Question

我是Android环境中的新手，因此我想知道这种情况下的最佳做法。

我在Android中有一个扫描仪应用程序，根据每次扫描的结果，我有方法startActivityForResult，我可以根据结果调用不同的活动。

我的代码的初始版本......我在每个Activity中复制/粘贴相同的方法，显然这是一种犯罪，我知道它很糟糕。

现在有了更多时间，我想更正这一部分，为此，我使用方法startActivityForResult创建了一个独立活动，并想在每个活动中调用此方法，但没有工作：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)

我正在考虑使用Fragments，但最后我认为这是另一回事..

Android中这种情况下的最佳做法是什么？

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

正如评论中所提到的，你不能只是实例化一个活动。

您应该将控制活动更改为创建适当意图的工厂

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
    }

}

然后你的onActivityResult会开始活动

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
        }
}

Android Helper Class可以调用几个Activity

1 个答案: