When I change orientation portrait to landscape (or landscaper to portrait), a function is restarted. I want the function is saved in Android. I'm making a calculator. I don't want operator buttons to be enable before number buttons is clicked. So I made a function that make operator buttons click after number buttons is clicked. However, when I clicked a number to calculate, then change orientation, the operator buttons are not enable. It's supposed to be enable.
I mean, number click -> operator click -> number click -> equals button click -> the result is showed, this is okay. But number click -> change orientation -> operator buttons are not enable.... This is my code
You have two options:
Go to the manifest file and set the orientation of the activity to
either landscape or portrait.
Save some state that your activity holds in a bundle. In OnCreate, the first thing you do is check if the bundle is null (it will be the first time). If it is not then read the bundle (it is the same one you saved) and reset all the states you saved. Save a bundle with your current state information every time at the end of OnCreate. This should fix your problem of resetting states, also allowing you to rotate the device.
This is a widely know concept and you should probably have used a search engine extensively before posting a question. Google is your friend. :)
when you change the orientation of the device your Activity is destroyed and recreated.so you must save the state with onSaveInstanceState()
before the activity is destroyed and than restore it.
moreover if you want to disable orientation change than simply set android:screenOrientation="portrait in you Manifest. read this to learn how to handle runtime changes in Android.
I know this may not be an appropriate question, but I want to know how a touch enabled OS like
android detects a button in an app and calls the appropriate handler? When programming an app we just give the alignment information of a particular button. So, how android keeps the mapping between a button and screen position? I think this is kindof dynamic because if you change the screen orientation or use zoom or something like that the button positions are changed dynamically. So, android must look at the touch position and decide whether a button is there or not and call the appropriate handler. How this all things put together?
I appreciate any reply.
My overriding question is this: In Android PreferenceActivity, how can I write an OnClickListener which will have the same functionality as pressing the Android back button as I navigate through PreferenceScreen defined menus? That is to say, I would like users of my App to explicity see a menu choice "Back" which will bring them to the previous menu, or bring them out of the menu activity to their previous activity if they are at the root of this particular PreferenceActivity session.
The android developer documents tell us
Note that this XML resource contains a preference screen holding another fragment, the Prefs1FragmentInner implemented here. This allows the user to traverse down a hierarchy of preferences; pressing back will pop each fragment off the stack to return to the previous preferences.
And they are correct about that. I navigate happily through my menus by clicking on PreferenceScreen items to get to that screen, and using the Android back button to go Back up a level. But I'm not sure a casual user really understands the "Back" button, I know I didn't until I read about it in Developer docs. SO I would would like them to have an explicit Preference defined menu choice whos OnClickListener duplicates the function of the Android back button.
So I tried to put in a Preference in my menu that would go back. Having determined that a not Overriden onBackPressed in a my subclass of PreferenceActivity just referred back to Activity.onBackPressed() which merely calls finish(), I tried this OnClickListener:
private OnPreferenceClickListener clickFinishesSuccessfully = new OnPreferenceClickListener() {
#Override
public boolean onPreferenceClick(Preference preference) {
finish();
return true;
}
};
As it turns out, this did NOT do the same thing as pressing the back button! Pressing this button always took me out of the PreferenceActivity entirely, back to the Activity from which I had called my PreferenceActivity. Specifically, it did NOT navigate back through my menus no matter how deep I was when I clicked it.
I am guessing here: When I have gotten to a submenu by clicking an onscreen preference which is really a PreferenceScreen, I am no longer in my own PreferenceActivity. I must be in some other Activity?
So my functional question: what can I put in my OnClickListener of my "Back" Preference to get the same function as the Android Back button navigating through my menus?
I think the casual user should know about the back button. The button is used everywhere so it might be a problem getting used in the first day but after that it's natural. Without being used to the "back" button I can hardly imagine doing the everyday tasks.
The preference you want to add just duplicates functionality and doesn't provide a consistent way with the rest of the system. If Google was considering back being an uncommon thing for casual users would have added that option in phone's Settings which is also a PreferenceActivity.
I have an application containing multiple activities.
At the moment the whole application contains about 8 activities. First I show a splash screen for a few seconds where all the preferences are loaded and set up (from sharedPreferences) - these are saved in a "Setting" class I made for this - this class basicly just have a bunch of static variables, so all activities in the app can read these and modify them as they need to.
EDIT: More data is getting stored in this class as the app runs, some of this is from a webservice - the data is parsed into obejcts and references to these obejcts are saved in the Settings class too (or a list of the objects).
My problem is then, that when users press the HOME key, the current activity is put in the background. If the activity is in the background for a long time (a lot of users "close" apps by pressing home instead of back), and then reopened it shows the activity that was running before HOME was pressed.
As an example - lets say the user starts the app, sees the Splash screen for a few seconds. The splash screen then starts a new activity and calls finish on itself.
This means that now the Activity stack is just the MainActivity (main menu). In the MainActivity I supply all the buttons with listeners in the onCreate method, and most buttons require some info from the Settings class mentioned above.
When I then press HOME and reopens the app a few hours later, none of the buttons works anymore - seems the graphic is reacting etc, but something still goes wrong. One of the buttons that should work even with all settings wiped will just open a dialog with some text in it.
The listener:
Button b = (Button)v.findViewById(R.id.id_b1);
b.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Dialog dialog = createDialog(MainActivity.this, DIALOG_CONST1);
dialog.show();
}
});
I have some constantst for dialog types, as I'm using some custom designs for the dialogs I have created a class to created the dialogs for me.
From the activity containing the button (simplified a bit):
public static Dialog createDialog(final Context c, int dialogId) {
Dialog dialog = null;
CustomDialog.Builder customBuilder;
switch (dialogId) {
...
case d1:
customBuilder = new CustomDialog.Builder(c, DIALOG_CONST1);
//Sets up the parapters to create the dialog afterwards
customBuilder.setTitle("Header").setMessage("Content")
.setPositiveButton("", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
dialog = customBuilder.create(); //Creates the dialog from the above settings
dialog.setCanceledOnTouchOutside(true);
break;
...
}
... //Set the width of the dialog
return dialog;
}
The CustomDialog class extends the Dialog class and then depending on the const it
s supplied with it inflates one of several dialog layouts and adds content etc. Works great normally, but after the app have been paused by HOME for a while, and things go wrong no dialog is shown when I press the button. I do se a flash of a loading dialog on the other buttons, but nothing happens afterwards - no dialog is shown. Strange thing is that if I press on the button again in the middle of the screen, I can't press it (grahics dont react), but when pressing once in the side of the screen and then in the middle the graphics do react, the dialogs does get cancelled when pressing outside, so I'm wondering if there is some very slim "transparent" dialog in the middle or something - I just have no clue why this would happen.
EDIT: Actually looking through the variables I save in Settings class I see that I do save the width and height in pixels of the screen. Width used to set the width of the custom dialogs to a certain % of the screen width. IF the Settings gets wiped, that might explain why I don't see any dialogs as width is set to 0... I really can't seem to figure what is happening if it's not all my variables in the Settings class that gets wiped - everything really do point to that.
dialog.getWindow().setLayout(Settings._widthpx - (Settings._widthpx/5), dialog.getWindow().getAttributes().height); //Width = 80%
Actually I have to admit that I don't really know what is causing this, as I'm rather new to Android. I suspect that the GC does delete all my variables after a while when the Settings class haven't been used - causing all settings to be wiped when the user returns a few hours later. This however does not explain why the buttons doesn't work (one of them require no setting).
This main activity can start other activities, and these can again launch new activities.
I think all my problems can be solved if I can just force the whole app to close when HOME is pressed, and thereby force it to be started from scratch whenever the icon is pressed - forcing the listeners on the buttons and the settings to be loaded.
I read on here about "android:clearTaskOnLaunch", " android:launchMode" and "android:finishOnTaskLaunch" but I'm not quite sure how to use these correct.
Anyone who could either explain to me why the buttons does not work, or what might happen to the variables in my Settings class when the app has been in the background for a while, or maybe give me a few good hints on how to use the "activity" settigns properly.
EDIT: The app will be running Android 1.6+, so I can't use any newer functions or anything...
Thank you very much
DO NOT override home key functionality. Maybe you'll find something, somewhere, that would allow you to do this. A god-fearing, standards-embracing application would not in any way override the home key.
Just put android:clearTaskOnLaunch=true in your manifest. This will ensure that your main activity will be launched everytime you press the launcher icon.
I suspect that the GC does delete all my variables after a while when
the Settings class haven't been used - causing all settings to be
wiped when the user returns a few hours later
Android is not that evil to do this to your app. It may kill your application, services, and whatever is running on the background after some time of inactivity and/or need for more memory, but will never leave your application hanging in there without your variables.
I had actually customized this for android 2.0 development 2.0.May be better options are available now.What I did was to declare all activities global and when you click home button from anywhere we check whether each of them is not null.If not null close them and set references to null.The activities are only declared globally.They are defined only when they are to be used.
If you are using Android 4.0 or higher, you can enable "Don't keep activities" in Developer options?. If you don't have a 4.0 device, then use the emulator.
you have to kill all the activities that are on the top of current activity on Home button and
for do that you have to override Home key functionality in which you have to write
Intent intent = new Intent(context,login.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
this will clear all the activities on the top of that activity where you press home key and switch it to login activity and
if you don't want to override Home key functionallity then you have to write only one in Androidmanifest.xml that is android:clearTaskOnLaunch=true from this when ever you click on app icon it will starts your 1st activity
I Suggest the second approach is best suted for you.
For posterity, in my app I just added finish(); in the onStop() method after everything i do there and it worked as a charm.
I have this app that originally has you take a picture, shows you a progress bar, and uploads it to a website.
What I want to add is something so that before the progress bar shows, an Intent starts an activity that loads a layout with a dropdown menu that allows you to choose a descriptor for the picture. Following this, once you hit the 'OK' button on this new layout, the program should return back to where it had left off and display the progress bar.
Does anyone have any ideas on how to achieve this?
It seems that all I really want is some way to tell the program to stall for a while to call an intent, and when the user hits 'OK', the code may resume.
You should be using OnActivityResult().. More information on the link below http://developer.android.com/reference/android/app/Activity.html#startActivityForResult(android.content.Intent, int)