Question

我创建了一个使用导航抽屉和内部静态片段的活动

@Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = null;

            switch (SectionNumber)
            {
                case 1:
                    rootView = inflater.inflate(R.layout.fragment_main, container, false);
                    break;
                case 2:
                    rootView = inflater.inflate(R.layout.fragment_movement, container, false);
                    movementActivity = new MovementActivity(context);
                    movementActivity .setUp();
                    break;
                case 3:
                    rootView = inflater.inflate(R.layout.fragment_main, container, false);
                    marketActivity = new MarketActivity(context);
                    marketActivity.loadMarkets(rootView);
                    break;
                case 4:
                    rootView = inflater.inflate(R.layout.fragment_main, container, false);
                    break;
            }
            return rootView;
        }

我的设置功能在movingActivity Activity

中

public void setUp()
{
    Intent intent = new Intent("com.google.zxing.client.android.SCAN");
    intent.putExtra("com.google.zxing.client.android.SCAN.SCAN_MODE", "QR_CODE_MODE");
    startActivityForResult(intent, 0);
}

和onActivityResult也在movementActivity中

public void onActivityResult(int requestCode, int resultCode, Intent intent)
        {
            Log.e("onActivityResult", "1");
            if(requestCode == 0)     {

                if(resultCode == RESULT_OK)         {
                    Log.e("onActivityResult", "3");


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

                    Log.e("onActivityResult", "2");
                    Log.i("xZing", "contents: "+contents+" format: "
                            +format);

                    // Handle successful scan
                }
                else if(resultCode == RESULT_CANCELED)
                {              // Handle cancel
                    Log.i("xZing", "Cancelled");
                }
            }
        }

问题是当我调用setup函数时出现此错误

07-13 05:26:32.803  20962-20962/com.baagmn.routingware E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
        at android.app.Activity.startActivityForResult(Activity.java:3204)
        at com.baagmn.routingware.Activities.SettingActivities.MovementActivity.setUp(MovementActivity.java:40)
        at com.baagmn.routingware.Activities.MainActivity$PlaceholderFragment.onCreateView(MainActivity.java:164)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:828)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1032)
        at android.app.BackStackRecord.run(BackStackRecord.java:622)
        at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1382)
        at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
        at android.os.Handler.handleCallback(Handler.java:605)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4627)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576)
        at dalvik.system.NativeStart.main(Native Method)

抱歉我的英语不好，我希望你明白我的问题

Answer 1

我猜你没有在该设备上安装zxing活动。

https://play.google.com/store/apps/details?id=com.google.zxing.client.android&hl=en

您使用的方法要求安装您的活动和独立的zxing活动。如果您想直接集成，则需要更复杂的计划。你可以做，但我没有在我面前。

但是，通常情况下，我希望错误比NPE更强，所以我错了。

Answer 2

在zxing中使用意图最安全的方法是使用IntentIntegrator类 - 这样可以优雅地处理条形码扫描器应用程序未安装在设备上的情况。要使用它，请在setUp（）方法中尝试：

public void setUp() {
    IntentIntegrator integrator = new IntentIntegrator(this);
    integrator.addExtra("SCAN_MODE", "QR_CODE_MODE");
    integrator.initiateScan();
}

当设备上com.google.zxing.client.android.SCAN不存在时，应该避免使用NPE。

从活动中打电话给zxing

2 个答案: