天气应用（JSON）数据未显示在textview中

Question

I finished my weather app on android studio in Java and XML but when I run the app the data isn't showing. I'm using open weather for my JSON data and I already gave the permissions in the XML manifesto to access location and internet. I am only testing the code with 3 variables

Weatherapp.ctemp.setText(String.valueOf(ctempreture));
Weatherapp.ftemp.setText(String.valueOf(ftempreture));
Weatherapp.ktemp.setText(String.valueOf(ktempreture));

I need to have those results from the JSON appear in my app somehow.

below is the main activity (weatherapp).

public class Weatherapp extends AppCompatActivity {
static TextView ctemp;
static TextView ftemp;
static TextView ktemp;
static TextView location;
static TextView pressure;
static TextView humidity;
static TextView mintempc;
static TextView mintempf;
static TextView mintempk;
static TextView maxtempc;
static TextView maxtempf;
static TextView maxtempk;
static TextView sealevel;
static TextView groundlevel;
static TextView windspeed;
static Button refresh;

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

    LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    Dowlode task = new Dowlode();
    String provider = locationManager.getBestProvider(new Criteria(), false);
    if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
        // TODO: Consider calling
        //    ActivityCompat#requestPermissions
        // here to request the missing permissions, and then overriding
        //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
        //                                          int[] grantResults)
        // to handle the case where the user grants the permission. See the documentation
        // for ActivityCompat#requestPermissions for more details.
        return;
    }
    Location locationn = locationManager.getLastKnownLocation(provider);
    Double lat = locationn.getLatitude();
    Double lng = locationn.getLongitude();
    task.execute("https://samples.openweathermap.org/data/2.5/weather?lat=35&lon=139&appid=4ba583d5302c8723764443f9d6f08116");
    ctemp = findViewById(R.id.ctemp);
    ftemp = findViewById(R.id.ftemp);
    ktemp = findViewById(R.id.ktemp);
    location = findViewById(R.id.location);
    pressure = findViewById(R.id.pressure);
    humidity = findViewById(R.id.humidity);
    mintempc = findViewById(R.id.mintempc);
    mintempf = findViewById(R.id.mintempf);
    mintempk = findViewById(R.id.mintempk);
    maxtempc = findViewById(R.id.maxtempc);
    maxtempf = findViewById(R.id.maxtempf);
    maxtempk = findViewById(R.id.maxtempk);
    sealevel = findViewById(R.id.sealevel);
    groundlevel = findViewById(R.id.groundlevel);
    windspeed = findViewById(R.id.windspeed);
    refresh = findViewById(R.id.refresh);
}

below is my download activity code

public class Dowlode extends AsyncTask<String,Void,String > {

@Override
protected String doInBackground(String... urls) {
    String result="";
    URL url;
    HttpURLConnection urlConnection =null;

    try {
        url=new URL(urls[0]);
        urlConnection=(HttpURLConnection) url.openConnection();
        InputStream in =urlConnection.getInputStream() ;
        InputStreamReader reader=new InputStreamReader(in);
        int data = reader.read();
        while (data!=-1){
            char current = (char) data;
            result += current;
            data = reader.read();

        }
        return result;
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    return null;
}

@Override
protected void onPostExecute(String s) {
    super.onPostExecute(s);

    try {
    JSONObject jsonObject = new JSONObject();

    JSONObject weather = new JSONObject(jsonObject.getString("main"));

    double tempreture = Double.parseDouble(weather.getString("temp"));
    int ctempreture = (int) (tempreture- 273.15 );
    int ftempreture = (int) (tempreture * 1.8-459.67);
    int ktempreture = (int) (tempreture);

    Weatherapp.ctemp.setText(String.valueOf(ctempreture));
    Weatherapp.ftemp.setText(String.valueOf(ftempreture));
    Weatherapp.ktemp.setText(String.valueOf(ktempreture));

    String location = jsonObject.getString("name");

    double pressure = Double.parseDouble(weather.getString("pressure"));
    String pressuree = pressure+ "pascal";

    double humidity = Double.parseDouble(weather.getString("humidity"));
    String humidityy= humidity+"";

    double temp_min = Double.parseDouble(weather.getString("temp_min"));
        int cmintemp = (int) (temp_min- 273.15 );
        int fmintemp = (int) (temp_min * 1.8-459.67);
        int kmintemp = (int) (temp_min);

    double temp_max = Double.parseDouble((weather.getString("temp_max")));
        int cmaxtemp = (int) (temp_max- 273.15 );
        int fmaxtemp = (int) (temp_max * 1.8-459.67);
        int kmaxtemp = (int) (temp_max);

    double sea_level = Double.parseDouble(weather.getString("sea_level"));
        int sealevel  = (int) (sea_level);

   double grnd_level = Double.parseDouble((weather.getString("grnd_level")));
        int groundlevel= (int) (grnd_level);

     JSONObject wind = new JSONObject(jsonObject.getString("wind"));

     double speed = Double.parseDouble((wind.getString("speed")));
     int speedd   = (int) (speed);

    } catch (Exception e) {
        e.printStackTrace();
    }
}
}

Answer 1

You are performing your async task before you do the findViewById stuff, so when you try to set the texts in the onPostExecute() method, the variables for the textviews are probably not set yet.

Also, you should better not use static variables in your activity. To avoid this, you can either put the Dowlode class inside your activity class, or you can pass the activity (or the relevant views) to the Dowlode class via a constructor.