Java getPlacesUrl上的NullPointerException（参数[0]）

我正在使用教程中包含的PlaceProvider.java来设置SearchView和集成Google Places API。本教程的代码似乎有很多缺陷——至少在与现有代码集成方面是如此。此特定错误将在MainActivity启动时立即抛出。它加载一秒钟，然后抛出错误：

03-10 00:17:27.716: E/AndroidRuntime(7895): FATAL EXCEPTION: ModernAsyncTask #1
03-10 00:17:27.716: E/AndroidRuntime(7895): java.lang.RuntimeException: An error occured while executing doInBackground()
...
03-10 00:17:27.716: E/AndroidRuntime(7895): Caused by: java.lang.NullPointerException
03-10 00:17:27.716: E/AndroidRuntime(7895):     at java.net.URLEncoder.encode(URLEncoder.java:92)
03-10 00:17:27.716: E/AndroidRuntime(7895):     at com.....PlaceProvider.getPlacesUrl(PlaceProvider.java:266)
03-10 00:17:27.716: E/AndroidRuntime(7895):     at com.....PlaceProvider.getPlaces(PlaceProvider.java:290)
03-10 00:17:27.716: E/AndroidRuntime(7895):     at 
com.....PlaceProvider.query(PlaceProvider.java:88)

从哪里开始调试此错误？谢谢下面是完整类和日志cat。我已经对日志中提到的行进行了评论

PlaceProvider.java：

public class PlaceProvider extends ContentProvider {

public static final String AUTHORITY = "com.....PlaceProvider"; //Removed for forum

public static final Uri SEARCH_URI = Uri.parse("content://"+AUTHORITY+"/search");

public static final Uri DETAILS_URI = Uri.parse("content://"+AUTHORITY+"/details");

private static final int SEARCH = 1;
private static final int SUGGESTIONS = 2;
private static final int DETAILS = 3;

// Obtain browser key from https://code.google.com/apis/console
String mKey = "key=MY_API_KEY"; //Removed for forum

// Defines a set of URIs allowed with this content provider
private static final UriMatcher mUriMatcher = buildUriMatcher();

private static UriMatcher buildUriMatcher() {

    UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);

    // URI for "Go" button
    uriMatcher.addURI(AUTHORITY, "search", SEARCH );

    // URI for suggestions in Search Dialog
    uriMatcher.addURI(AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY,SUGGESTIONS);

    // URI for Details
    uriMatcher.addURI(AUTHORITY, "details",DETAILS);

    return uriMatcher;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,
    String[] selectionArgs, String sortOrder) {
    Cursor c = null;

    PlaceJSONParser parser = new PlaceJSONParser();
    PlaceDetailsJSONParser detailsParser = new PlaceDetailsJSONParser();

    String jsonString = "";
    String jsonPlaceDetails = "";

    List<HashMap<String, String>> list = null;
    List<HashMap<String, String>> detailsList = null;

    MatrixCursor mCursor = null;

    switch(mUriMatcher.match(uri)){
    case SEARCH:
        // Defining a cursor object with columns description, lat and lng
        mCursor = new MatrixCursor(new String[] { "description","lat","lng" });

        // Create a parser object to parse places in JSON format
        parser = new PlaceJSONParser();

        // Create a parser object to parse place details in JSON format
        detailsParser = new PlaceDetailsJSONParser();

        // Get Places from Google Places API
        jsonString = getPlaces(selectionArgs); //This is line 88 in my code
        try {
            // Parse the places ( JSON => List )
            list = parser.parse(new JSONObject(jsonString));

            // Finding latitude and longitude for each places using Google Places Details API
            for(int i=0;i<list.size();i++){
                HashMap<String, String> hMap = (HashMap<String, String>) list.get(i);

                detailsParser =new PlaceDetailsJSONParser();

                // Get Place details
                jsonPlaceDetails = getPlaceDetails(hMap.get("reference"));

                // Parse the details ( JSON => List )
                detailsList = detailsParser.parse(new JSONObject(jsonPlaceDetails));

                // Creating cursor object with places
                for(int j=0;j<detailsList.size();j++){
                    HashMap<String, String> hMapDetails = detailsList.get(j);

                    // Adding place details to cursor
                    mCursor.addRow(new String[]{ hMap.get("description") , hMapDetails.get("lat") , hMapDetails.get("lng") });
                }

            }
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        c = mCursor;
        break;

    case SUGGESTIONS :

        // Defining a cursor object with columns id, SUGGEST_COLUMN_TEXT_1, SUGGEST_COLUMN_INTENT_EXTRA_DATA
        mCursor = new MatrixCursor(new String[] { "_id", SearchManager.SUGGEST_COLUMN_TEXT_1, SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA } );

        // Creating a parser object to parse places in JSON format
        parser = new PlaceJSONParser();

        // Get Places from Google Places API
        jsonString = getPlaces(selectionArgs);

        try {
            // Parse the places ( JSON => List )
            list = parser.parse(new JSONObject(jsonString));

            // Creating cursor object with places
            for(int i=0;i<list.size();i++){
                HashMap<String, String> hMap = (HashMap<String, String>) list.get(i);

                // Adding place details to cursor
                mCursor.addRow(new String[] { Integer.toString(i), hMap.get("description"), hMap.get("reference") });
            }
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        c = mCursor;
        break;

    case DETAILS :
        // Defining a cursor object with columns description, lat and lng
        mCursor = new MatrixCursor(new String[] { "description","lat","lng" });

        detailsParser = new PlaceDetailsJSONParser();
        jsonPlaceDetails = getPlaceDetails(selectionArgs[0]);
        try {
            detailsList = detailsParser.parse(new JSONObject(jsonPlaceDetails));
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        for(int j=0;j<detailsList.size();j++){
            HashMap<String, String> hMapDetails = detailsList.get(j);
            mCursor.addRow(new String[]{ hMapDetails.get("formatted_address") , hMapDetails.get("lat") , hMapDetails.get("lng") });
        }
        c = mCursor;
        break;
    }
    return c;
}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
    // TODO Auto-generated method stub
    return 0;
}

@Override
public String getType(Uri uri) {
    // TODO Auto-generated method stub
    return null;
}

@Override
public Uri insert(Uri uri, ContentValues values) {
    // TODO Auto-generated method stub
    return null;
}

@Override
public boolean onCreate() {
    // TODO Auto-generated method stub
    return false;
}

@Override
public int update(Uri uri, ContentValues values, String selection,
    String[] selectionArgs) {
    // TODO Auto-generated method stub
    return 0;
}

/** A method to download JSON data from url */
private String downloadUrl(String strUrl) throws IOException{
    String data = "";
    InputStream iStream = null;
    HttpURLConnection urlConnection = null;
    try{
        URL url = new URL(strUrl);

        // Creating an http connection to communicate with url
        urlConnection = (HttpURLConnection) url.openConnection();

        // Connecting to url
        urlConnection.connect();

        // Reading data from url
        iStream = urlConnection.getInputStream();

        BufferedReader br = new BufferedReader(new InputStreamReader(iStream));

        StringBuffer sb = new StringBuffer();

        String line = "";
        while( ( line = br.readLine()) != null){
            sb.append(line);
        }

        data = sb.toString();

        br.close();

    }catch(Exception e){
       Log.d("Exception while downloading url", e.toString());
    }finally{
        iStream.close();
        urlConnection.disconnect();
    }
    return data;
}

private String getPlaceDetailsUrl(String ref){

    // reference of place
    String reference = "reference="+ref;

    // Sensor enabled
    String sensor = "sensor=false";

    // Building the parameters to the web service
    String parameters = reference+"&"+sensor+"&"+mKey;

    // Output format
    String output = "json";

    // Building the url to the web service
    String url = "https://maps.googleapis.com/maps/api/place/details/"+output+"?"+parameters;

    return url;
}

private String getPlacesUrl(String qry){

    try {
        qry = "input=" + URLEncoder.encode(qry, "utf-8"); //This is line 266
    } catch (UnsupportedEncodingException e1) {
        e1.printStackTrace();
    }

    // Sensor enabled
    String sensor = "sensor=false";

    // place type to be searched
    String types = "types=geocode";

    // Building the parameters to the web service
    String parameters = qry+"&"+types+"&"+sensor+"&"+mKey;

    // Output format
    String output = "json";
    // Building the url to the web service
    String url = "https://maps.googleapis.com/maps/api/place/autocomplete/"+output+"?"+parameters;
    return url;
}

private String getPlaces(String[] params){
    // For storing data from web service
    String data = "";
    String url = getPlacesUrl(params[0]); //This is line 290
    try{
        // Fetching the data from web service in background
        data = downloadUrl(url);
    }catch(Exception e){
        Log.d("Background Task",e.toString());
    }
    return data;
}

private String getPlaceDetails(String reference){
    String data = "";
    String url = getPlaceDetailsUrl(reference);
    try {
        data = downloadUrl(url);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return data;
  }
}

---

在将

qry

传递到

encode（）

方法之前，请检查其是否为空，如下所示

try {

    if (qry != null) {

        qry = "input=" + URLEncoder.encode(qry, "utf-8"); //This is line 266

    }

} catch (UnsupportedEncodingException e1) {
    e1.printStackTrace();
}

---

qry为空。。。请退房

try {

    if (qry != null) {

        qry = "input=" + URLEncoder.encode(qry, "utf-8"); //This is line 266

    }

} catch (UnsupportedEncodingException e1) {
    e1.printStackTrace();
}