Use of non-final variable in runOnUiThread

Question

I'm making a weather application for Android and I'm trying to use a non-final variable from my Thread in runOnUiThread. However, I'm not allowed to do this.

What am I doing wrong?

Beneath is code from the whole activity. The thread is parsing xml from yr.no.

public class WeatherActivity extends Activity implements OnClickListener {

ImageView forecastImage;
TextView updateWeatherText;
TextView temperatureText;
TextView cloudinessText;
TextView windspeedText;
TextView precipitationText;

Thread updateWeather = new Thread(new GetWeather());
Thread updateWeatherFromButton = new Thread(new GetWeather());

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

    forecastImage = (ImageView) findViewById(R.id.forecastIcon);

    updateWeatherText = (TextView) findViewById(R.id.updatingWeatherText);

    temperatureText = (TextView) findViewById(R.id.temperatureText);
    cloudinessText = (TextView) findViewById(R.id.cloudinessText);
    windspeedText = (TextView) findViewById(R.id.windspeedText);
    precipitationText = (TextView) findViewById(R.id.precipitationText);

    updateWeather.start();

    Button refreshButton = (Button) findViewById(R.id.refreshButton);
    refreshButton.setOnClickListener(this);
}

class GetWeather implements Runnable {

    public void run() {

        try {

            String temp;
            String windspeed;
            String cloudiness;
            String precipitation;


            URL weatherURL = new URL(
                    "http://api.yr.no/weatherapi/locationforecast/1.8/?lat=62.39;lon=17.30");

            XmlPullParserFactory parserFactory = XmlPullParserFactory
                    .newInstance();
            XmlPullParser parser = parserFactory.newPullParser();

            parser.setInput(weatherURL.openStream(), null);

            updateWeatherText.setText("Updating...");
            int parserEvent = parser.getEventType();
            while (parserEvent != XmlPullParser.END_DOCUMENT) {

                switch (parserEvent) {

                case XmlPullParser.TEXT:
                    String tag = parser.getName();

                    if (tag.compareTo("temperature") == 0) {
                        temp = parser.getAttributeValue(
                                null, "value") + " 'C";
                    } else if (tag.compareTo("windSpeed") == 0) {
                        windspeed = parser.getAttributeValue(
                                null, "mps") + " m/s";

                    } else if (tag.compareTo("cloudiness") == 0) {
                        if (Integer.parseInt(parser.getAttributeValue(null,
                                "percent")) >= 0
                                && Integer
                                        .parseInt(parser.getAttributeValue(
                                                null, "percent")) <= 12.5) {
                            cloudiness = "Klart";
                        } else if (Integer.parseInt(parser
                                .getAttributeValue(null, "percent")) > 12.5
                                && Integer
                                        .parseInt(parser.getAttributeValue(
                                                null, "percent")) < 25) {
                            cloudiness = "Mestadels klart";
                        } else if (Integer.parseInt(parser
                                .getAttributeValue(null, "percent")) >= 25
                                && Integer
                                        .parseInt(parser.getAttributeValue(
                                                null, "percent")) < 75) {
                            cloudiness = "Växlande molnighet";
                        } else if (Integer.parseInt(parser
                                .getAttributeValue(null, "percent")) >= 75
                                && Integer
                                        .parseInt(parser.getAttributeValue(
                                                null, "percent")) < 87.5) {
                            cloudiness = "Mestadels mulet";
                        } else if (Integer.parseInt(parser
                                .getAttributeValue(null, "percent")) >= 87.5
                                && Integer
                                        .parseInt(parser.getAttributeValue(
                                                null, "percent")) <= 100) {
                            cloudiness = "Mulet";
                        }

                    } else if (tag.compareTo("precipitation") == 0) {
                        if (Integer.parseInt(parser.getAttributeValue(null, "minvalue")) > 0) forecastImage.setBackgroundResource(R.drawable.rain);
                        precipitation = "Mellan "
                                        + parser.getAttributeValue(null,
                                                "minvalue")
                                        + " mm och "
                                        + parser.getAttributeValue(null,
                                                "maxvalue") + " mm";
                    }
                    break;
                }
                parserEvent = parser.next();

                runOnUiThread(new Runnable() {

                    public void run() {
                        temperatureText.setText(temp);
                        windspeedText.setText(windspeed);
                        cloudinessText.setText(cloudiness);
                        precipitationText.setText(precipitation);

                        if (cloudiness.compareTo("Klart") == 0){
                            forecastImage.setBackgroundResource(R.drawable.sunny);
                        } else if ( cloudiness.compareTo("Mestadels klart" ) == 0) {
                            forecastImage.setBackgroundResource(R.drawable.sunny);
                        }
                          else if ( cloudiness.compareTo("Växlande molnighet") == 0) {
                              forecastImage.setBackgroundResource(R.drawable.cloudy);
                        } else if ( cloudiness.compareTo("Mestadels mulet") == 0) {
                            forecastImage.setBackgroundResource(R.drawable.overcast);
                        } else if ( cloudiness.compareTo("Mulet") == 0) {
                            forecastImage.setBackgroundResource(R.drawable.overcast);
                        }                           
                    }
                });
            }
            updateWeatherText.setText("Last updated: "
                    + System.currentTimeMillis());

        } catch (Exception e) {
        }
    }
}

public void onClick(View v) {

    switch (v.getId()) {

    case R.id.refreshButton:
        updateWeatherFromButton.start();

    }
}

score 1 · Answer 1 · answered Apr 16 '12 at 18:30

1

As some have already pointed out you can't. One workaround is to reassign the non final variable to a final variable before defining the Runnable:

String aNonFinalString = "a";
aNonFinalString = "b";

final String aFinalString = aNonFinalString;

runOnUiThread(new Runnable() {
    public void run() {
        useYourString(aFinalString);
     }
}

answered Apr 16 '12 at 18:30

assylias

321,522
82
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1

This is wrong. The value of aNonFinalString may change by the time your run method is executed. There is a reason why it should be 'final'. – Anirudh Apr 16 '12 at 20:10
@Anirudh Not sure I understand what you mean. I don't use aNonFinalString in the runnable, which the whole point. – assylias Apr 16 '12 at 20:18
I was trying to say that the developer @user1258829 may not be expecting a possibly 'stale' value i.e. final String aFinalString = aNonFinalString; when the runnable actually runs. aNonFinalString may be changed based on some logic. But the runnable will only provide a snapshop of the value with the final variable. – Anirudh Apr 16 '12 at 20:21
@Anirudh Ok understood what you mean. In which case he can use accessors. – assylias Apr 16 '12 at 20:23

score 0 · Answer 2 · edited May 23 '17 at 10:34

0

You can't..it is Java you can't use outer variables inside anonymous inner class unless it is declared final. Refer to this question to get more details

edited May 23 '17 at 10:34

Community

1
1

answered Apr 16 '12 at 18:26

Mahdi Hijazi

4,424
3
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29

Use of non-final variable in runOnUiThread

2 Answers2