How to write text file in SDCARD in Android

Here is the full Source code for write file:

public class MainActivity extends Activity {
private String stringFile;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
stringFile="This is the test string file";
writeFile(stringFile);

}

private void writeFile(String stringFile2) {
try {
            File myFile = new File("/sdcard/testWriteFile.txt");
            myFile.createNewFile();
            FileOutputStream fOut = new FileOutputStream(myFile);
            OutputStreamWriter myOutWriter = 
                                    new OutputStreamWriter(fOut);
            myOutWriter.append(stringFile2);
            myOutWriter.close();
            fOut.close();
            Toast.makeText(getBaseContext(),
                    "Done writing SD 'mysdfile.txt'",
                    Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            Toast.makeText(getBaseContext(), e.getMessage(),
                    Toast.LENGTH_SHORT).show();
        }

}

}

Finally you don't forget to declared permission in your androidmanifest.xml file.
----------------

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />


Output looks like this:

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Convert UTF-8 encoded NSData to NSString in ios

UTF-8 encoded NSData from windows server and I want to convert it to NSString for iPhone. Since data contains characters (like a degree symbol) which have different values on both platforms,  convert data to string following way.




If the data is not null-terminated, you should use -initWithData:encoding:

NSString* newStr = [[NSString alloc] initWithData:theData encoding:NSUTF8StringEncoding];

If the data is null-terminated, you should instead use -stringWithUTF8String: to avoid the extra \0 at the end.

NSString* newStr = [NSString stringWithUTF8String:[theData bytes]];

if you are doing this, remember this: using "stringWithUTF8String:" on a string that is not null-terminated, the result is unpredictable.

or simple call this for this

+(id)stringWithUTF8String:(const char *)bytes.

Happy Coding !!!

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Android Developer @ TripCraft in USA

Looking for an experienced Android developer to build native mobile apps for business and consumer needs within the travel and hospitality industry.  This role will primarily focus on Android, but having iOS experience is a big plus.
The mobile solutions we develop (native & browser) are powered by cloud servers that handle content, marketing, customer, and other business needs.  Our cloud platform is built with Linux, PostgreSQL, Ruby on Rails, HTML5, and uses XML / JSON for data exchange.  It is hosted on Amazon, Engine yard, and/or Heroku.
Candidates MUST be located in the USA and be able to work during typical EST hours.  Candidates located in the New England area that are willing to come to Waltham for occasional meetings and in-office development will be given a priority.

Skills & Requirements

Skills:

• Experienced Android / Java developer that can write code while keeping an eye on performance and architecture.
• Experience with consuming RESTful web services using JSON.
• Experience with In-app database and advanced UX a big plus.
• Experience with Voice Recognition (Siri, Nuance, etc.) a big plus.
• Familiarity with database design a plus.
• Familiarity with creating and maintaining automated unit tests.
• Familiarity with Git (or similar).

Approach:

• Top-down thinker and developer to ensure what we produce is extensible, reusable, and scalable
• Great communicator and team player as you bridge the gap between wireframes, designs, challenging requirements, and a growing code base
• Team player that doesn't mind leading and following as needed.
• Deliverable-oriented. Be able to break down larger business requirements into smaller technical tasks, which you can achieve and iterate on in a short amount of time, in order to continually demonstrate forward progress to us and our clients.

About TripCraft

TripCraft offers mobile solutions for the travel industry.
TripCraft is the travel industry’s first mCommerce platform that provides mobile solutions for clients like Mandarin Oriental Hotels, Caesars Entertainment, Amadeus International, and sbe Entertainment.  TripCraft is located in Waltham, Ma.
We don’t pick sides when it comes to mobile development and are as comfortable with native apps and mobile websites as we are with iOS, Android and Windows operating systems.
We have the heart and soul of a start-up, but the wisdom and experience of travel industry veterans.  Our culture is fun, casual, and flexible.  Like working from home?  So do we!  At TripCraft, we place emphasis on creativity and productivity, not office cubicles.  We are a collection of self-starters, team players, and stellar communicators.
Permanent candidates preferred, but will consider contractor-to-perm in situations.  Interested applicants can send the resume to Mike.Murray@TripCraft.com.  For more information about TripCraft, visit our website at http://www.tripcraft.com.

Apply Now

Happy Job !!!

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Action Bar Demo in Android

The action bar is a window feature that identifies the user location, and provides user actions and navigation modes. Using the action bar offers your users a familiar interface across applications that the system gracefully adapts for different screen configurations.
Lessons

---

Setting Up the Action Bar

Learn how to add a basic action bar to your activity, whether your app supports only Android 3.0 and higher or also supports versions as low as Android 2.1 (by using the Android Support Library).

Adding Action Buttons

Learn how to add and respond to user actions in the action bar.

Styling the Action Bar

Learn how to customize the appearance of your action bar.

Overlaying the Action Bar

Learn how to overlay the action bar in front of your layout, allowing for seamless transitions when hiding the action bar.

Here is the example of Action Bar demo App

first define menu in   res/menu/main.xml:

<menu xmlns:android="http://schemas.android.com/apk/res/android" >

    <item
        android:id="@+id/refresh"
        android:alphabeticShortcut="r"
        android:icon="@drawable/ic_action_refresh"
        android:orderInCategory="100"
        android:showAsAction="always"/>
    <item
        android:id="@+id/share"
        android:actionProviderClass="android.widget.ShareActionProvider"
        android:icon="@drawable/ic_action_share"
        android:orderInCategory="1"
        android:showAsAction="collapseActionView"
        android:title="Share"/>
    <item
        android:id="@+id/update"
        android:icon="@drawable/db_update_24"
        android:orderInCategory="100"
        android:showAsAction="collapseActionView"
        android:title="Update"/>

</menu>

Now define for refresh icons with circling with progress in to: res/layout/actionbar_indeterminate_progress.xml 

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_height="wrap_content"
   android:layout_width="56dp"
   android:minWidth="56dp">
    <ProgressBar android:layout_width="32dp"
       android:layout_height="32dp"
       android:layout_gravity="center"/>
</FrameLayout>

another xml file defined in layout: res/layout/main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:ads="http://schemas.android.com/apk/res-auto"
    android:id="@+id/relativeLayout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#00FFFF" >

</RelativeLayout>


Now finally add your project MainActivity java file with full code:

package com.example.searchdemo;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;
import android.annotation.TargetApi;
import android.os.Build;
import android.view.ViewConfiguration;
import android.widget.ShareActionProvider;

@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
public class MainActivity extends Activity {
private int toast_time = 100;
private Menu optionsMenu;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
getOverflowMenu();
}

// check strictmode and ignore it
private void strictMode() {
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);
}
}


// inflate for action bar
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
this.optionsMenu = menu;
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

// handle click events for action bar items
@SuppressLint("NewApi")
@Override
public boolean onOptionsItemSelected(MenuItem item) {

switch (item.getItemId()) {

case R.id.refresh:
// showToast(getResources().getString(R.string.refresh));
setRefreshActionButtonState(true);
Intent intent = getIntent();
finish();
startActivity(intent);
// setRefreshActionButtonState(false);
return true;

case R.id.share:
// showToast("Share was clicked.");
String shareBody="Sharing Message";
ShareActionProvider myShareActionProvider = (ShareActionProvider) item
.getActionProvider();

Intent myIntent = new Intent();
myIntent.setAction(Intent.ACTION_SEND);
myIntent.putExtra(Intent.EXTRA_TEXT, shareBody);
myIntent.setType("text/plain");

myShareActionProvider.setShareIntent(myIntent);

return true;
case R.id.update:
showToast("Update");
return true;
default:
return super.onOptionsItemSelected(item);
}
}


@TargetApi(Build.VERSION_CODES.HONEYCOMB)
@SuppressLint("NewApi")
public void setRefreshActionButtonState(final boolean refreshing) {
if (optionsMenu != null) {
final MenuItem refreshItem = optionsMenu.findItem(R.id.refresh);
if (refreshItem != null) {
if (refreshing) {
refreshItem
.setActionView(R.layout.actionbar_indeterminate_progress);
} else {
refreshItem.setActionView(null);
}
}
}
}



// put the other two menu on the three dots (overflow)
private void getOverflowMenu() {

try {

ViewConfiguration config = ViewConfiguration.get(this);
java.lang.reflect.Field menuKeyField = ViewConfiguration.class
.getDeclaredField("sHasPermanentMenuKey");
if (menuKeyField != null) {
menuKeyField.setAccessible(true);
menuKeyField.setBoolean(config, false);
}
} catch (Exception e) {
e.printStackTrace();
}

}

// so that we know something was triggered
public void showToast(String msg) {
Toast.makeText(this, msg, toast_time).show();
}

}

here is the output of above demo app snapshots:

Hope, this demo helpful for developing apps.

Do you want more about action bar go following links:
http://developer.android.com/guide/topics/ui/actionbar.html

https://developer.android.com/training/basics/actionbar/index.html

https://www.youtube.com/watch?v=4BOE9TeUY1w

http://developer.android.com/design/patterns/actionbar.html

http://www.androidhive.info/2013/11/android-working-with-action-bar/

http://jgilfelt.github.io

Happy Coding !!!

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Calculate Square pair in array in Java

Count Square Pairs in Java based on arrays. From the array here is the name function countSquarePairs  using for calculate square pairs.

Lets first define array:

int [] sparray= new int[] {9, 0, 2, -5, 7};

then calculated square pairs from this function:


private static int countSquarePairs(int[] sparray) {
int count=0;
// TODO Auto-generated method stub
if (sparray.length<=1) {
return 0;
}
else {
//Arrays.sort(sparray);


    int i, j, temp;  //be sure that the temp variable is the same "type" as the array
    for ( i = 0; i < sparray.length - 1; i ++ ) 
    {
         for ( j = i + 1; j < sparray.length; j ++ )
         {
              if( sparray[ i ] > sparray[ j ] )         //sorting into descending order
              {
                      temp = sparray[ i ];   //swapping
                      sparray[ i ] = sparray[ j ];
                      sparray[ j ] = temp; 
               }           
         }
    }

System.out.println("---"+Arrays.toString(sparray));
for (int y = 0; y < sparray.length-1; y++) {
for (int z = y+1; z < sparray.length; z++) {
int tem=sparray[y]+sparray[z];
int square=(int)Math.sqrt(tem);
if (tem==square*square) {
count+=1;
}
}
}
}
return count;
}
Here is the final print how many square pair values in existing arrays:

System.out.println("No of countSquarePairs=="+countSquarePairs(sparray));


Output of above arrays:

No of countSquarePairs==4

Happy Coding!!!

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How do you get a timestamp in programming language?

Get time timestamp in Java:
first import the file
import java.sql.Timestamp;
          import java.util.Date;

and, then just defined following code

         java.util.Date date= new java.util.Date();
      System.out.println(new Timestamp(date.getTime()));

Get timestamp in Java script:

the following returns the number of milliseconds since the epoch.

     new Date().getTime();

Or on browsers that support ES5 (notably not IE8 and earlier), you can use Date.now:

      Date.now();

which is really easily shimmed for older browsers:

      if (!Date.now) {
        Date.now = function() { return new Date().getTime(); };
    }

Get timestamp in IOS:


NSString * timestamp = [NSString stringWithFormat:@"%f",[[NSDate date] timeIntervalSince1970] * 1000];

(times 1000 for milliseconds, otherwise, take that out)

If You're using it all the time, it might be nice to declare a macro

#define TimeStamp [NSString stringWithFormat:@"%f",[[NSDate date] timeIntervalSince1970] * 1000]

Then Call it like this:

NSString * timestamp = TimeStamp;

Or as a method:

- (NSString *) timeStamp {
    return [NSString stringWithFormat:@"%f",[[NSDate date] timeIntervalSince1970] * 1000];
}



Get timestamp in PHP:

here is the function get timestamp in php:

<?php
$t=time();
echo($t . "<br>");
echo(date("Y-m-d",$t));
?>


Get timestamp in C#:

Function that creates a timestamp in c#

public static String GetTimestamp(this DateTime value)
{
    return value.ToString("yyyyMMddHHmmssffff");
}

Get timestamp in Python:

here is the simple way to get time in python;

Python 2.7.3 (default, Apr 24 2012, 00:00:54) 
[GCC 4.7.0 20120414 (prerelease)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import time
>>> ts = time.time()
>>> print ts
1355563265.81
>>> import datetime
>>> st = datetime.datetime.fromtimestamp(ts).strftime('%Y-%m-%d %H:%M:%S')
>>> print st
2012-12-15 01:21:05
>>>

Get timestamp in Perl:

getting time in perl for this way:


If you want to control the format of the timestamp, I usually throw in a subroutine like the following. This will return a scalar in the format of "20120928 08:35:12".

sub getCurrentTime {

    my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst)=localtime(time);
    my $nice_timestamp = sprintf ( "%04d%02d%02d %02d:%02d:%02d",
                                   $year+1900,$mon+1,$mday,$hour,$min,$sec);
    return $nice_timestamp;
}

Then change your code to:

my $timestamp = getCurrentTime ();



Happy Coding!!!

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Declare an array, Converting an array to list and create ArrayList (ArrayList) from array (T[]) in Java

Declare an Array in Java

You can either use array declaration or array literal (but only when you declare and affect the variable right away, array literals cannot be used for re-assigning an array).

For primitive types:

int[] myIntArray = new int[3];
int[] myIntArray = {1,2,3};
int[] myIntArray = new int[]{1,2,3};

For classes, for example String, it's the same:

String[] myStringArray = new String[3];
String[] myStringArray = {"a","b","c"};
String[] myStringArray = new String[]{"a","b","c"};


Converting an array to list in Java

Integer[] spam = new Integer[] { 1, 2, 3 };
Arrays.asList(spam);

Or

ArrayList<String> stock_list = new ArrayList<String>();
stock_list.add("stock1");
stock_list.add("stock2");
String[] stockArr = new String[stock_list.size()];
stockArr = stock_list.toArray(stockArr);
for(String s : stockArr)
System.out.println(s);


and
Create ArrayList (ArrayList<T>) from array (T[]) in Java

new ArrayList<Element>(Arrays.asList(array))

Or

Element[] array = new Element[] { new Element(1),new Element(2),new Element(3) };

The simplest answer is to do:

List<Element> list = Arrays.asList(array);


Happy Coding!!!

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Reverse String in Java and Android

Are you getting problem during reverse string in java or android, here is the simple solution fro reverse string.

First things, Just define this string:

        String tempString = "AndroidandJavaTutorials";
        String reverseString = new StringBuffer(tempString).reverse().toString();
        System.out.printf(" original String -> %s , reversed String %s  %n", tempString, reverseString);
   

        tempString = "pRAndroid";
        reverseString = new StringBuilder(tempString).reverse().toString();
        System.out.printf(" original String- > %s , reversed String %s %n", tempString, reverseString);

Now, Call the funtion, where exactly process of reserve:

public static String reverse(String source){
        if(source == null || source.isEmpty()){
            return source;
        }    
        String reverse = "";
        for(int i = source.length() -1; i>=0; i--){
            reverse = reverse + source.charAt(i);
        }
   
        return reverse;
    }

Final output of above tempString:

 original String -> AndroidandJavaTutorials , reversed String slairotuTavaJdnadiordnA  
 original String- > pRAndroid , reversed String diordnARp 

Happy Coding!!!

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Common Errors while Developing Android Application

• NullPointer error
  
  1. when i use un initialized variable or object we are creating. (Java)
  2. when we use some layout out view that is not in xml what we set in context.(Android)

• ClassCast Exception
  • when a program attempts to cast a an object to a type with which it is not compatible. (eg: when i try to use a linear layout which is declared as a relative layout in xml layout).

• StackOverflowError
  • it can also occur in correctly written (but deeply recursive) programs.(java and android)
  • when a program becomes infinitely recursive.
  • we create layout (deep and complex) that exceeds that stack of platform or virtual machine . recursive or too much of layout will create Stack overflow error in Android
  • Too many inner layouts.

• ActivityNotFoundException: Unable to find explicit activity class exception
  
  • The activity is not declared in manifest.

• Android securityException
  • You need to declare all permission in the application Manifest that your application check this link (internet, access to contact,gps,wifi state,write to SDCard, etc).

• OutofMemoryError
  • when a request for memory is made that can not be satisfied using the available platform resources . mainly using bit map, gallery , etc.

• Application Not Responding (ANR)
  
  • Mainly comes when you are making network function,or some long process.

  this will block UI Thread so user can not do any work. to avoid ANR read this & this
  

This are thing i mainly get while creating Android Project.

• Try to use Try - Catch block in All Place of program. Dont leave your catch block empty as this can hide errors:

Yes:

 try{
    // try something
  } catch (Exception e) {
      Log.e("TAG", "Exception in try catch", e);
      return false;
  }
  return true;

No:

  try{
    // try something
  } catch (Exception e) {
    return false;
  }
  return true;

Use proper Naming conversion for all variable and ID's in Layout.*

---

 one article from net it contains some error now i am adding that alos if it have redundancy please forgive me.

Issue : My previously nice RelativeLayout is making an ugly heap or some elements aren't visible anymore...What's going on ??? I just moved an element in it... Solution : Never forget that in a RelativeLayout, elements are referenced and placed in relation to their neighbours. Maybe there is something wrong in the hierarchy of relationship between your element. Try opening the outline view in Eclipse and clicking each element to see where there is a rupture.

Issue : Circular dependencies cannot exist in RelativeLayout Solution : You have probably written the same dependency in two different way. For instance an ImageView as the attribute android:layout_toRightOf a TextView and the TextView has android:layout_toLeftOf the ImageView. Only one of them is necessary
Issue : I wrote a style for one of my view/layout, but when I apply it in my xml, I have no display in the layout viewer of Eclipse Solution : Unfortunately, this seems to be a bug of the android ADT, I reported it but no news so far. Anyway, no panic, styles are working well, but they aren't displayed properly in Eclipse. Just build the app and launch it on the emulator or phone and you will see if everything is fine or not.

Issue : Toast is written properly but nothing is displayed Solution : This is a common error of use : just add the .show() method to show the Toast and see if it is working well

Issue : I tried to display a String from strings.xml but I just had a number like 0x7f060001 Solution : This is not a bug, just a display due to the way android deals with resources. When you want to retrieve a resource, you have to use a method like getString(R.id.something), getDrawable, …Otherwise, you just display the reference written in the R class

Issue : Some change in code doesn't have any effect in the application Solution : there are 2 options, either you have forgotten something like the .show() of the Toast, or the emulator is not updating properly your application. In that case, you have to check the option “Wipe user Data” in your launch configuration of the emulator in Eclipse.

Issue : How to display borders on my table? Solution : There is no direct way to do that in android, you have to use a trick :http://www.droidnova.com/display-borders-in-tablelayout,112.html

Issue : the emulator is writing in japaneese withtout you having changed any parameter Solution : This happens sometimes, quite easy to fix, just long click in any EditText field, and change the input type to what you want

Issue : I can't get the Context Menu to appear in the emulator Solution : long click on emulator does not seem to register on every kind of view, you have to push the button in the center of the 4 directionnal arrows

Issue : I'm following a tutorial about map route but I can't get it work, android does not find a package Solution : You might have been following a tutorial written for 1.5 SDK. At this time, there was a package to display route in android, but it was removed in the next SDK and is not available anymore. It just not possible anymore. There seems to be a trick with KML files but nothing official

Issue : Sending coordinates to the emulator gives wrong position Solution : ensure that you wrote the coordinate like 51.16548 and not 51,16548 nor 5116548

Issue : Only the original thread that created a view hierarchy can touch its views. Solution : You must have tried to update a view content from another thread than the UI thread. 2 options to patch this : either create a handler in your UI thread and post your Runnable to this handler OR use the method runOnUIThread to run the lines of code that are doing the update


Issue : accessing localhost 127.0.0.1 doesn't work Solution : it works, you are just not doing it the right way : use 10.0.2.2

Source

Happy Coding!!!

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Sr. Android Engineer @ New York

American Express aggressively compete in an exciting space that features both emerging technology and financial services firms – and we’re now embarking on an exciting transformation.  We are building an energetic, high-performance team with a nimble and creative mindset to drive our technology and products.  American Express is a powerful brand, a great place to work, and has unparalleled scale.  We deliver innovative payment products and services at a rapid pace, serving our customers seamlessly across physical, digital, mobile, and social media.  Join us!

You will be part of product teams that deliver world class Cardmember experiences on multiple channels like native iOS, Android, web, social integration, java services / api’s - working in a fast-paced, start-up like environment. We are looking for passionate, hands-on software engineers who know good code from bad code. We expect our engineers to bring their innovative ideas with proof of concepts & pitches for new investment / product opportunities.  This organization has launched multiple mobile apps including the American Express mobile apps for iOS & Android, Near Field Communication wallet pilot, Innovative card-member features like auto-matching of receipts to transactions, and APIs for third-party sites like Express Checkout.

Responsibilities include:

    This engineer owns all technical aspects of software development for assigned applications – performs hands-on architecture, design and development of systems
    Mentors Engineers & may have management responsibilities over 2-3 Engineers
    Helps drive consistent development practices – tools & common components
    This engineer develops deep understanding of tie-ins with other systems and platforms within the supported domains  
    Contributes to blueprint & assists Product Managers with annual planning of feature sets that impact multiple platforms  
    Typically spends 50%+ of time writing code & testing in support of product/platform release with ongoing sprints    
    Identifies opportunities to adopt innovative technologies
    This “Rebel with a cause” looks beyond the obvious for continuous improvement opportunities

Qualifications

This high energy Senior Engineer must have:

    6+ years of software development experience    
    A BS or MS degree in computer science, computer engineering or other technical discipline, or equivalent work experience    
    Demonstrated experience in Agile development    
    Has hands-on expertise with application design, software development and testing    
    Ability to coach junior engineers    
    Demonstrated willingness to learn new technologies and takes pride in how fast they develop working software    
    Ability to enable business capabilities through innovation in the mobile domain    
    Ability to effectively communicate across 3rd parties, technical and business product managers on solution design    
    Expertise in using Android UI Framework including push notification, geolocation    
    Experience with the Android platform, Java, and Android developer tools    
    Objected Oriented Analysis and Design expertise    
    Experience in Multi Threaded programming    
    Thorough understanding of XML, JSON , Web Services technologies and data structure fundamentals    
    Has experience with a variety of software languages is a plus    
    Proven record of design and development of mobile applications in an Enterprise setting is a plus  
    Having Apps published in the Google Play Store is a plus    
    Experience with payments technology is a plus

Relocation assistance may be available.

MG2A

American Express is an equal opportunity employer and makes employment decisions without regard to race, color, religion, sex, national origin, protected veteran status, disability status, or any other status protected by law. Click here to view the “EEO is the Law” poster. If the link does not work, please copy and paste the following URL in a new browser window:

http://www.dol.gov/ofccp/regs/compliance/posters/ofccpost.htm

ReqID: 14002310

How to apply

https://jobs.americanexpress.com/jobs/724642/New-York-New-York-Sr-Android-Engineer?lang=en-US&src=JB-12200

Jobs From: http://careers.stackoverflow.com/jobs/61902/sr-android-engineer-american-express?a=51IV7XP9L2

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R cannot be resolved to a variable in Android

First you may clean the project, then run the project. If this does not work then follow the following links:

• Here is the best way to solve this problem: Android Development- Where is my R.Java file?
• R cannot be resolved - Android error
• R cannot be resolved to a variable
• R cannot be resolved to a variable -- mailing list entry
• Fixed: R cannot be resolved to a variable

Source

Make sure that anything the R. links to is not broken. Fix all errors in your XML files. If anything in the ADKs are broken, R will not regenerate.

If you somehow hit something and created import android.R in your activity, remove it.

Run Project -> Clean. This will delete and regenerate R and BuildConfig.

Make sure Project -> Build Automatically is ticked. If not, build it manually via Menu -> Project -> Build Project .

Wait a few seconds for the errors to disappear.

If it doesn't work, delete everything inside the /gen/ folder

If it still doesn't work, try right-clicking your project -> Android Tools -> Fix Project Properties.

Check your *.properties files (in the root folder of your app folder) and make sure that the links in there are not broken.

Right-click your project > properties > Android. Look at the Project Build Target and Library sections on the right side of the page. Your Build Target should match the target in your AndroidManifest.xml. So if it's set to target 17 in AndroidManifest, make sure that the Target Name is Android 4.2. If your Library has an X under the reference, remove and re-add the library until there's a green tick. This might happen if you've moved a few files and folders around -  Source

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Android Auto Developer Overview

Android Auto extends the Android platform into the car. When users connect their Android handheld device to a compatible vehicle, Android Auto provides a car-optimized Android experience on the vehicle's screen. Users interact with compatible apps and services through voice actions and the vehicle's input controls.

The Android Auto SDK lets you easily extend your existing apps to work in the car, without having to worry about vehicle-specific hardware differences. You can use many Android APIs and services you are already familiar with. Android Auto provides an easy to use UI model and supports notifications and voice actions:

Media UI

Android Auto defines interaction models and car-specific UI patterns for apps. The first version of Android Auto supports media apps, such as music, podcast, live radio, and audio news apps.

Notifications

The platform will integrate with existing Android APIs for notifications. Users will get car appropiate notifications from Android apps on the vehicle's screen.

Voice Actions

Android Auto supports a set of voice actions to interact with compatible apps and services. Apps can respond to the voice actions they're interested in, such as playing a particular song or taking a note.

Easy Development Workflow

To extend an existing Android app for Android Auto, you implement a set of interfaces and services defined in the platform. You can reuse existing functionality and many Android APIs you already know.

We’ll release the Android Auto SDK in the coming months, which will let you test your Android Auto experience on a regular Android device.

Design

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Android Auto extends users' digital ecosystem into their cars, allowing drivers to stay connected to their virtual worlds while staying focused on the road ahead.

Because driving is the primary activity in the car, any digital experiences should be designed to complement and augment that activity. They should never demand the user's attention.

Designing for cars is fundamentally different than designing for phones or tablets, and requires rethinking how experiences unfold. Because attention is limited and not all tasks are possible in the car, effective apps leverage the entire set of devices that drivers have, leveraging the app experience on those devices, outside of the car, to set the stage for simple experiences while driving.

Android Auto experiences are:

Glanceable and simple. Driving requires users' full attention. In-car software should not. Android Auto was designed to simplify not only the UI, but to optimize interactions and require less thinking, induce lower cognitive load, and ultimately, be safer. Effective apps provide just enough information in the minimum amount of time the user needs to glance at it and return their attention back to the road. Apps should also reduce the number of features to only those that are safe and drive-appropriate.

Predictive, yet predictable. Android Auto leverages rich, contextual awareness to keep the driver informed about important situations during the drive. Rich, timely help is combined with predictable functions. Effective apps make use of the patterns for common tasks and show timely information only when relevant.

Connected. By leveraging the user's personal ecosystem of apps and services, Android Auto promotes a continuous experience from phone to car to other devices. The user's music, destinations, and virtual ecosystem are always available to augment the drive. Experiences that leverage personal context and other devices are naturally part of Android Auto.

Naturally integrated. Android Auto blends the user's apps with the car, creating a truly integrated experience that leverages what is unique about each car. By using the screens, controls, and capabilities of the vehicle, Android Auto feels like an extension of the car.

Architecture

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The Android Auto app shows your app's customized UI on the vehicle's screen. To communicate with the Android Auto app, your media app implements a set of media interfaces.

  Figure 1 - Architecture of Android Auto.

The architecture consists of the following components:

Media App - Runs a media service that exposes content through browsing and playback APIs. The service provides content to the Android Auto app. This is your Android app.

Android Auto App - Creates the UI and handles user interactions. This app uses a media client to request content from the media service running in the media app. The client requests data from the media service and monitors service states.

Vehicle Display - Shows app content and supports user interaction via on-screen soft buttons and other components, such as physical buttons or steering wheel controls.

Android media apps must implement binders to these APIs:

• Browsing - Enables a media client to browse a hierarchy of a user’s media collection, presented as a virtual file system with containers (similar to directories) and items (similar to files).
• Playback - Enables a media client to control media playback and monitor playback state through callbacks.

User Interface

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The Android Auto app uses a car-specific UI model to display content and user interaction opportunities. Android Auto provides you with a standard UI designed to minimize driver distraction. You do not have to test a custom UI for for driver distraction, which is a lengthy and expensive process involving multiple legislations across the globe and different standards for each vehicle OEM.

The UI defines interfaces for browsing, searching, and listening to content from media apps. You can customize the UI colors, action icons, background images, and more.

Launcher

The launcher shows all the compatible media apps installed on the user’s Android device and lets users select one of them from an scrollable list:

  Figure 2. The launcher.

Primary App UI

After the user selects a media app, the display shows the primary app UI. You can customize this UI to show your own icons, app name, and background images. Figure 3 shows an example of a customized UI:

  Figure 3. A customized UI.

User Actions

The primary app UI supports four main actions on the action bar, four auxiliary actions on the overflow bar, and the Returnaction. You can use standard controls and customize the actions and icons, as shown in Figure 4.

  Figure 4. Custom extra actions.

Drawer Transitions

For browse actions, the display shows the drawer transition as shown in Figure 5.

  Figure 5. Generic and customized drawers.

After the transition from the primary app UI to the drawer UI, the drawer appears on the center. The customized drawer UI shows the media containers and media files provided by the media service in your app. You can also customize drawers with icons for list items.

Day and Night Transitions

All the UIs support different color schemes for day and night. The platform provides the state (day or night) and makes adjustments automatically.

  Figure 6. Day and night modes.

Customizing UIs

To customize the UI, you provide the following app-specific resources and actions to the Android Auto media client:

• Resources - App logo, app name, theme colors, and background images.
• Actions - Multiple custom actions; for example: Thumbs Up/Down, Favorite, and Bookmark. These actions are app-specific.

If provided, the media client automatically uses them in the UI.

Development Process

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Note: When released, the Android Auto SDK will provide media service interfaces, an APK for handheld devices that simulates the Android Auto app, and other tools for Android Auto development.

To create a media app for Android Auto, you include an Android service in your app that implements the media service interfaces provided by the Android Auto SDK. These interfaces define functionality for browsing and finding content, playing media, customizing the UI, and performing app-specific actions.

The media service interfaces present the content library as a navigable tree and enable clients to play media, get album art, obtain theme resources for the UI, and invoke app-specific actions.

You don’t have to create a new app for Android Auto: you can extend your existing Android app with implementations of the media service interfaces. Your service exposes your app’s media content, theme resources, and app-specific actions using the methods and data types specified by the media service interfaces. This simplifies the development cycle because:

• You do not have to maintain a separate project for Android Auto
• You can reuse existing functionality from your Android app

The Android Auto client presents the customized UI to users and invokes the functionality from your service as needed. This has two additional advantages:

• Your app does not implement a UI for Android Auto
• Your app does not manage user interactions directly

This also means that you do not have to worry about vehicle-specific hardware differences such as screen resolutions, software interfaces, knobs and touch controls.

Testing Your App on an Android Device

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The Android Auto SDK includes an APK with a media client implementation, which is similar to those available in compatible vehicles. To test your app with this client:

1. Get an Android device with a similar form factor to a dashboard screen (like a Nexus 7).
2. Configure the device for Android development.
3. Install the APK for the media client from the Android Auto SDK on the device.
4. Install the APK for your app on the device.
5. Open the media client app from the Android Auto SDK on the device.
6. Select your app from the list of available services.

The customized UI for your app appears on the client. You can navigate the content library and play media. If your app provides app-specific actions, these actions appear in the UI controls.

Running Your App on Android Auto

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Media apps are available on the Google Play Store for compatible Android devices. When users connect their Android device to a compatible vehicle, the Android Auto media client shows a list of all the Android apps installed on the phone that implement the media service interfaces.

When users select one of these apps, the Android Auto media client uses the app’s service to respond to user input and invoke the methods in the media service interfaces to build the UI, navigate the content library, and play media.

Source: Official Blog

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