Android - How to retrieve data from activity

I am new to android so please excuse the newbie question. I have a game I am trying to port from an old Java applet to android. My goal is to get this functional and then post an article on a site like CodeProject (or a better one if there are ones more appropriate). The idea is to show that a person brand new to android development can create an app in a reasonable amount of time.

I am making some progress but have run into a problem. I have the main activity in which the user interacts with. I then created a menu item that in turn starts a second activity (call it child) with a modest number of checkbox's, seekbar's etc to fill in parameters. I can successfully pass the class containing all the options from main to child. But I cannot get the child to pass this data back to the main. First here is my main code that starts the child activity:

public void addBalls()
{
    Intent myIntent = new Intent(this, GameOptions.clas开发者_运维技巧s);

    Bundle b = new Bundle();
    b.putSerializable("options", gameParams);
    myIntent.putExtras(b);
    startActivityForResult(myIntent,STATIC_OPTIONS_VALUE);
}

The data passed to the child (and hopefully back again) is:

public class GameOptionParams implements Serializable
{
    private static final long serialVersionUID = 1L;

    public int speedBarPosition;
    public int vgravityBarPosition;
    public int mgravityBarPosition;
    public int viscosityBarPosition;
    public int restititionBarPosition;
    public boolean trace;
    public boolean collide;
    public boolean mush;
    public boolean wrap;
    public boolean flicker;
}

And here is the expected return (again in main)

@Override 
public void onActivityResult(int requestCode, int resultCode, Intent data) 
{     
  super.onActivityResult(requestCode, resultCode, data); 
  switch(requestCode) 
  { 
    case (STATIC_OPTIONS_VALUE) : 
    { 
      if (resultCode == Activity.RESULT_OK) 
      { 
          //retrieve intended options
          Bundle b = data.getExtras();
          gameParams = (GameOptionParams) b.getSerializable("options");
      } 
      break; 
    } 
  } 
}

The child activity successfully receives the gameParams data. It then interacts with the user to update the values and then I attempt to return it but it does not seem to get sent to main. Here is the child code in the onStop() override. Maybe this code should not be in the onStop() override but I can't determine where else to place it.

@Override
public void onStop()
{
    super.onStop();

    //read widget values
    gameParams.speedBarPosition     = speedBar.GetPosition();
    gameParams.vgravityBarPosition      = vgravityBar.GetPosition();
    gameParams.mgravityBarPosition      = mgravityBar.GetPosition();
    gameParams.viscosityBarPosition = viscosityBar.GetPosition();
    gameParams.restititionBarPosition   = restititionBar.GetPosition();

    //todo save to persistent   
    Intent resultIntent = new Intent(this, TiltBall2ImpactActivity.class);
    Bundle b = new Bundle();
    b.putSerializable("options", gameParams);
    resultIntent.putExtras(b);
    setResult(Activity.RESULT_OK, resultIntent);
}

Back in the main onActivityResult override I always see requestCode=0, resultCode=0, data=null. I assume this is a typical newbie problem, I have been reading the sdk documentation, user forums etc and have come close to a solution but just not quite there yet. Any help would be appreciated.

---

Since this is sort of a setting menu for the game, I assume you are going to need these values for more than one activity. If so you extend the android.app.Application class.

In that class you can create attributes to hold your values. In any activity you can call

MyApplication myApp = (MyApplication)getApplicationContext();

where myApp is a singleton. So you will get the values you set from another activity.

You will need to add this code to your application tag in the manifest file for it to work

android:name=".MyApplication"

If you need to keep these values for next startup of the application, you need to use SharedPreferences. This is a good tutorial for that

http://saigeethamn.blogspot.com/2009/10/shared-preferences-android-developer.html

---

Assuming in your 'child' activity, the user has to press an 'OK' or 'Save' button then put the code to set the gameParams parameters in the button's onClick(...) handler.

Use the default constructor for instantiating the Intent, example...

Intent resultIntent = new Intent();

...then after creating the Bundle and adding gameParams to it and calling setResult(...), simply call finish() to terminate the 'child' activity. There aren't many occasions that I can think of to override onStop() and I suspect you don't want to be using it to attempt returning the Intent.