Implementation Streaming for Android

Streaming Measurement in Android

This chapter describes the basic use of the sensor for the measurement of streaming content.

Properties of the Library

Property	Default	Description
tracking	true	If this property is set to `false` , no requests are sent to the measuring system
debug	false	If the value is set to `true`, the debug messages are issued by the library
timeout	10	Timeout Setting for the HTTP-Request

Lifecycle of the Measurement

This chapter explaines step by step the use of the sensor and the measurement of streaming content . The following steps are necessary in order to measure a content.

Generating the sensor
Implementation of the adapter
Beginning of the measurement
End of the measurement

Generating the Sensor

When you start the app the sensor must be instantiated once. It is not possible to change the site name or the application name after this call.

String site = ...;    // will delivered by the measurement provider
Spring appName = ...; // will delivered by the measurement provider
SpringStreams sensor = new SpringStreams(site, appName, getApplicationContext());

The site name and application name is specified by the operator of the measurement system.

Implementation of the Adapter

In principle it is possible to measure any media library with an adapter, that is available within an app to use streaming content .

Therefore the protocol Meta and the interface StreamAdapter must be implemented. The meta object supplies the information regarding the used player, the player version and the screen size.

The library must be able to read continously the current position on a stream in seconds or the current position of player.

package de.spring.mobile;

/**
 * This adapter must be used to support some players by the library.
 * 
 * @see Meta
 * @see SpringStreams
 * @see SpringStreams#track(StreamAdapter, java.util.Map)
 * 
 * @author <a href="mailto:support@spring.de">spring GmbH &amp; Co.KG</a>
 */
public interface StreamAdapter {

	public interface Meta {
		public String getPlayerName();
		public String getPlayerVersion();
		public int getScreenWidth();
		public int getScreenHeight();
	}
	
	public Meta getMeta();
	
	public int getPosition();
	
	public int getDuration();
	
	public int getWidth();
	
	public int getHeight();	
}

Beginning of the Measurement

This chapter explains step by step how a streaming content is transferred to the library for the measurement.

In the library an adapter for class android.widget.VideoView

The source code for this implementation can be found in Appendix A and in the library.

The following code block shows an example for the use of the library.

 
// Create a sensor once in the application
SpringStreams sensor = new SpringStreams(site, appName, getApplicationContext());
...
 
public MyVideoActivity extends Activity {
	
	private static SpringStreams sensor;
	private Stream stream;
 
	public MyVideoActivity(SpringStreams sensor) {
		if(MyVideoActivity.sensor == null) 
			MyVideoActivity.sensor = sensor;
	}
 
	@Override
	protected void onStart() {
		Map<String, Object> atts = new HashMap<String, Object>();
		atts.put("stream", "android/teststream");
		stream = sensor.track(new VideoViewAdapter(this.videoView), atts);
		super.onStart();
	}
	
	@Override
	protected void onStop() {
		stream.stop();
		super.onStop();
	}
 
	...
}

First, the player and the object needs to be instantiated, that is able to deliver the current position on a stream in seconds. In the second step the adapters must be produced, which implements this requirement accurately.

Then an NSDictionary is generated in order to formulate more detailed information about the stream. Therefore the attribute stream must always be specified

The attribute stream is always required and must be specified for each measurement

Next, the method track is called with the adapter and the description property of the stream. From this point on, the stream is measured by the library as long as the application remains in foreground and the measured data are cyclically transmitted to the measuring system.

When the application goes into the background , all measurements are stopped and closed, i.e. when the application comes to the foreground again, the method track must be called again.

A stream is measured as long as the Activity is in the foreground. When the Activity goes into the background, the current status is transmitted to the measurement system and the measurement stops. If the stream should be measured again, when the application will come back to the foreground, the method track must be called again.

End of the Measurement

After the measurement of a stream has been started, this stream is measured by the sensor. The measurement can be stopped by calling the method stop on the stream object. All measurements will be automatically stopped by the library, when the application goes into the background.

// start streaming measurement
Stream *stream = sensor.track(adapter, atts);
...
// stop measurement programmatically
stream.stop();

If the stream should be measured again, when the Activity comes to the foreground or after the method stop has been called, the method track must be called again.

Ending the application

If the application is closed, the method unload can be called. This call sends the current state of the measurements to the measuring system and then terminates all measurements. This method is automatically called by the library, when the application goes into the background.

...
sensor.unload();

Using the SpringStreamsActivity

In the library is a SpringStreamsActivity included, that can be used to largely automate the measurement. The source code of this class can be found in Appendix B and in the library.

public class VideoPlayer extends SpringStreamsActivity {

	VideoView videoView;

	/**
	 * 
	 */
	public VideoPlayer() {
		super("test", "Streaming Test App");
	}
	
	
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		
		videoView = ...; 
	}

	@Override
	protected void onStart() {
		Map<String, Object> atts = new HashMap<String, Object>();
		atts.put("stream", "android/teststream");
		super.track(new VideoViewAdapter(this.videoView), atts);
		super.onStart();
	}
}

Appendix A

In the following example, the adapter has been implemented for the VideoView from the standard API.

/**
 * Implementation of an adapter for the {@link VideoView} in standard 
 * android api.
 * 
 * @author <a href="mailto:support@spring.de">spring GmbH &amp; Co.KG</a>
 */
public class VideoViewAdapter implements StreamAdapter {

		
	private VideoView videoView;
	
	public VideoViewAdapter(VideoView videoView) {
		if(videoView == null) 
			throw new NullPointerException("videoView may not be null");
		this.videoView = videoView;
	}

	@Override
	public Meta getMeta() {
		return new Meta() {
			public String getPlayerName() {
				return "android.widget.VideoView";
			}
			public String getPlayerVersion() {
				return Build.VERSION.RELEASE;
			}
			public int getScreenHeight() {
				return (((WindowManager)videoView.getContext().getSystemService(Context.WINDOW_SERVICE))
                                       .getDefaultDisplay()).getHeight();
			}
			public int getScreenWidth() {
				return (((WindowManager)videoView.getContext().getSystemService(Context.WINDOW_SERVICE))
					.getDefaultDisplay()).getWidth();
			}
		};
	}
	
	@Override
	public int getPosition() {
		return (int)Math.round(videoView.getCurrentPosition()/1000.0);
	}

	@Override
	public int getDuration() {
		return (int)Math.round(videoView.getDuration()/1000.0);
	}

	@Override
	public int getWidth() {
		return videoView.getWidth();
	}

	@Override
	public int getHeight() {
		return videoView.getHeight();
	}
}

Appendix B

The source code of class SpringStreamsActivity

package de.spring.mobile;

import java.util.Map;
import android.app.Activity;
import android.os.Bundle;

/**
 * 
 * @author  <a href="mailto:support@spring.de">spring GmbH &amp; Co.KG</a>
 */
public abstract class SpringStreamsActivity extends Activity {
	private static SpringStreams sensor;
	private static int instances = 0;
	private Stream stream;
	
	
	public SpringStreamsActivity(String site, String appName) {
		this(site, appName, 10);
	}
	
	public SpringStreamsActivity(String site, String appName, int timeout) {
		if(site == null) throw new NullPointerException("parameter site may not be null");
		if(appName == null) throw new NullPointerException("parameter appName may not be null");
		
		if(sensor == null) {
			sensor = new SpringStreams(site, appName, getApplicationContext());
			sensor.setTimeout(timeout);
		}
	}
	public Stream getStream() {
		return stream;
	}
	public void setSensorDebug(boolean debug) {
		sensor.setDebug(debug);
	}
	
	public boolean isSensorDebug() {
		return sensor.isDebug();
	}
	
	public void setTracking(boolean tracking) {
		sensor.setTracking(tracking);
	}
	
	public boolean isTracking() {
		return sensor.isTracking();
	}	
	
	public void track(StreamAdapter adapter, Map<String, Object> atts) {
		if(this.stream != null) {
			stream.stop();
			stream = null;
		}
		stream = sensor.track(adapter, atts);
	}
	/**
	 * @see android.app.Activity#onCreate(android.os.Bundle)
	 */
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		instances++;
		super.onCreate(savedInstanceState);
	}
	
	
	/**
	 * @see android.app.Activity#onStop()
	 */
	@Override
	protected void onStop() {
		if(stream != null) {
			stream.stop();
			stream = null;
		}
		super.onStop();
	}
	
	/**
	 * @see android.app.Activity#onDestroy()
	 */
	@Override
	protected void onDestroy() {
		instances--;
		if(instances <= 0) {
			sensor.unload();
			sensor = null;
			stream = null;
		}
		super.onDestroy();
	}
}