Android IntentService, how to write a background service keep polling data and notify Activity for Change.

Let me put a simple test application, One activity and One Service. for the service, it will do the background job like networking, computation. and notify the Acidity to do some UI side rendering or notification to User.

first , Create one Simple Android application with just one Activity,

public class UIActivity extends Activity {     /** Called when the activity is first created. */         TextView tv;     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         tv=new TextView(this);         tv.setText("hello,World");         setContentView(tv);     }         }

then Add one Handler in the activity which will be called by the bakcground service when there are any change get triggered,

Handler handler=new Handler()     {         @Override         public void handleMessage(Message msg) {             //get data from msg                         String result=msg.getData().getString("result");             tv.setText(result);             Log.d("xxxxx", "get data" + result);             super.handleMessage(msg);         }     };

then Create one Service inherited from IntentService, here we defined a timer which will do the periodic checking and send back data change to activity,

public class BackService extends IntentService {     public BackService()     {         super("myintentservice");     }             Messenger messenger;     Timer t=new Timer();             @Override     protected void onHandleIntent(Intent intent) {         messenger=(Messenger) intent.getExtras().get("handler");                 t.schedule(new TimerTask() {                         @Override             public void run() {                 // just call the handler every 3 Seconds                                 Message msg=Message.obtain();                 Bundle data=new Bundle();                 data.putString("k", "value" + System.currentTimeMillis() );                 msg.setData(data);                                 try {                     messenger.send(msg);                 } catch (RemoteException e) {                     // TODO Auto-generated catch block                     e.printStackTrace();                 }             }         }, 100,3000);             } }

for Activity, need to specify the handler through putextra and start the service,

public void onCreate(Bundle savedInstanceState) {      super.onCreate(savedInstanceState);      tv=new TextView(this);      tv.setText("hello,World");      setContentView(tv);           Intent i=new Intent(this, BackService.class);      i.putExtra("handler", new Messenger(this.handler));      this.startService(i);      }

remember to register the backservice into the manifest.xml,
when you run the app, you will see the textview will change every 3 seconds,

run adb logcat XXXXX:D *:S, even the activity is brought to background , the Activity still get the change from service,

How to : QT Hello world localization and I18N

When you installed QT SDK, it came with several useful tools to do the I18N and localization, I’ll put a very basic QT program and show the basic steps to localize the app to support different local /languages.

Create a Basic QT hello world application, make sure all user-visible strings are used as translatable strings (using tr function)
Create a empty QT Project using QT creator,

then add a new source file,

#include <QtGui> int main(int argc, char * argv[]) {     QApplication app(argc,argv);     QPushButton * button=new QPushButton(QObject::tr("Hello,World!"));     button->show();     app.exec(); }

then run the app by pressing F5, you will see the hello world button,
 

Now we are going to add the Chinese and Japanese Support to the app.

>>> go the the project folder, Run a command called Lupdate(include in the sdk ), to extract all translatable strings to a file,

here default.ts is just a xml file as the content bellows,


>>>now use the linguist tool to translate it into Japanese, run “linguist” In the qt shell or click the tool from start-menu
open the default.ts, and chose Japanese as the target language,

put the translation for hello world in Japanese, and click to mark done, then Save it as  as jp.ts

Now quite the translation tool and start over again to translate it to Chinese, and export to cn.ts
>>>compile the cn.ts and jp.ts to binary format using lrelease

>>> now in the app, load those two qm files,

QApplication app(argc,argv); QTranslator translator ; QLocale curent; if(curent==QLocale::Chinese) { translator.load("F:\\helloworld\\cn.qm"); app.installTranslator(&translator); } if(curent==QLocale::Japanese) { translator.load("F:\\helloworld\\jp.qm"); app.installTranslator(&translator); } QPushButton * button=new QPushButton(QObject::tr("Hello,World")); button->show(); app.exec();

Now, if you setup your current locale to Japanese, you will see the JP version of helloword

or you can change the default local in code,

QLocale::setDefault(QLocale::Japanese);

 

How to: install ADB driver for Motorola Xoom

Download and install the Driver from Motorola,
 http://developer.motorola.com/docstools/USB_Drivers/


in your xoom device, enable the USB debugging under application section settings,


then in windows, it will find new device and apply the ADB driver.

Now you can run adb devices, to see the device is there

for all other non-google device, here is the list of their drivers,
http://developer.android.com/sdk/oem-usb.html

Hadoop: How to install and test PIG

like install and test Hive on hadoop cluster, Pig is another end-user facing analytical tools for Hadoop. unlike SQL style query for Hive, Pig use the scripting language which will be more familiar to Sys admins.

Download Pig From Yahoo, http://www.apache.org/dyn/closer.cgi/pig

Unzip the files and go the bin folder, only change is we need to add the hadoop conf folder to the class path. then pig knows how to deal with hadoop cluster,

# cygwin path translation if $cygwin; then     CLASSPATH=`cygpath -p -w "$CLASSPATH"`     PIG_HOME=`cygpath -d "$PIG_HOME"`     PIG_LOG_DIR=`cygpath -d "$PIG_LOG_DIR"` fi #add hadoop conf folder to the classpath export CLASSPATH=$CLASSPATH:/usr/lib/hadoop/conf

After that, you can run the ./bin/pig to start the shell of Pig,

Here are the Pig syntax.
http://pig.apache.org/docs/r0.8.0/cookbook.html

Hadoop, java.lang.ClassCastException: org.apache.hadoop.io.LongWritable cannot be cast to org.apache.hadoop.io.Text

If you work on a Mapper which expects the file format of keyvalue, and forget to specify the inputformat to jobconf, you will get the following errors.

java.lang.ClassCastException: org.apache.hadoop.io.LongWritable cannot be cast to org.apache.hadoop.io.Text at MR.map(MR.java:1) at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50) at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:358) at org.apache.hadoop.mapred.MapTask.run(MapTask.java:307) at org.apache.hadoop.mapred.Child.main(Child.java:170)

here is why,

for the jobconf, the default inputformat is TextInputFormat,

you will get Key/value type of longwritable/text in your Map function.
if you put something like Text as the key, you will get the classcast exception

public void map(Text key, Text value, OutputCollector<Text, Text> collector, Reporter paramReporter) throws IOException {

So always remember to specify the InputFormat.