I wrote some code in Android Studio for downloading content from the web. The build shows
"error: illegal start of expression"
and I'm not able to figure out the error. While checking for the error, I was asked to search for missing semi-colons and opening or closing braces. I have checked both and can't find any error.
The code is:
import androidx.appcompat.app.AppCompatActivity;
import android.os.AsyncTask;
import android.os.Bundle;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
public class DownloadTask extends AsyncTask<String,Void,String>
{
#Override
protected String doInBackground(String... urls) {
String result = "";
URL url;
HttpURLConnection urlConnection = null;
try{
url= new URL(urls[0]);
urlConnection = (HttpURLConnection) url.openConnection();
InputStream in = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(in);
int data = reader.read();
while(data!=-1){
char current = (char) data;
result + = current;
data = reader.read();
}
return result;
}
catch (Exception e){
e.printStackTrace();
return null;
}
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DownloadTask task = new DownloadTask();
String result = null;
try {
// result = task.execute("http://www.posh24.se/kandisar").get();
}
catch (Exception e){
e.printStackTrace();
}
}
}
I think you have space between result + = current; try below line
result += current;
Related
I am learning android development and in a tutorial i am following demonstrated how to download a web page and print it into logs with AsyncTask class but the problem is, app is hanging ( ui elements not appearing neither in emulator nor in my phone ) and when the ui elements appear ( after a long time say 5 minutes) the html source in log is not showing
here is the code
package com.example.slimshady.downloadhtml;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import javax.net.ssl.HttpsURLConnection;
public class MainActivity extends AppCompatActivity {
public class DownloadTask extends AsyncTask<String, Void, String>{
#Override
protected String doInBackground(String... buttoks) {
URL url;
HttpURLConnection httpURLConnection = null;
String result = "";
// try catch for if malformed url
try {
url = new URL(buttoks[0]);
httpURLConnection = (HttpURLConnection)url.openConnection();
InputStream in = httpURLConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(in);
int data = reader.read();
while(data != -1)
{
char current = (char)data;
result+=current;
data = reader.read();
}
return result;
} catch (Exception e) {
e.printStackTrace();
return "failed";
}
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DownloadTask downloadTask = new DownloadTask();
try {
String content = downloadTask.execute("https://www.google.com").get();
Log.i("returned STring", content.toString());
}catch (Exception e)
{
e.printStackTrace();
}
}
}
everything seems ok but still no html source logging and what can be the cause for the ui elements appearing alot later than they should ? i mean the whole reason for an AsyncTask is that they run independent of the main thread so the ui elements are not effected by the task am i right ?
The issue is , you are invoking get which will block your thread until you get the response so simply use
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new DownloadTask().downloadTask.execute("https://www.google.com");
}
and update UI in onPostExecute
You can also improve the code using StringBuffer and BufferReader as
public class DownloadTask extends AsyncTask<String, Void, String>{
#Override
protected String doInBackground(String... buttoks) {
URL url;
HttpURLConnection httpURLConnection = null;
String result = "";
StringBuffer buf = new StringBuffer();
// try catch for if malformed url
try {
url = new URL(buttoks[0]);
httpURLConnection = (HttpURLConnection)url.openConnection();
InputStream in = httpURLConnection.getInputStream();
BufferedReader reader =new BufferedReader(new InputStreamReader(in));
if (is != null) {
while ((result = reader.readLine()) != null) {
buf.append(result);
}
}
return buf.toString();
} catch (Exception e) {
e.printStackTrace();
return "failed";
}
}
#Override
... onPostExecute(String str){
// update UI here
}
}
//[(START)File:ThirdActivity.java] -->
package com.example.caleb.splash_screen;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.io.IOException;
import java.io.OutputStream;
public class ThirdActivity extends AppCompatActivity {
//public String text = "https://jsonparsingdemo-cec5b.firebaseapp.com/jsonData/moviesDemoItem.txt";
public TextView text;
private void writeStream(OutputStream out){
String output = "Hello world";
// out.write(output.getBytes());
//out.flush();
}
/*private String readStream(InputStream is) {
try {`enter code here`
ByteArrayOutputStream bo = new ByteArrayOutputStream();
int i = is.read();
while(i != -1) {
bo.write(i);
i = is.read();
}
return bo.toString();
} catch (IOException e) {
return "";
}
}*/
//[(START) readStream -->
private String readStream(InputStream in) throws IOException {
BufferedReader bin = new BufferedReader(new InputStreamReader(in));
//temporary
try {
StringBuilder sb = new StringBuilder();
String inputLine;
while ((inputLine = bin.readLine()) != null) {
sb.append(inputLine);
}
return sb.toString();
} finally {
}
}
//[(END) readStream -->
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_third2);
text = (TextView)findViewById(R.id.textView);
new JSONTask().execute("https://jsonparsingdemo-cec5b.firebaseapp.com/jsonData/moviesDemoItem.txt");
}
}
//[(END)File:ThirdActivity] -->
//[(START)File:JSONTask] -->
package com.example.caleb.splash_screen;
import android.app.Activity;
import android.content.Context;
import android.os.AsyncTask;
import android.support.v4.widget.TextViewCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.TextView;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
/**
* Created by Caleb on 12/17/2017.
*/
public class JSONTask extends AsyncTask<String,String,String> {
//final TextView txt = (TextView)findViewById(R.id.textView);
private Context context;
public JSONTask(Activity ThirdActivity) {
context = ThirdActivity;
}
#Override
protected String doInBackground(String... params) {
BufferedReader reader = null;
HttpURLConnection urlConnection = null;
//{(START)] Working Connection:ALERT! Error within code will cause crash -->
try {
URL url = new URL(params[0]);
Log.w("testing", "test");
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(false);
urlConnection.connect();
//urlConnection.setChunkedStreamingMode(0);
//OutputStream out = new BufferedOutputStream(urlConnection.getOutputStream());
//writeStream(out);
/*int a = urlConnection.getResponseCode();
String b = String.valueOf(a);
Log.e(b, "yesssssssssssssssss");*/
InputStream in = urlConnection.getInputStream();
//InputStream in = new BufferedInputStream(urlConnection.getInputStream());
reader = new BufferedReader(new InputStreamReader(in));
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line);
}
/*String data = readStream(in);
/*final TextView textView = (TextView) findViewById(R.id.textView);
textView.setText("hello");
*/
return buffer.toString();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
//{(END)] Working Connection -->
return null;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
TextView text = (TextView) ((AppCompatActivity) context).findViewById(R.id.textView);
text.setText(result);
}
}
//[(END)File:JSONTask] -->
/Desired Effect/
Blockquote
I would like to pull data from the json file that the url points to and change the TextView within the UI called textView. I don't understand how to access the findviewbyid within the AsyncTask. I've looked all throughout the internet and couldn't find anything :( Any suggestions are greatly appreciated!!
try weak reference to get textview in asynctask
//call async task
new JSONTask(yourTextView).execute();
//in your async task
private final WeakReference<TextView> textViewReference;
public JSONTask (TextView textView){
textViewReference = new WeakReference<TextView>( textView);
}
#Override
protected void onPostExecute() {
TextView textView = textViewReference.get();
//set values to text view
}
I'm using OkHttp to do the same task in my apps
HTTP/2 support allows all requests to the same host to share a socket.
Connection pooling reduces request latency (if HTTP/2 isn’t available).
Transparent GZIP shrinks download sizes.
Response caching avoids the network completely for repeat requests.
Add this dependency
implementation 'com.squareup.okhttp3:okhttp:3.9.1'
Then create/code a new Class named OkHttpHandler
class OkHttpHandler extends AsyncTask<String, String, String> {
OkHttpClient client = new OkHttpClient();
private volatile String data;
public String getResult() {
return data;
}
#Override
protected String doInBackground(String... params) {
try {
Request.Builder builder = new Request.Builder();
builder.url(params[0]);
Request request = builder.build();
Response response = client.newCall(request).execute();
return response.body().string();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
data = s;
}
}
}
and use it like this way
String str = new OkHttpHandler().execute("http://www.<TEST>.com/json").get();
I also suggest to check whether Wi-fi-Connected/Bluetooth-Connected or PhoneData-Enabled is false if true/else, Proceed to your code
I am trying to run a simple app that extracts html from a page and displays it in the logs.
Here is the Java code:
package com.example.khkr.jsondemo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public class DownloadTask extends AsyncTask<String,Void,String>
{
#Override
protected String doInBackground(String... params) {
URL url;
String result = "";
try {
url = new URL(params[0]);
HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
urlConnection.connect();
InputStream in = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(in);
int data = reader.read();
while (data!=-1)
{
char current = (char)data; result+=current;
data = reader.read();
}
return result;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try {
JSONObject jsonObject = new JSONObject(result);
String weatherInfo = jsonObject.getString("weather");
Log.i("Weather content",weatherInfo);
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
The problem is I don't see any errors in the code , but when I try to run the app, I get the following Logs which never make sense to me. Here are the logs:
https://gist.github.com/khkr/d96396ff6f8e34b3e9a430a805b735a7
I am having a problem.
I can't figure out why the following code won't work.
It's a simple app that sends a GET request to some php fragment that supposed to insert a row in a table.
I can't understand why it doesn't work.
Please help.
java:
package com.example.michael.biyum;
import android.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
final AlertDialog alertDialog = alertDialogBuilder.create();
Button startBtn = (Button) findViewById(R.id.btn);
final TextView t = (TextView) findViewById(R.id.hello);
startBtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
URL url;
HttpURLConnection urlConnection = null;
try {
url = new URL("http://www.chatty.co.il/biyum.php?q=mkyong");
urlConnection = (HttpURLConnection) url.openConnection();
InputStream in = urlConnection.getInputStream();
InputStreamReader isw = new InputStreamReader(in);
int data = isw.read();
while (data != -1) {
char current = (char) data;
data = isw.read();
Toast.makeText(getApplicationContext(),"GET:"+current,Toast.LENGTH_LONG).show();
System.out.print(current);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
}
});
}
}
php:
<?php
require('connect.inc.php');
$update_offline="INSERT INTO offline_waiters (user_partner,mail,chat_room) VALUES(0,'gavno','gavno')";
$query_run= mysqli_query($conn,$update_offline);
echo "new";
?>
It's a simple test that should enter a new row in my table.
When I make the request manualy via a browser it works fine.
Once again please help me understand where is the problem.
You need to get the network operation off of the main thread.
I just got this working and tested using an AsyncTask:
class MyAsyncTask extends AsyncTask<Void, Void, String> {
#Override
protected String doInBackground(Void... params) {
StringBuilder result = new StringBuilder();
URL url;
HttpURLConnection urlConnection = null;
try {
url = new URL("http://www.chatty.co.il/biyum.php?q=mkyong");
urlConnection = (HttpURLConnection) url.openConnection();
InputStream in = urlConnection.getInputStream();
InputStreamReader isw = new InputStreamReader(in);
int data = isw.read();
while (data != -1) {
char current = (char) data;
data = isw.read();
result.append(current);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
return result.toString();
}
#Override
protected void onPostExecute(String result) {
Toast.makeText(getApplicationContext(),"GET:"+result,Toast.LENGTH_LONG).show();
}
}
Just execute the AsyncTask from your click listener:
startBtn.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View v) {
new MyAsyncTask().execute();
});
Result in the Toast:
I have created local DAtabase, with MongoDB and NODEJS, and now i want to parse databse data with my android app, i think i write java code right , but it doesn not work, please help.
Thanks
Here is my Java code.
package com.example.hakobm.buttonparsing;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class MainActivity extends AppCompatActivity {
protected TextView tvData;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvData = (TextView)findViewById(R.id.tvJsonItem);
new JSONTask().execute("http://localhost:3000/api/people");
}
public class JSONTask extends AsyncTask<String,String,String>{
#Override
protected String doInBackground(String... params) {
HttpURLConnection connection = null;
BufferedReader reader = null;
int statusCode = 0;
try {
URL url = new URL(params[0]);
connection = (HttpURLConnection) url.openConnection();
connection.setRequestProperty("Content-Type","application/json");
connection.setRequestMethod("GET");
connection.connect(); //connect to server
statusCode = connection.getResponseCode();
if (statusCode == 200) {
System.out.println("Server responded with code: " + statusCode);
InputStream stream = connection.getInputStream();
reader = new BufferedReader(new InputStreamReader(stream));
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("people");
StringBuffer finalBufferdData = new StringBuffer();
for (int i = 0; i < parentArray.length(); i++) {
JSONObject finalObj = parentArray.getJSONObject(i);
String peopleName = finalObj.getString("name");
Integer age = finalObj.getInt("age");
finalBufferdData.append(peopleName + "-->" + age + "\n");
}
return finalBufferdData.toString(); //pases result to PostExecute
}else{
Log.i("Hakob_log","Error");
}
}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();
}
}
return null;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
tvData.setText(result);
}
}