Question

您好我的应用程序有问题。在我将它们改为parcelable之后，我的类首先是可序列化的，并且出现了问题。问题是，当我浏览应用程序内部的碎片时，有时它会崩溃。请希望在这里我可以得到一些帮助这是我的2个类和logcat消息。谢谢你的关注

City.java

public class City implements Parcelable {
    private String code;
    private String name;

    private List<CityWeather> weathers ;


    public City() {
        super();
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = code;
    }
    public List<CityWeather> getWeathers() {
        if(weathers == null) {
            weathers = new ArrayList<CityWeather>();
        }
        return weathers;
    }
    public void addCityWeather(CityWeather w) {
        getWeathers().add(w);
    }

    public void addCityWeathers(List<CityWeather> w) {
        getWeathers().addAll(w);
    }



    public City(Parcel in) {
        readFromParcel(in);
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(code);
        dest.writeString(name);
        dest.writeTypedList(weathers);
    }

    private void readFromParcel(Parcel in) {
        code = in.readString();
        name = in.readString();
        in.readTypedList(weathers, CityWeather.CREATOR);
    }

    public static final Parcelable.Creator<City> CREATOR = new Parcelable.Creator<City>() {
        public City createFromParcel(Parcel in) {
            return new City(in);
        }

        public City[] newArray(int size) {
            return new City[size];
        }
    };


    @Override
    public int describeContents() {
        // TODO Auto-generated method stub
        return 0;
    }
}

CityWeather.java

public class CityWeather implements Parcelable {


    private String date;
    private String weatherDescription;
    private int weatherCode;
    private String currentTemperature;
    private String minTemperature;
    private String maxTemperature;
    private String humadity;
    private String wind;
    private String day;
    private String temperatureUnit;



    public String getTemperatureUnit(){
        return temperatureUnit;
    }
    public void setTemperatureUnit(String temperatureUnit){
        this.temperatureUnit = temperatureUnit;
    }
    public String getDate() {
        return date;
    }
    public void setDate(String date) {
        this.date = date;
    }
    public String getWeatherDescription() {
        return weatherDescription;
    }
    public void setWeatherDescription(String weatherDescription) {
        this.weatherDescription = weatherDescription;
    }
    public int getWeatherCode() {
        return weatherCode;
    }
    public void setWeatherCode(int weatherCode) {
        this.weatherCode = weatherCode;
    }
    public String getCurrentTemperature() {
        return currentTemperature;
    }
    public void setCurrentTemperature(String currentTemperature) {
        this.currentTemperature = currentTemperature;
    }
    public String getMinTemperature() {
        return minTemperature;
    }
    public void setMinTemperature(String minTemperature) {
        this.minTemperature = minTemperature;
    }
    public String getMaxTemperature() {
        return maxTemperature;
    }
    public void setMaxTemperature(String maxTemperature) {
        this.maxTemperature = maxTemperature;
    }
    public String getHumadity() {
        return humadity;
    }
    public void setHumadity(String humadity) {
        this.humadity = humadity;
    }
    public String getWind() {
        return wind;
    }
    public void setWind(String wind) {
        this.wind = wind;
    }
    public String getDay() {
        return day;
    }
    public void setDay(String day) {
        this.day = day;
    }



    protected CityWeather(Parcel in) {
        date = in.readString();
        weatherDescription = in.readString();
        weatherCode = in.readInt();
        currentTemperature = in.readString();
        minTemperature = in.readString();
        maxTemperature = in.readString();
        humadity = in.readString();
        wind = in.readString();
        day = in.readString();
        temperatureUnit = in.readString();
    }

    public CityWeather() {
        // TODO Auto-generated constructor stub
    }
    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(date);
        dest.writeString(weatherDescription);
        dest.writeInt(weatherCode);
        dest.writeString(currentTemperature);
        dest.writeString(minTemperature);
        dest.writeString(maxTemperature);
        dest.writeString(humadity);
        dest.writeString(wind);
        dest.writeString(day);
        dest.writeString(temperatureUnit);
    }

    @SuppressWarnings("unused")
    public static final Parcelable.Creator<CityWeather> CREATOR = new Parcelable.Creator<CityWeather>() {
        @Override
        public CityWeather createFromParcel(Parcel in) {
            return new CityWeather(in);
        }

        @Override
        public CityWeather[] newArray(int size) {
            return new CityWeather[size];
        }
    };
}

和logcat消息

02-16 17:30:23.014: E/AndroidRuntime(15818): FATAL EXCEPTION: main
02-16 17:30:23.014: E/AndroidRuntime(15818): java.lang.RuntimeException: Unable to start activity ComponentInfo{ge.mobility.weather/ge.mobility.weather.activity.MainActivity}: java.lang.NullPointerException 
02-16 17:30:23.014: E/AndroidRuntime(15818): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2355)
02-16 17:30:23.014: E/AndroidRuntime(15818): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2391) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at android.app.ActivityThread.access$600(ActivityThread.java:151) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1335) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at android.os.Handler.dispatchMessage(Handler.java:99) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at android.os.Looper.loop(Looper.java:155) 02-16 17:30:23.014: E/AndroidRuntime(15818): at android.app.ActivityThread.main(ActivityThread.java:5520) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at java.lang.reflect.Method.invokeNative(Native Method) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at java.lang.reflect.Method.invoke(Method.java:511) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1029) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:796) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at dalvik.system.NativeStart.main(Native Method) 
02-16 17:30:23.014: E/AndroidRuntime(15818): Caused by: java.lang.NullPointerException 
02-16 17:30:23.014: E/AndroidRuntime(15818): at android.os.Parcel.readTypedList(Parcel.java:1754) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at ge.mobility.weather.entity.City.readFromParcel(City.java:62) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at ge.mobility.weather.entity.City.(City.java:49) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at ge.mobility.weather.entity.City$1.createFromParcel(City.java:67) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at ge.mobility.weather.entity.City$1.createFromParcel(City.java:1) 
02-16 17:30:23.014: E/AndroidRuntime(15818): at android.os.Parcel.readParcelable(Parcel.java:2108)

Answer 1

在没有初始化天气列表的情况下调用createFromParcel时，可能会发生NPE。

尝试替换

private List<CityWeather> weathers;

带

private List<CityWeather> weathers = new ArrayList<CityWeather>();

Answer 2

我猜天气是空的。你应该确保在解组你的对象之前实例化列表。

 private void readFromParcel(Parcel in) {
    code = in.readString();
    name = in.readString();
    in.readTypedList(weathers, CityWeather.CREATOR); //HERE IT FAILS
}

试试这个

 private void readFromParcel(Parcel in) {
    code = in.readString();
    name = in.readString();
    if(weathers == null){
      weathers = new ArrayList<CityWeather>();
    }
    in.readTypedList(weathers, CityWeather.CREATOR);
}

Answer 3

替代方法是使用Gson将对象转换为JSONObject。

初始活动

Intent activity = new Intent(MyActivity.this,NextActivity.class);
activity.putExtra("myObject", new Gson().toJson(myobject);
startActivity(activity);

下一个活动

Sting jsonMyObject;
Bundle extras = getIntent().getExtras();
if (extras != null) {
   jsonMyObject = extras.getString("myObject");
}
MyObject myObject = new Gson().fromJson(jsonMyObject, MyObject.class);

parcelable classes app崩溃

3 个答案: