I have an app that connects to bluetooth and displays information received.
when pressing back, the activity isn't killed and I can go back to the activity and everything is the same. The activity collects the data in the background and everything is okay
I have a button, that when pressed, kills all activities (including the activity that displays the data).
When I try to create that activity again, the data keeps coming, and I can still handle it and write it to a file, but it won't show it in the UI. It seems the setText function in the handler doesn't work after the activity is created the second time (setText does work outside of the handler).
The boolean value synced is true if the activity is created a second time.
This is OnCreate
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_admin);
loading_panel = findViewById(R.id.loadingPanel);
loading_panel.setVisibility(View.GONE);
connectionButton = (Button) findViewById(R.id.connection_button);
gsrTextView = (TextView) findViewById(R.id.gsr_textview);
emgTextView = (TextView) findViewById(R.id.emg_textview);
adxlTextView = (TextView) findViewById(R.id.adxl_textview);
fsrTextView = (TextView) findViewById(R.id.fsr_textview);
textviews_set=true;
if(synced)
{
setConnected(currMac);
manageConnection();
Button sync_button = (Button) findViewById(R.id.sync_button);
sync_button.setText(R.string.synced_text);
}
// more code
}
Implementation of OnBackPressed:
#Override
public void onBackPressed() {
Intent i = new Intent(AdminActivity.this, MainActivity.class);
i.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(i);
}
This is (part of) the handler:
#SuppressLint("HandlerLeak")
public final Handler handler = new Handler() {
#Override
public void handleMessage(#NonNull Message msg) {
super.handleMessage(msg);
switch (msg.what) {
//a lot of code for other cases
case READ_SUCCESS:
String s = (String) msg.obj;
showData(s);
break;
}
}
}
This is (part of) showData:
private void showData(String s) {
// todo: 1.parse the json; 2.show data (json components) on the textViews
try {
//Log.d(LOG_TAG, "the new string is " + s);
JSONObject json = new JSONObject(s);
// Collect the sensors measurements
String gsrMeasure = json.getString("gsr");
String emgMeasure = json.getString("emg");
String adxlMeasure = json.getString("adxl");
String fsrMeasure = json.getString("fsr");
String time_str = json.getString("time");
// Show the data
if(textviews_set) {
runOnUiThread(new Runnable() {
#Override
public void run() {
Log.d(LOG_TAG, "ABOUT TO SET TEXT");
gsrTextView.setText(gsrMeasure);
emgTextView.setText(emgMeasure);
adxlTextView.setText(adxlMeasure);
fsrTextView.setText(fsrMeasure);
}
});
}
//more code
}
}
I even made sure that I'm running the setText on UI thread even though it works on the first run of the activity without the runOnUiThread
I also thought that maybe the handler is called before the findViewByIDs are called but I used a boolean variable textviews_set to make sure it doesn't happen
It is worth mentioning that when I create the activity for the first time, the bluetooth device isn't connected and thus the handler isn't running, so there's a really good chance that the problem lies there. I just don't know exactly where, or how to solve it.
I found out what the problem was, if anyone gets stuck with the same issue.
I declared all the textviews as non-static, thus when creating the activity the second time, for some reason the handler still referred to the textviews of the first instance of the activity.
All I had to do was declare the textviews in the class as static, so when I create the activity for the second time, the textviews are already declared and refer to the actual textviews in the xml.
Based on the information provide the follow is the best suggestion.
So try the following in onCreate() before textviews_set=true;
gsrTextView.setText(" ");
emgTextView.setText(" ");
adxlTextView.setText(" ");
fsrTextView.setText(" ");
Hope this solves issue.
Reference:
How do I declare a TextView variable so that I can use it anywhere?
Related
I am trying to get a QR code to be encoded based on data collected throughout the other fragments and sent to the MainActivity. Then, at the end, I want to call getAllData(), which returns all data in one string. It will do this when a FloatingActionButton is clicked (fabGenerate). Currently, it will load the fragment, and when you click on the fab, it will go into the correct case (R.id.fabGenerate) and run until "//error here". Also, I do NOT get an error message, due to the crash only occurring on the emulator.
String data;
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.fabGenerate:
Activity activity = getActivity();
if (activity != null && activity instanceof MainActivity) {
data = ((MainActivity) activity).getAllData(); //error here
}
qrgEncoder = new QRGEncoder(data, null, QRGContents.Type.TEXT, ((MainActivity)getActivity()).getDimen());
break;
}
}
I have tried first having data within the qrgEncoder line, where it will only do
qrgEncoder = new QRGEncoder(((MainActivity) getActivity).getAllData(), null, QRGContents.Type.TEXT, ((MainActivity)getActivity()).getDimen());
This did not work, and would still crash ONLY when it was run, not built.
I have also tried using Toast.makeText's to print a line, which determined that the error is within this piece of code.
Currently i managed to create the buttons dynamically on a view
Here is the my code to create the buttons;
public void Add_on(View v) {
AlertDialog.Builder mbuilder = new AlertDialog.Builder(Mb.this);
View mview = getLayoutInflater().inflate(R.layout.activity_mb1, null);
EditText number = (EditText) mview.findViewById(R.id.etnum);
Button Create = (Button) mview.findViewById(R.id.etcreate);
Button Cancel = (Button) mview.findViewById(R.id.etcancel);
Create.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view){
if (!number.getText().toString().isEmpty())
{
Toast.makeText(Mb.this, "Number can be NULL",Toast.LENGTH_SHORT).show();
LinearLayout yenilayout = new LinearLayout(Mb.this);
int n =1;
for(int i=0; i<n; i++)
{
Button yeniButton = new Button(Mb.this);
yenilayout.addView(yeniButton);
yeniButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(Mb.this, "Button is working",Toast.LENGTH_SHORT).show();
}
});
}
altlayout.addView(yenilayout);
} else {
Toast.makeText(Mb.this, "Number cannot be NULL",Toast.LENGTH_SHORT).show();
}
}
});
But whenever i recall the activity, the buttons are no longer exist. So May i know can i place the button there permanently?
Thank you for suggestions
You can use Bundle to save an activity's state and recreate it in the onCreate() method. This works for a particular instance of Activity, so can be used to save data concerning selection, or user input etc., but not data that you need to be persistent across application launches.
To use the Bundle, override the onSaveInstanceState(Bundle) and onRestoreInstanceState(Bundle) methods in the Activity class. You can use methods from Bundle to save whatever data you like in a map, and get it back in onRestoreInstanceState(Bundle), which is called in onStart().
The default implementations already handle most UI stuff though, and I would have thought this would keep track of your buttons for you, so it may be that your question is actually about associating some persistent data with your application. (this also means that if you do override the above methods, you should make sure to call the super methods in the first line of your implementation).
If you need persistent data across application launches, then the quickest and easiest way would be to use SharedPreferences, see this answer for an example.
Below is the code which I'm using to return a number which should be 1 when the button is clicked. However when I try to get that number from another class, it always stays 0.
As you might recognize, I tried to change the number in the onClickListener and returned it below.
I also tried to use the onPause command so that it will return the number onPause but it still doesn't work.
public class MainActivity extends Activity {
public int number;
Button btnAngled;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
btnAngled = (Button) findViewById(R.id.btnAngled);
final Intent intent = new Intent(this, angledForeheadActivity.class);
btnAngled.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
number = 1;
startActivity(intent);
}
});
}
#Override
protected void onPause() {
super.onPause();
}
public int getNumber() {
return number;
}
}
I try to get the code in another class with:
MainActivity a = new MainActivity();
int number = a.getNumber();
Sorry for the noob question..
declare the variable as static variable. Then you can simply obtain the result you want since there is only one copy of that variable. If you want to pass the value using intent, you can call putExtra() of intent to carry information to another activity.
Intent reference page
What you actually want is getting the number from another Class. Don't mix the job with button click together. You should setup the concept of model to store data and seperate UI and data, UI just change/get the data.
I suggest you either of the two ways
Store the number in some global model, then you can get the number from another Class.
User Android Broadcast to transfer the data
Use static variable in Activity is not a good idea, it may cause memroy leak, though it can solve your problem.
I'm using Eclipse for windows 7 and I am making an informative application(just text and offline content).
In my app I have about 180 buttons. Each button will lead to another screen. I need to know how to make each button lead to a specific screen?
And also, is there a way to like duplicate the code and not spend hours copying and pasting the code 180 times?
Check my code below for the first two screens:
That's for the MainActivity.java:
public void addListenerOnButton() {
final Context context = this;
button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent = new Intent(context, MainActivity2.class);
startActivity(intent);
}
});
}
I mean that code is only for one single button. Am I supposed to repeat this for every single button?
and also a question, how many classes should I do? 180 main activities, 180 fragment_main.xml and 180 activity_main.xml?
That's my idea, since your application is just a "informative application" you can create two activities:
Main activity with buttons
"Information page"
To do it i need info about how you get this informations:
In a SQLite Database.
In a string-array
Personally, i prefer a SQLite DB it allows you to improve it without problems in the future.
About the Information activity:
Example: in your layout you have a TextView where will be added the text which this activity should be passed.
To make it dynamic in your case we pass the string to show using Intents, in our onCreate we add something like this:
Intent intent = getIntents();
String stringToDisplay = null;
if (intent != null)
{
stringToDisplay = intent.getStringExtra (EXTRA_STRING_CONTENT);
}
getIntents will get the Intent object which is created and passed to it by our main activity. getStringExtra is a simple method which says to Android: i want to get the string which is saved with the key EXTRA_STRING_CONTENT (it's something like a Map)
EXTRA_STRING_CONTENT is a field which we used to make sure we don't make any error in passing data, since we need to use the same name when we pass it (in MainActivity) and when we read it (InformationActivity)
public static final String EXTRA_STRING_CONTENT = "EXTRA_STRING_CONTENT";
Ok, we are done.
We now only need to set the string to our TextView:
TextView infoTextView = (TextView) findViewById(R.id.infotextview);
infoTextView.setText (stringToDisplay);
Stop it.
Now we should go to our MainActivity code and modify our addListenerOnButton
final Context context = this;
button = (Button) findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent = new Intent(context, MainActivity2.class);
startActivity(intent);
}
});
Well, i will focus on this two lines
Intent intent = new Intent(context, MainActivity2.class);
startActivity(intent);
We need to pass the string to display here, how?
Before we used getStringExtra now it's similar (note: it's the same Intent class) but now we need the putExtra method, the compiler will select the correct overload for us so we just need to do
String stringToDisplay = "Hello world";
intent.putExtra(InformativeActivity.EXTRA_STRING_CONTENT, stringToDisplay);
(Note: InformativeActivity.EXTRA_STRING_CONTENT)
With the current code we will always sent Hello world to the second activity but we need something of dynamic based on the button... well now this depends on how you get the data.
If it's a string-array, you can save the string-array in an array and then based on the button (if it's the first sent string index 0, etc.).
An example:
int buttonId = 1; // it will be a general variable, if it's button 1 it will be 0, if 2-1 etc.
String[] informations = getResources().getStringArray(R.array.infos); // in a real code you should move it outside the `onClick` code and put it in a static final field.
intent.putExtra(InformativeActivity.EXTRA_STRING_CONTENT, informations[buttonId]); // it's the same of above
If you understand the concept you will know how to adapt the code based on your needs.
There are some cases where you need more info or what you want to sent is something which is better if managed by the second activity (example: in a sqlite database you could sent only the id of the line and read lines in the second activity based on this id)
Some things which you could change:
Avoid to call it MainActivity2, it's not so helpful as name
You don't need really to save Context, you could just use MainActivity.this
Try to make your addListenerOnButton more general, example take as argument a Button and set the listener to it.. don't read it from XML you will end up with 180 methods for every button.
I am a beginner in developing and I know the question may sounds very basic but, let me cut to the chase: here is my class
public class MainActivity extends Activity {
private ListView lvPhone;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lvPhone = (ListView)findViewById(R.id.listPhone);
List<PhoneBook> listPhoneBook = new ArrayList<PhoneBook>();
listPhoneBook.add(new PhoneBook(
BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher),
"blah_blah", "384765345667", "something#someprovider.com"));
listPhoneBook.add(new PhoneBook(
BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher),
"blah_blah", "34856834796", "something#someprovider.com"));
listPhoneBook.add(new PhoneBook(
BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher),
"blah_name", "868734633", "something#someprovider.com"));
PhoneBookAdapter adapter = new PhoneBookAdapter(this, listPhoneBook);
lvPhone.setAdapter(adapter);
}
}
and here I'd like it to be "attached" so then when the button is clicked the phone book comes up.
public void addListenerOnButton(){
imageButton = (ImageButton) findViewById(R.id.pb_button);
imageButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View arg0) {
Toast.makeText(MyAndroidAppActivity.this,//phone_book goes here
"ImageButton is clicked!", Toast.LENGTH_SHORT).show();//no toaster instead
}
});
}
Would any of you please help? This is going to be really helpful for me. And please if you do answer, try to explain as you're explaining to a "Java_moron" :) (as through as possible please)
[Now I did try the chat room, no reputation point so that didn't happen and I tried to google as much as possible couldn't find anything helpful; maybe there was answer but my lack of knowledge failed me.]
Thank you,
[EDIT: Or instead of using the phone book class, how can I call contacts from phone's native contact list? Anything would be helpful really.]
The best option to start would be to activate a native activity that will bring up phone book contacts and show them to the user as a list. Selected contacts is then passed to starting activity.
Explanation:
You can learn how to start an activity and receive result from the following link:
http://developer.android.com/training/basics/intents/result.html
Basically the main code do that is as follows:
static final int PICK_CONTACT_REQUEST = 1; // The request code
...
private void pickContact() {
Intent pickContactIntent = new Intent(Intent.ACTION_PICK, new Uri("content://contacts"));
pickContactIntent.setType(Phone.CONTENT_TYPE); // Show user only contacts w/ phone numbers
startActivityForResult(pickContactIntent, PICK_CONTACT_REQUEST);
}
Note that the user will be calling the startActivityForResult method this will start a new activity and once that activity is finished the System will call onActivityResult() method of the original Activity and here you will receive results to which contacts has been selected.