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Change text content depending on button clicked within the same class

My problem is exactly like this link but it's not in android.
I have one button on a layout and two buttons on an another one. On my application, ClickScreen activity can be triggered by either FirstCase activity or SecondCase activity.
I tried to make a conditional statement on my ClickScreen for which activity is triggered but couldn't handle it. I don't want to create two more classes to do this since it's not an efficient technique.
private void goTo2ndPage() {
Intent i3 = new Intent(this, ClickScreen.class);
startActivity(i3);
}
public class ClickScreen extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.click_screen);
}
}

As we discussed in comments. It looks like what you really want is to add extra data in your intent so that Started Activity can get it and act accordingly.
Check out this post !

Finish Activity() from a separate myJavaClass.java

I have tried almost all the solutions from SO but no success :(.
I have a simple myJavaClass.java with a couple of functions.
One of the functions in myJavaClass : startActivity() starts MyCustomActivity
public startActivity(Context context)
{
Intent intent = new Intent(context, MyCustomActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK |Intent.FLAG_ACTIVITY_SINGLE_TOP);
context.startActivity(intent);
}
This launches MyCustomActivity() as expected.
Now I have another function in myJavaClass.java to close/finish MyCustomActivity but it is not able to do so!
I have tried
Making MyCustomActivity SingleTop in manifest and creating the activity via an intent as above
Passing an activity instance to "this" in onCreate() of MyCustomActivity and calling MyCustomActivity.activity.finish() from myJava.class but that doesnt work as well
Please help me. I have been stuck here for hours now. I know the solution is very simple and conceptual but I am a newbie. Just building Java/Android concepts!
EDIT
MyCustomActivity
public Activity activity;
OnCreate()
{
...
this = activity;
}
MyJavaClass
public closeActivity(Context context)
{
Activity customActivity = MyCustomActivity.activity;
customActivity.finish();
}

I think that what you are trying to do is fundamentally bad. For a start, outside of the Activity code, there are no guarantees that the activity still exists - the memory manager may have cleaned it up, the user may have pressed Back etc. Think of Activities as independent entities - you can start them, and you can optionally get a result back when they finish what they're doing, but that's it.
Think about whether you really have to programmatically close the activity from outside it - I'd say this is an unusual design, but there are circumstances where it may be appropriate.
If so, what I think you want is a publish/subscribe system whereby MyCustomActivity can register a listener with MyJavaClass, and then receive a callback whereupon it can 'finish' itself.
public Activity activity implements FinishListener
{
public void onCreate(...)
{
//where does MyJavaClass come from? see in a minute
MyJavaClass myjava = getMyJavaclass();
myJava.addFinishListener( this );
}
public void onFinishCallback()
{
this.finish();
}
}
and
public class MyJavaClass
{
private List<FinishListener> finishListeners = ...;
public void addFinishListener( FinishListener fl )
{
this.finishListeners.add(fl);
}
public closeActivity(Context context)
{
for ( FinishListener fl : finishListeners )
{
fl.onFinishCallback();
}
}
}
and
public interface FinishListener
{
void onFinishCallback();
}
Now the only remaining issue is how to get MyJavaClass from the Activity. That's up to you - you may already know how, you may be able to put it in your Application implementation, it could be a singleton (bad), the listeners could be static (bad) or various other options.
Oh, and don't forget to remove the listener again in the Activity's onDestroy() method!

Just try this....
public closeActivity(Activity _activity)
{
_activity.finish();
}

you can't finish activity from other class until you have the reference of instance of Activity in that class, give the reference in that class and call finish() method to stop the activity.
activity.finish();

How to go back from second screen to first screen

How to switch layouts? First, I have a class Main where is onCreate (setContentView(R.layout.main);) and then I call, another class with command:
setContentView(secondClass);
In this class, I draw with Canvas and this work just fine. I also create button to go back in first "class" (R.layout.main), but I don't know how to do it.
Now my program is basic a graph shower. In first class you type your function and them second class draw it. But how to go back in first class to type another function. This "back" button or arrow witch every Android phone have, send me out of program not back on insert part.
In secondClass I can't create onCreate method, but I also tried the following and they didn't work:
Intent abc = new Intent("bla.bla.bla.FIRSTCLASS");
startActivity(abc);
and
Intent abc = new Intent(SecondClass.this,FirstClass.class);
startActivity(greNaPrvoOkno);

If you want to use a custom view (as I understood, you are extending the View class), you can do it in the following way;
Consider you are showing the second class from your Main activity like this;
setContentView(new SecondClass(getApplicationContext(), MainActivity.this));
And you Second class is this (suppose);
// I am using onClickListener to go back to main view. You do whatever you like.
public class SecondClass extends View implements OnClickListener {
// This is needed to switch back to the parent activity
private Activity mParentActivity = null;
public SecondClass(Context context, Activity parentActivity) {
super(context);
mParentActivity = parentActivity;
setOnClickListener(this);
}
#Override
public void onClick(View v) {
// Set the Main view back here.
mParentActivity.setContentView(R.layout.main);
}
}
Disclaimer: This code will do what you have asked for, but may cause other problems.
As advised by #Mudassir, you should use two different activities for two screens. It will give you better control, and your code will be easy to understand and maintain.

On the Onclick event of the button you have to write finish(); that's it..

Both of your classes are Activities yes? IF so then in your second activity you will simply call finish() and your activity will close revealing your first activity again.

When I have used multiple intents in my android application, I have created a new activity through:
Intent abc = new Intent(this, SecondClass.class);
startActivity(abc);
When the button is pressed in your second class, I would then either call finish(); on the class, or create a new intent like so:
Intent abc = new Intent(this, FirstClass.class);
startActivity(abc);
However, this method has the disadvantage that if a user wanted to use the back button, they may have to scroll through many layers of activities.

You should create another activity for your second class but not just set the main activity to a new view setContentView(secondClass).
For an easier modification, You could try to set the view back to setContentView(R.layout.main) first.
You still need to configure the widgets(e.g. TextView) on it when you set it back.
You don't have to startActivity again to go back.
Just call finish() in your second activity when you want to finish the current activity and go back:
e.g. When user press the back button in your second activity
mButtonBack.setOnClickListener(new Button.OnClickListener()
{
public void onClick(View v)
{
finish();
}
}

How to force main Acivity to wait for subactivity in Android?

I am calling a subactivity from main activity. This subactivity should take few numbers from user (i'm using Edit text control to achieve this), save them to static variable in another class and terminate. I want main activity to wait for subactivity but both are just running simultaneously. Even doing sth like that doesn't help:
Thread t = new Thread(new Runnable(){
public void run(){
Log.v("==================", "run "+new Date());
startActivityForResult(new Intent(ctx,myCustomSubactivity.class),1);
} });
Log.v("==================", "calling run "+new Date());
t.start();
try {
t.join();
} catch (InterruptedException e) {Log.v("==================", "can't join");}
Log.v("==================", "back from activity "+new Date());
do you know how to force main activity to wait? Thread.wait() method is not supported in Android(program throws error).

May be I'm missing something but why don't just use startActivityForResult and onActivityResult mechanism? You could get result from you subactivity from intent it was resulted with.
Edit: BTW as far as I understand, if you will run Object.wait() from Activity code if will hold UI tread whitch can result in Application not responding error.

I agree with Nikolay this is definitely the android way to do this.
Start the subactivity with startActivityForResult in the sub activity use setResult to add an result code and an intent with all the numbers you need in the data bundle.
In your first activity overwrite onActivityResult and retrieve the numbers from the Intent.
If you use the static variable this seems easier in the first moment but it is very insecure and there are some cases this may not work. If your program is send to the background your activities will be saved but if the phone runs low on memory the system will close your program and after the user resumes it everything looks like the moment the user left it but the static variables will be recreated to their initialization value.
Try to get used to the way the android activity lifecycle works. Using this approach will result in fewer used memory and a much better user experience.

Check out the Notepad example, it covers exactly this situation. And as others have said, the Android way is to have your first activity start up your second activity (not sub-activity!) and asynchronously listen for a response (not pause or wait, no need for joining, etc.).

Well... you can do it like this (btw, there's not straight forward way):
Have a singleton class, let's call it Monitor:
public class Singleton
{
private Singleton() { }
private static Singleton instance = new Singleton();
public static Singleton getInstance() {
return instance;
}
}
public class ParentActivity extends Activity
{
private void startAndWait()
{
Intent i = new Intent();
// initialize i
startActivityForResult(i);
Singleton si = Singleton.getInstance();
synchronized(si)
{
si.wait();
}
//do remaining work
}
}
public class ChildActivity extends Activity
{
protected void onCreate(Bundle savedInstance)
{
//do all the work
Singleton si = Singleton.getInstance();
synchronized(si)
{
si.notify();
}
}
}

I'm not here to judge if it's a good pattern or not but if you really need an activity to wait for a sub-activity, you can try this approach:
define an object (lock) over which the two activities get synchronized; this can (should) also work as the object to exchange data between those two activities and thus should be defined as static
in parent activity, start an async task (as the UI main thread cannot be in waiting state)
in the async task, start your sub-activity
the async task waits on the lock till it gets notified
the sub-activity does whatever it needs and notifies the waiting thread when it finishes
I did a similar thing in my app and IMHO had a good reason for this (not to bother a user with login screen upon app start or resume, the app tries to re-use credentials stored in a secured place and only in case it fails, it shows this login screen. So yes, basically any activity in my app can get "paused" and waits till the user provides correct credentials in the login activity upon which the login screen finishes and the app continues exactly where it got paused (in the parent activity).
In the code it would be something like this:
ParentActivity:
public class ParentActivity extends Activity {
private static final String TAG = ParentActivity.class.getSimpleName();
public static class Lock {
private boolean condition;
public boolean conditionMet() {
return condition;
}
public void setCondition(boolean condition) {
this.condition = condition;
}
}
public static final Lock LOCK = new Lock();
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.parent_layout);
// do whatever logic you need and anytime you need to stat sub-activity
new ParentAsyncTask().execute(false);
}
private class ParentAsyncTask extends AsyncTask<Boolean, Void, Boolean> {
#Override
protected Boolean doInBackground(Boolean... params) {
// do what you need and if you decide to stop this activity and wait for the sub-activity, do this
Intent i = new Intent(ParentActivity.this, ChildActivity.class);
startActivity(i);
synchronized (LOCK) {
while (!LOCK.conditionMet()) {
try {
LOCK.wait();
} catch (InterruptedException e) {
Log.e(TAG, "Exception when waiting for condition", e);
return false;
}
}
}
return true;
}
}
}
ChildActivity:
public class ChildActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.child_layout);
// do whatever you need in child activity, but once you want to finish, do this and continue in parent activity
synchronized (ParentActivity.LOCK) {
ParentActivity.LOCK.setCondition(true);
ParentActivity.LOCK.notifyAll();
}
finish();
// if you need the stuff to run in background, use AsyncTask again, just please note that you need to
// start the async task using executeOnExecutor method as you need more executors (one is already occupied), like this:
// new ChildAsyncTask().executeOnExecutor(ChildAsyncTask.THREAD_POOL_EXECUTOR, false);
}
}

Android AsyncTask context behavior

I've been working with AsyncTasks in Android and I am dealing with an issue.
Take a simple example, an Activity with one AsyncTask. The task on the background does not do anything spectacular, it just sleeps for 8 seconds.
At the end of the AsyncTask in the onPostExecute() method I am just setting a button visibility status to View.VISIBLE, only to verify my results.
Now, this works great until the user decides to change his phones orientation while the AsyncTask is working (within the 8 second sleep window).
I understand the Android activity life cycle and I know the activity gets destroyed and recreated.
This is where the problem comes in. The AsyncTask is referring to a button and apparently holds a reference to the context that started the AsyncTask in the first place.
I would expect, that this old context (since the user caused an orientation change) to either become null and the AsyncTask to throw an NPE for the reference to the button it is trying to make visible.
Instead, no NPE is thrown, the AsyncTask thinks that the button reference is not null, sets it to visible. The result? Nothing is happening on the screen!
Update: I have tackled this by keeping a WeakReference to the activity and switching when a configuration change happens. This is cumbersome.
Here's the code:
public class Main extends Activity {
private Button mButton = null;
private Button mTestButton = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mButton = (Button) findViewById(R.id.btnStart);
mButton.setOnClickListener(new OnClickListener () {
#Override
public void onClick(View v) {
new taskDoSomething().execute(0l);
}
});
mTestButton = (Button) findViewById(R.id.btnTest);
}
private class TaskDoSomething extends AsyncTask<Long, Integer, Integer>
{
#Override
protected Integer doInBackground(Long... params) {
Log.i("LOGGER", "Starting...");
try {
Thread.sleep(8000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return 0;
}
#Override
protected void onPostExecute(Integer result) {
Log.i("LOGGER", "...Done");
mTestButton.setVisibility(View.VISIBLE);
}
}
}
Try executing it and while the AsyncTask is working change your phones orientation.

AsyncTask is not designed to be reused once an Activity has been torn down and restarted. The internal Handler object becomes stale, just like you stated. In the Shelves example by Romain Guy, he simple cancels any currently running AsyncTask's and then restarts new ones post-orientation change.
It is possible to hand off your Thread to the new Activity, but it adds a lot of plumbing. There is no generally agreed on way to do this, but you can read about my method here : http://foo.jasonhudgins.com/2010/03/simple-progressbar-tutorial.html

If you only need a context and won't use it for ui stuff you can simply pass the ApplicationContext to your AsyncTask.You often need the context for system resources, for example.
Don't try to update the UI from an AsyncTask and try to avoid handling configuration changes yourself as it can get messy. In order to update the UI you could register a Broadcast receiver and send a Broadcast.
You should also have the AsyncTask as a separate public class from the activity as mentioned above, it makes testing a lot easier. Unfortunately Android programming often reinforces bad practices and the official examples are not helping.

This is the type of thing that leads me to always prevent my Activity from being destroyed/recreated on orientation change.
To do so add this to your <Activity> tag in your manifest file:
android:configChanges="orientation|keyboardHidden"
And override onConfigurationChanged in your Activity class:
#Override
public void onConfigurationChanged(final Configuration newConfig)
{
// Ignore orientation change to keep activity from restarting
super.onConfigurationChanged(newConfig);
}

To avoid this you can use the answer givin here: https://stackoverflow.com/a/2124731/327011
But if you need to destroy the activity (different layouts for portrait and landscape) you can make the AsyncTask a public class (Read here why it shouldn't be private Android: AsyncTask recommendations: private class or public class?) and then create a method setActivity to set the reference to the current activity whenever it is destroyed/created.
You can see an example here: Android AsyncTask in external class