Caching Objects in Android Internal Storage

Android provides several options for persisting application data, such as SQLite Databases, SharedPreferences, internal and external storage.

In this post we’ll take a look how we can use the internal storage to persist application data. By default, files saved to internal storage are private to the application and they cannot be accessed by other applications. When the application is uninstalled, the files are removed.

To create and write a file to internal storage, openFileInput(); should be used. This opens a private file associated with the Context’s application package for writing. If the file does not already exits, then it is first created.

openFileInput() returns a FileInputStream, and we could use its write() method, which accepts a byte array as argument, to write the data. However, in the below example we will wrap the FileInputStream into an ObjectOutputStream which provides 2 convenient methods  for writing and reading objects: writeObject() and readObject().

So, lets  pretend that we need to save a List of some objects. The model class of our object looks like this:

public class Entry implements Serializable{
   private String name;

   public Entry(String name) {
      this.name = name;
   }

   public String getName() {
      return name;
   }
}

Make sure that the model class implements Serializable, otherwise you may get a java.io.NotSerializableException when attempting to write the object on internal storage.

Below is the utility class that provides 2 methods, one for storing objects to internal storage, and another for retrieving objects from internal storage.

public final class InternalStorage{

   private InternalStorage() {}

   public static void writeObject(Context context, String key, Object object) throws IOException {
      FileOutputStream fos = context.openFileOutput(key, Context.MODE_PRIVATE);
      ObjectOutputStream oos = new ObjectOutputStream(fos);
      oos.writeObject(object);
      oos.close();
      fos.close();
   }

   public static Object readObject(Context context, String key) throws IOException,
         ClassNotFoundException {
      FileInputStream fis = context.openFileInput(key);
      ObjectInputStream ois = new ObjectInputStream(fis);
      Object object = ois.readObject();
      return object;
   }
}

An this is how InternalStorage class can be used to persist and retrieve data from internal storage.

// The list that should be saved to internal storage.
List<Entry> entries = new ArrayList<Entry>();
entries.add(new Entry("House"));
entries.add(new Entry("Car"));
entries.add(new Entry("Job"));

try {
   // Save the list of entries to internal storage
   InternalStorage.writeObject(this, KEY, entries);

   // Retrieve the list from internal storage
   List<Entry> cachedEntries = (List<Entry>) InternalStorage.readObject(this, KEY);

   // Display the items from the list retrieved.
   for (Entry entry : cachedEntries) {
     Log.d(TAG, entry.getName());
   }
} catch (IOException e) {
   Log.e(TAG, e.getMessage());
} catch (ClassNotFoundException e) {
   Log.e(TAG, e.getMessage());
}

 

Advertisements

Taking a screenshot of current Activity in Android

In this post I’ll show how you can take a screenshot of your current Activity and save the resulting image on /sdcard.

The idea behind taking a screenshot actually is pretty simple: what we need to do is to get a reference of the root view and  generate a bitmap copy of this view.

screenshot

Considering that we want to take the screenshot when a button is clicked, the code will look like this:

findViewById(R.id.button1).setOnClickListener(new OnClickListener() {
   @Override
   public void onClick(View v) {
       Bitmap bitmap = takeScreenshot();
       saveBitmap(bitmap);
   }
});

 

First of all we should retrieve the topmost view in the current view hierarchy, then enable the drawing cache, and after that call getDrawingCache().

Calling getDrawingCache(); will return the bitmap representing the view or null if cache is disabled, that’s why setDrawingCacheEnabled(true); should be set to true prior invoking  getDrawingCache().

public Bitmap takeScreenshot() {
   View rootView = findViewById(android.R.id.content).getRootView();
   rootView.setDrawingCacheEnabled(true);
   return rootView.getDrawingCache();
}

 

And the method that saves the bitmap image to external storage:

 public void saveBitmap(Bitmap bitmap) {
    File imagePath = new File(Environment.getExternalStorageDirectory() + "/screenshot.png");
    FileOutputStream fos;
    try {
        fos = new FileOutputStream(imagePath);
        bitmap.compress(CompressFormat.JPEG, 100, fos);
        fos.flush();
        fos.close();
    } catch (FileNotFoundException e) {
        Log.e("GREC", e.getMessage(), e);
    } catch (IOException e) {
        Log.e("GREC", e.getMessage(), e);
    }
}

 

Since the image is saved on external storage, the WRITE_EXTERNAL_STORAGE permission should be added AndroidManifest to file:

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

Using Custom Fonts in Android

By default Android comes with three standard fonts: Droid Sans (default font), Droid Serif, and Droid Sans Mono. They all can be applied to any view that supports styling, such as TextView, Button, by specifying the “android:typeface” attribute in the XML declaration with any of these values: sans, serif, monospace.


<TextView
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Sans"
   android:typeface="sans" />

<TextView
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Serif"
   android:typeface="serif" />

<TextView
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Monospace"
   android:typeface="monospace" />

android standard fonts

 

Using custom fonts in Android is pretty straightforward. First find a free font and put it in the assets/fonts directory. (It’s not mandatory to have a /fonts directory, but if I have a lot of stuff in the /assets directory I organize them in separate directories). Then get a reference to your TextView and create a Typeface object specifying the font path. Lastly, apply the typeface to the TextView.

In this particular example I used the font: christmaseve.ttf

TextView textView = (TextView) findViewById(R.id.textView);
Typeface tf = Typeface.createFromAsset(getAssets(), "fonts/christmaseve.ttf");
textView.setTypeface(tf);

android custom fonts

 

RuntimeException: Native typeface cannot be made

If you get this exception while trying to integrate the custom font into your application, make sure the path to the font file is correct, and the font name is spelled correctly. I noticed I was getting this exception when my font path was misspelled, for example writing “.tff” instead of “.ttf”, or forgetting to add the “fonts/” prefix to the path.

Custom font used in this example provided by: http://bythebutterfly.com

Integrating Google Analytics SDK (V2) with Android

The Google Analytics SDK for Android makes it easy for developers to collect valuable statics about how the users are using their app.

Here are some features that Android Google Analytics SDK offers:

  • The number of active users that are using the application
  • Usage of specific features
  • The number and type of application crashes
  • From where in the world the application is used
  • And many other useful metrics.

Just to illustrate the integration process lets create a simple proof of concept application with 2 activities: MainActivity and AboutActivity, and 2 buttons: Rate and Share.

Our mission is to integrate Google Analytics SDK with the application, to:

  • track activity views, (MainActivity and About)
  • track events (how many times the buttons “Rate”, and “Share” are clicked)

android google analytics sdk

If you are searching for Google Analytics I’m assuming you are already pretty familiar with Android and could create the proof of concept application yourself, so I will skip this step and concentrate solely on integration.

 

1. Downloading the SDK

Go to downloads page and download GoogleAnalyticsAndroid.zip Version 2.0. Extract the archive and add libGoogleAnalyticsV2.jar to your project’s /libs directory.

At the moment of writing this post, Google provides two versions: version 1.5.1 (legacy), and version 2.0 beta. Still if the Version 2 of SDK is beta, I highly suggest you choose this version, over the 1.5.1 (legacy).
The reason not to choose SDK 1.5.1 is that it uses a tracking model that is designed to track visitors to traditional websites and interaction with widgets in traditional web pages.

The new “App” profiles and reports will only accept data from version 2 or higher of the SDK.

 

2. Creating a Google Analytics account

Before starting to use the SDK you first must create an account at: http://www.google.com/analytics/

  1. Sign in to your account.
  2. Click Admin.
  3. Click Account list (just below the menu bar)
  4. Click +New Account
  5. When asked what you would like to track, select App property.android app profile
  6. Enter all the necessary information and click Get Tracking ID.

Now that you have a Tracking ID, you can begin the integration with the application. The first step is to update the AndroidManifest file.

 

3. Updating AndroidManifest file.

Add folowing permissions to the AndroidManifest file:

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

 

4. Creating the analytics.xml file

In version 2 of Google Analytics SDK for Android, the tracking settings are managed from an xml resource file called: analytics.xml. You will need to create this file in res/values directory, and add your tracking ID as well as other settings here.


<?xml version="1.0" encoding="utf-8"?>
<resources>

   <!-- Replace placeholder ID with your tracking ID -->
   <string name="ga_trackingId">UA-00000000-0</string>

   <!-- Enable Activity tracking -->
   <bool name="ga_autoActivityTracking">true</bool>

   <!-- Enable debug -->
   <bool name="ga_debug">true</bool>

   <!-- The screen names that will appear in your reporting -->
   <string name="com.testgoogleanalytics.MainActivity">MainActivity</string>
   <string name="com.testgoogleanalytics.About">About</string>

   <!--
   The inverval of time after all the collected data
   should be sent to the server, in seconds.
   -->
   <integer name="ga_dispatchPeriod">30</integer>

</resources>

 

5. Tracking activities.

To track activities add the tracking methods to the onStart() and onStop()  of each of your activities.


// Example of tracking MainActivity
public class MainActivity extends Activity {
   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
   }

   @Override
   protected void onStart() {
      super.onStart();
      EasyTracker.getInstance().activityStart(this); // Add this method
   }

   @Override
   protected void onStop() {
      super.onStop();
      EasyTracker.getInstance().activityStop(this); // Add this method
   }
}

One thing to note here is that EasyTraker requires a context before you can use it. If you attempt to call any of its methods but did not pass first a context, you may end up with an IllegalStateException.

In the above example, in  the onStart()  and onStop() methods the context is passed as an argument to activityStart() and activityStop(), but  if you need to make EasyTracker calls in other classes or methods, you’ll need to call EasyTracker’s setContext(Context context) method first:

Context context= this;  // Get current context.
EasyTracker.getInstance().setContext(context);  // Set context
// EasyTracker is now ready for use.

 

6. Tracking events

Tracking events is just as easy as tracking activities, you just need a Tracker object and call the trackEvent(String category, String action, String label, int value) method.

public class MainActivity extends Activity {

   private Tracker tracker;

   @Override
   public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);

      // Set context
      EasyTracker.getInstance().setContext(getApplicationContext());
      // Instantiate the Tracker
      tracker = EasyTracker.getTracker();

      // Add tracking functionality to "Rate" button
      Button rate = (Button) findViewById(R.id.rate);
      rate.setOnClickListener(new OnClickListener() {
         @Override
         public void onClick(View arg0) {
            // The rest of your code
            tracker.trackEvent("Buttons Category", "Rate", "", 0L);
         }
      });

      // Add tracking functionality to "Share" button....
   }
}

In this particular example I don’t need a label nor a value, that is why I set for the last 2 parameters of trackEvent() method, an empty string a 0 (zero), but depending of your needs you may populate them with some data.

 

7. Debugging

Debugging helps you deal with troubleshooting, and make you sure that the data actually is sent to the server. To set the Google Analytics in debug mode, add the following setting in the analytics.xml


<bool name="ga_debug">true</bool>

Once your are in debug mode, you can watch the log information in LogCat:

 

Waiting for the big moment!

If everything is configured correctly, the reports should appear on live. Usually it takes about 24 hours to see the data in your account.

android actions google analytics

 

 

What happens if my application is used when no network is available?

Just in case you asked this yourself…, all the events are persisted in a local storage, and they will be sent the next time your app is running and dispatch is called.

 

Last but not least

One important thing not to be forgotten: you must indicate to your users, either in the application itself or in your terms of service, that you reserve the right to anonymously track and report a user’s activity inside of your app.

Android Google Analytics SDK offers more than tracking activities and events, see: https://developers.google.com/analytics/devguides/collection/android/v2/ to get the most out of it.

Please visit the Android Tutorials page for more tutorials.

Android Asset Studio – The easiest way to create icons for your android apps!

Android asset studio

Android Asset Studio is an online utility that lets you generate all kind of icons you may need for your android applications, starting with launcher icons, action bar and tab icons, notification icons, and menu icons. It even includes a simple 9-patch generator allowing you to create 9-patch images.

One of the trickier parts when creating the icons is that you should create them for all kinds of resolutions: ldpi, mdpi, hdpi, and xhdpi. With Android Asset Studio this is as simple as uploading an image. The tool generates automatically for you all the versions of the icon under all resolutions, and make them available as a downloadable zip archive.

The icons may be generated from an image uploaded, or from a clipart library, or from text. It’s a very convenient tool and I highly recommend using it if you want to have professional, good looking icons on all resolutions.

Amazing Cracked Screen

Hello everyone,

In this weekend I made a simple application just for fun – Amazing  Cracked Screen, the main purpose being to trick your friends and make fun of them! Basically, what does the application is to simulate a broken phone screen.
The application includes 6 different broken screens, and provides the ability to set up a delay time when the app should start, so you can manage to give the phone to your friend.

Just start the application, select the desired broken screen and have fun!

 

Amazing Cracked Screen

How to create popups in Android

In this post I’ll show you how to create a popup window in Android. A popup window can be used to display an arbitrary view, and it can be very convenient in cases when you want to display an additional information, but don’t want or it’s not appropriate to launch a new activity or  display a dialog.

The final output should look like this:

Android Popup

We will use the PopupWindow class to create the popup.

One thing I would like to mention is that we want the popup to be attached to the button that opened it. For example if the “Show Popup” button from the screenshot above would be positioned in the middle of the screen, we want the popup window stick to the button’s position. To achieve this, first we should get the button’s “x” and “y” position on the screen, and pass them to the popup window. Then will we use an offset to align the popup properly – a bit to the right, and a bit down, so it won’t overlap the whole button.

Another think I would like to mention is that we will use a 9 patch background image for the popup, so it will look more fancy. But of course you can skip it and put any background you want, or no background at all.

9 patch image:

9 patch image

Put the image into res/drawable directory.

 

1. Create a new project in Eclipse:
Project: TestPopup
Activity: TestPopupActivity

2. Open layout/main.xml file and add a button


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#CCC"
android:orientation="vertical" >

<Button
   android:id="@+id/show_popup"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Show Popup" />

</LinearLayout>

3. Create a new layout file: layout/popup_layout.xml that defines the layout of popup.


<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="wrap_content"
   android:id="@+id/popup"
   android:layout_height="wrap_content"
   android:background="@drawable/popup_bg"
   android:orientation="vertical" >

<TextView
   android:id="@+id/textView1"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Popup"
   android:textAppearance="?android:attr/textAppearanceLarge" />

<TextView
   android:id="@+id/textView2"
   android:layout_marginTop="5dp"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="This is a simple popup" />

<Button
   android:id="@+id/close"
   android:layout_marginTop="10dp"
   android:layout_gravity="center_horizontal"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="Close" />

</LinearLayout>

 

4. And now the most interesting part. Open the TestPopupActivity and fill it with below code. Carefully read the comments to understand what’s going on.


public class TestPopupActivity extends Activity {

//The "x" and "y" position of the "Show Button" on screen.
Point p;

@Override
public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main);

   Button btn_show = (Button) findViewById(R.id.show_popup);
   btn_show.setOnClickListener(new OnClickListener() {
     @Override
     public void onClick(View arg0) {

       //Open popup window
       if (p != null)
       showPopup(TestPopupActivity.this, p);
     }
   });
}

// Get the x and y position after the button is draw on screen
// (It's important to note that we can't get the position in the onCreate(),
// because at that stage most probably the view isn't drawn yet, so it will return (0, 0))
@Override
public void onWindowFocusChanged(boolean hasFocus) {

   int[] location = new int[2];
   Button button = (Button) findViewById(R.id.show_popup);

   // Get the x, y location and store it in the location[] array
   // location[0] = x, location[1] = y.
   button.getLocationOnScreen(location);

   //Initialize the Point with x, and y positions
   p = new Point();
   p.x = location[0];
   p.y = location[1];
}

// The method that displays the popup.
private void showPopup(final Activity context, Point p) {
   int popupWidth = 200;
   int popupHeight = 150;

   // Inflate the popup_layout.xml
   LinearLayout viewGroup = (LinearLayout) context.findViewById(R.id.popup);
   LayoutInflater layoutInflater = (LayoutInflater) context
     .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
   View layout = layoutInflater.inflate(R.layout.popup_layout, viewGroup);

   // Creating the PopupWindow
   final PopupWindow popup = new PopupWindow(context);
   popup.setContentView(layout);
   popup.setWidth(popupWidth);
   popup.setHeight(popupHeight);
   popup.setFocusable(true);

   // Some offset to align the popup a bit to the right, and a bit down, relative to button's position.
   int OFFSET_X = 30;
   int OFFSET_Y = 30;

   // Clear the default translucent background
   popup.setBackgroundDrawable(new BitmapDrawable());

   // Displaying the popup at the specified location, + offsets.
   popup.showAtLocation(layout, Gravity.NO_GRAVITY, p.x + OFFSET_X, p.y + OFFSET_Y);

   // Getting a reference to Close button, and close the popup when clicked.
   Button close = (Button) layout.findViewById(R.id.close);
   close.setOnClickListener(new OnClickListener() {

     @Override
     public void onClick(View v) {
       popup.dismiss();
     }
   });
}
}