Android Helper类调用多个活动

Question

I'm a newbie in Android environment, therefore I want to know the best practice in this case.

I have a scanner App in Android, depending the result of each scan I have the method startActivityForResult where I can call different Activities depending of the result.

The initial version of my code... I copy/paste the same method in each Activity, obviously this is a crime, and I know it's awful.

Now with more time, I want to correct this part, for that, I created a Independent Activity with the method startActivityForResult , with the idea to call this method in each Activity, but didn't work: NullPointerException .

@Override
    public void onActivityResult(int requestCode, int resultCode, Intent intent) {

            if (requestCode == SCANNER_REQUEST_CODE) {
                // Handle scan intent
                if (resultCode == Activity.RESULT_OK) {

                    ControllerActivity controllerActivity = new ControllerActivity ();
                    controllerActivity.getActivity(requestCode, resultCode, intent);

                } else if (resultCode == Activity.RESULT_CANCELED) {
                    // Handle cancel
                }
            } else {
                // Handle other intents
            }
    }

---

04-15 17:31:09.279: W/dalvikvm(923): threadid=1: thread exiting with uncaught exception (group=0x40018578)
04-15 17:31:09.289: E/AndroidRuntime(923): FATAL EXCEPTION: main
04-15 17:31:09.289: E/AndroidRuntime(923): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=123, result=-1, data=Intent { act=client.android.SCAN flg=0x80000 (has extras) }} to activity {reader/reader.MainActivity}: java.lang.NullPointerException
04-15 17:31:09.289: E/AndroidRuntime(923):  at android.app.ActivityThread.deliverResults(ActivityThread.java:2536)
04-15 17:31:09.289: E/AndroidRuntime(923):  at android.app.ActivityThread.handleSendResult(ActivityThread.java:2578)

I was thinking to use Fragments, but finally I thought this is for another thing..

What is the best practise in this cases in Android?

public class ControllerActivity extends Activity {

            public void getActivity (int requestCode, int resultCode, Intent intent) {

                        String contents = intent.getStringExtra("SCAN_RESULT");

                        Data data = new Data(contents);
                        Utils utils = new Utils ();

                        String formatName = intent.getStringExtra("SCAN_RESULT_FORMAT");

                        Intent reportActivity = new Intent(this, ReportActivity.class);
                        Intent decodeActivity = new Intent(this, DecodeActivity.class);


                        if (data.Matrix (contents, formatName)){

                            reportActivity.putExtra("IdValue", data.getId());
                            reportActivity.putExtra("PerfValue", data.getPerf());
                            reportActivity.putExtra("MpIdValue", data.getMpId());


                            startActivity(reportActivity);

                        }else if(data.isPool(contents, formatName)){

                            decodeActivity.putExtra("MandValue",dataMatrix.getMand());
                            decodeActivity.putExtra("MaterialValue", decodeActivity.getMaterialNummer());


                            startActivity(decodeActivity);

                        }

Answer 1

As mentioned in comments you cannot just instantiate an Activity.

You should change your control activity to a factory that creates the appropiate Intent

class ControllerIntentBuilder
{
    public static Intent create(Content context, int requestCode, int resultCode, Intent resultIntent)
    {

        String contents = resultIntent.getStringExtra("SCAN_RESULT");

        Data data = new Data(contents);

        String formatName = intent.getStringExtra("SCAN_RESULT_FORMAT");
        if (data.Matrix(contents, formatName))
        {
            Intent activityIntent = new Intent(context, ReportActivity.class);
            activityIntent.putExtra("IdValue", data.getId());
            activityIntent.putExtra("PerfValue", data.getPerf());
            activityIntent.putExtra("MpIdValue", data.getMpId());

            return activityIntent;
        }

        // and so on for other conditions
    }

}

Then your onActivityResult will the one starting the activity

public void onActivityResult(int requestCode, int resultCode, Intent intent) 
{

        if (requestCode == SCANNER_REQUEST_CODE) {
            // Handle scan intent
            if (resultCode == Activity.RESULT_OK) {

                Intent intent = ControllerIntentBuilder.create(this, requestCode, resultCode, intent);
                startActivity(intent);;

            } else if (resultCode == Activity.RESULT_CANCELED) {
                // Handle cancel
            }
        } else {
            // Handle other intents
        }
}