Develop Reference

How to save the state of a button in AndroidStudio?

I am new at programing in Java and I am taking a course of Android application. I am building a button inside an activity. But when I exit the activity, the button changes to it's original state. I know I am not doing anything to save its state, but how do I do it?
Here is the xml file (only the button part):
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/Catch"
android:id="#+id/button"
android:onClick="toggleCatch" />
And here is toggleCatch:
private boolean isCaught = false;
#SuppressLint("SetTextI18n")
public void toggleCatch(View view) {
Button button = findViewById(R.id.button);
if (isCaught) {
button.setText("Catch");
isCaught = false;
} else {
button.setText("Release");
isCaught = true;
}
}
What could I do to make it work?

you should store the data that indicate on it state in some place:
1. SQLlite
2. Server
3. SharedPreference
and then when you create the activity you set the state of the btn based on the data you loaded.
if you do it just for practice, I believe that the sharepreference will be just fine.
https://developer.android.com/training/data-storage/shared-preferences
to store any data locally in the sharedPreference:
SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putBoolean("SOME_NAME_FOR_YOUR_VARIABLE_EX_BTN_STATE", trueOrFalse);
editor.commit();
to get the saved data:
SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
boolean stateBtn = sharedPref.getBoolean("SOME_NAME_FOR_YOUR_VARIABLE_EX_BTN_STATE", defaultValueForExTrue);
sharedPref.getBoolean can be used also for sharedPref.getString, sharedPref.getInt Etc..
hope that helped..
My recommendation for you is to read about the subjects above.(SQLlite, SharedPreference)

You need to save button state in persistent storage; there are several types of persistent storage that Android supports, like SharedPreference, DataBase, internal/external storage File... The most appropriate for your question is the SharedPreference as it stores small data.
To achieve that in your code sample
public static final String PREFS_NAME = "PREFS_NAME";
public static final String BUTTON_STATUS = "status";
private boolean isCaught = false;
#SuppressLint("SetTextI18n")
public void toggleCatch(View view) {
Button button = findViewById(R.id.button);
if (isCaught) {
button.setText("Catch");
isCaught = false;
} else {
button.setText("Release");
isCaught = true;
}
SharedPreferences prefs = getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = prefs.edit();
editor.putBoolean(BUTTON_STATUS, isCaught);
editor.apply();
}
And you need to retrieve the value again from the shared preference when the app is launched, so in your activity onCreate() method:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button button = findViewById(R.id.button);
SharedPreferences prefs = getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
isCaught = prefs.getBoolean(BUTTON_STATUS, false);
if (isCaught) {
button.setText("Release");
} else {
button.setText("Catch");
}
}

Shared preference value is null in my second acivity

I need to use string data inside OnReceivedDataMethod into second activity in order to save those string data into file but currently i have empty data into my file
SharedPreferences sp;
UsbSerialInterface.UsbReadCallback mCallback = new UsbSerialInterface.UsbReadCallback() { //Defining a Callback which triggers whenever data is read.
#Override
public void onReceivedData(byte[] arg0) {
try {
data = new String(arg0, "UTF-8");
data.concat("/n");
sp = getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);
SharedPreferences.Editor et = sp.edit();
et.putString("key",data);
et.apply();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
};
In second activity
protected void onCreate(Bundle savedInstanceState) {
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
desiredPreference = sharedPreferences.getString("key","data");
Toast.makeText(this,"spdata"+desiredPreference,Toast.LENGTH_LONG).show();
}

The Value is null because you used PreferenceManager.getDefaultSharedPreferences(this) which returns preference with this activity name and it's different from the other preference you used in your first activity. Instead, you should call your preference in the same way you called it in your first activity.
SharedPreferences prefs = getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);
String desiredPreference = sharedPreferences.getString("key","data");
To know more about the difference you can check the documentation and this answer.

Do something like this,
For storing
SharedPreferences sharedPref = this.getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("key", data);
editor.commit();
for Retriving
SharedPreferences sharedPref = this.getPreferences(Context.MODE_PRIVATE);
String checkDate = sharedPref.getString("key","");

Shared preferences? (Extremely simple issue!?)

I am just trying to store the users input from an editText in a Shared Preference, but it is not working:
editText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
#Override
public boolean onEditorAction(TextView v, int keycode, KeyEvent event) {
Log.v(TAG, keyword.getString("keyword", "mDefault")); //IT LOGS OUT THE DEFAULT STRING EVEN **AFTER** STORING THE PREFERENCES BEFORE
if (keycode == EditorInfo.IME_ACTION_SEND) {
editText.setText(editText.getText().toString());
keywordEditor.putString("keyword", editText.getText().toString());
keywordEditor.commit();
Log.v(TAG, keyword.getString("keyword", "default")); //CORRECT! THIS LINE WORKS
}
}
return true;
});
When I first edit the text, I will first get a log of "mDefault" which is normal, since nothing is stored in the shared preference.
Then, I store something in the shared preference, and to make sure it stored, I log and I get a log of what I typed. Which means the shared preference data WAS stored.
Heres the problem: After I have stored something in the shared preference, I go to a different activity, and I come back, and all the data stored in the shared preference is GONE!
The very first log still says mDefault after navigating through activities.
What could the problem be?
EDIT:
Here is my instantiation:
onCreate:
keyword = PreferenceManager.getDefaultSharedPreferences(this); //Making a shared preferences
keywordEditor = keyword.edit();

Maybe you don't save on setOnEditorActionListener. Save when you go to a different activity. Because when it goes to different activity the setOnEditorActionListener editText.getText().toString() it returns null.

STORING PREFERENCES:
SharedPreferences pref = getSharedPreferences("MyPrefs",Context.MODE_PRIVATE);
// We need an editor object to make changes
SharedPreferences.Editor edit = pref.edit();
// Set/Store data
edit.putString("username", "Rishabh");
edit.putString("password", "rishabh123");
// Commit the changes
edit.commit();
RETRIEVING PREFERENCES:
SharedPreferences pref = getSharedPreferences("MyPrefs", Context.MODE_PRIVATE);
String username = pref.getString("username", "");
String password= pref.getString("password", "");
Log.d(TAG, username);
Log.d(TAG, password);

Adding this as an example in case you missed a key components. This is currently working for me:
public class Main2Activity extends ActionBarActivity {
private SharedPreferences keyword;
private SharedPreferences.Editor keywordEditor;
private String TAG = "TAG";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
keyword = PreferenceManager.getDefaultSharedPreferences(this); //Making a shared preferences
keywordEditor = keyword.edit();
final EditText editText = (EditText) findViewById(R.id.et_text);
findViewById(R.id.btn_launch).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(Main2Activity.this, Main22Activity.class);
startActivity(intent);
}
});
editText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
#Override
public boolean onEditorAction(TextView v, int keycode, KeyEvent event) {
Log.v(TAG, "Initial: " + keyword.getString("keyword", "mDefault")); //IT LOGS OUT THE DEFAULT STRING EVEN **AFTER** STORING THE PREFERENCES BEFORE
if (keycode == EditorInfo.IME_ACTION_SEND) {
editText.setText(editText.getText().toString());
keywordEditor.putString("keyword", editText.getText().toString());
keywordEditor.commit();
Log.v(TAG, "Saving in prefs: " + keyword.getString("keyword", "default")); //CORRECT! THIS LINE WORKS
}
return true;
}
});
}
}
From a fresh install:
I typed in "test" and hit the send button on keyboard therefore invoked the onEditorAction
Then clicked on launch new activity -> hit back button and typed in "test2" and hit send button.
The following is the log out put:
02-29 23:26:42.068 18105-18105/com.example.naveed.myapplication V/TAG: Initial: mDefault
02-29 23:26:42.136 18105-18105/com.example.naveed.myapplication V/TAG: Saving in prefs: test
02-29 23:26:53.281 18105-18105/com.example.naveed.myapplication V/TAG: Initial: test
02-29 23:26:53.338 18105-18105/com.example.naveed.myapplication V/TAG: Saving in prefs: test2
As you can see initially it was "mDefault" then "test" was saved. I launched a new activity and came back. Next time the initial was "test" since it was saved last time and "test2" was the new value saved.

Create SharedPreferences class
public class SharedPreferenceClass
{
// Shared Preferences
SharedPreferences pref;
// Editor for Shared preferences
SharedPreferences.Editor editor;
// Context
Context _context;
// Shared pref mode
int PRIVATE_MODE = 0;
// Sharedpref file name
private static final String PREF_NAME = "INTELLIJ_AMIYO";
public static final String KEY_SET_VALUE= "KEY_SET_VALUE";
public SharedPreferenceClass(Context context){
this._context = context;
pref = _context.getSharedPreferences(PREF_NAME, 0);
editor = pref.edit();
}
public void setUserDATA(String data)
{
editor.remove(KEY_SET_VALUE);
editor.putString(KEY_SET_VALUE, data);
editor.commit();
}
public String getUserDATA()
{
String getData= pref.getString(KEY_SET_VALUE, null);
return getData;
}
}
Now call this in your Activity section globally
SharedPreferenceClass sharedPrefClassObj;
& call onCreate(Bundle savedInstanceState) section
sharedPrefClassObj = new SharedPreferenceClass(getApplicationContext());
Now add this
editText.setOnEditorActionListener(new TextView.OnEditorActionListener() {
#Override
public boolean onEditorAction(TextView v, int keycode, KeyEvent event) {
if (keycode == EditorInfo.IME_ACTION_SEND) {
editText.setText(editText.getText().toString());
sharedPrefClassObj.setUserDATA(editText.getText().toString()); // Set data
// Get data sharedPrefClassObj.getUserDATA();
}
}
return true;
});

Very important: you need a Preference name (for example: "MY_PREFS_NAME") to set and retrieve the values:
SharedPreferences.Editor keywordEditor = context.getSharedPreferences("MY_PREFS_NAME", MODE_PRIVATE).edit();
Use the same constant Preference name and it will give you the same preferences in any point of your app.

Load strings from sharedpreferences in EditText (two classes)

I have two different activity's. First one only showed to the user first time - to store phonenumber inside sharedprefs. I think the problem is my load from prefs method but just in case I will leave everything here to make it more relevant to future users. It looks like in both activitys the "mobilnummer" is saved - but I am having problem to display them.
The idea is it to be overwritten if user updates it - I think the method will do that?
OnStartUp.java
public static final String PREFS_NAME = "MobileNumberSaved";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mobilnummer = (EditText) findViewById(R.id.mobilnummer);
final Button button = (Button) findViewById(R.id.ntonboarding);}
public void SaveToMobile(View v) {
if (mobilnummer.getText().toString().length() >= 8) {
FragmentedUser.SaveMobile(mobilnummer.getText().toString()); // just saves to Parse.com (This works)
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString("mobilnummer", mobilnummer.toString());
editor.commit();
}
}
Profile
EditText mobilnummer;
public static final String PREFS_NAME = "MobileNumberSaved";
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mobilnummer = (EditText) findViewById(R.id.mobilnummer);
This is the issue/problem i think! (Code below)
SharedPreferences MobileNumberSaved = this.getSharedPreferences("mobilnummer", Context.MODE_PRIVATE);
String tempMobilnummer = mobilnummer.getText().toString();
mobilnummer.setText(tempMobilnummer);
// IF user wants to change mobilenumber
mobilnummer.setOnEditorActionListener(new TextView.OnEditorActionListener() {
#Override
public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {
boolean handled = false;
if (actionId == EditorInfo.IME_ACTION_SEND) {
if (mobilnummer.getText().toString().length() >= 8)
FragmentedUser.SaveMobile(mobilnummer.getText().toString());
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString("mobilnummer", mobilnummer.toString());
editor.commit();
tlfstatus.setImageResource(R.drawable.ok);
handled = true;
}
return handled;
}
});

I think here is your error:
SharedPreferences MobileNumberSaved = this.getSharedPreferences("mobilnummer", Context.MODE_PRIVATE);
//here it should be MobileNumberSaved instead of mobilnummer, because tehre is no sense to set the same text to the textView again after you got it from there
String tempMobilnummer = MobileNumberSaved.getText().toString();
mobilnummer.setText(tempMobilnummer);
But the correct way to get a value from shared preferences is something like this:
SharedPreferences prefs = getSharedPreferences(PREFS_NAME, MODE_PRIVATE);
String savedMobileNumber = prefs.getString("mobilnummer", "");
mobilnummer.setText(savedMobileNumber);
Update: when you save the value in the shared preferences, you save only the editText, not it's value, so do something like this when saving:
SharedPreferences.Editor editor = settings.edit();
//mobilnumber is your EditText, so get it's text like this
editor.putString("mobilnummer", mobilnummer.getText().toString());
editor.commit();
And everything else is still the same that I wrote above

Using SharedPreferences between Activity

I have a configuration page which has a form on it. When the button is pressed, I want to save that value to a SharedPreference. This SharedPreference value then needs to be accessed from elsewhere in my app.
I am trying to save the value like the below. I want to save the collectionID so I can use it elsewhere
public class ConfigPage extends Activity {
public static final String PREFS_NAME = "MyPrefsFile";
Button mButton;
EditText mEdit;
String collectionID;
String key = "GregKey";
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.config);
getActionBar().hide();
mButton = (Button)findViewById(R.id.setCollection);
mEdit = (EditText)findViewById(R.id.collectionName);
mButton.setOnClickListener(
new View.OnClickListener()
{
public void onClick(View view)
{
collectionID = mEdit.getText().toString();
Log.d("EditText", collectionID);
SharedPreferences settings =
getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString(key, collectionID);
editor.commit();
}
});
}
}
Once it has been saved, I then need to access it in another class, however I can't figure out how to do this. The example above crashes the application at the moment so something isn't quite right

I want to save the collectionID so I can use it elsewhere
Use mButton Button onClick event for saving EditText text in SharedPreferences as :
mButton.setOnClickListener( new View.OnClickListener()
{
public void onClick(View view)
{
collectionID = mEdit.getText().toString();
Log.d("EditText", collectionID);
// save value here in SharedPreferences
SharedPreferences settings =
ConfigPage.this.getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString(collectionID, collectionID);
editor.commit();
}
});

Your crash occurs because your value is null:
String savedID;
You need to add a value to the variable:
String savedID = "somevalue";
Also, your key is null as long as the Button is not pressed which will also lead to a crash.
The putString(String key, String value) method enables you to store a specific value with a specific key, that can later be used to reaccess the stored value.
Example:
String key = "somekey";
String value = "yourvaluetostore";
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString(key, value); // store the value
editor.commit();
In another Activity:
String key = "somekey";
SharedPreferences sharedPreferences = getSharedPreferences(PREFS_NAME, 0);
// get the value "" is default
String value = sharedPreferences.getString(key, "");
All you need in the other Activity is the key you stored the value with. With this key, you can pull the correct stored value out of the SharedPreferences. --> The key is needed to identify the value.

Since you are using the part of code :
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString(collectionID, savedID);
editor.commit();
Log.d("Saved as", savedID);
in the onCreate method, that translates to
...
editor.putString(null, null);
Log.d("Saved as", null);
Correct your code so that you fill those elements before. I guess you wanted to make the save in the OnClick part

Yes something its not quite right here because as i see you are saving nothing. on shared pref you should have a "key" which will be use to identify the saved value in your example it should be something like this
public class ConfigPage extends Activity {
public static final String PREFS_NAME = "MyPrefsFile";
public static final String COLLECTIONID_KEY = "COLLECTIONID_KEY";
Button mButton;
EditText mEdit;
String collectionID;
String savedID;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.config);
getActionBar().hide();
mButton = (Button)findViewById(R.id.setCollection);
mEdit = (EditText)findViewById(R.id.collectionName);
mButton.setOnClickListener(
new View.OnClickListener()
{
public void onClick(View view)
{
collectionID = mEdit.getText().toString();
Log.d("EditText", collectionID);
}
});
SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString(COLLECTIONID_KEY, collectionID);
editor.commit();
Log.d("Saved as", COLLECTIONID_KEY);
}
}
then to retrieve it :
SharedPreferences sharedPreferences = getSharedPreferences(PREFS_NAME, 0);
String mySavedCollectionID = sharedPreferences.getString(COLLECTIONID_KEY);
and make sure that its done on the Onclick event otherwise you might end up with crash again because after the on-click event in your code the lines below will run anyway and save null!