Develop Reference

How to work with big HTML String?

I want to get an HTML from a web page, remove some tags from the code and display it using a TextView... But those HTMLs are too big to be temporaly stored into a String...
When I try this way:
String html = "myBigHTML";
myTextView.setText(fromHtml(html));
compiler says error: constant string too long
If I put the html into a .txt and try this way:
InputStream is = getAssets().open("html.txt");
tvTeste.setText(fromHtml(convertStreamToString(is)));
public static String convertStreamToString(InputStream is) throws Exception {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line).append("\n");
}
reader.close();
return sb.toString();
}
It works but the app gets soooo slow, almost freezes... And also, if I store it in a .txt I couldn't work with the tags...
.:: EDIT ::.
My onCreate() method as asked...
private TextView tvTeste;
private InputStream is;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_frequencia);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
tvTeste = (TextView)findViewById(R.id.tvTeste);
try {
is = getAssets().open("html.txt");
} catch (IOException e) {
e.printStackTrace();
}
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String strLine;
List<String> stringList = new ArrayList<>();
try {
while ((strLine = br.readLine()) != null) {
stringList.add(strLine);
}
} catch (Exception e) {
e.printStackTrace();
}
tvTeste.setText(fromHtml(TextUtils.join("",stringList)));
}

Let's try this: each line of HTML text is a String. Each String is inside a List of String.
So, some pseudocode:
List<String> stringList = new ArrayList<>();
while (htmlHandler.next()) {
stringList.add(fromHtml(htmlHandler.readLine()));
}
myTextView.setText(joinStringArray(stringList));
Where joinStringArray uses a StringBuilder to produce a single big String object.
Basically you shouldn't read the entire web page, but you should read it sequentially.

Another point to mark. You should avoid any time consuming process that blocks the activity. try the same using, for example an AsyncTask.
Please check https://developer.android.com/reference/android/os/AsyncTask.html

Reading a URL page with the help of Threads - Android

I was being a bit naive, thinking I can read webpages the same way as you do in Java, but apparently you need to use threads or AsyncTask. Which I have no prior experience in and are proving to be hassle.
I've read http://www.vogella.com/tutorials/AndroidBackgroundProcessing/article.html (3. point) which I semi understand but when I try to implement into my problem it all falls apart.
Here's my problem:
I need to read from an URL, it's a RSS feed.
Parse it all together
Insert it into ListView (arrayadapter)
This is my AsyncTask class, that I tried to recreate. I just want it to return a buffered reader, or the whole page but it's always null.
private class DownloadWebPageTask extends AsyncTask<String, Void, BufferedReader> {
#Override
protected BufferedReader doInBackground(String... urls) {
BufferedReader bs;
URL url = null;
try {
url = new URL(urls[0]);
} catch (MalformedURLException e) {
e.printStackTrace();
}
try {
bs = new BufferedReader(new InputStreamReader(url.openStream(), "UTF-8"));
return bs;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(BufferedReader result) {
br = result;
}
}
public RSS() throws IOException, ExecutionException, InterruptedException {
DownloadWebPageTask dl = new DownloadWebPageTask();
dl.execute(new String[] {"http://www.promet.si/dc/PROMET.ROADEVENTS.PP.RSS.SL"});
}
I'm sorry if this is a stupid question, but I don't fully understand posts explaining this and I have to solve this problem. I just need the page's content in any way shape or form. (Can be a String, BufferedReader)

#Override
protected String doInBackground(String... urls) throws IOException {
URLConnection connection = new URL(urls[0]).openConnection();
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(connection.getInputStream()),"UTF-8");
StringBuilder stringBuilder = new StringBuilder();
String buffer;
while ((buffer = bufferedReader.readLine()) != null) {
stringBuilder.append(buffer);
}
return stringBuilder.toString();
}
Use the buffered reader to read line by line in the background thread, and make it return string.

Java Wget Bz2 file

I'm trying to webget some bz2 files from Wikipedia, I don't care whether they are save as bz2 or unpacked, since I can unzip them locally.
When I call:
public static void getZip(String theUrl, String filename) throws IOException {
URL gotoUrl = new URL(theUrl);
try (InputStreamReader isr = new InputStreamReader(new BZip2CompressorInputStream(gotoUrl.openStream())); BufferedReader in = new BufferedReader(isr)) {
StringBuffer sb = new StringBuffer();
String inputLine;
// grab the contents at the URL
while ((inputLine = in.readLine()) != null) {
sb.append(inputLine + "\r\n");
}
// write it locally
Wget.createAFile(filename, sb.toString());
} catch (MalformedURLException mue) {
mue.printStackTrace();
} catch (IOException ioe) {
throw ioe;
}
}
I get a part of the unzipped file, never more than +- 883K.
When I don't use the BZip2CompressorInputStream, like:
public static void get(String theUrl, String filename) throws IOException {
try {
URL gotoUrl = new URL(theUrl);
InputStreamReader isr = new InputStreamReader(gotoUrl.openStream());
BufferedReader in = new BufferedReader(isr);
StringBuffer sb = new StringBuffer();
String inputLine;
// grab the contents at the URL
while ((inputLine = in.readLine()) != null) {
sb.append(inputLine);// + "\r\n");
}
// write it locally
Statics.writeOut(filename, false, sb.toString());
} catch (MalformedURLException mue) {
mue.printStackTrace();
} catch (IOException ioe) {
throw ioe;
}
}
I get a file of which the size is the same as it suppose to (compared to the KB not B). But also a message that that the zipped file is damaged, also when using byte [] instead of readLine(), like:
public static void getBytes(String theUrl, String filename) throws IOException {
try {
char [] cc = new char[1024];
URL gotoUrl = new URL(theUrl);
InputStreamReader isr = new InputStreamReader(gotoUrl.openStream());
BufferedReader in = new BufferedReader(isr);
StringBuffer sb = new StringBuffer();
// grab the contents at the URL
int n = 0;
while (-1 != (n = in.read(cc))) {
sb.append(cc);// + "\r\n");
}
// write it locally
Statics.writeOut(filename, false, sb.toString());
} catch (MalformedURLException mue) {
mue.printStackTrace();
} catch (IOException ioe) {
throw ioe;
}
}
Finally, when I bzip2 the inputstream and outputstream, I get a valid bzip2 file, but of the size like the first one, using:
public static void getWriteForBZ2File(String urlIn, final String filename) throws CompressorException, IOException {
URL gotoUrl = new URL(urlIn);
try (final FileOutputStream out = new FileOutputStream(filename);
final BZip2CompressorOutputStream dataOutputStream = new BZip2CompressorOutputStream(out);
final BufferedInputStream bis = new BufferedInputStream(gotoUrl.openStream());
final CompressorInputStream input = new CompressorStreamFactory().createCompressorInputStream(bis);
final BufferedReader br2 = new BufferedReader(new InputStreamReader(input))) {
String line = null;
while ((line = br2.readLine()) != null) {
dataOutputStream.write(line.getBytes());
}
}
}
So, how do I get the entire bz2 file, in either bz2 format or unzipped?

A bz2 file contains bytes, not characters. You can't read it as if it contained characters, with a Reader.
Since all you want to do is download the file and save it locally, all you need is
Files.copy(gotoUrl.openStream(), Paths.get(fileName));

Handling IOExceptions in Android

I'm creating an app where I need a function to get plain text from a website. I am able to get the text and print it out on my PC just fine, but when I try running it on an Android device, the app won't start.
I believe it has something to do with throwing an IOException. I've been reading that I am not supposed to do that because I don't define the interface. Is there a way to get around this? Android Studio won't compile my code if I don't throw the exception.
The function:
public String getText(String site) throws IOException {
// Make a URL to the web page
URL url = new URL(site);
// Get the input stream through URL Connection
URLConnection con = url.openConnection();
InputStream is =con.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
// read each line and return the final text
String res = "";
String line = null;
while ((line = br.readLine()) != null) {
//System.out.println(line);
res += line;
}
return res;
}
And this is how Android Studio makes me run it in the onCreate method:
String text = null;
try {
text = getText("http://myWebsite.com");
} catch (IOException e) {
e.printStackTrace();
}
Toast.makeText(getApplicationContext(), text, Toast.LENGTH_LONG).show();

First, read your logcat - you should see your exception there with full stacktrace. Second, there is nothing wrong with catching IOException, but you must do something with it once cached - like inform user of problem in functionality - like no more space, etc.
And this is how Android Studio makes me run it in the onCreate method:
this is a problem, because your are getting data from your site on UI thread, you must do it from worker thread, ie. AsyncTask.

You can not do it in the main thread
try this
class MyTask extends AsyncTask<Void, Void, String>{
private String site;
MyTask(String site) {
this.site = site;
}
#Override
protected String doInBackground(Void... params) {
try {
URL url = new URL(site);
URLConnection con = url.openConnection();
InputStream is =con.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
// read each line and return the final text
String res = "";
String line = null;
while ((line = br.readLine()) != null) {
//System.out.println(line);
res += line;
}
return res;
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
if(s != null){
Toast.makeText(getApplicationContext(), s, Toast.LENGTH_LONG).show();
}
}
}
where to get a string is used as
new MyTask("http://myWebsite.com").execute()

Reading a textfile using InputStream

How can I read a text file like in android app:
"1.something written
2.in this file
3.is to be read by
4.the InputStream
..."
so I can be returned a string like:
"something written\nin this file\nis to be read by\nthe InputStream"
what I thought of is(Pseudocode):
make an inputstream
is = getAssest().open("textfile.txt"); //in try and catch
for loop{
string = is.read() and if it equals "." (i.e. from 1., 2., 3. etc) add "/n" ...
}

try this
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;
import java.io.*;
public class FileDemo1 extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
try {
playWithRawFiles();
} catch (IOException e) {
Toast.makeText(getApplicationContext(), "Problems: " + e.getMessage(), 1).show();
}
}
public void playWithRawFiles() throws IOException {
String str = "";
StringBuffer buf = new StringBuffer();
InputStream is = this.getResources().openRawResource(R.drawable.my_base_data);
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
if (is != null) {
while ((str = reader.readLine()) != null) {
buf.append(str + "\n" );
}
}
} finally {
try { is.close(); } catch (Throwable ignore) {}
}
Toast.makeText(getBaseContext(), buf.toString(), Toast.LENGTH_LONG).show();
}
}

Use BufferedReader to read the input stream. As BufferedReader will read text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines. InputStream represents an input stream of bytes. reader.readLine() will read the file line by line.
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
StringBuilder out = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
out.append(line); // add everything to StringBuilder
// here you can have your logic of comparison.
if(line.toString().equals(".")) {
// do something
}
}

File fe = new File("abc.txt");
FileInputStream fis = new FileInputStream(fe);
byte data[] = new byte[fis.available()];
fis.read(data);
fis.close();
String str = new String(data);
System.out.println(str);