问题
I have following code to use weatherlib to get weather condition in android using android studio.
My activity:
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;
import com.survivingwithandroid.weather.lib.WeatherClient;
import com.survivingwithandroid.weather.lib.WeatherClientDefault;
import com.survivingwithandroid.weather.lib.WeatherConfig;
import com.survivingwithandroid.weather.lib.exception.LocationProviderNotFoundException;
import com.survivingwithandroid.weather.lib.exception.WeatherLibException;
import com.survivingwithandroid.weather.lib.model.CurrentWeather;
import com.survivingwithandroid.weather.lib.provider.IWeatherProvider;
import com.survivingwithandroid.weather.lib.provider.WeatherProviderFactory;
import com.survivingwithandroid.weather.lib.provider.openweathermap.OpenweathermapProviderType;
import java.util.List;
public class MainActivity extends Activity {
private Context ctx;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
WeatherClient client = WeatherClientDefault.getInstance();
client.init(ctx);
WeatherConfig config = new WeatherConfig();
config.unitSystem = WeatherConfig.UNIT_SYSTEM.M;
config.lang = "en"; // If you want to use english
config.maxResult = 5; // Max number of cities retrieved
config.numDays = 6; // Max num of days in the forecast
client.updateWeatherConfig(config);
IWeatherProvider provider = null;
try {
//provider = WeatherProviderFactory.createProvider(new YahooProviderType(), config);
provider = WeatherProviderFactory.createProvider(new OpenweathermapProviderType(), config);
//provider = WeatherProviderFactory.createProvider(new WeatherUndergroundProviderType(), config);
client.setProvider(provider);
}
catch (Throwable t) {
// There's a problem
}
try {
client.searchCityByLocation(WeatherClient.createDefaultCriteria(), new WeatherClient.CityEventListener() {
@Override
public void onCityListRetrieved(List<City> cityList) {
// Here your logic when the data is available
}
@Override
public void onWeatherError(WeatherLibException wle) {
}
@Override
public void onConnectionError(Throwable t) {
}
});
} catch (LocationProviderNotFoundException e) {
e.printStackTrace();
}
client.getCurrentCondition("29222451", new WeatherClient.WeatherEventListener() {
@Override
public void onWeatherRetrieved(CurrentWeather weather) {
// Here we can use the weather information to upadte the view
String text = weather.currentCondition.getCondition();
String text2 = weather.currentCondition.getDescr();
float temp = weather.temperature.getTemp();
Toast.makeText(getApplicationContext(), "Condition :" + text + " Description " + text2 + " Temperature " + temp,
Toast.LENGTH_LONG).show();
}
@Override
public void onWeatherError(WeatherLibException t) {
}
@Override
public void onConnectionError(Throwable t) {
}
});
}
I get the following error for this:
java.lang.RuntimeException: Unable to start activity ComponentInfo{MainActivity}: java.lang.NullPointerException: Attempt to invoke interface method 'void com.survivingwithandroid.weather.lib.provider.IWeatherProvider.setConfig(com.survivingwithandroid.weather.lib.WeatherConfig)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'void com.survivingwithandroid.weather.lib.provider.IWeatherProvider.setConfig(com.survivingwithandroid.weather.lib.WeatherConfig)' on a null object reference
at com.survivingwithandroid.weather.lib.WeatherClientDefault.updateWeatherConfig(WeatherClientDefault.java:104)
i.MainActivity.onCreate(MainActivity.java:41)
at android.app.Activity.performCreate(Activity.java:5933)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
at android.app.ActivityThread.access$800(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5221)
回答1:
client.updateWeatherConfig(config); must be called after initializing provider as:
WeatherClient client = WeatherClientDefault.getInstance();
client.init(ctx);
WeatherConfig config = new WeatherConfig();
config.unitSystem = WeatherConfig.UNIT_SYSTEM.M;
config.lang = "en"; // If you want to use english
config.maxResult = 5; // Max number of cities retrieved
config.numDays = 6; // Max num of days in the forecast
IWeatherProvider provider = null;
try {
//provider = WeatherProviderFactory.createProvider(new YahooProviderType(), config);
provider = WeatherProviderFactory.createProvider(new OpenweathermapProviderType(), config);
//provider = WeatherProviderFactory.createProvider(new WeatherUndergroundProviderType(), config);
client.setProvider(provider);
}
catch (Throwable t) {
// There's a problem
}
client.updateWeatherConfig(config);
回答2:
I guess you didn't import the project correctly or you didnt the right permission to the project.
来源：https://stackoverflow.com/questions/27481420/unable-to-execute-activity-in-android-for-weatherlib