Develop Reference

Dont open second activity if android back button is pressed

i am trying to implement below code every thing works fine how ever
here is the situation i am facing
mainactivity just has a button to open splashactivity
splash activity does the parsing part then opens the listactvity
my workflow is if user has clicked on the button in main activity
it opens the splash activity and redirects to listactivty the
problem occurs when on the splash activity if a user clicks the
andorid back button it does go back to the mainactivity however the
parsing in splashactivity continues and user is redirected to
listactivty this thing should not happen, when user on splash
activity has clicked backbutton it should go back to mainactivity
and stay there itself
how can this be done
package com.site.name;
public class SplashActivity extends Activity {
RSSFeed feed;
String fileName;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.splash);
fileName = "TDRSSFeed.td";
Intent i = getIntent();
int position = i.getExtras().getInt("position");
String[] country = i.getStringArrayExtra("country");
// //public String RSSFEEDURL = "http://blogname.blogspot.com//feeds/posts/default/-/Awards?alt=rss";
Toast.makeText(getApplicationContext(), country[position], Toast.LENGTH_SHORT).show();
//Toast.makeText(getApplicationContext(), country[position], Toast.LENGTH_SHORT).show();
File feedFile = getBaseContext().getFileStreamPath(fileName);
ConnectivityManager conMgr = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
if (conMgr.getActiveNetworkInfo() == null) {
// No connectivity. Check if feed File exists
if (!feedFile.exists()) {
// No connectivity & Feed file doesn't exist: Show alert to exit
// & check for connectivity
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage(
"Unable to reach server, \nPlease check your connectivity.")
.setTitle("TD RSS Reader")
.setCancelable(false)
.setPositiveButton("Exit",
new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog,
int id) {
finish();
}
});
AlertDialog alert = builder.create();
alert.show();
} else {
// No connectivty and file exists: Read feed from the File
Toast toast = Toast.makeText(this,
"No connectivity!",
Toast.LENGTH_LONG);
toast.show();
//feed = ReadFeed(fileName);
startLisActivity(feed);
}
} else {
// Connected - Start parsing
new AsyncLoadXMLFeed().execute();
}
}
private void startLisActivity(RSSFeed feed) {
Bundle bundle = new Bundle();
bundle.putSerializable("feed", feed);
// launch List activity
Intent intent = new Intent(SplashActivity.this, ListActivity.class);
intent.putExtras(bundle);
startActivity(intent);
overridePendingTransition(R.anim.slide_in, R.anim.slide_out);
// kill this activity
finish();
}
private class AsyncLoadXMLFeed extends AsyncTask<Void, Void, Void> {
#Override
protected Void doInBackground(Void... params) {
// Obtain feed
DOMParser myParser = new DOMParser();
Intent i = getIntent();
int position = i.getExtras().getInt("position");
String[] country = i.getStringArrayExtra("country");
//feed = myParser.parseXml(RSSFEEDURL);
//feed = myParser.parseXml("http://blogname.blogspot.com//feeds/posts/default/-/Awards?alt=rss");
feed = myParser.parseXml("http://blogname.blogspot.com//feeds/posts/default/-/" + country[position] + "?alt=rss");
if (feed != null && feed.getItemCount() > 0)
WriteFeed(feed);
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
startLisActivity(feed);
}
}
// Method to write the feed to the File
private void WriteFeed(RSSFeed data) {
FileOutputStream fOut = null;
ObjectOutputStream osw = null;
try {
fOut = openFileOutput(fileName, MODE_PRIVATE);
osw = new ObjectOutputStream(fOut);
osw.writeObject(data);
osw.flush();
}
catch (Exception e) {
e.printStackTrace();
}
finally {
try {
fOut.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
#Override
public void onBackPressed() {
//Include the code here
return;
}
}

You can cancel parsing the feed in MainActivity's onRestart() as this is one method of MainActivity that will be called when you press back from your Parsing Activity.
You can read more about Activity Life Cycle here.

For detecting the Back button press event use the following method
#Override
public void onBackPressed() {
// do something on back.
// Change your activity by calling intent
return;
}

If you want to do anything with your back button then you have to override it manually.
#Override
Public void onBackPressed() {
//do whatever you want to do as your question is quite confusing.
return;
}

Android FTP Server

I am using the following code to make the android device a ftp server (Android Internal storage). I am getting the exception of os.android.NetworkOnMainThread. I have tried to put the onStart code in the AsyncTask but app never executes and crashes on launch. Any help regarding the ftp server on Android will be great as i have no idea how to get it working.
Here is the MainActivity Code
package com.googlecode.simpleftp;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Toast;
public class FTPServer extends Activity {
private static int COMMAND_PORT = 2121;
static final int DIALOG_ALERT_ID = 0;
private static ExecutorService executor = Executors.newCachedThreadPool();
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.my_menu, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id.new_game:
System.out.println("New game button is pressed!");
//newGame();
return true;
case R.id.quit:
System.out.println("Quit button is pressed!");
showDialog(DIALOG_ALERT_ID);
return true;
default:
return super.onOptionsItemSelected(item); }
}
#Override
protected Dialog onCreateDialog(int id){
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?")
.setCancelable(false).setPositiveButton("yes", new DialogInterface.OnClickListener(){
#Override
public void onClick(DialogInterface dialog, int id){
FTPServer.this.finish();
}
})
.setNegativeButton("No", new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
return alert;
}
HEre is the ServerPI Code
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class ServerPI implements Runnable{
private Socket clientSocket;
private BufferedReader in;
private PrintWriter out;
private String baseDir;
private String relativeDir;
private String absoluteDir;
private String fileName;
private String filePath;
public ServerPI(Socket incoming) throws IOException{
this.clientSocket = incoming;
in = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
out = new PrintWriter(this.clientSocket.getOutputStream(), true);
baseDir = new File("").getAbsolutePath();
relativeDir = "/";
absoluteDir = baseDir + relativeDir;
fileName = "";
filePath = absoluteDir + "/" + fileName;
}
private void readCommandLoop() throws IOException {
String line = null;
reply(220, "Welcome to the SimpleFTP server!");
while((line = in.readLine()) != null){
int replyCode = executeCommand(line.trim());
if(replyCode == 221){
return;
}
}
}
private int executeCommand(String trim) {
// TODO Auto-generated method stub
return 0;
}
public int reply(int statusCode, String statusMessage){
out.println(statusCode + " " + statusMessage);
return statusCode;
}
#Override
public void run(){
try{
this.readCommandLoop();
} catch (IOException e){
e.printStackTrace();
}
finally {
try {
if(in != null){
in.close();
in = null;
}
if(out != null){
out.close();
out = null;
}
if (clientSocket != null){
clientSocket.close();
clientSocket = null;
}
}
catch (IOException e){
e.printStackTrace();
}
}
}
}
I have put the code in the AsyncTask, here it is
private class LongOperation extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... params) {
ServerSocket s = null;
Socket incoming = null;
try{
s = new ServerSocket(COMMAND_PORT);
String ip = (s.getInetAddress()).getHostAddress();
Context context = this.getApplicationContext();
CharSequence text = ip;
int duration = Toast.LENGTH_LONG;
Toast toast = Toast.makeText(context, text, duration);
Thread.sleep(1000);
toast.show();
while(true){
incoming = s.accept();
executor.execute(new ServerPI(incoming));
}
}
catch(Exception e){
System.out.println(e.toString());
e.printStackTrace();
}
finally{
try
{
if(incoming != null)incoming.close();
}
catch(IOException ignore)
{
//ignore
}
try
{
if (s!= null)
{
s.close();
}
}
catch(IOException ignore)
{
//ignore
}
}
return "Executed";
}
#Override
protected void onPostExecute(String result) {
}
#Override
protected void onPreExecute() {
}
#Override
protected void onProgressUpdate(Void... values) {
}
}
Iam calling the longOpertation in onCreate method. What is the problem that the app crashes on launch.
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fullscreen);
new LongOperation().execute();
}

Maybe because you didn't set up the permissions in the manifest? You've to set permission for internet usage.
If this doesn't work, please tell us which line is it throwing the exception.

while(true){ incoming = s.accept(); ...} You cannot put that in OnStart(). That should be done in a thread. So ServerSocket s = null; should be a variable of you activity.

So I went with Swiftp application (open source) as a service in my application which helped me to achieve my task. Thanks everyone who stepped forward to help. Here is the link if someone wants to follow

Please post your code here.
NetworkOnMainthreadException occurs because you maybe running Network related operation on the Main UI Thread. You should use asynctask for this purpose
This is only thrown for applications targeting the Honeycomb SDK or higher. Applications targeting earlier SDK versions are allowed to do networking on their main event loop threads, but it's heavily discouraged.
http://developer.android.com/reference/android/os/NetworkOnMainThreadException.html
class TheTask extends AsyncTask<Void,Void,Void>
{
protected void onPreExecute()
{ super.onPreExecute();
//display progressdialog.
}
protected void doInBackground(Void ...params)//return result here
{
//http request. do not update ui here
//call webservice
//return result here
return null;
}
protected void onPostExecute(Void result)//result of doInBackground is passed a parameter
{
super.onPostExecute(result);
//dismiss progressdialog.
//update ui using the result returned form doInbackground()
}
}
http://developer.android.com/reference/android/os/AsyncTask.html. Check the topic under the heading The 4 Steps.
A working example of asynctask # To use the tutorial in android 4.0.3 if had to work with AsynxTasc but i still dont work?.
The above makes a webserive call in doInBakckground(). Returns result and updates the ui by setting the result in textview in onPostExecute().

You can not do network operation in main thread in android 3.0 higher. Use AsyncTask for this network operation. See this for further explanation

How to return the result from the asynctask to an activity in android?

I have created a Login activity which uses another class - LoginService which is an AsyncTask for the network communication.
public void onClick(View view) {
if (editTextPassword.getText().toString() != null & editTextUsername.getText().toString() != null){
new LoginService(editTextUsername.getText().toString(), editTextPassword.getText().toString()).execute();
if(loginSuccess!=false){
//Used to move to the Cases Activity
Intent casesActivity = new Intent(getApplicationContext(), CasesActivity.class);
startActivity(casesActivity);
}else{
Toast.makeText(getApplicationContext(),"Incorrect Details", Toast.LENGTH_LONG).show();
}
}
else{
//Display Toaster for error
Toast.makeText(getApplicationContext(),"Please enter your details", Toast.LENGTH_LONG).show();
}
}
Before the LoginService has finished executing, the activity has already moved to another activity via the Intent variable. I do not understand why. The idea of the LoginService is to validate the credentials of the user. If it returns true, then it can switch to the other activity.

You do not want to do this in this way. The .execute() will begin as soon as possible, but there is no guarantee (and perhaps guaranteed not to) that it will get your loginSuccess value back to you in time.
Everything after new LoginService(...).execute(); should be moved into onPostExecute():
private Context mContext = null;
public void setContext(Context context) {
mContext = context;
}
#Override
protected void onPostExecute(Void result) {
if(loginSuccess!=false){
//Used to move to the Cases Activity
Intent casesActivity = new Intent(mContext, CasesActivity.class);
startActivity(casesActivity);
}else{
Toast.makeText(mContext,"Incorrect Details", Toast.LENGTH_LONG).show();
}
}
Then, you have to call setContext() like so:
LoginService service = new LoginService(editTextUsername.getText().toString(), editTextPassword.getText().toString());
service.setContext(getApplicationContext());
service.execute();

You should move
Intent casesActivity = new Intent(getApplicationContext(), CasesActivity.class);
startActivity(casesActivity);
}else{
Toast.makeText(getApplicationContext(),"Incorrect Details", Toast.LENGTH_LONG).show();
}
into LoginService's onPostExecute.
In this way you are sure the asynctask has finished its work.
In any case it's quite strange the other activity gets started, it might be because of an old assignement of loginSuccess to true

How to return the result from the asynctask?
Catch the result of AsyncTask from onPostExecute().
#Override
public void onPostExecute(Boolean result)
{
boolean loginSuccess = result;
if(loginSuccess!=false) {
Intent casesActivity = new Intent(getApplicationContext(), CasesActivity.class);
startActivity(casesActivity);
}
else {
Toast.makeText(getApplicationContext(),"Incorrect Details", Toast.LENGTH_LONG).show();
}
}
The data type of result in AsyncTask depends on the 3rd Type parameter.
Sometimes we think execute() method of AsyncTask will return a result which is wrong. It will return an AsyncTask itself

http-request from Button VS from Class

i got a class i made, that makes a simple GET request and displays toast messege with the response...
if i call the function from a bottom event click it displays the messege with the data returned, just ok.
but if i call the same function from a brodcast reciver class, it just showing the massege with the data '' (null)
i belive that it showing the massege before i could get the data, and with the button it waits for the data..
how can i make it work from the brodcast reciver?
the class:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import android.app.Activity;
import android.content.Context;
import android.widget.Toast;
public class myclass{
public static void doHttpRequest(String param1, Context context){
String ret="";
try {
URL url = new URL("http://website.com/page?param="+param1);
HttpURLConnection con = (HttpURLConnection) url
.openConnection();
ret=readStream(con.getInputStream());
} catch (Exception e) {
e.printStackTrace();
}
CharSequence text = "return data- "+ret;
int duration = Toast.LENGTH_LONG;
Toast toast = Toast.makeText(context, text, duration);
toast.show();
}
private static String readStream(InputStream in) {
BufferedReader reader = null;
String line = "";
String alllines = "";
try {
reader = new BufferedReader(new InputStreamReader(in));
while ((line = reader.readLine()) != null) {
alllines=alllines+line;
}
return alllines;
} catch (IOException e) {
e.printStackTrace();
} finally {
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return alllines;
}
}
from the button it works fine:
final Button button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
myclass.doHttpRequest("blabla", getBaseContext());
}});
from the brodcast reciver witch in different class it won't return data, but shows the toast..
public class CustomBroadcastReceiver extends BroadcastReceiver {
private static final String TAG = "CustomBroadcastReceiver";
#Override
public void onReceive(Context context, Intent intent) {
myclass.doHttpRequest("blabla", context);
break;
} }
}
please HELP.... :) THANKS

All fixed.. it's seems to be a project settings error, or premmisions error (but i had the premissions in the manifest... must not apply in the apk while compiling)
i copied the classes to enother project made by erlier version of eclipse, and it's works there like a charm...
thanks anyway..
i tried for hours to fix it in the code.. and it was the settings....

I created a myclass.java and CustomBroadcastReceiver.java and tried your code by removing the break statement and one extra curly brace from the CustomBroadcastReceiver.java class and it worked fine for me.
The following code in Activity class demonstrates registering, uninteresting receiver and a Handler for a sample/test broadcast.
CustomBroadcastReceiver customBroadcastReceiver;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
customBroadcastReceiver = new CustomBroadcastReceiver();
registerReceiver(cusoBroadcastReceiver, new IntentFilter("com.example.app.testbroadcast"));
// For test broadcast only.
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
// TODO Auto-generated method stub
sendBroadcast(new Intent("com.example.app.testbroadcast"));
}
}, 2000);
}
#Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
unregisterReceiver(customBroadcastReceiver);
}
Hope this helps.

Android - app force closes when no Internet connection

package info.testing;
import java.io.IOException;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.select.Elements;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.webkit.WebView;
import android.widget.Toast;
public class SoupActivity extends Activity {
private static final String TAG = "SoupActivity";
private static final String DATA = null;
private String data = null;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
if(savedInstanceState != null)
{
data = savedInstanceState.getString(DATA);
showResults();
}
else
{
parsePage();
}
}
protected void parsePage(){
Document doc = null;
try {
doc = Jsoup.connect("http://www.mydata.html").get();
Toast.makeText(this, R.string.success, Toast.LENGTH_SHORT).show();
} catch (IOException e) {
Toast.makeText(this, R.string.error, Toast.LENGTH_SHORT).show();
}
Elements rows = doc.select("tr[class]");
data = "<table>" + rows.toString() + "</table>";
showResults();
}
protected void showResults(){
WebView web = (WebView)findViewById(R.id.web);
web.loadData(data, "text/html", "utf-8");
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState){
savedInstanceState.putString(DATA, data);
super.onSaveInstanceState(savedInstanceState);
}
#Override
public void onRestoreInstanceState(Bundle savedInstanceState){
if(savedInstanceState != null)
{
data = savedInstanceState.getString(DATA);
}
super.onRestoreInstanceState(savedInstanceState);
}
}
Flash/Flex developer here starting to get in to Android development, I must admit I am loving it so far, but obviously taking a long time to work out why things happen the way they do.
So the problem I have is that my app crashes without an Internet connection - The application (process.testing) has stopped unexpectedly. This only happens when there is no internet connection and works perfectly if there is one. The only part of my code that accesses the Internet is in a try catch block, can anyone see what I'm doing wrong or how I can handle the error when there is no Internet connection available?

You can use this function to see if a connection is available :
/**
* Check the network state
* #param context context of application
* #return true if the phone is connected
*/
public static boolean isConnected(Context context) {
ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
if (netInfo != null && netInfo.isConnected()) {
return true;
}
return false;
}

When you have no internet connection, doc is probably null and you get NullPointerException because you don't check this case:
Document doc = null;
try {
// connect throws an exception, doc still null
doc = Jsoup.connect("http://www.mydata.html").get();
Toast.makeText(this, R.string.success, Toast.LENGTH_SHORT).show();
} catch (IOException e) {
Toast.makeText(this, R.string.error, Toast.LENGTH_SHORT).show();
}
// dereferencing null (doc) throws NullPointerException
Elements rows = doc.select("tr[class]");