I hawe many view's in my application and now the problem is how to go back from one view to another.
What I could do it by set back Buttons in every view but i would like to use the android back hard button.
I have tried something like this:
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if(keyCode==KeyEvent.KEYCODE_BACK)
{
finish();
}
return false;
}
But the problem is that this will close my application.
Could you please guide me for a proper solution, for example to memorize the last view was set and then to come back to this view or something like this.
Here is the code with which I am changing the view (it's a method in my main activity):
public void CheckIfUserIsLogedIn ()
{
int userPresence = localDatabase.CheckUserPresence();
if (userPresence == 0)
{
setContentView(R.layout.main);
}
else
{
setContentView(R.layout.userlogedon);
}
}
Thank you.
Look!
You are doing this wrong way..
An Activity class should only have on content View. (because it is recommended way and easy to use and implement).
And if you want to go to next View, show it under another separate Activity.
when you will finish it, you will be automatically redirected to previous Activity.
(and you don't need to memorize the Previous View :) )
See here, how to work with Activity Stacks.
I am not sure to understand your problem correctly because Android do all that for you automatically. Once a view is opened when you switch to another view it is paused (on screen but has not focus) or stopped (has no focus)
http://developer.android.com/reference/android/app/Activity.html
If the current view (activity) has been launched by the previous view (activity), pressing the back button will make you "close" the current view and go back to the previous one automatically.
Now two things :
Perhaps your are simply opening all views wihtin the same activity by showing on or off components which is a bad way of doing and is not recommended by android. What you should do is 1 view = 1 activity.
You are thinking like "iPhone/iPad" where you have to implements back buttons in the "views". In android you don't need to do so. Putting the "finish" command in your code at that point seem to close the application which make me think you have programmed as explained in point 1.
Hope it helps
EDIT:
To start a new activity do it like this
startActivity(new Intent(this, MyOtherActivity.class));
you put this in your code where you want to load the new view (activity)
Now if you want to transfer some information between activities you must do something like this :
Intent myIntent; //intent declaration
int aNumber = 10; // info to send to other activity
String aString = "abcd"; // info to send to other activity
// link Intent to the other activity
myIntent = new Intent(view.getContext(), MyOtherActivity.class)
//put the extra info
myIntent.putExtra("myNumber", aNumber);
myIntent.putExtra("myString", aString);
//start the new view/activity
startActivity(myIntent);
and in the new opened activity you retrieve the infos like this (in the oncreate usually)
int aNumber;
String aString;
#Override
public void onCreate(Bundle savedInstanceState) {
aNumber= getIntent().getExtras().getInt("myNumber");
aString= getIntent().getExtras().getString("myString");
}
Actually i m not sure that understand exactly but..
take a map or a shared preference and at the back button set last View on map or Shared preference .
At the calling or at start activity fetch the data which have stored you.
this will helps you.
Related
I have an app that hold post information in an activity. in this activity related posts listed in bottom of post. User by clicking on related post can go to post activity and see that post info and related posts too.
As you can see in image, I have Activity A that holds post and it's related posts. When user Click on post I send user to Activity A with new post id and fill activity by new data.
But I think this is not Right way!
should I used Fragment instead of Activity?
Opening another Instance of an Activity on top of another is simplest way of navigating a content graph. User can simply press back, and go to previously opened content, until user reaches back to starting Activity, then the application closes. Though pretty straight forward, this particular approach has two issues:
It may happen that a lot of Instances of same activity are on the stack, utilising a large amount of device resources like memory.
You don't have a fine grained control over Activity Stack. You can only launch more activities, finish some, or have to resort to intent flags like FLAG_CLEAR_TOP etc.
There is another approach, that re-uses the same Activity instance, loads new content in it while also remembering the history of content that was loaded. Much like a web browser does with web page urls.
The Idea is to keep a Stack of content viewed so far. Loading new content pushes more data to stack, while going back pops the top content from stack, until it is empty. The Activity UI always displays the content from top of the stack.
Rough Example:
public class PostActivity extends AppCompatActivity {
// keep history of viewed posts, with current post at top
private final Stack<Post> navStack = new Stack<>();
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// get starting link from intent extras and call loadPost(link)
}
private void loadPost(String link){
// Load post data in background and then call onPostLoaded(post)
// this is also called when user clicks on a related post link
}
private void onPostLoaded(Post post){
// add new post to stack
navStack.push(post);
// refresh UI
updateDisplay();
}
private void updateDisplay(){
// take the top Post, without removing it from stack
final Post post = navStack.peek();
// Display this post data in UI
}
#Override
public void onBackPressed() {
// pop the top item
navStack.pop();
if(navStack.isEmpty()) {
// no more items in history, should finish
super.onBackPressed();
}else {
// refresh UI with the item that is now on top of stack
updateDisplay();
}
}
#Override
protected void onDestroy() {
super.onDestroy();
// cancel any background post load, release resources
}
}
I would choose:
activity/fragment depends on complexity with:
horizontal recyclerview with custom expanded card view
and inside this expanded card view second vertical recyclerview :)
Here's what you can try.
Create a PostActivity which is a shell for fragments. Inside this activity you can just replace fragments using FragmentTransaction.
Your PostActivity can now have a PostFragment which will hold post and related posts. Now on click of post you can replace PostFragment with PostDetailFragment with postID being sent to the new fragment as a bundle. The PostDetailFragment will now display details according to id.
Check here: http://www.vogella.com/tutorials/Android/article.html#components_fragments
By seeing the picture the way i would implement is i would have create an activity with a bottom listview for your items and on top there would be a framelayout for holding fragments . when user click on any list item i would load the respective fragment in the activity
It all depends on what you are trying to achieve. What would you expect to happen when the user touches the back button after going down a couple of levels? If you want to the application to exit, no matter how deep in the sequence they have gone, then the best solution in my opinion is to simply reload the same activity with the new data and invaliding the affected views. If you need the back button to take the user back to the previous data, then the next question would be if you are keeping track of the past data breadcrumb. If so, then just intercept the back button and load the previous data for as long as there is data in your stack, or exit if you get to the top. If you don't want to keep track of the previous data chain, then instead of loading one activity with the new data, you can start a new activity of the same class, but with the new data. Android with keep the track of activities and each back button touch would close the running activity and take the user to the previous activity. Choice of activity versus fragment is just yours. You can use fragments that hold the data that you want to change after each user touch, create new ones when needed, disconnect the previous ones, and connect the new ones. You will need to do some extra work to make sure the back button works correctly (depending on you want the back button to behave). Based on what I can tell, it is simpler to just have one activity and load new data when needed and keep a trail of data changes, if you need to be able to go back.
It can be achieved using activity alone. Though I preferred moving all related UI to fragment.
You can use Navigator class.
Here the steps:
1. Add Navigator Class
public class Navigator {
private static Navigator instance;
public synchronized static Navigator getInstance() {
if (instance == null) {
instance = new Navigator();
}
return instance;
}
public void navigateToActivityA(Context context) {
Intent activity= AActivity.getCallingIntent(context);
context.startActivity(activity);
}
}
2. Add the calling method to your Activity class.
public static Intent getCallingIntent(Context context) {
return new Intent(context, AActivity.class);
}
3. Call the activity with the following code in your caller activity.
Navigator.getInstance().navigateToActivityA(this);
I suggest that you read about AndroidCleanArchitecture
For this task...
0) Starting new activity
I read again about question, and understood that you need advice for starting activity. So, starting new activity it's Ok, your main problem will be with another things (see below).
But lets talk about starting another data. Using Fragment instead doesn't resolve your task, fragments helps with different screen work. Using for example just data refreshing as a variant. You may use just single activity and refresh only data, it will look much better, if you also add animation, but not better than starting activity.
Using Fragment helps your with different screen actions. And maybe, answering on your question - it will be most suitable solution. You just use single acitivity - PostActivity, and several fragments - FragmentMainPost, FragmentRelated - which will be replaced, each other, by selecting from related post.
1) Issues with returning back
Lets imagine, that users clicks to new one activity and we loaded new data. It's Ok, and when Users clicks over 100 activities and receiving a lot of information. It's Ok, too. But main question here it's returning back (also another about caching, but lets leave it, for now).
So everyone know, it's bad idea to save a lot of activities in stack. So for my every application, with similar behavior we override onBackPressed in this activity. But how, lets see the flow below:
//Activities most have some unique ID for saving, for ex, post number.
//Users clicks to 100 new activities, just start as new activity, and
//finish previous, via method, or setting parameter for activity in AndroidManifest
<activity
noHistory=true>
</activity>
....
//When activity loaded, save it's activity data, for ex, number of post
//in some special place, for example to our Application. So as a result
//we load new activity and save information about it to list
....
// User now want return back. We don't save all stack this activities,
// so all is Ok. When User pressing back, we start action for loading
//activities, saved on our list..
.....
onBackPressed () {
//Getting unique list
LinkedTreeSet<PostID> postList =
getMyApplication().getListOfHistory();
//Getting previous Post ID based on current
PostID previousPostID = postList.get(getCurrentPost());
//Start new activity with parameter (just for ex)
startActivity(new Intent().putExtra(previousPostID));
}
RESULT
I found this as the best solution for this tasks. Because in every time - we work only with single activity!
I want to develop an application that, at the beginning, checks a variable's value and, basing on this value, starts the activity A or the activity B, something like this:
protectec void onCreate(...){
boolean b = checkVariable();
if(b){
startActivityA();
} else {
startActivityb();
}
}
What I'm doing
This is the method I have currently implemented:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_limitation);
varChecker = new VarChecker(this);
if(varChecker.getRemainingUses() <= 0){
limitReached();
} else if(varChecker.isFirstTime()){
firstTime();
} else {
startMainActivity();
}
}
This is an activity that must be shown the first time the application is executed. Else, depending on the getRemainingUses() result, it must start the activity A or the activity B automatically.
The question
Is there any way to do what I want, without the need of create a new Activity, specially to avoid the super.onCreate(savedInstanceState) and the setContentView(R.layout.activity_limitation)?
Is there any way to do what I want, without the need of creating a new
Activity, specially to avoid the super.onCreate(savedInstanceState)
and the setContentView(R.layout.activity_limitation)?
I had a similar problem some time ago. As far as I know, It's not possible to avoid calling super.onCreate(savedInstance) and setContentView(R.layout.activity_limitation). It's design of the Android activity.
I see the following possible solutions:
if you want to choose an appropriate activity by e.g. clicking a
button, then you just need to create a new Intent basing on a
variable and there's no problem.
if you want to choose an activity in
a different moment of the flow - e.g. during the application start you can:
create a single activity for two options, use fragments and switch between them
create "dummy" activity with an empty layout, create an intent and switch to an appropriate activity basing on a variable and finish "dummy" activity. Please note that this solution is a kind of workaround and it's worth to spend some time to figure out something better, but I'm not sure if there is a recommended solution for such use cases.
Im working on a little game and having some issues.
There is the Menu
public void onClick(View arg0) {
// TODO Auto-generated method stub
switch (arg0.getId()){
case R.id.bStartGame:
Intent a = new Intent(Menu.this, Action.class);
startActivityForResult(a, 1);
break; }
then the activity which starts a surfaceview
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(new GameView(this));
}
and then the the surfaceView with the game mechanics.
Most of my code is in this view.
Now I have the problem to find a good solution for the gameoverscreen.
If I start a new activity inside the surfaceview, it works - but i dont get the result() which is the score achieved during a session.
So now I wanted to ask you guys how to solve this issue.
I thought of a way, but dont know how to implement it.
It would be to pass the highscore from the surfaceview to the activity and set it as a result(which the menu activity gets back) there.
And start an xml file via dialog, which would be the gameoverscreen and as soon as the player touches the back button he gets back to the menu where he can see his achieved score.
Can you please tell me how to code this?
Kind regards
Denis
There's a number of ways to solve this:
-use startActivityForResult and then send it back from your new activity, catching it in the old activity using onActivityResult (check https://developer.android.com/reference/android/app/Activity.html)
-do what i did (the lazy, hacky way :): start the new activity with startActivity() and add the highscore as extra data added to the intent. In your new activity, use getIntent().getInt (ow whatever) to get the sent score data and do with it what you will. Then close that activity and you'll return to the previous one holding your surfaceview.
NOW THE TRICK: before you start your new activity with it's score added to the intent, just run the same score calculation in your surfaceview's activity as you would in your new activity! That way, when you return to your surfaceview's activity, you will still have the correct, new score (if stored/onresume'd correctly; don't forget to add it to your save/restore state and/oror the surfaceview's private variables)!
The only downside is that you'll have two location you have to update your scoring mechanics at. And it's not good programming. But it works and it's easy.
[Update Solution]
Referring to the post in the link
ViewPager PagerAdapter not updating the View
public void onSomeButtonClicked(View view) { // registered to Button's android:onClick in the layout xml file
Log.w(TAG,"Some button clicked !!");
getIntent().setAction(IntentManager.Intents.ACTION_SPAWN_LIST_BY_SOMETHING);
mViewPager.getAdapter().notifyDataSetChanged();
}
// And inside my PagerAdapter
#Override
public int getItemPosition(Object object) {
return 0;
}
Fixed all my problems, i just used Intent.setAction().
[Update to below Post]
My problem is i have a ViewPager PagerAdapter in my Main Activity. On clicking one of the 3 buttons., any specific intent will be fired (i used intent, i could have gone with just State variable as well, just that i pass some Uri with the intent). What happens is., i do
public void onSomeButtonClicked(View view) { // registered to Button's android:onClick in the layout xml file
Log.w(TAG,"Some button clicked !!");
getIntent().setAction(IntentManager.Intents.ACTION_SPAWN_LIST_BY_SOMETHING);
mViewPager.getAdapter().notifyDataSetChanged();
}
This is why i was guessing maybe i should just do startActivity again, with the new Intent Action on the same Activity.
Spawning a new Activity, i would have to redraw every other view in the layout which is basically the same code, for the most part in the current activity.
Any suggestions here? Please help
[Original Post]
I have a PagerAdapter and 3 Buttons in the my Main Activity. This activity is enter from Main Launcher.
When i press any one of the buttons, the Intent Action is changed.
My question:
The changed Intent action reflects some changed view in the ViewPager and does_not spawn a new Activity as such, only the view is updated.
What approach should i take to get this task?
Can i start the currentActivity using startActivity() and different Intent actions on button click?
or is there any other efficient way in android to do this?
[No need code, just explanation of logic / method would suffice]
Thanks in advance
If you are saying that you are trying to use startActivity to bring up the same activity again, and its not working, it could be because you set something like singleTop in your Android manifest.
If you are asking whether or not you should use an intent to change the state of your Activity, then the answer is "it depends". If the user would expect the back button to return your app to its previous state (instead of going back to the home screen), then it might be a good choice for you. If that is the case, however, I would ask why not just make 2 different Activities? Otherwise, just do as Dan S suggested and update the state of your Activity as the user interacts with it.
You can always use the onNewIntent() hook. Do something like this in your activity:
protected void onNewIntent(Intent intent){
//change your activity based on the new intent
}
Make sure to set the activity to singleTop in your manifest. Now whenever startActivity is called the onNewIntent() will be executed. Also, note that per the documentation:
Note that getIntent() still returns the original Intent. You can use setIntent(Intent) to update it to this new Intent.
I have an activity which has multiple screens depending on which buttons the user clicks.
What should I do if I need to handle back button in this activity. i.e. When I press to back button it has to go previous screen of my activity.
I am really new to android. can any body help me to solve this problem
Thanks for reading.
I guess that by multiple screens you mean you have some layouts and change them with setContentView(). You'll have to override the back button's behavior, keep a history of user navigation between various screens (if there's no forced path) and have the back button code set content to the previous screen.
Overriding the back button is easy if you're on API >= 5: see onBackPressed().
If you want also backward compatibility you'll find something here and here.
As this is usually all done automatically by Android with activities, consider having multiple activities instead of a single activity with multiple screens.
override onBackPressed() function in your activity and write the desired code in it for the intent firing.
You can do this by handling the KeyDown event and adding some condition( like taking a static variable and at each activity assign different value to the static variable ) at each actvity.
See the following code:
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK)) {
if(condition 1)
{
Intent i=new Intent("com.prac.A"); // A is your another activity in com.prac package
startAcitvity(i);
}
else if(condition 2)
{
Intent i=new Intent("com.prac.B");
startAcitvity(i);
}
else
{
Intent i=new Intent("com.prac.C");
startAcitvity(i);
}
}
return false;
}
Hope this will help you.