i make app with two activities.
firs has:
2 ExitText(login and password);
button(confirm, save data with SharedPreferences, intent to second activity).
second one:
2 TextView(get login and password with SharedPreferences);
button(clear data on SharedPreferences, intent to firsActivity).
how to make next: while there are some data on SharedPreferences - app will be started from the 2nd screen.
for example, i made:
if (user!=null && pass!=null){ Intent enterIntent = new Intent(MainActivity.this,SecondActivity.class);
startActivity(enterIntent);
}
but, technically it first run the firstActivity and than go to the secondOne. if there are some method to start app with the another activity (not mainOne)?
You won't be able to check to see if there are values in SharedPreferences before entering one Activity.
What you can do is check the value before displaying the UI (before calling setContentView(R.layout.my_layout)), and either continue along, or start the next Activity.
public class MyStartActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SharedPreferences preferences = getSharedPreferences("my_prefs", Context.MODE_PRIVATE);
if (preferences.contains("my_key")) {
// start next Activity
}
setContentView(R.layout.my_layout);
}
}
If you don't want the first one on the back stack, you can call finish() after starting the second one (or use appropriate flag(s) on intent).
Another approach would be to have only one activity with to fragments and decide dynamically which one set on start. With fragments you can also easily change layouts on button click or on back pressed.
I'm not sure if it will work, because app has to start at the first activity. First activity checks login and pass at share preferences and then you can go to the second activity
try this
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SharedPreferences preference = getSharedPreferences("my_prefs", Context.MODE_PRIVATE);
if (preference.getSting("key",null)!= null) {
// start new Activity
//finish this activity so it not in back stack
} else {
setContentView(R.layout.my_layout);
}
}
Related
I'm writing an app with 8 different Activities that are all interconnected(accessible from one another). I'm wondering how I can have the app always reopen from a full close (not just home button click but from closing the background activity) with the same screen it was exited from.
For example, from my Splash Screen I navigate to a home screen. From that home screen I navigate to the Settings. Now, I click the multi-tab viewer and close all apps. How can I have Settings(or wherever I had left off) become the launching activity when the app is reopened?
Thanks in advance!
You can use SharedPreferences to store the class name of the latest Activity. Later, when relaunch, you can redirect to it from the Splash Screen.
You can do that simply by using SharedPreferences. When you launch an activity, it changes it's last activity value in SharedPreferences to point at that activity.
When you close the app and then reopen it, your Main/Launcher activity (Which may be your Splash Screen) then checks for this value and launches the activity according to this value which represents the last activity the app was on.
Here is the code that would fit the Main/Launcher activity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String lastActivity = getDefaults("LAST_ACTIVITY", MainActivity.this);
Intent intentLastActivity;
// use an if statement to find out which activity it is
if(!lastActivity.equals("") || !lastActivity.equals(null)){
if(lastActivity.equals("home")){
intentLastActivity = new Intent(MainActivity.this, HomeActivity.class);
}else if(lastActivity.equals("settings")){
intentLastActivity = new Intent(MainActivity.this, SettingsActivity.class);
// add more else-if statements for the other activities.
}
startActivity(intentLastActivity); // launch the last activity
finish(); // finish/close the current activity.
}
}
public static void setDefaults(String key, String value, Context context) {
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
SharedPreferences.Editor editor = preferences.edit();
editor.putString(key, value);
editor.apply();
}
public static String getDefaults(String key, Context context) {
SharedPreferences preferences = PreferenceManager.getDefaultSharedPreferences(context);
return preferences.getString(key, null);
}
Once that code is placed in your Main/Launcher activity. You can then set this last activity value in SharedPreferences in other activities when they are launched.
Code placed in the other activities (in the onCreate method):
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings);
// we are at the settings activity. Change last activity value to settings
MainActivity.setDefaults("LAST_ACTIVITY","settings",this);
}
Luckily the methods to change the last activity are accessible in other activities.
If you're able to implement this well in your app. It should work as you want it to.
HOPE THIS HELPS!
I have QR scanner app. There are 3 activities in the app.
1) Main activity - Button to open camera and start scanning
2) QR activity - Scan a QR code
3) Web Activity - On successful scanning, open a web page in the app
Here, the Main activity and QR activity should only launch once, only after the initial install. I read somewhere about using shared preferences. But I am a little confused as to where do I check the variable, as in which activity. Should I check my shared variable in the Main Activity?
This is my first app. Sorry if this is a silly doubt.
It's correct, you have to do it with SharedPreferences.
Here is a good explaination about how to use them
On the first activity shown, you have to add in the onCreate method those lines:
//this retrieve the sharedpreference element
SharedPreference myPref = this.getSharedPreferences(
"prefName", Context.MODE_PRIVATE);
//this retrieve the boolean "firstRun", if it doesn't exists, it places "true"
var firstLaunch = myPref.getBoolean("firstLaunch", true);
//so, if it's not the first run do stuffs
if(!firstLaunch){
//start the next activity
finish();
}
//else, if it's the first run, add the sharedPref
myPref.edit().putBoolean("firstLaunch", false).commit();
hope this helps
To complete #Pier Giorgio Misley answer you can put the "firstLaunch" check on your Main Activity or alternatively put it in another "splash" activity
For putting it in the main activity simply set the ui to some neutral color until you decide if you should finish the activity and launch the Web Activity or show the Main Activity logic
Alternatively, you can create a "splash" screen which can function as a bridge activity (which shows some logo or a nice background color) which check the varible and decide which activity to open Android splash
As pier mentioned, saving that it has been seen once is the way to go. However, I have found on some older devices, shared preferences is not reliable!
I recommend instead using SQLite database.
Create a table as follows
TABLE NAME: SEEN_ACTIVITY
Column 1: ID INT PRIMARY KEY
Column 2: SEEN VARCHAR
Then, once the activity has been launched, check if there is a record for id = '0' in SEEN_ACTIVITY. If not, then insert one as follows, (0, true).
Then, every time the app launches, check to see if the record exists of (0, true). If not, launch the extra activity.
My MainActivity.java
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_splash);
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
SharedPreferences settings = getSharedPreferences("prefName",MODE_PRIVATE);
boolean firstLaunch = settings.getBoolean("firstLaunch", true);
if(firstLaunch == false) {
SharedPreferences.Editor editor=settings.edit();
editor.putBoolean("firstRun",true);
editor.commit();
Intent i = new Intent(SplashActivity.this, MainActivity.class);
startActivity(i);
finish();
}
else {
Intent i = new Intent(SplashActivity.this, ScannerActivity.class);
startActivity(i);
finish();
}
}
}, SPLASH_TIME_OUT);
}
Wrote this code in a new Splash Activity
I have plugged in lock screen logic into my app. It shows ComfirmPatternActivity (above my MainActivity) which controls graphical pin code input to be correct.
When onCreate() method of MainActivity is call everything is OK. But I also want to lock screen when I simply turn app down not destroying MainActivity. So it goes from onRestart() -> onResume(). In onResume() I placed method handleLockScreen(); as in onCreate(). But for now I got into infinite loop hich shows me ComfirmPatternActivity screen for ages. It seamed out that the last command of code in ComfirmPatternActivity after user inputs correct pin - is Activity finish(). After that finish() Im redirected to MainActivity.onResume() - prev Activity on the stack - in which I again start ComfirmPatternActivity() and so on. I want resume logic only in case user pressed on app icon again, not in case top Activity is destroyed. How this can be handled? Thx in advance.
MainActivity
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
handleLockScreen();
setContentView(R.layout.activity_main);
}
protected void onResume() {
super.onResume();
handleLockScreen();
..
public void handleLockScreen(){
SharedPreferences prefs = this.getSharedPreferences("LOCK_SCREEN",
Context.MODE_PRIVATE);
String lock_screen_code = prefs.getString("LOCK_SCREEN_CODE","");
if (lock_screen_code.isEmpty()) {
Intent intent = new Intent(this, SampleSetPatternActivity.class);
this.startActivity(intent);
}
else{
Intent intent = new Intent(this, SampleConfirmPatternActivity.class);
this.startActivity(intent);
}
}
public class SampleConfirmPatternActivity extends ConfirmPatternActivity {
SharedPreferences prefs = this.getSharedPreferences("LOCK_SCREEN",
Context.MODE_PRIVATE);
String patternSha1 = prefs.getString("LOCK_SCREEN_CODE","");
return TextUtils.equals(PatternUtils.patternToSha1String(pattern), patternSha1);
... finish() is called further in this activity
}
This finish() returns to my onResume() which triggers all over again. And I want handle onResume() only in case smth external happend to my app like user returned to my app etc. I dont want get back to onResume() when pin code is checked and everything is OK.
You could possibly declare a boolean (global to application) in LockScreen Activity to fix this issue and tell(to the MainActivity) if it is coming to onResume from outside or from LockScreen (y)
I have a lot of activities in my app, and I want that if the user closes the app in activity 13 for example, when opening the app at another time the activity returns in activitty n° 13. how can I do this? thank in advance
You could use SharedPreferences to keep track of the last used activity.
Then you can redirect the user in the onCreate of your main activity to the correct activity, and call finish on your main activity.
This could look something like this:
#Override
protected void onCreate(Bundle savedInstanceState)
(...)
int last_activity = getLastActivityIdFromSharedPreferences();
if (last_activity == 1)
{
this.startActivity(new Intent(this, ActivityOne.class));
finish();
}
(...)
}
my main.xml file is just dummy. I want to start different activites based on the condition. If the password is found in shared pref file, the login activity should be launched, and if password is not found, the configuration activity should be launched. it is working fine but when I press the back key from keypad, the main activity is shown (I mean the blank screen because there is nothing) How can I avoid this?
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
prefs = getSharedPreferences(preffilename, MODE_PRIVATE);
final String password = prefs.getString("password",null);
if(password == null)
{
Intent i = new Intent(getApplicationContext(), Configuration.class);
startActivity(i);
}
else
{
Intent i = new Intent(getApplicationContext(), Login.class);
startActivity(i);
}
}
Call finish() from your main activity after calling startActivity(), this will remove main activity from stack.
What is your expectation when you pressed the back button? You might want to put those code in onResume() so it always get called when the main activity is brought back from the stack.