Jobs item = new Gson().fromJson(parentArray.get(i).toString(), Jobs.class);
list.add(item);
}
} else {
response = connection.getResponseMessage();
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} finally {
if (connection != null)
connection.disconnect();
try {
if (reader != null)
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
nextStep();
}
}
});
t.start();
return list;
}
public Boolean sendJobs(final List<Jobs> job, final String... params) {
final Boolean[] result = {false};
Thread t = new Thread(new Runnable() {
#Override
public void run() {
URL url = null;
HttpURLConnection conn = null;
try {
url = new URL(params[0]);
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/json");
conn.setDoInput(true);
conn.setDoOutput(true);
String str = new Gson().toJson(job);
Log.d(TAG, str);
byte[] outputInBytes = str.getBytes();
OutputStream os = conn.getOutputStream();
os.write(outputInBytes);
os.flush();
int responseCode = conn.getResponseCode();
String response = null;
if (responseCode == HttpsURLConnection.HTTP_OK) {
String line;
BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
while ((line = br.readLine()) != null) {
response += line;
}
result[0] = true;
} else {
response = conn.getResponseMessage();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
conn.disconnect();
nextStep();
}
}
});
t.start();
return result[0];
}
}
Whenever a thread ends, it calls the nextStep() method, which starts the next trhead.
I have a problem with parsing a tag inside a Json object.
My json code is structured like that:
{"giocatori":[{"nome":"Giovanni","cognome":"Muchacha","numero":"1","ruolo":"F-G"},
{"nome":"Giorgio","cognome":"Rossi","numero":"2","ruolo":"AG"},
{"nome":"Andrea","cognome":"Suagoloso","numero":"3","ruolo":"P"},
{"nome":"Salvatore","cognome":"Aranzulla","numero":"4","ruolo":"G"},
{"nome":"Giulio","cognome":"Muchacha","numero":"5","ruolo":"F"}]}
I got the code that let me get the Json file from here: Get JSON Data from URL Using Android? and I'm trying to parse a tag (for example the "nome" tag) into a Json object.
This is the code I got:
public class MainActivity extends AppCompatActivity {
Button btnHit;
TextView txtJson;
ProgressDialog pd;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnHit = (Button) findViewById(R.id.btnHit);
txtJson = (TextView) findViewById(R.id.tvJsonItem);
btnHit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
new JsonTask().execute("https://api.myjson.com/bins/177dpo");
}
});
}
private class JsonTask extends AsyncTask<String, String, String> {
protected void onPreExecute() {
super.onPreExecute();
pd = new ProgressDialog(MainActivity.this);
pd.setMessage("Please wait");
pd.setCancelable(false);
pd.show();
}
protected String doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line+"\n");
Log.d("Response: ", "> " + line);
}
return buffer.toString();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.disconnect();
}
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
if (pd.isShowing()){
pd.dismiss();
}
txtJson.setText(result);
}
}
}
I've never worked with this type of file so I'll really appreciate your help!
You can use something like this:
try {
String servResponse = response.toString();
JSONObject parentObj = new JSONObject(servResponse);
JSONArray parentArray = parentObj.getJSONArray("giocatori");
if (parentArray.length() == 0) {
//if it's empty, do something (or not)
} else {
//Here, finalObj will have your jsonObject
JSONObject finalObj = parentArray.getJSONObject(0);
//if you decide to store some value of the object, you can do like this (i've created a nomeGiocatori for example)
nomeGiocatori = finalObj.getString("nome");
}
} catch (Exception e) {
Log.d("Exception: ", "UnknownException");
}
I use this kind of code all the time, works like a charm.
This is an rssfeed and everything compiles and I don't think i am missing anything but my app wont launch and there is a warning about my OnCreate never being used. I am unsure if this is related to the problem.
public class MainActivity extends AppCompatActivity {
private TextView src;
private Button btn;
protected void OnCreate(Bundle SavedInstanceState) {
super.onCreate(SavedInstanceState);
setContentView(R.layout.activity_main);
src = (TextView) findViewById(R.id.text);
btn = (Button)findViewById(R.id.Fetch);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
fetch();
}
});
}
public void fetch() {
Downloader d = new Downloader();
d.execute("https://en.wikipedia.org/wiki/Main_Page");
try {
src.setText(d.get());
} catch (Exception e) {
Log.e("Error to thread", e.toString());
}
}
class Downloader extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
String result = null;
try {
URL url = new URL(urls[0]);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
InputStream in = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line = null;
while ((line = reader.readLine()) != null) {
result = result + line;
}
conn.disconnect();
reader.close();
} catch (Exception e) {
Log.e("error to fetching", e.toString());
}
return result;
}
}
The correct writing is onCreate, not OnCreate. Try to change that.
OnCreate --> onCreate and use #Override
I require a GET reequest from my own server to be extracted from the web and then displayed on screen with a TextView.
I have set up a GET Request.
public class GetMethodEx {
public String getInternetData() throws Exception{
BufferedReader in = null;
String data = null;
try
{
HttpClient client = new DefaultHttpClient();
URI website = new URI("http://www.mybringback.com");
HttpGet request = new HttpGet();
request.setURI(website);
HttpResponse response = client.execute(request);
in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
StringBuffer sb = new StringBuffer("");
String l = "";
String nl = System.getProperty("line.separator");
while ((l = in.readLine()) !=null){
sb.append(l + nl);
}
in.close();
data = sb.toString();
return data;
} finally{
if (in != null){
try{
in.close();
return data;
}catch (Exception e){
e.printStackTrace();
}
}
}
}
}
And I have set up on my main thread to extract the information and display it in a text view.
public class Home extends Activity {
TextView httpStuff;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.httpexample);
httpStuff = (TextView) findViewById(R.id.tvhttp);
GetMethodEx test = new GetMethodEx();
String returned;
try {
returned = test.getInternetData();
httpStuff.setText(returned);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
However, the Textview doesnt seem to change?
Can someone help me please.
Change your code using AsyncTask if you want to make any network operation from Ui Thread as:
public class Home extends Activity {
TextView httpStuff;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.httpexample);
httpStuff = (TextView) findViewById(R.id.tvhttp);
new LongOperation().execute("");
}
private class LongOperation extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... params) {
GetMethodEx test = new GetMethodEx();
String returned;
try {
returned = test.getInternetData();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return returned;
}
#Override
protected void onPostExecute(String result) {
// Update Ui here
httpStuff.setText(result);
}
}
}
Android OS > = 3.0
does not allow NetworkRequest on main UI thread.
Use AsyncTask to call webrequest.