在现有项目中使用 Zebra Library 时出现 NullPointer

Question

实际上，我正在尝试将 zebra EMDK 库实施到我现有的项目中。我已逐步执行以下 guide 并且在一个新项目中一切正常，但是当我尝试在我的项目中使用该库时出现以下错误：

2019-03-13 15:24:55.720 4671-4678/it.gabtamagnini.realco E/art: Failed sending reply to debugger: Broken pipe
2019-03-13 15:25:01.239 4671-4671/it.gabtamagnini.realco E/AndroidRuntime: FATAL EXCEPTION: main
    Process: it.gabtamagnini.realco, PID: 4671
    java.lang.RuntimeException: Unable to start activity ComponentInfo{it.gabtamagnini.realco/it.gabtamagnini.realco.InventarioActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.contentEquals(java.lang.CharSequence)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2666)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2727)
        at android.app.ActivityThread.-wrap12(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1478)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6123)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.contentEquals(java.lang.CharSequence)' on a null object reference
        at it.gabtamagnini.realco.InventarioActivity.handleDecodeData(InventarioActivity.java:1160)
        at it.gabtamagnini.realco.InventarioActivity.onCreate(InventarioActivity.java:129)
        at android.app.Activity.performCreate(Activity.java:6723)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2619)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2727) 
        at android.app.ActivityThread.-wrap12(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1478) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6123) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)

获取空指针的代码：

  private void handleDecodeData(Intent i) {
        //Check the intent action is for us
        if (i.getAction().contentEquals("com.symbol.emdksample.RECVR")) {
            //Get the source of the data
            String source = i.getStringExtra("com.motorolasolutions.emdk.datawedge.source");

            //Check if the data has come from the Barcode scanner
            if (source.equalsIgnoreCase("scanner")) {
                //Get the data from the intent
                String data = i.getStringExtra("com.motorolasolutions.emdk.datawedge.data_string");

                //Check that we have received data
                if(data != null && data.length() > 0)
                {
                    Toast.makeText(InventarioActivity.this,data,Toast.LENGTH_LONG).show();
                }
            }
        }
    }

Answer 1

该教程很旧 - 数据捕获配置文件最近已弃用。如果您在较新的设备上尝试此操作，那么我怀疑 com.motorolasolutions... Intents 已被删除，因为字符串 extra 已经 'com.symbol.datawedge.data_string 相当长一段时间了。我建议阅读 https://developer.zebra.com/community/home/blog/2018/06/03/moving-from-the-emdk-data-capture-profile-to-datawedge which explains what has happened to the Data Capture profile but if you are looking for a known working sample then http://www.darryncampbell.co.uk/2017/12/13/tutorial-scan-with-datawedge-intent-output-on-zebra-devices/ 应该是一个很好的起点。

为了清楚起见，我为 Zebra 工作

在现有项目中使用 Zebra Library 时出现 NullPointer

NullPointer while using Zebra Library in yet existing project

android

barcode-scanner