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Get & Set Value of my Activity from a fragment - Android

I would like know how can I get and set a value of my activity from my fragment?? is that possible?
below is my activity and the attribute 'myStation' is the value I want get and set from my fragment.
public class MyActivity extends Activity
implements NavigationDrawerFragment.NavigationDrawerCallbacks {
public static Station myStation;
In my fragment I can execute 'getActivity()' but I really don't know if I can do that. if I'm wrong, what is the correct process?¿
Thanks.

If the fragment is only used in that activity, then you can simply cast the activity. Otherwise you'll have to verify that it is the correct activity perhaps using instance of.
Let's look at the simpler case:
public class MyActivity extends Activity {
private boolean myFlag;
public boolean getMyFlag() {
return myFlag;
}
public void setMyFlag(boolean myFlag) {
this.myFlag = myFlag;
}
And here would be the fragment to adjust the flag.
public class MyUniqueFragment extends Fragment {
public void updateActivityFlag(boolean myFlag) {
MyActivity myActivity = (MyActivity) getActivity();
myActivity.setMyFlag(myFlag);
}
}

Call function from jar in MainActivity

First time I'm trying to make my own .jar file. It works, but now I want to give feedback to the MainActivity. So I want to call a function 'receiveSerial()' in the MainActivity.
So the MainActivity must always implement the function 'receiveSerial()' when including my .jar.
.jar file (part of the) code:
package com.hoeks.ma.bluetooth;
import java.util.Set;
import ...
public class Blauwe{
..
private Activity ma;
public Blauwe(Activity m){
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
ma = (Activity)m;
}
..
public void sendSerial(String s) {
ma.receiveSerial(s); // This line give Eclipse error "Add cast to ma"
// When I add the cast it is not working
}
MainActivity
import com.hoeks.ma.bluetooth.Blauwe;
....
public void receiveSerial(String s) {
javascr.setSerial(s);
}
Note: I do not post the whole code because the code is a big mess right now, its not good for the readability.

1) create interface
public interface ReceiveSerialCallback{
public void receiveSerial(String s);
}
2) add interface implementation in MainActivity
public class MainActivity implements ReceiveSerialCallback{
...
public void receiveSerial(String s) {
// serial received
}
}
3) update Blauwe class
private ReceiveSerialCallback callback;
...
public void setReceiveSerialCallback(ReceiveSerialCallback callback) {
this.callback = callback;
}
...
public void sendSerial(String s) {
callback.receiveSerial(s);
}
4) set inteface callback object to Blauwe class in MainActivity
Blauwe b = new Blauwe();
b.setReceiveSerialCallback(this);

You have to cast because receiveSerial(String) is not a method of Activity, but MainActivity. I would create an interface (with method sendSerial) that MainActivity should implement, and save a reference of this interface in Blauwe class, instead of an Activity instance.

Finishing an activity from a standard java class

I am currently working on an android project and I have an activity, lets call it MyActivity and this activity calls a standard Java class called MyClass.
I need MyClass to finish the MyActivity activity but I can't find out how to do this. I thought I might be able to pass the context to the standard java class and call context.finish() but this doesn't appear to be available.
How can I do this, thanks for any help you can offer.

You can pass the Context, but you will need to cast it to an Activity (or simply pass the Activity itself), although this in general seems like a bad practice.

The most secure solution uses listener and a Handler. It is complex, but ensures a non direct call to finish activity.
Your listener:
interface OnWantToCloseListener{
public void onWantToClose();
}
Class that should close activity.
class MyClass {
private OnWantToCloseListener listener;
public void setWantToCloseListener(OnWantToCloseListener listener){
this.listener = listener;
}
private void fireOnWantToClose(){
if(this.listener != null)
listener.onWantToClose();
}
}
When you want to close your activity you must call fireOnWantToClose() method.
public MyActivity extends Activity{
public void onCreate(){
final int CLOSE = 1; //number to identify what happens
MyClass my_class = new MyClass();
final Handler handler = new Handler(){
public void handleMessage(Message msg){
if(msg.what == CLOSE)
MyActivity.this.finish();
}
});
my_class.setOnWantToCloseListener(new OnWantToCloseListener(){
public void onWantToClose(){
handler.sendEmptyMessage(CLOSE);
}
});
}
}
This is secure because Activity is not finished directly by MyClass object, it is finished through a listener that orders a handler to finish activity. Even if you run MyClass object on a second thread this code will works nice.
EDIT: CLOSE var added I forget to declare and initialize this.

Pass the MyActivity to MyClass as an Activity. From there you can call myActivity.finish();
For example:
private Activity myActivity;
public MyClass(Activity myActivity){
this.myActivity = myActivity;
}
public void stopMyActivity(){
myActivity.finish();
}
And in MyActivity:
MyClass myClass = new MyClass(this);
This is risky, because you're holding a reference to an Activity, which can cause memory leaks.

If your java class is a nested inner class, you can use:
public class MyActivity extends Activity {
public static class JavaClass {
public void finishActivity() {
MyActivity.finish();
}
}
}
Otherwise you'll have to pass the java class a Context (i.e. pass it a reference to this, since Activity extends Context) and store it as a private instance variable.

Extend Activity and ActivityGroup

I'm writing an application in which i have a set of code which i want to be available in all of my Activities and ActivityGroups. However, to achieve this, I have extended my activities as:
//custom Activity
public abstract class BaseActivity extends Activity
//custom ActivityGroup
public abstract class BaseActivityGroup extends ActivityGroup
//implemented activities in my app
public class PickUser extends BaseActivity
//and
public class Home extends BaseActivityGroup
Now the thing is, whatever the custom code i write in BaseActivity, I have to write the same in BaseActivityGroup too (as in current implementation). This is prone to code-sync problems and i believe not a good technique.
So, how can i make my extensions in such a way that I only write custom code in BaseActivity and my BaseActivityGroup extends ActivityGroup - which is conceived from BaseActivity class?
If i observe how android does this, so the ActivityGroup in android extends Activity class. And I also want to write my custom ActivityGroup class (known as BaseActivityGroup) that actually extends BaseActivity (which is an extended Activity).
Any ideas/suggestions?

First of all ActivityGroups are bad and should not be used. They are deprecated and it is preferred to use a single activity with multiple fragments.
If you must use an activitygroup you are probably best of by implementing a delegate pattern.
Create a delegate that handles all the common methods such as onCreate, onResume and use that in the bases. In this example I save a reference to the activity in the delegate. This circular referencing might not be the pretties. An alternative is to pass on the activity to the methods in the delegate.
public class ActivityDelegate() {
private Activity mActivity;
public ActivityDelegate(final Activity activity) {
mActivity = activity;
}
public void onCreate(final Bundle savedInstanceState) {
// Do stuff.
}
}
public abstract class BaseActivity extends Activity {
private ActivityDelegate mDelegate = new ActivityDelegate(this);
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mDelegate.onCreate(savedInstanceState);
}
...
}
public abstract class BaseActivityGroup extends ActivityGroup {
private ActivityDelegate mDelegate = new ActivityDelegate(this);
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mDelegate.onCreate(savedInstanceState);
}
...
}

Add an extra final class, called Base.
This one will only contain methods to be called by the other Base classes, such as for instance:
public static boolean createOptionsMenu(final Menu menu,
final MenuInflater inflater) {
inflater.inflate(R.menu.main_menu, menu);
return true;
}
Then, in your BaseActivity and BaseActivityGroup classes, you would call:
#Override
public final boolean onCreateOptionsMenu(final Menu menu) {
return Base.createOptionsMenu(menu, getMenuInflater());
}
Hope it helps!

Just Extend everything to BaseActivity including BaseGroupActivity as everything is a child of Activity in android

you can put your login in a separate file under a method. now call the same method from both BaseActivity and BaseActivityGroup if you need activity instance in file . pass context through constructor

How to use setContentView(int) from class which does not extend Activity

I need to call the setContentView(int) from my main Activity from another class which does not extends Activity.
In my custom class I've got the private Context context; var that is passed from the Activity in the Constructor but I can't figure out how to acces the Activity methods using the context variable.

If your context is an instance of Activity class, simple class cast should work:
Activity a = (Activity) context;
a.setContentView(R.layout.your_layout);

One solution (may not be the most elegant) is to pass the calling activity to the other class, not just the context.

You would have to pass in a reference to the Activity you're using.
Something like this
class ActivityA extends Activity{
#Override
public void onCreate(Bundle state){
super.onCreate(state);
ClassA myclass = new ClassA(this);
}
}
And then Class A would have:
class ClassA {
public ClassA(Activity yourActivity){
... Get your view here ....
yourActivity.setContentView(view);
... do more things...
}
}