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我想用来自 JSON 链接的数据填充网格视图。检索数据后如何填充网格视图。它基本上是一个天气应用程序。

这是我的 JSON 解析器类：

public class JSONWeatherParser {

public static WeatherForecast getForecastWeather(String data) throws JSONException  {

    WeatherForecast forecast = new WeatherForecast();

    // We create out JSONObject from the data
    JSONObject jObj = new JSONObject(data);

    JSONArray jArr = jObj.getJSONArray("list"); // Here we have the forecast for every day

    // We traverse all the array and parse the data
    for (int i=0; i < jArr.length(); i++) {
        JSONObject jDayForecast = jArr.getJSONObject(i);

        // Now we have the json object so we can extract the data
        DayForecast df = new DayForecast();

        // We retrieve the timestamp (dt)
        df.timestamp = jDayForecast.getLong("dt");

        // Temp is an object
        JSONObject jTempObj = jDayForecast.getJSONObject("temp");

        df.forecastTemp.day = (float) jTempObj.getDouble("day");
        df.forecastTemp.min = (float) jTempObj.getDouble("min");
        df.forecastTemp.max = (float) jTempObj.getDouble("max");
        df.forecastTemp.night = (float) jTempObj.getDouble("night");
        df.forecastTemp.eve = (float) jTempObj.getDouble("eve");
        df.forecastTemp.morning = (float) jTempObj.getDouble("morn");

        // Pressure & Humidity
        df.weather.currentCondition.setPressure((float) jDayForecast.getDouble("pressure"));
        df.weather.currentCondition.setHumidity((float) jDayForecast.getDouble("humidity"));

        // ...and now the weather
        JSONArray jWeatherArr = jDayForecast.getJSONArray("weather");
        JSONObject jWeatherObj = jWeatherArr.getJSONObject(0);
        df.weather.currentCondition.setWeatherId(getInt("id", jWeatherObj));
        df.weather.currentCondition.setDescr(getString("description", jWeatherObj));
        df.weather.currentCondition.setCondition(getString("main", jWeatherObj));
        df.weather.currentCondition.setIcon(getString("icon", jWeatherObj));

        forecast.addForecast(df);
    }



    return forecast;
}   


private static JSONObject getObject(String tagName, JSONObject jObj)  throws JSONException {
    JSONObject subObj = jObj.getJSONObject(tagName);
    return subObj;
}

private static String getString(String tagName, JSONObject jObj) throws JSONException {
    return jObj.getString(tagName);
}

private static float  getFloat(String tagName, JSONObject jObj) throws JSONException {
    return (float) jObj.getDouble(tagName);
}

private static int  getInt(String tagName, JSONObject jObj) throws JSONException {
    return jObj.getInt(tagName);
}

}

GridViewAdapter 类：

public class GridViewAdapter extends BaseAdapter {
private Context mContext;
private int numDays;
private WeatherForecast forecast;
private final static SimpleDateFormat sdf = new SimpleDateFormat("E, dd-MM");
private DayForecast dayForecast;
private ImageView iconWeather;

public GridViewAdapter(int numDays, WeatherForecast forecast) {
    this.numDays = numDays;
    this.forecast = forecast;
}

public int getCount() {
    return numDays;
}

public Object getItem(int position) {
    return null;
}

public long getItemId(int position) {
    return 0;
}

// create a new ImageView for each item referenced by the Adapter
public View getView(int position, View convertView, ViewGroup parent) {
    //ImageView imageView;
    //ImageView icon;
    TextView temp;
    TextView date;


    if (convertView == null) {  // if it's not recycled, initialize some attributes


        //icon = new ImageView(mContext);
        temp = new TextView(mContext);
        date = new TextView(mContext);

        LayoutInflater inflater = (LayoutInflater)   mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        convertView = inflater.inflate(R.layout.grid_icon, parent, false);

    }



    temp=(TextView)convertView.findViewById(R.id.text);
    temp.setText( (int) (dayForecast.forecastTemp.min - 275.15) + "-" + (int) (dayForecast.forecastTemp.max - 275.15) );
    date=(TextView)convertView.findViewById(R.id.date);
    date.setText(DateUtils.formatDateTime(mContext, System.currentTimeMillis(), DateUtils.FORMAT_SHOW_DATE | DateUtils.FORMAT_NUMERIC_DATE ));

    return convertView;
    //JSONIconWeatherTask task = new JSONIconWeatherTask();
    //task.execute(new String[]{dayForecast.weather.currentCondition.getIcon()});

    /*imageView.setImageResource(mThumbIds[position]);*/
    //return imageView;
}
public void setForecast(DayForecast dayForecast) {

    this.dayForecast = dayForecast;

}

我的异步任务：

private class JSONForecastWeatherTask extends AsyncTask<String, Void, WeatherForecast> {

    @Override
    protected WeatherForecast doInBackground(String... params) {

        String data = ( (new WeatherHttpClient()).getForecastWeatherData(params[0], params[1], params[2]));
        WeatherForecast forecast = new WeatherForecast();
        try {
            forecast = JSONWeatherParser.getForecastWeather(data);
            System.out.println("Weather ["+forecast+"]");

        } catch (JSONException e) {             
            e.printStackTrace();
        }
        return forecast;

}

@Override
    protected void onPostExecute(WeatherForecast forecastWeather) {         
        super.onPostExecute(forecastWeather);
        GridView gridView;
        gridView = (GridView) findViewById(R.id.gridview);

        gridView.setAdapter(new GridViewImageAdapter(Integer.parseInt(forecastDaysNum), forecastWeather));
    }

} 日志

09-27 00:03:10.132：E/AndroidRuntime(29848)：致命异常：主要 09-27 00:03:10.132：E/AndroidRuntime(29848)：java.lang.NullPointerException 09-27 00:03:10.132： E/AndroidRuntime(29848): 在 android.app.Activity.findViewById(Activity.java:1843) 09-27 00:03:10.132: E/AndroidRuntime(29848): 在 com.example.weatherforecast.MainActivity$JSONForecastWeatherTask.onPostExecute (MainActivity.java:205) 09-27 00:03:10.132: E/AndroidRuntime(29848): 在 com.example.weatherforecast.MainActivity$JSONForecastWeatherTask.onPostExecute(MainActivity.java:1) 09-27 00:03:10.132 : E/AndroidRuntime(29848): 在 android.os.AsyncTask.finish(AsyncTask.java:631) 09-27 00:03:10.132: E/AndroidRuntime(29848): 在 android.os.AsyncTask.access$600(AsyncTask .java:177) 09-27 00:03:10.132: E/AndroidRuntime(29848): 在 android.os.AsyncTask$InternalHandler。handleMessage(AsyncTask.java:644) 09-27 00:03:10.132: E/AndroidRuntime(29848): 在 android.os.Handler.dispatchMessage(Handler.java:99) 09-27 00:03:10.132: E/ AndroidRuntime(29848): 在 android.os.Looper.loop(Looper.java:137) 09-27 00:03:10.132: E/AndroidRuntime(29848): 在 android.app.ActivityThread.main(ActivityThread.java:5234 ) 09-27 00:03:10.132: E/AndroidRuntime(29848): at java.lang.reflect.Method.invokeNative(Native Method) 09-27 00:03:10.132: E/AndroidRuntime(29848): at java. lang.reflect.Method.invoke(Method.java:525) 09-27 00:03:10.132: E/AndroidRuntime(29848): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:799 ) 09-27 00:03:10.132: E/AndroidRuntime(29848): 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566) 09-27 00:03:10.132: E/AndroidRuntime(29848 ）：在达尔维克。system.NativeStart.main（本机方法）

我仍然是Java的初学者。

4

1 回答 1

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我没有看到您的 GridView 适配器代码。首先，您应该为 GridView 编写一个单独的类 - 适配器，其中方法getView()必须被覆盖（请参阅有关 GridView 适配器的类似问题）。当您检索数据时，您应该为您的适配器调用 notifyDataSetChanged() 方法 - 这将使用新数据刷新 GridView。

很好的例子如何自定义gridview http://www.mkyong.com/android/android-gridview-example/

并且不要忘记调用adapter.notifyDataSetChanged();

于 2013-09-25T19:38:55.697 回答