Android Helper類調用多個活動

Question

我是Android環境中的新手，因此我想了解這種情況下的最佳做法。

我在Android中有一個掃描儀應用程序，具體取決於每次掃描的結果，我具有方法startActivityForResult ，在其中可以根據結果調用不同的Activity。

我的代碼的初始版本...我在每個Activity中復制/粘貼相同的方法，顯然這是犯罪，而且我知道這很糟糕。

現在，我有更多時間要更正此部分，為此，我使用startActivityForResult方法創建了一個獨立活動，其想法是在每個活動中調用此方法，但沒有用： 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)

我當時想使用Fragments，但最終我認為這是另一回事。

在這種情況下，Android的最佳做法是什么？

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

如評論中所述，您不能僅實例化一個活動。

您應該將控制活動更改為創建適當意圖的工廠

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
    }

}

然后，您的onActivityResult將啟動活動

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
        }
}