Thiemo's Android, IP-Symcon und Raspberry Welt

Details: Geschrieben von admin; Kategorie: Android; Veröffentlicht: 01. Januar 2018; Zugriffe: 331

Hallo,

wenn folgende Meldung kommt (String concatenation '+' in loop; ... usually it is preferable to replace it with explicit calls to StringBuilder.append() or StringBuffer.append()

Dann kann man das vorhandene Coding relativ einfach umbauen.

Hier ein Beispiel:

Coding mit Warnung:

private String getRestOfSplit(String text) {
 StringTokenizer tokens = new StringTokenizer(text, " ");
 tokens.nextToken();// this will contain password
 String second = "";
 
 // loop through tokens
 while (tokens.hasMoreTokens()) {
 second = second + " " + tokens.nextToken();
 }
 
 //Log.d(TAG, "Text rest with trim is: " + second);
 return second.replaceFirst("^ *", "");
 }

private String getRestOfSplit(String text) {
 StringTokenizer tokens = new StringTokenizer(text, " ");
 tokens.nextToken();// this will contain password
 String second = "";

 // loop through tokens
 while (tokens.hasMoreTokens()) {
 second = second + " " + tokens.nextToken();
 }

 //Log.d(TAG, "Text rest with trim is: " + second);
 return second.replaceFirst("^ *", "");
 }

Neues Coding:

 private String getRestOfSplit(String text) { //example input for text: "password do some things"
 StringTokenizer tokens = new StringTokenizer(text, " ");
 tokens.nextToken(); // this will contain "password", we don't need it so we don't assign it to a variable
 StringBuilder second = new StringBuilder(); //changed to StringBuilder; here we want "do some things"
 
 // loop through tokens
 while (tokens.hasMoreTokens()) {
 // second = second + " " + tokens.nextToken(); old coding
 second.append(" ").append(tokens.nextToken()); //new coding
 }
 
 //Log.d(TAG, "Text rest with trim is: " + second);
 //return second.replaceFirst("^ *", ""); old coding
 return second.toString().replaceFirst("^ *", ""); //new coding replace first blank with nothing (eliminate the space)
 }

 private String getRestOfSplit(String text) { //example input for text: "password do some things"
 StringTokenizer tokens = new StringTokenizer(text, " ");
 tokens.nextToken(); // this will contain "password", we don't need it so we don't assign it to a variable
 StringBuilder second = new StringBuilder(); //changed to StringBuilder; here we want "do some things"

 // loop through tokens
 while (tokens.hasMoreTokens()) {
 // second = second + " " + tokens.nextToken(); old coding
 second.append(" ").append(tokens.nextToken()); //new coding
 }

 //Log.d(TAG, "Text rest with trim is: " + second);
 //return second.replaceFirst("^ *", ""); old coding
 return second.toString().replaceFirst("^ *", ""); //new coding replace first blank with nothing (eliminate the space)
 }

Details: Geschrieben von admin; Kategorie: Android; Veröffentlicht: 01. Januar 2018; Zugriffe: 444

Bewertung: 5 / 5

Um folgende Android Studio Meldung "This AsyncTask class should be static or leaks might occur" zu vermeiden, kann man entsprechend in einen Async Task über eine Hilfsklasse sämtliche Parameter übergeben.

Hier ein Beispiel (wobei location bereits ermittelt wurde; siehe diverse Android Foren/Hilfen auf Google). Mittels result wird das Ergebnis von der Methode doInBackground in die Methode postExecute vom AsyncTask übergeben

 String link = "https://maps.googleapis.com/maps/api/geocode/json?latlng="+location.getLatitude()+","+location.getLongitude()+"&amp;key=YourAPIKey";
 GetLocationDownloadTask getLocation = new GetLocationDownloadTask();
 MyTaskParams params = new MyTaskParams(context, link, "");
 getLocation.execute(params);

 String link = "https://maps.googleapis.com/maps/api/geocode/json?latlng="+location.getLatitude()+","+location.getLongitude()+"&key=YourAPIKey";
 GetLocationDownloadTask getLocation = new GetLocationDownloadTask();
 MyTaskParams params = new MyTaskParams(context, link, "");
 getLocation.execute(params);

//private class to put parameter to AsyncTask
 private static class MyTaskParams {
 Context context;
String urlString;
 String result;
 
 MyTaskParams(Context context, String urlString, String result) {
 this.context = context;
this.urlString = urlString;
 this.result = result;
 }
 }
 
 public static class GetLocationDownloadTask extends AsyncTask<MyTaskParams, Void, MyTaskParams> {
 
 @Override
 protected MyTaskParams doInBackground(MyTaskParams... params) {
String urlString = params[0].urlString;  //fetch parameter; other parameter for example params[0].context we do not need in doInBackground method
 StringBuilder sb = new StringBuilder();
 URL url;
 HttpURLConnection urlConnection;
 try {
 url = new URL(urlString);
 urlConnection = (HttpURLConnection) url.openConnection();
 InputStream is = urlConnection.getInputStream();
 InputStreamReader inputStreamReader = new InputStreamReader(is);
 
 int data = inputStreamReader.read();
 
 while (data != -1) {
 char curr = (char) data;
 //result += curr;
 sb.append(curr);
 data = inputStreamReader.read();
 }
 params[0].result = sb.toString();
 return params[0];
 } catch (Exception e) {
 e.printStackTrace();
 }
 return null;
 }
 
 @Override
 protected void onPostExecute(MyTaskParams myTaskParams) {
 super.onPostExecute(myTaskParams);
 
 if (myTaskParams != null) {
 try {
 JSONObject locationObject = new JSONObject(myTaskParams.result);
 JSONObject locationAddress = locationObject.getJSONArray("results").getJSONObject(0).getJSONObject("formatted_address");
 updateAddress(locationAddress.toString(), myTaskParams.context);
 } catch (JSONException e) {
 e.printStackTrace();
 }
 }
 }
 
 private void updateAddress(String address, Context context) {
 //Log.d(TAG, "updateAddress");
 
 //Send to your app broadcast receiver for new address
 Intent filterRes = new Intent();
 filterRes.setAction("YOURACTION");
 filterRes.putExtra("address", address);
 context.sendBroadcast(filterRes);
 }
 
 }

//private class to put parameter to AsyncTask
 private static class MyTaskParams {
 Context context;
String urlString;
 String result;

 MyTaskParams(Context context, String urlString, String result) {
 this.context = context;
this.urlString = urlString;
 this.result = result;
 }
 }

 public static class GetLocationDownloadTask extends AsyncTask<MyTaskParams, Void, MyTaskParams> {

 @Override
 protected MyTaskParams doInBackground(MyTaskParams... params) {
String urlString = params[0].urlString;  //fetch parameter; other parameter for example params[0].context we do not need in doInBackground method
 StringBuilder sb = new StringBuilder();
 URL url;
 HttpURLConnection urlConnection;
 try {
 url = new URL(urlString);
 urlConnection = (HttpURLConnection) url.openConnection();
 InputStream is = urlConnection.getInputStream();
 InputStreamReader inputStreamReader = new InputStreamReader(is);

 int data = inputStreamReader.read();

 while (data != -1) {
 char curr = (char) data;
 //result += curr;
 sb.append(curr);
 data = inputStreamReader.read();
 }
 params[0].result = sb.toString();
 return params[0];
 } catch (Exception e) {
 e.printStackTrace();
 }
 return null;
 }

 @Override
 protected void onPostExecute(MyTaskParams myTaskParams) {
 super.onPostExecute(myTaskParams);

 if (myTaskParams != null) {
 try {
 JSONObject locationObject = new JSONObject(myTaskParams.result);
 JSONObject locationAddress = locationObject.getJSONArray("results").getJSONObject(0).getJSONObject("formatted_address");
 updateAddress(locationAddress.toString(), myTaskParams.context);
 } catch (JSONException e) {
 e.printStackTrace();
 }
 }
 }

 private void updateAddress(String address, Context context) {
 //Log.d(TAG, "updateAddress");

 //Send to your app broadcast receiver for new address
 Intent filterRes = new Intent();
 filterRes.setAction("YOURACTION");
 filterRes.putExtra("address", address);
 context.sendBroadcast(filterRes);
 }

 }

Android Programmierung - StringBuilder String concatenation '+' in loop

Android Programmierung - static AsyncTask

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