CODEWITHSUNDEEP
androidandroid-layout
Kanwar Saad
Kanwar Saad

Reputation: 2329

Android Application Init and global objects

Hi I am new to android programming and I was having some issues in application initialization. I will explain app structure first and then problems.

The application has a thread which should always run and listen on Datagram socket. Whenever a message is received it takes appropriate actions. On certain actions I needed Context object and I also use Handler object for passing data to UI thread. Both of these objects were initialized in my Thread class's constructor by passing from main activity's OnCreate method. Now I am having the problem that whenever my activity is switched or I tilt the phone, all objects in main activity are recreated and the references which I passed before to Thread class of Handler and Context becomes invalid.

How should I handle this problem. Thanks in advance. Application structure is like this.

public class MainActivity extends Activity {
    private Context ctx;
    Handler handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            Bundle bundle = msg.getData();
            String mtype = bundle.getString("mtype");

            // DO SOME STUFF HERE //

        }

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        // OTHER INITIALIZATIONS //

        ctx = this;
        rxThread = new ControlReceiver(ctx, handler);
        rxThread.start();

    }
};

The thread class is like this.

public class ControlReceiver extends Thread {
    private Context context;
    private Handler handler;


    ControlReceiver(Context c, Handler h){
        context = c;
        handler = h;
    }

    public void run() {

        // DO STUFF HERE //

        // SEND MESSAGE TO UI //
        msg = handler.obtainMessage();
        bundle = new Bundle();
        bundle.putString("mtype", "ECHTB");
        msg.setData(bundle);
        handler.sendMessage(msg);

    }
};

Upvotes: 1

Views: 3178

Answers (2)

Gomoku7
Gomoku7

Reputation: 1372

There seems to be two school for managing objects that have an application lifecycle:

  • singleton
  • application objects

Here's the so topic about it : Singletons vs. Application Context in Android?

I think it mainly depends on the use case and in your particular code sample I would favor the creation of a singleton which would keep the controlreceiver alive and available to any activity (to be more precise, the singleton would manage the lifecycle of the controlreceiver).

Upvotes: 1

edestrero
edestrero

Reputation: 516

my two ways to avoid objects recreation on phone rotation: 1) force the orientation (vertical/horizontal) in the manifest for that activity

<activity
android:name=".MainMenu"
android:screenOrientation="portrait" >
</activity>

2) manage the orientation, in the manifest declaring your activity will take care of changes

<activity
android:name=".tools.ToolGPSRecorder"
android:configChanges="keyboardHidden|orientation|screenSize"
android:screenOrientation="sensor" >
</activity>

in this case, in the activity the event onConfigurationChanged will be fired whire rotating the phone, in this event you will load a layout, that could be a specific layout-land one.

i.e.
@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    MyLog.d("ToolGPSRecorder.onConfigurationChanged");
    setContentView(R.layout.tool_gpsrecorder);
    ResetTimersAndLogs();
    ShowCoveredDistance();
    UpdateRecordingTime();
    ...

Upvotes: 0

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