I'm a rookie programmer, and I'm trying to setup a function to pass a TextView or an array of TextViews to a function, so it can be called at various points in the activity.
public class ScoreboardActivity extends Activity {
...
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_scoreboard);
...
final TextView STATVIEW1A = (TextView) findViewById(R.id.place_stat1a); //Team 1
final TextView STATVIEW1B = (TextView) findViewById(R.id.place_stat1b);
final TextView STATVIEW1C = (TextView) findViewById(R.id.place_stat1c);
final TextView STATVIEW1D = (TextView) findViewById(R.id.place_stat1d);
final TextView STATVIEW2A = (TextView) findViewById(R.id.place_stat2a); //Team 2
final TextView STATVIEW2B = (TextView) findViewById(R.id.place_stat2b);
final TextView STATVIEW2C = (TextView) findViewById(R.id.place_stat2c);
final TextView STATVIEW2D = (TextView) findViewById(R.id.place_stat2d);
//final TextView[] STATVIEW = {STATVIEW1A,STATVIEW1B,STATVIEW1C,STATVIEW1D,
// STATVIEW2A,STATVIEW2B,STATVIEW2C,STATVIEW2D};
...
postStats();
... or
postStats(STATVIEW[]);
I want to have a routine to post the (8) TextViews on my activity_scoreobard layout. I have tried just referencing the STATVIEW1A in the function:
public void postStats () {
STATVIEW1AX.setText("#dumps: " + Integer.toString(DUMP1[GAME_NO]));
}
I have also tried referencing each of the TextViews from passing an array of TextViews in the function:
public void postStats (TextView[] VIEWSTAT) {
VIEWSTAT[6].setText("#dumps: "+ Integer.toString(DUMP2[GAME_NO]));
}
While both don't show errors in Eclipse, the program does not like either situation.
Generally it's not a good idea to pass them to function...
but if you want you can try something like this...
TextView[] STATVIEW = new TextView[SIZE];
then to initialize
STATVIEW[0] = (TextView) findViewById(R.id.place_stat1a); //Team 1
STATVIEW[1] = (TextView) findViewById(R.id.place_stat1b);
......
then pass your Array
postStats(STATVIEW);
Alternative would be
create a method and pass the values and set them to TextViews
something like this
public void fillData(String[] data)
{
for (int i=0;i<STATVIEW.length;i++)
{
STATVIEW[i].setText(data[i]);
}
}
It is better to use an array of WeakReference objects to hold the references to your Text views and initialize this array in the OnCreate method of your activity, using this method everytime that system destroy your activity the references to the items can be garbage collected automatically and you won't cause memory leaks. As far as i know the standard way for holding a reference to an ephemeral object like the activity itself or a views on it is to use WeakReference objects.
For understanding what a WeakReference is read the following article on Wikipedia:
http://en.wikipedia.org/wiki/Weak_reference
Also read this page:
https://developer.android.com/reference/java/lang/ref/WeakReference.html
Instead of Overloading postStats() function you can try using postStats(TextView... VIEWSTAT). In this function you can check the number of arguments by VIEWSTAT.length.
ArrayList<TextView> tmpArrayList = new ArrayList<TextView>();
for(int y=0; y<10; y++)
{
tmpArrayList.add(getTextView(txtBoxCount++));
}
this.postStats(tmpArrayList);
private TextView getTextView(int i)
{
int id=0;
try {
id = R.id.class.getField("textview" + i).getInt(0);
}
catch (IllegalArgumentException e) {
e.printStackTrace();
}
catch (SecurityException e) {
e.printStackTrace();
}
catch(IllegalAccessException e) {
e.printStackTrace();
}
catch (NoSuchFieldException e) {
e.printStackTrace();
}
textview = (TextView)findViewById(id);
textview.setTag("0");
return textview;
}
public void postStats (ArrayList<TextView> viewstat) {
//do some work here
}
Related
I am trying to change the text of a TextView on my Activity. It happens in a method in the same class as the onCreate method. However, it does not work. I've googled it but found nothing.
This is the error I got:
Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference.
This is the Main Activity, where my TextView is located:
private static TextView welcome;
private static TextView counter;
private static int number;
private static SharedPreferences sharedPreferences;
#Override
protected void onCreate(Bundle savedInstanceState) {
//Shared Preferences getting called to see if the user has set his name
SharedPreferences sharedpreferences = getSharedPreferences("name", Context.MODE_PRIVATE);
//Getting number
this.number = sharedpreferences.getInt("number", 0);
this.sharedPreferences = sharedpreferences;
Boolean continueName = false;
//Checking if name is set
if (!sharedpreferences.getBoolean("nameSet", false)) {
//If name is not set
Intent intent = new Intent(this, Name.class);
startActivity(intent);
} else {
//if name was already set, default activity pops Up
continueName = true;
}
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//getting counter and setting it
TextView count = (TextView) findViewById(R.id.txtNumber);
this.counter = count;
//Actionlistener to +1 Button
ActionListeners al = new ActionListeners();
Button plusOne = (Button) findViewById(R.id.btnAddOne);
plusOne.setOnClickListener(al.getPlusOneListener());
//Setting Text View Object
this.welcome = (TextView) findViewById(R.id.welcomeUser);
//If the name is set
if (continueName) {
this.welcome.setText(getString(R.string.welcome) + " " + sharedpreferences.getString("usersName", ""));
}
}
public void setNameNew() throws InterruptedException {
TextView welcomeThis = this.welcome;
new Thread(new Runnable() {
public void run() {
//Setting welcome text
SharedPreferences sp = getSharedPreferences("name", Context.MODE_PRIVATE);
welcomeThis.setText(getString(R.string.welcome) + " " + sp.getString("usersName", ""));
}
});
Thread.sleep(500);
this.welcome.setText(welcomeThis.getText());
}
public void changeViewNumber(int number) {
//Setting new number
this.counter.setText(number);
}
}
Weird is, that the setNameNew method is working and can change the text of the TextField. But the changeViewNumber method is not working.
Im on the activity where the TextView is located. I can't figure it out. May you please help me?
You can call setText for a TextView anywhere in the class as long as the TextView is referenced. When you say one function is working and the other isn't, it's because the reference for the counter is incorrect.
Your counter reference
TextView count = (TextView) findViewById(R.id.txtNumber);
this.counter = count;
Your welcome reference
this.welcome = (TextView) findViewById(R.id.welcomeUser);
You should be referencing the view the way you referenced welcome. You'll want to change the counter reference to the following.
this.counter = (TextView)findViewById(R.id.txtNumber)
Your count variable does nothing and should be removed.
I would also like to make additional notes for your code. You are using the keyword this, it isn't necessary for your code.
The this keyword refers to the current object in a method or constructor.
The most common use of the this keyword is to eliminate the confusion between class attributes and parameters with the same name (because a class attribute is shadowed by a method or constructor parameter.
I would also strongly recommend not putting the main thread to sleep, if the thread is sleeping and action is required it will cause your app to crash.
This is useless
TextView count = (TextView) findViewById(R.id.txtNumber);
this.counter = count;
Just do
counter = findViewById(R.id.txtNumber);
This is because you've declared welcome variable globally in class and initialized in onCreate but you forget to initialize counter on the OnCreate method which is why it is throwing a null pointer exception.
this.counter = (TextView) findViewById(R.id.txtNumber);
just initialize your counter variable just like you did on your welcome variable.
The problem was, that I tried to set the text of a TextView with an Integer
The fix was:
String numberString = Integer.toString(number);
counter.setText(numberString);
I've searched all the posts I can find, and none seem to help with my situation. I have an android project that uses web services to pull down hourly weather data and populate a listView with the results.
The weird problem I'm having is that when I debug the project on my android phone, the main activity is blank and the listView isn't populated. If I run the project from android studio with my phone locked, and then unlock my phone the app opens on my phone with all of the listView properly formatted and populated.
I feel like it's a race condition issue between the asynctask and the adapter, but I can't seem to resolve it. I tried making my asyncTask an inner private class and calling notifyDataSetChanged on the adapter inside the onPostExecute method, but to no avail. I feel it must be something simple, but I'm relatively new to Android dev, so I'm stuck.
I have three classes that I'll post the pertinent code from
MainActivity.java (onCreate)
public class MainActivity extends ActionBarActivity {
ArrayList<Weather> w = new ArrayList<Weather>();
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DownloadWeatherTask myTask = new DownloadWeatherTask(w);
WeatherAdapter myAdapter = new WeatherAdapter(this,w);
ListView l = (ListView) findViewById(R.id.weatherList);
l.setAdapter(myAdapter);
myTask.execute();
}
}
WeatherAdapter.java
public class WeatherAdapter extends ArrayAdapter<Weather>{
public WeatherAdapter(Context context, ArrayList<Weather> weather) {
super(context, R.layout.item_weather, weather);
}
public View getView(int position, View convertView, ViewGroup parent) {
// Get the data item for this position
Weather forecast = getItem(position);
// Check if an existing view is being reused, otherwise inflate the view
if (convertView == null) {
convertView = LayoutInflater.from(getContext()).inflate(R.layout.item_weather, parent, false);
}
// Lookup view for data population
TextView tvTime = (TextView) convertView.findViewById(R.id.listTime);
TextView tvDescr = (TextView) convertView.findViewById(R.id.listDescr);
TextView tvTemp = (TextView) convertView.findViewById(R.id.listTemp);
TextView tvHumid = (TextView) convertView.findViewById(R.id.listHumid);
ImageView ivWeather = (ImageView) convertView.findViewById(R.id.weatherImg);
// Populate the data into the template view using the data object
tvTime.setText(forecast.time);
tvDescr.setText(forecast.description);
tvTemp.setText(forecast.temperature+"°(F)");
tvHumid.setText(forecast.humidity+"% humidity");
ivWeather.setImageBitmap(forecast.weatherImg);
// Return the completed view to render on screen
return convertView;
}
}
DownloadWeatherTask.java
public class DownloadWeatherTask extends AsyncTask<Void,Void,Void>{
ArrayList<Weather> data;
public DownloadWeatherTask(ArrayList<Weather> a){
data = a;
}
public ArrayList<Weather> getData() {
return data;
}
protected Void doInBackground(Void...params) {
try {
String website = "http://api.wunderground.com/api/1111111111111/geolookup/q/autoip.json";
URL site = new URL(website);
HttpURLConnection weatherUnderground = (HttpURLConnection) site.openConnection();
weatherUnderground.connect();
JsonParser weatherParser = new com.google.gson.JsonParser();
JsonElement weatherJson = weatherParser.parse(new InputStreamReader((InputStream) weatherUnderground.getContent()));
JsonObject weatherObj = weatherJson.getAsJsonObject();
String zip = weatherObj.get("location").getAsJsonObject().get("zip").getAsString();
String city = weatherObj.get("location").getAsJsonObject().get("city").getAsString();
String state = weatherObj.get("location").getAsJsonObject().get("state").getAsString();
String hourly = "http://api.wunderground.com/api/111111111111/hourly/q/" + state + "/" + city + ".json";
URL hourlySite = new URL(hourly);
HttpURLConnection hourlyConnection = (HttpURLConnection) hourlySite.openConnection();
hourlyConnection.connect();
com.google.gson.JsonParser hourlyParser = new com.google.gson.JsonParser();
JsonElement hourlyWeatherJson = weatherParser.parse(new InputStreamReader((InputStream) hourlyConnection.getContent()));
JsonArray weatherArr = hourlyWeatherJson.getAsJsonObject().get("hourly_forecast").getAsJsonArray();
int l = weatherArr.size();
for (int i = 0; i < l; i++) {
String date = weatherArr.get(i).getAsJsonObject().get("FCTTIME").getAsJsonObject().get("pretty").getAsString();
String temp = weatherArr.get(i).getAsJsonObject().get("temp").getAsJsonObject().get("english").getAsString();
String condition = weatherArr.get(i).getAsJsonObject().get("condition").getAsString();
String humidity = weatherArr.get(i).getAsJsonObject().get("humidity").getAsString();
String iconUrl = weatherArr.get(i).getAsJsonObject().get("icon_url").getAsString();
Bitmap icon = getBitmapFromURL(iconUrl);
data.add(new Weather(date, condition, temp, humidity, icon));
}
} catch (IOException e) {
Log.e("Error: ",e.toString());
}
return null;
}
protected void onPostExecute(Void...params){
}
}
Below are links to my screenshots showing the app not populating the listView, and the app working properly when the program is run while the phone is initially locked.
Any help would be greatly appreciated!!
Thanks
In postExecute(), you need to update the adapter's List and then invoke its notifyDataSetChanged method. I suspect that you were forgetting to update the adapter's data.
The other option is to create a new adapter with the new data, and set the new adapter on the ListView.
I figured out what the issue was! I hadn't added #Override to my onPostExecute() method so it was never being called.
I added the notifyDataSetChanged to my onPostExecute as suggested, which worked once I added the #override to my method.
It is always the little things that stump me for hours.
I have an onPostExecute method from an AsyncTask class that looks like so:
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
showColumnCounts();
dataDownloadCompleteToast();
}
The toast works just fine. However, my showColumnCounts() method refuses to work. It works just fine on the main thread. I use it during onCreate() just not here. I thought the onPostExecute ran on the UI thread?
Here is my showColumnCounts() method if it is relevant.
public void showColumnCounts() {
TextView totalView = (TextView) findViewById(R.id.totalColumn2);
TextView ignoredView = (TextView) findViewById(R.id.ignoredColumn2);
TextView rView = (TextView) findViewById(R.id.rColumn2);
Cursor c = myDB.getEmptyRColumn("");
int count = c.getCount();
if (count == 0) {
c.close();
return;
}
String unread = String.valueOf(count);
String total = getTotalCount();
int tTotal = Integer.parseInt(total);
int r = tTotal - count;
String read = String.valueOf(r);
totalView.setText(total);
ignoredView.setText(unread);
rView.setText(read);
c.close();
}
I've been fiddling with it for a while now assuming the answer should be obvious but I'm calling uncle. Can't figure it.
Edit***** 6/30
I THINK I've found my problem. In my background thread I am using a parse.com method "query.findInBackground" which I assume is starting a third thread? I'm trying to update this to "query.find" and I'm hoping that will fix.
First of all you should move all your TextView declarations inside your onCreate method
if you want to change or perform some UI operation, if you want to perform some non UI based operations while the thread is running then do that in doInBackground() method
You should move …setText(...) lines into
runOnUiThread(new Runnable(){
void run(){
// UI stuff
});
You need to tell where is your async class located and the showColumnCounts() function located.
If they both where in different class then you should create a context to call the function from the async class.
Take this as example and try.
Example:
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.main);
new AsyncClass(this);
super.onCreate(savedInstanceState);
}
public void showColumnCounts() {
TextView totalView = (TextView) findViewById(R.id.totalColumn2);
TextView ignoredView = (TextView) findViewById(R.id.ignoredColumn2);
TextView rView = (TextView) findViewById(R.id.rColumn2);
Cursor c = myDB.getEmptyRColumn("");
int count = c.getCount();
if (count == 0) {
c.close();
return;
}
String unread = String.valueOf(count);
String total = getTotalCount();
int tTotal = Integer.parseInt(total);
int r = tTotal - count;
String read = String.valueOf(r);
totalView.setText(total);
ignoredView.setText(unread);
rView.setText(read);
c.close();
}
public class AsyncClass extends AsyncTask<String, Void, Boolean> {
private Activity activity;
public AsyncClass(Activity main_activity) {
this.activity = main_activity;
}
#Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
activity.showColumnCounts();
dataDownloadCompleteToast();
}
}
}
If you want to do some UI change process in background running operation(ASYNC TASK),you write that codes in UI thread. Example:
YourActivity.this.runOnUiThread(
new Runnable()
void run()
{
//UI changes
showColumnCounts();
});
I want to create a connection through socket but I'm having trouble with the graphic of my App:
This is my activity:
public class Messaggi2 extends ActionBarActivity{
LinearLayout mLayout;
ScrollView scroll;
EditText scriviMessaggi;
Button invia;
Socket connessione;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.messaggi2);
mLayout = (LinearLayout) findViewById(R.id.LinearScrollLayout);
scroll = (ScrollView) findViewById(R.id.scrollView2);
scriviMessaggi = (EditText) findViewById(R.id.Scrivi);
invia = (Button) findViewById(R.id.Invia);
LavoraDietro asd = new LavoraDietro(connessione);
asd.execute();
}
private TextView createNewTextView(String text) {
final LinearLayout.LayoutParams lparams = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT); final TextView textView = new TextView(this);
textView.setLayoutParams(lparams);
textView.setText(text);
textView.setBackgroundResource(R.drawable.balloon_broadcast_incoming_pressed);
return textView;
}
private TextView createNewTextViewSent(String text) {
final LinearLayout.LayoutParams llparams = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
llparams.gravity = Gravity.RIGHT;
final TextView textViewSent = new TextView(this);
textViewSent.setLayoutParams(llparams);
textViewSent.setText(text);
textViewSent.setBackgroundResource(R.drawable.balloon_outgoing_normal);
return textViewSent;
}
public void AggiungiTextALlayout(String messaggio){
mLayout.addView(createNewTextView(messaggio));
aggiornaScroll();
}
public void AggiungiTextInviatoALlayout(String messaggio){
mLayout.addView(createNewTextViewSent(messaggio));
aggiornaScroll();
}
public void aggiornaScroll(){
scroll.post(new Runnable() {
#Override
public void run() {
scroll.fullScroll(View.FOCUS_DOWN);
}
});
}
}
This is my AsynTask class:
public class LavoraDietro extends AsyncTask<Void, Void, Socket> {
Socket connessione;
boolean vediSeDeviPartire;
Messaggi2 mess = new Messaggi2();
public LavoraDietro(Socket connessione){
this.connessione = connessione;
}
#Override
protected Socket doInBackground(Void... params){
try {
InetAddress local = InetAddress.getByName("192.168.1.71");
connessione = new Socket(local , 7000);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
return null;
}catch(Exception e){
e.printStackTrace();
}
return connessione;
}
#Override
protected void onPostExecute(Socket result) {
super.onPostExecute(result);
if(result != null){
vediSeDeviPartire = true;
mess.AggiungiTextALlayout("Sono connesso al server");
mess.AggiungiTextALlayout("I canali sono aperi..");
}
else{
mess.AggiungiTextALlayout("ERRORE CONNESSIONE AL SERVER ");
}
}
}
Using this code when I start my app the connection is established and then it crashes. What I see on my Logcat is this Exception:
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
So I tried to delete the content of my onPostExecute and everything works perfect. So the mistake is to try to call the method AggiungiTextAlLayout on my AsyncTask class.
Can someone help me with this? Can someone suggest me something? I'm new in this field so I know that this is a stupid thing but I need help.
Thanks guys in advance
EDITED WITH THE SOLUTION
Thanks to Ataulm I got the problem and I solved it I changed the costructor of my LavoraDietro class (unfortunatly I can't change the name of variables and classes in English. But next time I ll use english Name of course )
LavoraDietro Class
public class LavoraDietro extends AsyncTask<Void, Void, Socket> {
Socket connessione;
boolean vediSeDeviPartire;
Messaggi2 action;
public LavoraDietro(Socket connessione, Messaggi2 action){
this.connessione = connessione;
this.action = action;
}
#Override
protected Socket doInBackground(Void... params){
try {
InetAddress local = InetAddress.getByName("192.168.1.71");
connessione = new Socket(local , 7000);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
return null;
}catch(Exception e){
e.printStackTrace();
}
return connessione;
}
#Override
protected void onPostExecute(Socket result) {
super.onPostExecute(result);
if(result != null){
vediSeDeviPartire = true;
action.AggiungiTextALlayout("Sono connesso al server");
action.AggiungiTextALlayout("I canali sono aperi..");
}
else{
action.AggiungiTextALlayout("ERRORE CONNESSIONE AL SERVER ");
}
}
}
And in the Messaggi2 class I changed the call of the constructor in this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.messaggi2);
mLayout = (LinearLayout) findViewById(R.id.LinearScrollLayout);
scroll = (ScrollView) findViewById(R.id.scrollView2);
scriviMessaggi = (EditText) findViewById(R.id.Scrivi);
invia = (Button) findViewById(R.id.Invia);
LavoraDietro asd = new LavoraDietro(connessione, this);
asd.execute();
Your AsyncTask has a reference to mess which is an object of type Messaggi2.
Messaggi2 is a subclass of Activity. You attempt, inside your AsyncTask, to create a new instance of that class.
The Android system has no awareness of this object; it has called none of the life cycle methods, such as onCreate() where the activity's layout would typically be inflated. This means that none of your views are inflated nor even initialised.
When you call mess.AggiungiTextALlayout("Sono connesso al server");, mLayout is null.
The NPE you see may likely not even be this one.
TL;DR: don't instantiate your Activity objects like Java objects; use them as specified within the Android framework.
I suspect you have this Activity starting correctly somewhere. The mistake is that you've not associated that activity with your Asynctask. When you create LavoraDietro, you pass a reference to the Socket in the constructor; you can also pass a reference to your activity, and assign that to the mess field, instead of calling new Messaggi2(). I'm not advocating this structure. But that is the issue at hand.
A few general tips to help you avoid this in future / or spot it faster:
be consistent with your naming; it's difficult to read your code when you're switching between English and Italian.
it's equally difficult for others to read your code if you don't maintain follow Java conventions with class/method names.
When you're extending Activity, it's typical to append the word "Activity" after your class; in this example new Messaggi2Activity() would have been easier to spot.
Where you're able, pass a Class's dependencies as parameters in the constructor; don't rely on constructing these dependencies yourself inside that class. Once you do this, you can begin to draw lines around what your class is responsible for; the less it's responsible for, the harder it is for your class to mess up.
That problem is for put a variable with no "data", verify your variables
In my Activity I have to add 10 times the same TextView.
Is it possible to load the definition of textview from layout.xml and repeat it programmatically?
for(int i=0;i<10;i++){
Textview text = new TextView(this);
mainlayout.add(text);
}
public class YourClassName extends Activity
{
#Override
public void onCreate(Bundle bundle)
{
super.onCreate(bundle);
// set activity layout
setContentView(R.layout.some_activity_layout);
LinearLayout mainActivityLayout = (LinearLayout)findViewById(R.id.main_layout);
LayoutInflater li = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
// then see previous answer
// loop n times {
TextView yourTextView = _li.inflate(R.layout.text_view_layout, null);
mainActivityLayout.addView(yourTextView);
// } end loop
}
}
You may want to read this article on reusing UI components: http://developer.android.com/resources/articles/layout-tricks-reuse.html