Android color code in xml

Here is the some listing android color code defined in xml, you must define in res/values/colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
 <color name="White">#FFFFFF</color>
 <color name="Ivory">#FFFFF0</color>
 <color name="LightYellow">#FFFFE0</color>
 <color name="Yellow">#FFFF00</color>
 <color name="Snow">#FFFAFA</color>
 <color name="FloralWhite">#FFFAF0</color>
 <color name="LemonChiffon">#FFFACD</color>
 <color name="Cornsilk">#FFF8DC</color>
 <color name="Seashell">#FFF5EE</color>
 <color name="LavenderBlush">#FFF0F5</color>
 <color name="PapayaWhip">#FFEFD5</color>
 <color name="BlanchedAlmond">#FFEBCD</color>
 <color name="MistyRose">#FFE4E1</color>
 <color name="Bisque">#FFE4C4</color>
 <color name="Moccasin">#FFE4B5</color>
 <color name="NavajoWhite">#FFDEAD</color>
 <color name="PeachPuff">#FFDAB9</color>
 <color name="Gold">#FFD700</color>
 <color name="Pink">#FFC0CB</color>
 <color name="LightPink">#FFB6C1</color>
 <color name="Orange">#FFA500</color>
 <color name="LightSalmon">#FFA07A</color>
 <color name="DarkOrange">#FF8C00</color>
 <color name="Coral">#FF7F50</color>
 <color name="HotPink">#FF69B4</color>
 <color name="Tomato">#FF6347</color>
 <color name="OrangeRed">#FF4500</color>
 <color name="DeepPink">#FF1493</color>
 <color name="Fuchsia">#FF00FF</color>
 <color name="Magenta">#FF00FF</color>
 <color name="Red">#FF0000</color>
 <color name="OldLace">#FDF5E6</color>
 <color name="LightGoldenrodYellow">#FAFAD2</color>
 <color name="Linen">#FAF0E6</color>
 <color name="AntiqueWhite">#FAEBD7</color>
 <color name="Salmon">#FA8072</color>
 <color name="GhostWhite">#F8F8FF</color>
 <color name="MintCream">#F5FFFA</color>
 <color name="WhiteSmoke">#F5F5F5</color>
 <color name="Beige">#F5F5DC</color>
 <color name="Wheat">#F5DEB3</color>
 <color name="SandyBrown">#F4A460</color>
 <color name="Azure">#F0FFFF</color>
 <color name="Honeydew">#F0FFF0</color>
 <color name="AliceBlue">#F0F8FF</color>
 <color name="Khaki">#F0E68C</color>
 <color name="LightCoral">#F08080</color>
 <color name="PaleGoldenrod">#EEE8AA</color>
 <color name="Violet">#EE82EE</color>
 <color name="DarkSalmon">#E9967A</color>
 <color name="Lavender">#E6E6FA</color>
 <color name="LightCyan">#E0FFFF</color>
 <color name="BurlyWood">#DEB887</color>
 <color name="Plum">#DDA0DD</color>
 <color name="Gainsboro">#DCDCDC</color>
 <color name="Crimson">#DC143C</color>
 <color name="PaleVioletRed">#DB7093</color>
 <color name="Goldenrod">#DAA520</color>
 <color name="Orchid">#DA70D6</color>
 <color name="Thistle">#D8BFD8</color>
 <color name="LightGrey">#D3D3D3</color>
 <color name="Tan">#D2B48C</color>
 <color name="Chocolate">#D2691E</color>
 <color name="Peru">#CD853F</color>
 <color name="IndianRed">#CD5C5C</color>
 <color name="MediumVioletRed">#C71585</color>
 <color name="Silver">#C0C0C0</color>
 <color name="DarkKhaki">#BDB76B</color>
 <color name="RosyBrown">#BC8F8F</color>
 <color name="MediumOrchid">#BA55D3</color>
 <color name="DarkGoldenrod">#B8860B</color>
 <color name="FireBrick">#B22222</color>
 <color name="PowderBlue">#B0E0E6</color>
 <color name="LightSteelBlue">#B0C4DE</color>
 <color name="PaleTurquoise">#AFEEEE</color>
 <color name="GreenYellow">#ADFF2F</color>
 <color name="LightBlue">#ADD8E6</color>
 <color name="DarkGray">#A9A9A9</color>
 <color name="Brown">#A52A2A</color>
 <color name="Sienna">#A0522D</color>
 <color name="YellowGreen">#9ACD32</color>
 <color name="DarkOrchid">#9932CC</color>
 <color name="PaleGreen">#98FB98</color>
 <color name="DarkViolet">#9400D3</color>
 <color name="MediumPurple">#9370DB</color>
 <color name="LightGreen">#90EE90</color>
 <color name="DarkSeaGreen">#8FBC8F</color>
 <color name="SaddleBrown">#8B4513</color>
 <color name="DarkMagenta">#8B008B</color>
 <color name="DarkRed">#8B0000</color>
 <color name="BlueViolet">#8A2BE2</color>
 <color name="LightSkyBlue">#87CEFA</color>
 <color name="SkyBlue">#87CEEB</color>
 <color name="Gray">#808080</color>
 <color name="Olive">#808000</color>
 <color name="Purple">#800080</color>
 <color name="Maroon">#800000</color>
 <color name="Aquamarine">#7FFFD4</color>
 <color name="Chartreuse">#7FFF00</color>
 <color name="LawnGreen">#7CFC00</color>
 <color name="MediumSlateBlue">#7B68EE</color>
 <color name="LightSlateGray">#778899</color>
 <color name="SlateGray">#708090</color>
 <color name="OliveDrab">#6B8E23</color>
 <color name="SlateBlue">#6A5ACD</color>
 <color name="DimGray">#696969</color>
 <color name="MediumAquamarine">#66CDAA</color>
 <color name="CornflowerBlue">#6495ED</color>
 <color name="CadetBlue">#5F9EA0</color>
 <color name="DarkOliveGreen">#556B2F</color>
 <color name="Indigo">#4B0082</color>
 <color name="MediumTurquoise">#48D1CC</color>
 <color name="DarkSlateBlue">#483D8B</color>
 <color name="SteelBlue">#4682B4</color>
 <color name="RoyalBlue">#4169E1</color>
 <color name="Turquoise">#40E0D0</color>
 <color name="MediumSeaGreen">#3CB371</color>
 <color name="LimeGreen">#32CD32</color>
 <color name="DarkSlateGray">#2F4F4F</color>
 <color name="SeaGreen">#2E8B57</color>
 <color name="ForestGreen">#228B22</color>
 <color name="LightSeaGreen">#20B2AA</color>
 <color name="DodgerBlue">#1E90FF</color>
 <color name="MidnightBlue">#191970</color>
 <color name="Aqua">#00FFFF</color>
 <color name="Cyan">#00FFFF</color>
 <color name="SpringGreen">#00FF7F</color>
 <color name="Lime">#00FF00</color>
 <color name="MediumSpringGreen">#00FA9A</color>
 <color name="DarkTurquoise">#00CED1</color>
 <color name="DeepSkyBlue">#00BFFF</color>
 <color name="DarkCyan">#008B8B</color>
 <color name="Teal">#008080</color>
 <color name="Green">#008000</color>
 <color name="DarkGreen">#006400</color>
 <color name="Blue">#0000FF</color>
 <color name="MediumBlue">#0000CD</color>
 <color name="DarkBlue">#00008B</color>
 <color name="Navy">#000080</color>
 <color name="Black">#000000</color>
</resources>

you can use simply:

int myColor = getResources().getColor(R.color.myColor);
Then, to use this color in a TextView, use the following:

myTextView.setTextColor(myColor);

In Xml
android:drawable="@color/YOUR_COLOR_HERE"
android:textColor="@color/text_color"

Source: stackoverflow

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How to make RATE APP in android

Here is the how to rate app in andorid, are you already publish app on google play then, do this in your app,

first you have to define this RateThisApp.java file in your app folder.

package co.happybirthday;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.DialogInterface.OnCancelListener;
import android.content.DialogInterface.OnClickListener;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.net.Uri;
import android.util.Log;

import java.util.Date;


public class RateThisApp {

    private static final String TAG = RateThisApp.class.getSimpleName();

    private static final String PREF_NAME = "RateThisApp";
    private static final String KEY_INSTALL_DATE = "rta_install_date";
    private static final String KEY_LAUNCH_TIMES = "rta_launch_times";
    private static final String KEY_OPT_OUT = "rta_opt_out";

    private static Date mInstallDate = new Date();
    private static int mLaunchTimes = 0;
    private static boolean mOptOut = false;

    private static Config sConfig = new Config();

    public static final boolean DEBUG = false;

    public static void init(Config config) {
        sConfig = config;
    }

    public static void onStart(Context context) {
        SharedPreferences pref = context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE);
        Editor editor = pref.edit();
        // If it is the first launch, save the date in shared preference.        if (pref.getLong(KEY_INSTALL_DATE, 0) == 0L) {
            Date now = new Date();
            editor.putLong(KEY_INSTALL_DATE, now.getTime());
            log("First install: " + now.toString());
        }
        // Increment launch times        int launchTimes = pref.getInt(KEY_LAUNCH_TIMES, 0);
        launchTimes++;
        editor.putInt(KEY_LAUNCH_TIMES, launchTimes);
        log("Launch times; " + launchTimes);

        editor.commit();

        mInstallDate = new Date(pref.getLong(KEY_INSTALL_DATE, 0));
        mLaunchTimes = pref.getInt(KEY_LAUNCH_TIMES, 0);
        mOptOut = pref.getBoolean(KEY_OPT_OUT, false);

        printStatus(context);
    }

   
    public static boolean showRateDialogIfNeeded(final Context context) {
        if (shouldShowRateDialog()) {
            showRateDialog(context);
            return true;
        } else {
            return false;
        }
    }

    
    private static boolean shouldShowRateDialog() {
        if (mOptOut) {
            return false;
        } else {
            if (mLaunchTimes >= sConfig.mCriteriaLaunchTimes) {
                return true;
            }
            long threshold = sConfig.mCriteriaInstallDays * 24 * 60 * 60 * 1000L;  // msec            if (new Date().getTime() - mInstallDate.getTime() >= threshold) {
                return true;
            }
            return false;
        }
    }

    public static void showRateDialog(final Context context) {
        AlertDialog.Builder builder = new AlertDialog.Builder(context);
        int titleId = sConfig.mTitleId != 0 ? sConfig.mTitleId : R.string.rta_dialog_title;
        int messageId = sConfig.mMessageId != 0 ? sConfig.mMessageId : R.string.rta_dialog_message;
        builder.setTitle(titleId);
        builder.setMessage(messageId);
        builder.setPositiveButton(R.string.rta_dialog_ok, new OnClickListener() {
            @Override            public void onClick(DialogInterface dialog, int which) {
                String appPackage = context.getPackageName();
                Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id=" + appPackage));
                context.startActivity(intent);
                setOptOut(context, true);
            }
        });
        builder.setNeutralButton(R.string.rta_dialog_cancel, new OnClickListener() {
            @Override            public void onClick(DialogInterface dialog, int which) {
                clearSharedPreferences(context);
            }
        });
        builder.setNegativeButton(R.string.rta_dialog_no, new OnClickListener() {
            @Override            public void onClick(DialogInterface dialog, int which) {
                setOptOut(context, true);
            }
        });
        builder.setOnCancelListener(new OnCancelListener() {
            @Override            public void onCancel(DialogInterface dialog) {
                clearSharedPreferences(context);
            }
        });
        builder.create().show();
    }

    private static void clearSharedPreferences(Context context) {
        SharedPreferences pref = context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE);
        Editor editor = pref.edit();
        editor.remove(KEY_INSTALL_DATE);
        editor.remove(KEY_LAUNCH_TIMES);
        editor.commit();
    }

   
    private static void setOptOut(final Context context, boolean optOut) {
        SharedPreferences pref = context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE);
        Editor editor = pref.edit();
        editor.putBoolean(KEY_OPT_OUT, optOut);
        editor.commit();
    }

    
    private static void printStatus(final Context context) {
        SharedPreferences pref = context.getSharedPreferences(PREF_NAME, Context.MODE_PRIVATE);
        log("*** RateThisApp Status ***");
        log("Install Date: " + new Date(pref.getLong(KEY_INSTALL_DATE, 0)));
        log("Launch Times: " + pref.getInt(KEY_LAUNCH_TIMES, 0));
        log("Opt out: " + pref.getBoolean(KEY_OPT_OUT, false));
    }

   
    private static void log(String message) {
        if (DEBUG) {
            Log.v(TAG, message);
        }
    }

    
    public static class Config {
        private int mCriteriaInstallDays;
        private int mCriteriaLaunchTimes;
        private int mTitleId = 0;
        private int mMessageId = 0;

        public Config() {
            this(7, 10);
        }

       
        public Config(int criteriaInstallDays, int criteriaLaunchTimes) {
            this.mCriteriaInstallDays = criteriaInstallDays;
            this.mCriteriaLaunchTimes = criteriaLaunchTimes;
        }

        
        public void setTitle(int stringId) {
            this.mTitleId = stringId;
        }

        public void setMessage(int stringId) {
            this.mMessageId = stringId;
        }
    }
}

Now you defined required string file in string.xml file.

<string name="rta_dialog_title">Rate this app</string>
<string name="rta_dialog_message">If you enjoy using this app, would you mind taking a moment to rate it? It won\'t take more than a minute. Thank you for your support!</string>
<string name="rta_dialog_ok">Rate now</string>
<string name="rta_dialog_cancel">Later</string>
<string name="rta_dialog_no">No, thanks</string>

Finally, defined in you MainActivity.java file, when click RateApp button.

RateThisApp.showRateDialog(MainActivity.this);

then you have got like this output.



Happy Coding!!!

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Toast tutorial in Android

Basically , toast is important when you want to display some message to user or to give some notify message whenever user going to wrong direction or going to right direction too. It is also used for when task is completed or done or something getting error.

Lets discuss first , what is the structure in toast.There are two method we can display toast in android, one is programmatically or other is making custom layout.

1. Programmatically display toast method

Toast.makeText(getActivity(), "This is  the Toast message!",    Toast.LENGTH_LONG).show();

 in toast there is two time duration when can toast display in android;

int LENGTH_LONG Show the view or text notification for a long period of time.
int LENGTH_SHORT Show the view or text notification for a short period of time.This is the default.

2.Customize your toast

showToast(getActivity(), "Done");

and function like

public static void showToast(Activity acivity,  String stringToast) {
// TODO Auto-generated method stub

// TODO Auto-generated method stub

// get the LayoutInflater and inflate the custom_toast layout
LayoutInflater inflater = acivity.getLayoutInflater();
View layout = inflater.inflate(R.layout.customtoast, (ViewGroup) acivity.findViewById(R.id.toast_layout_root));

// get the TextView from the custom_toast layout
TextView text = (TextView) layout.findViewById(R.id.custom_toast_message);
text.setText(stringToast);

// create the toast object, set display duration,
// set the view as layout that's inflated above and then call show()
Toast toast = new Toast(acivity);
toast.setDuration(Toast.LENGTH_SHORT);
toast.setGravity(Gravity.CENTER, 0, 0);
toast.setView(layout);
toast.show();

}


Layout looks like
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/toast_layout_root"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@color/appcolor"
    android:orientation="vertical" >

    <ImageView
        android:id="@+id/custom_toast_image"
        android:layout_width="60dp"
        android:layout_height="40dp"
        android:layout_centerHorizontal="true"
        android:contentDescription="@string/app_name"
        android:src="@drawable/icon" />

    <TextView
        android:id="@+id/custom_toast_message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/custom_toast_image"
        android:layout_centerHorizontal="true"
        android:layout_margin="10dp"
        android:contentDescription="content display"
        android:text=""
        android:textSize="15sp"
        android:textColor="@color/white" />

</RelativeLayout>

and are you want to more cusomize and learn more about toast , please go to http://developer.android.com/reference/android/widget/Toast.html

Happy Coding :)

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Free Developing Android Apps Course

Udacity offers the first course in the Android Developer Nanodegree, Developing Android Apps is the foundation of our advanced Android curriculum. This course blends theory and practice to help you build great apps the right way. In this course, you'll work with instructors step-by-step to build a cloud-connected Android app, and learn best practices of mobile development, and Android development in particular.

Syllabus

Lesson 1: Create Project Sunshine with a Simple UI (5-8 hrs)

Lesson 2: Connect Sunshine to the Cloud (8-10 hrs)

Lesson 3: Create New Activities and Navigate Apps with Intents (8-10 hrs)

             Optional Project: Popular Movies, Stage 1 (5-10 hours)

Lessons 4: Use Content Providers and Loaders to Persist and Recover Data (15-20 hrs)

Lesson 5: Implement Rich and Responsive Layouts (8-10 hrs)

Lesson 6: Use Services and Notifications to Run in the Background (5-8 hrs)

              Optional Project: Popular Movies, Stage 2 (4-6 hours)

Final Project (10-20 hours)

 

Instructors & Partners

▸ Reto Meie, Instructor

▸ Katherine Kua, Instructor

▸ Dan Galpin, Instructor

▸ Alexander Lucas, Instructor

▸ Sarah Spikes, Course Developer

▸ James Williams, Course Developer

▸ Lyla Fujiwara , Course Developer

 Learn Full Course

 

 

 

 

 

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Create Yes/No Dialog Box in Android

Are you wan to  create  Yes/No Dialog Box in Android. Here is the simple example to create yes / no dialog box when button click event.

first you have to defined on xml file:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="CreateYesNo" />

</RelativeLayout>


Now , Define button and click with  display dialog box .

public class YesNoButton extends Activity {
/* (non-Javadoc)
 * @see android.app.Activity#onCreate(android.os.Bundle)
 */
Button btnYesNo;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.yesno);
btnYesNo=(Button) findViewById(R.id.button1);
btnYesNo.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {
displayYesNo();

}
});
}

protected void displayYesNo() {
DialogInterface.OnClickListener dialogClickListener = new DialogInterface.OnClickListener() {
   @Override
   public void onClick(DialogInterface dialog, int which) {
       switch (which){
       case DialogInterface.BUTTON_POSITIVE:
           //Yes button clicked
        Toast.makeText(getApplicationContext(), "Yes Button Click", Toast.LENGTH_SHORT).show();
           break;

       case DialogInterface.BUTTON_NEGATIVE:
           //No button clicked
        Toast.makeText(getApplicationContext(), "NO Button Click", Toast.LENGTH_SHORT).show();
           break;
       }
   }
};

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure?").setPositiveButton("Yes", dialogClickListener)
   .setNegativeButton("No", dialogClickListener).show();

}
}

Here is the snapshots of this application:

Happy Coding!!!

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Close or hide the Android Soft Keyboard from code

Are you trying to  make close or hide the Soft Keyboard in your app using code. here is the solution .

Force Android to hide the virtual keyboard using the InputMethodManager, calling hideSoftInputFromWindow, passing in the token of the window containing your edit field.

EditText myEditText = (EditText) findViewById(R.id.myEditText);  
InputMethodManager imm = (InputMethodManager)getSystemService(
      Context.INPUT_METHOD_SERVICE);
imm.hideSoftInputFromWindow(myEditText.getWindowToken(), 0);

This will force the keyboard to be hidden in all situations. In some cases you will want to pass in InputMethodManager.HIDE_IMPLICIT_ONLY as the second parameter to ensure you only hide the keyboard when the user didn't explicitly force it to appear (by holding down menu).

Happy Codting

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Some common HTTP methods and status codes

Some common HTTP methods

Method	Description	Safe	Idempotent
GET	Requests a specific representation of a resource	Yes	Yes
PUT	Create or update a resource with the supplied representation	No	Yes
DELETE	Deletes the specified resource	No	Yes
POST	Submits data to be processed by the identified resource	No	No
HEAD	Similar to GET but only retrieves headers and not the body	Yes	Yes
OPTIONS	Returns the methods supported by the identified resource	Yes	Yes

Some common HTTP status codes

Status Range	Description	Examples
100	Informational	100 Continue
200	Successful	200 OK
201	Created
202	Accepted
300	Redirection	301 Moved Permanently
304	Not Modified
400	Client error	401 Unauthorized
402	Payment Required
404	Not Found
405	Method Not Allowed
500	Server error	500 Internal Server Error
501	Not Implemented

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What is the difference between match_parent and fill_parent?

Matt Ball answered in stackoverflow. which is got more upvoted.
    They're the same thing (in API Level 8+). Use match_parent.

    FILL_PARENT (renamed MATCH_PARENT in API Level 8 and higher), which means that the view wants to be as big as its parent (minus padding)
or
fill_parent (renamed match_parent in API Level 8) tells your view to become as big as its parent view group will allow
    fill_parent: The view should be as big as its parent (minus padding). This constant is deprecated starting from API Level 8 and is replaced by match_parent.

this also defined in official android site: developer.android.com/reference/android/view/ViewGroup.LayoutParams.html

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Differences between the px, dip, dp and sp units in Android

A dimension value defined in XML. A dimension is specified with a number followed by a unit of measure. For example: 10px, 2in, 5sp. The following units of measure are supported by Android:

px is one pixel. scale-independent pixels ( sp ) and density-independent pixels ( dip ) you want to use sp for font sizes and dip for everything else.

dp

Density-independent Pixels - An abstract unit that is based on the physical density of the screen. These units are relative to a 160 dpi (dots per inch) screen, on which 1dp is roughly equal to 1px. When running on a higher density screen, the number of pixels used to draw 1dp is scaled up by a factor appropriate for the screen's dpi. Likewise, when on a lower density screen, the number of pixels used for 1dp is scaled down. The ratio of dp-to-pixel will change with the screen density, but not necessarily in direct proportion. Using dp units (instead of px units) is a simple solution to making the view dimensions in your layout resize properly for different screen densities. In other words, it provides consistency for the real-world sizes of your UI elements across different devices.

sp

Scale-independent Pixels - This is like the dp unit, but it is also scaled by the user's font size preference. It is recommend you use this unit when specifying font sizes, so they will be adjusted for both the screen density and the user's preference.

pt

Points - 1/72 of an inch based on the physical size of the screen.

px

Pixels - Corresponds to actual pixels on the screen. This unit of measure is not recommended because the actual representation can vary across devices; each devices may have a different number of pixels per inch and may have more or fewer total pixels available on the screen.

mm

Millimeters - Based on the physical size of the screen.

in

Inches - Based on the physical size of the screen.

Note: A dimension is a simple resource that is referenced using the value provided in the name attribute (not the name of the XML file). As such, you can combine dimension resources with other simple resources in the one XML file, under one <resources> element.

To make it absolutely clear - try to never use anything but sp or dp unless you absolutely have to. Using sp/dp will make your Android applications compatible with multiple screen densities and resolutions

Resources: http://developer.android.com/guide/topics/resources/more-resources.html#Dimension

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Android Developer Tutorials

Android invasion, Sydney, Australia (Photo credit: Pranav Bhatt)

1. Building Your First App

   After you've installed the Android SDK, start with this class to learn the basics about Android app development.
   1. Creating an Android Project
   2. Running Your Application
   3. Building a Simple User Interface
   4. Starting Another Activity

2. Managing the Activity Lifecycle

   How Android activities live and die and how to create a seamless user experience by implementing lifecycle callback methods.
   1. Starting an Activity
   2. Pausing and Resuming an Activity
   3. Stopping and Restarting an Activity
   4. Recreating an Activity

3. Supporting Different Devices

   How to build your app with alternative resources that provide an optimized user experience on multiple device form factors using a single APK.
   1. Supporting Different Languages
   2. Supporting Different Screens
   3. Supporting Different Platform Versions

4. Building a Dynamic UI with Fragments

   How to build a user interface for your app that is flexible enough to present multiple UI components on large screens and a more constrained set of UI components on smaller screens—essential for building a single APK for both phones and tablets.
   1. Using the Support Library
   2. Creating a Fragment
   3. Building a Flexible UI
   4. Communicating with Other Fragments

5. Saving Data

   How to save data on the device, whether it's temporary files, downloaded app assets, user media, structured data, or something else.
   1. Saving Key-Value Sets
   2. Saving Files
   3. Saving Data in SQL Databases

6. Interacting with Other Apps

   How to build a user experience that leverages other apps available on the device to perform advanced user tasks, such as capture a photo or view an address on a map.
   1. Sending the User to Another App
   2. Getting a Result from the Activity
   3. Allowing Other Apps to Start Your Activity

7. Sharing Content

   How to take your app interaction to the next level by sharing information with other apps, receive information back, and provide a simple and scalable way to perform Share actions with user content.
   1. Sending Content to Other Apps
   2. Receiving Content from Other Apps
   3. Adding an Easy Share Action

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Saving Activity state in Android

 
The introduction to Managing the Activity Lifecycle briefly mentions that when an activity is paused or stopped, the state of the activity is retained. This is true because the Activity object is still held in memory when it is paused or stopped—all information about its members and current state is still alive. Thus, any changes the user made within the activity are retained so that when the activity returns to the foreground (when it "resumes"), those changes are still there.

You need to override onSaveInstanceState(Bundle savedInstanceState) and write the application state values you want to change to the Bundle parameter like this:

Override
public void onSaveInstanceState(Bundle savedInstanceState) {
  super.onSaveInstanceState(savedInstanceState);
  // Save UI state changes to the savedInstanceState.
  // This bundle will be passed to onCreate if the process is
  // killed and restarted.
  savedInstanceState.putBoolean("MyBoolean", true);
  savedInstanceState.putDouble("myDouble", 1.9);
  savedInstanceState.putInt("MyInt", 1);
  savedInstanceState.putString("MyString", "Welcome back to Android");
  // etc.
}

The Bundle is essentially a way of storing a NVP ("Name-Value Pair") map, and it will get passed in to onCreate and also onRestoreInstanceState where you'd extract the values like this:

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
  super.onRestoreInstanceState(savedInstanceState);
  // Restore UI state from the savedInstanceState.
  // This bundle has also been passed to onCreate.
  boolean myBoolean = savedInstanceState.getBoolean("MyBoolean");
  double myDouble = savedInstanceState.getDouble("myDouble");
  int myInt = savedInstanceState.getInt("MyInt");
  String myString = savedInstanceState.getString("MyString");
}

You'd usually use this technique to store instance values for your application (selections, unsaved text, etc.).

CAREFUL: you need to call super.onSaveInstanceState(savedInstanceState) before adding your values to the Bundle, or they will get wiped out on that call (Droid X Android 2.2).

The savedInstanceState is only for saving state associated with a current instance of an Activity, for example current navigation or selection info, so that if Android destroys and recreates an Activity, it can come back as it was before. See the documentation for onCreate and onSaveInstanceState
For more long lived state, consider using a SQLite database, a file, or preferences. See Saving Persistent State.

Resources:
http://developer.android.com/guide/components/activities.html
http://stackoverflow.com/questions/151777/saving-activity-state-in-android

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