I am studying Mobile Application Developer and I am just a beginner. So, forgive me if the question is silly.
I am creating a simple Quiz App. I have MainActivity which act as a welcoming screen.
public class MainActivity extends AppCompatActivity {
private Button startBt; //the user will enter this button to go the SecondActivity
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
startBt = findViewById(R.id.startBt);
startBt.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent i = new Intent(MainActivity.this, SecondActivity.class);
startActivity(i);
}
});
}
}
Then, I have a SecondActivity which suppose to ask the user a question and get the answer as a String and then increment the score if the answer is correct. There is 10 question. So, I want to use a loop to iterate through all questions. Also, inside the loop there is OnKeyListener which indicate when the user press Enter and compare the user answer to the saved answer.
public class SecondActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
String[] questions = getResources().getStringArray(R.array.questions);
String[] answers = getResources().getStringArray(R.array.answers);
TextView questionTv = findViewById(R.id.questionTv);
final EditText answerEt = findViewById(R.id.answerPt);
TextView scoreTv = findViewById(R.id.scoreTv);
int scoreCounter = 0;
for (int i=0; i<10; i++) {
answerEt.setText("");
scoreTv.setText(scoreCounter);
questionTv.setText(questions[i]);
answerEt.setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getKeyCode() == KeyEvent.KEYCODE_ENTER) {
if (**answerEt**.getText().toString().equals(**answers[i]**)) {
Toast t = Toast.makeText(getApplicationContext(), "Correct",Toast.LENGTH_LONG);
t.show();
**scoreCounter++;**
return true;
}
else
return false;
} else
return false;
}
});
}
}
}
Now, please check the bold part of the code. I cannot access answerEt, scoreCounter, answer[i] because they are not final. They should be final because I am working with an inner class. Here is the problem, if I will make them final, I will not have the ability to modify them. However, scoreCounter should be incremented to show the user score. Also the i should be incremented to iterate through the answer[]. One will say "make them Global". Sadly, I tried this and my program crashed. So, How I can solve this?
Thanks in advance
pass on responsibility to check for correct answer to a separate function.
private boolean checkAnswer(EditText et, final int questionID) {
if (et.getText().toString().equals(answers[questionID])) {
Toast t = Toast.makeText(getApplicationContext(), "Correct", Toast.LENGTH_LONG);
t.show();
scoreCounter++;
return true; // for correct answer.
}
return false; // for incorrect answer.
}
Modify your loop to use above function like this :
for (int i = 0; i < 10; i++) {
final int currentQuestionID = i;
answerEt.setText("");
scoreTv.setText(scoreCounter);
questionTv.setText(questions[i]);
answerEt.setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getKeyCode() == KeyEvent.KEYCODE_ENTER) {
return checkAnswer((EditText) (v), currentQuestionID);
}
return false;
}
});
}
I am writing a program where I call multiple layouts on the same activity but then i noted that when i switch layouts, the changes made before the switch are not restored and onSavedInstanceState(Bundle outState) is not called. I have tried to manually call the method but i can't get the Bundle outState.
So the question really is: How do I get and store the current state of an activity to be recalled and/or restored at a time of my choosing?
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_contact_view);
// more code
}
#Override
public void onBackPressed() {
if (layoutId == R.layout.activity_contact_view) exit();
else if (layoutId == R.layout.main) {
Toast.makeText(NsdChatActivity.this, "Successful back button action", Toast.LENGTH_SHORT).show();
setContentView(R.layout.activity_contact_view);
refreshContactList();
}
}
And then from a seperate class
public void updateList(final int found) {
LinearLayout layxout = (LinearLayout) ((Activity)mContext).getWindow().getDecorView().findViewById(R.id.others);
TextView t = new TextView(mContext);
t.setClickable(true);
t.setText(found + ". " + activity.sNames.get(found));
t.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT));
t.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
//show chat view
activity.setContentView(R.layout.main);
TextView name = (TextView)activity.findViewById(R.id.clientName);
name.setText(activity.sNames.get(found).split(" \\(")[0]);
final ScrollView scroll = (ScrollView)activity.findViewById(R.id.scroll);
scroll.setOnFocusChangeListener(new View.OnFocusChangeListener() {
#Override
public void onFocusChange(View view, boolean b) {
scroll.fullScroll(View.FOCUS_DOWN);
}
});
}
});
layxout.addView(t);
}
I might be late for that but what you could do is to keep your sate as a member of the class. That way you can restore the state anytime you want.
Bundle mState;
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
// Save the state
savedInstanceState = mState;
super.onSaveInstanceState(savedInstanceState);
}
#Overrite
public void onRestoreInstanceState(Bundle savedInstance){
mState = savedInstance;
Restore();
}
public void Restore(){
//access your state and restore
}
Also you shouldn't use setContentView to switch between views it's expensive way to do it. You might want to check ViewSwitcher or ViewFlipper or someway to implement Fragments.
May be you should have a look at Application Fundamentals
Android calls onSaveInstanceState() before the activity becomes vulnerable to being destroyed by the system, but does not bother calling it when the instance is actually being destroyed by a user action (such as pressing the BACK key)
so you call multiple layouts on the same activity may not cause the above situation. For more details, you can refer to the question Android: Saving a state during Android lifecycle. Hope that helps!
The layout of my app contains a TextView and a toggle Button. When the toggle Button is turned ON an AlertDialog appears and the user is prompted to give the time for the countdown to start. It works fine if I dont change the orientation while it counts down. However when I change orientation while the countdown keeps running the Dialog Box reappears which shouldn't. I know that changing orientation destroys and recreates my activity so given the fact that toggle button was ON before the activty is destroyed when it is recreated it continuous to be ON as it should be. So my question is if there is a way for the AlertDialog not to appear after the orientation change.
I have tried adding the following but it didnt work
Declared as class variable
public static final String TOGGLE_BUTTON_STATE = "OFF";
Trying to set the toggle Button to true
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d(TAG, "onCreate: created.............");
mTextTime = (TextView) findViewById(R.id.textView);
mToggleButton = (ToggleButton) findViewById(R.id.toggleButton);
if((savedInstanceState != null) && TOGGLE_BUTTON_STATE.equals("ON")) {
Log.d(TAG, "onCreate: created after changing orientation........");
mToggleButton.setChecked(true);
}
mToggleButton.setOnCheckedChangeListener(this);
saving the state before it is destroyed
#Override
public void onSaveInstanceState(Bundle outState) {
if(mToggleButton.isChecked()) {
Log.d(TAG, "onSaveInstanceState: toggleButton is checked...........****");
outState.putString(TOGGLE_BUTTON_STATE, "ON");
}else {
Log.d(TAG, "onSaveInstanceState: toggleButton is not checked...........*****");
outState.putString(TOGGLE_BUTTON_STATE, "OFF");
}
super.onSaveInstanceState(outState);
}
//Listener for the ToggleButton
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
// Toast.makeText(this, "ON", Toast.LENGTH_SHORT).show();
// TOGGLE_BUTTON_ON = true;
//getting the xml user_input to java
LayoutInflater inflater = LayoutInflater.from(this);
View view = inflater.inflate(R.layout.user_input, null);
//search inside the view for the text_input
mTextUserInput = (EditText) view.findViewById(R.id.text_input);
//We create the builder and we use it to add functionality to the dialog
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Please Enter The Time");
//We create the user_input that has only the editext widget that we gonna use to get the
//time from the user
builder.setView(view);
builder.setPositiveButton("OK", this);
builder.setNegativeButton("Cancel", this);
builder.show();
} else {
// OFF selected and timer must stop
// TOGGLE_BUTTON_ON = false;
timer.stop();
}
}
ps The countdown timer keeps running properly even after orientation change
Your way of loading the previously stored state in onCreate is false. You are saving the state correctly (but i would prefer storing it as a boolean) - but you are not reading it correctly from the savedInstance.
The way i would do it:
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putBoolean("TOGGLE_BUTTON_STATE", mToggleButton.isChecked());
}
#Override
protected void onCreate(Bundle savedInstanceState) {
...
if(savedInstanceState != null) {
mToggleButton.setChecked(savedInstanceState.getBoolean("TOGGLE_BUTTON_STATE"));
}
mToggleButton.setOnCheckedChangeListener(this);
...
}
You can dismiss the alert dialog when the activity is going to be destroyed.
For example:
#Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
...
// Save the dialog in an instance variable
mDialog = builder.show();
}
#Override
public void onStop() {
if (mDialog != null) {
mDialog.dismiss();
}
super.onStop();
}
My app uses one activity and many fragments, the activity which extends AppCompatActivity inflates an xml file which has a LinearLayout among
other ViewGroups, the purpose of this LinearLayout is to hold 3 buttons not all are visible at start.
In code, I change the view of LinearLayout and
the view and texts of some of its buttons depending on the action taken in the current fragment. However their state is not maintained when the
activity is reCreated after phone home key press.
Saving visibility and text of each button every time one gets chnaged in SharedPreferences is too misssy, so I tried the below code but failed.
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (mMainButtons_LL != null) {
mMainButtons_LL = (LinearLayout) savedInstanceState.getSerializable("mainButtons");
} else {
mMainButtons_LL = (LinearLayout) findViewById(R.id.main_buttons_LL);
}
}
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putSerializable("mainButtons", (Serializable) mMainButtons_LL);
}
Change your code to something like this:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.id.your_layout); // << replace your layout id here
mMainButtons_LL = (LinearLayout) findViewById(R.id.main_buttons_LL);
if (savedInstanceState != null) {
mMainButtons_LL.setVisibility(savedInstanceState.getInt("visibility"));
mMainButtons_LL.setText(savedInstanceState.getString("text");
}
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("visibility", mMainButtons_LL.getVisibility());
outState.putString("text", mMainButtons_LL.getText.toString());
}
I have a Login screen which consists of 2 EditTexts for Username and Password. My requirement is that on orientation change , input data(if any) in EditText should remain as it is and a new layout should also be drawn. I have 2 layout xml files- one in layout folder and other in layout-land folder. I am trying to implement following 2 approaches but none of them is perfect:
(1) configChanges:keyboardHidden - In this approach, I don't provide "orientation" in configChanges in manifest file. So I call setContentView() method in both onCreate() and onConfigurationChanged() methods. It fulfills both my requirements. Layout is changed and input data in EditTexts also remains as it is. But it has a big problem :
When user clicks on Login button, a ProgressDialog shows until server-response is received. Now if user rotates the device while ProgressDialog is running, app crashes. It shows an Exception saying "View cannot be attached to Window." I have tried to handle it using onSaveInstanceState (which DOES get called on orientation change) but app still crashes.
(2) configChanges:orientation|keyboardHidden - In this approach, I provide "orientation" in manifest. So now I have 2 scenarios:
(a) If I call setContentView() method in both onCreate() and onConfigurationChanged(), Layout is changed accordingly but EditText data is lost.
(b) If I call setContentView() method in onCreate() , but not in onConfigurationChanged(), then EditText data is not lost but layout also not changes accordingly.
And in this approach, onSaveInstanceState() is not even called.
So I am in a really intimidating situation. Is there any solution to this problem? Please help. Thanx in advance.
By default, Edittext save their own instance when changing orientation.
Be sure that the 2 Edittexts have unique IDs and have the same IDs in both Layouts.
That way, their state should be saved and you can let Android handle the orientation change.
If you are using a fragment, be sure it has a unique ID also and you dont recreate it when recreating the Activity.
A better approach is to let android handle the orientation change. Android will automatically fetch the layout from the correct folder and display it on the screen. All you need to do is to save the input values of the edit texts in the onSaveInsanceState() method and use these saved values to initialize the edit texts in the onCreate() method.
Here is how you can achieve this:
#Override
protected void onCreate (Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.login_screen);
...
...
String userName, password;
if(savedInstanceState!=null)
{
userName = savedInstanceState.getString("user_name");
password= savedInstanceState.getString("password");
}
if(userName != null)
userNameEdtTxt.setText(userName);
if(password != null)
passEdtTxt.setText(password);
}
>
#Override
protected void onSaveInstanceState (Bundle outState)
{
outState.putString("user_name", userNameEdtTxt.getText().toString());
outState.putString("password", passEdtTxt.getText().toString());
}
Give the element an id and Android will manage it for you.
android:id="#id/anything"
in onConfigurationChanged method, first get the data of both the edit texts in global variables and then call setContentView method. Now set the saved data again into the edit texts.
There are many ways to do this. The simplest is 2(b) in your question. Mention android:configChanges="orientation|keyboardHidden|screenSize" in your manifest so that Activity doesn't get destroyed on Orientation changes.
Call setContentView() in onConfigChange(). but before calling setContentView() get the EditText data into a string and set it back after calling setContentView()
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
mEditTextData = mEditText.getText().tostring();//mEditTextData is a String
//member variable
setContentView(R.layout.myLayout);
initializeViews();
}
private void initializeViews(){
mEditText = (EditText)findViewById(R.id.edittext1);
mEdiText.setText(mEditTextData);
}
The following should work and is standard to the activities and fragments
#Override
public void onSaveInstanceState (Bundle outState)
{
outState.putString("editTextData1", editText1.getText().toString());
outState.putString("editTextData2", editText2.getText().toString());
super.onSaveInstanceState(outState);
}
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate();
... find references to editText1, editText2
if (savedInstanceState != null)
{
editText1.setText(savedInstanceState.getString("editTextData1");
editText2.setText(savedInstanceState.getString("editTextData2");
}
}
Im restoring instance to restore values and it works fine for me :)
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.addtask2);
if(savedInstanceState!=null)
onRestoreInstanceState(savedInstanceState);
}
Remove android:configChanges attribute from the menifest file and let android handle the orientation change your data in edittext will automatically remain.
Now The problem you mentioned is with the progress dialog force close this is because when the orientation is changed the thread running in backgroud is trying to update the older dialog component whihc was visible. You can handle it by closing the dialog on savedinstancestate method and recalling the proceess you want to perform onRestoreInstanceState method.
Below is a sample hope it helps solving your problem:-
public class MyActivity extends Activity {
private static final String TAG = "com.example.handledataorientationchange.MainActivity";
private static ProgressDialog progressDialog;
private static Thread thread;
private static boolean isTaskRunnig;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d(TAG, "onCreate");
setContentView(R.layout.main);
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new EditText.OnClickListener() {
#Override
public void onClick(View v) {
perform();
isTaskRunnig = true;
}
});
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
public void perform() {
Log.d(TAG, "perform");
progressDialog = android.app.ProgressDialog.show(this, null,
"Working, please wait...");
progressDialog
.setOnDismissListener(new DialogInterface.OnDismissListener() {
#Override
public void onDismiss(DialogInterface dialog) {
//isTaskRunnig = false;
}
});
thread = new Thread() {
public void run() {
Log.d(TAG, "run");
int result = 0;
try {
// Thread.sleep(5000);
for (int i = 0; i < 20000000; i++) {
}
result = 1;
isTaskRunnig = false;
} catch (Exception e) {
e.printStackTrace();
result = 0;
}
Message msg = new Message();
msg.what = result;
handler.sendMessage(msg);
};
};
thread.start();
}
// handler to update the progress dialgo while the background task is in
// progress
private static Handler handler = new Handler() {
public void handleMessage(Message msg) {
Log.d(TAG, "handleMessage");
int result = msg.what;
if (result == 1) {// if the task is completed successfully
Log.d(TAG, "Task complete");
try {
progressDialog.dismiss();
} catch (Exception e) {
e.printStackTrace();
isTaskRunnig = true;
}
}
}
};
#Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
Log.d(TAG, "onRestoreInstanceState" + isTaskRunnig);
if (isTaskRunnig) {
perform();
}
}
#Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Log.d(TAG, "onSaveInstanceState");
if (thread.isAlive()) {
thread.interrupt();
Log.d(TAG, thread.isAlive() + "");
progressDialog.dismiss();
}
}
As pointed out by Yalla T it is important to not recreate the fragment. The EditText will not lose its content if the existing fragment is reused.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setContentView(R.layout.activity_frame);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// Display the fragment as the main content.
// Do not do this. It will recreate the fragment on orientation change!
// getSupportFragmentManager().beginTransaction().replace(android.R.id.content, new Fragment_Places()).commit();
// Instead do this
String fragTag = "fragUniqueName";
FragmentManager fm = getSupportFragmentManager();
Fragment fragment = (Fragment) fm.findFragmentByTag(fragTag);
if (fragment == null)
fragment = new Fragment_XXX(); // Here your fragment
FragmentTransaction ft = fm.beginTransaction();
// ft.setCustomAnimations(R.xml.anim_slide_in_from_right, R.xml.anim_slide_out_left,
// R.xml.anim_slide_in_from_left, R.xml.anim_slide_out_right);
ft.replace(android.R.id.content, fragment, fragTag);
// ft.addToBackStack(null); // Depends on what you want to do with your back button
ft.commit();
}
Saving state = Saving (Fragment State + Activity State)
When it comes to saving the state of a Fragment during orientation change, I usually do this way.
1) Fragment State:
Save and Restore EditText value
// Saving State
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("USER_NAME", username.getText().toString());
outState.putString("PASSWORD", password.getText().toString());
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.user_name_fragment, parent, false);
username = (EditText) view.findViewById(R.id.username);
password = (EditText) view.findViewById(R.id.password);
// Retriving value
if (savedInstanceState != null) {
username.setText(savedInstanceState.getString("USER_NAME"));
password.setText(savedInstanceState.getString("PASSWORD"));
}
return view;
}
2) Activity State::
Create a new Instance when the activity launches for the first time
else find the old fragment using a TAG and the FragmentManager
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity);
fragmentManager = getSupportFragmentManager();
if(savedInstanceState==null) {
userFragment = UserNameFragment.newInstance();
fragmentManager.beginTransaction().add(R.id.profile, userFragment, "TAG").commit();
}
else {
userFragment = fragmentManager.findFragmentByTag("TAG");
}
}
You can see the the full working code HERE
Below code is work for me. Need to care two things.
Each Input Field (Edit Text or TextInputEditText) assign unique id.
Manifest activity declaration should have on configuration change attribute with below values.
android:configChanges="orientation|keyboardHidden|screenSize"
Sample activity declaration in manifest.
<activity
android:name=".screens.register.RegisterActivity"
android:configChanges="orientation|keyboardHidden|screenSize"
android:exported="true"
android:label="Registration"
android:theme="#style/AppTheme.NoActionBar" />
Sample declaration of
<com.google.android.material.textfield.TextInputLayout
android:id="#+id/inputLayout"
style="#style/Widget.MaterialComponents.TextInputLayout.OutlinedBox"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:boxCornerRadiusBottomEnd="#dimen/boxCornerRadiusDP"
app:boxCornerRadiusBottomStart="#dimen/boxCornerRadiusDP"
app:boxCornerRadiusTopEnd="#dimen/boxCornerRadiusDP"
app:boxCornerRadiusTopStart="#dimen/boxCornerRadiusDP">
<com.google.android.material.textfield.TextInputEditText
android:id="#+id/inputEditText"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:focusable="true"
android:fontFamily="#font/proxima_nova_semi_bold"
android:inputType="textCapWords"
android:lines="1"
android:textColor="#color/colorInputText"
android:textColorHint="#color/colorInputText" />
</com.google.android.material.textfield.TextInputLayout>
this may help you
if your android:targetSdkVersion="12" or less
android:configChanges="orientation|keyboardHidden">
if your android:targetSdkVersion="13" or more
android:configChanges="orientation|keyboardHidden|screenSize">