[英]JSON error Caused by: java.lang.NullPointerException
[英]Error receiving broadcast Intent caused by java.lang.NullPointerException
我有一個Cordova插件的代碼,該插件試圖掃描條形碼並發送回結果:
public class Scan extends CordovaPlugin {
private CallbackContext callbackContext;
private Intent intentService = new Intent("com.hyipc.core.service.barcode.BarcodeService2D");
private String strBarcode = "";
BroadcastReceiver receiver;
@Override
public boolean execute(String action, JSONArray data, CallbackContext callbackContext) throws JSONException {
if (action.equals("scan")) {
scan();
return true;
} else {
return false;
}
}
public void scan() {
IntentFilter filter = new IntentFilter();
filter.addAction("action_barcode_broadcast");
if (this.receiver == null) {
this.receiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().equals("action_barcode_broadcast")) {
strBarcode = intent.getExtras().getString("key_barcode_string");
callbackContext.success(strBarcode);
}
}
};
cordova.getActivity().startService(intentService);
cordova.getActivity().registerReceiver(this.receiver, filter);
}
}
}
當我運行它時,我的應用程序崩潰了,我在日志中得到了它:
07-18 08:53:28.583: E/AndroidRuntime(2345): FATAL EXCEPTION: main
07-18 08:53:28.583: E/AndroidRuntime(2345): java.lang.RuntimeException: Error receiving broadcast Intent { act=action_barcode_broadcast flg=0x10 (has extras) } in com.example.plugin.Scan$1@414f29f0
07-18 08:53:28.583: E/AndroidRuntime(2345): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:798)
07-18 08:53:28.583: E/AndroidRuntime(2345): at android.os.Handler.handleCallback(Handler.java:800)
07-18 08:53:28.583: E/AndroidRuntime(2345): at android.os.Handler.dispatchMessage(Handler.java:100)
07-18 08:53:28.583: E/AndroidRuntime(2345): at android.os.Looper.loop(Looper.java:194)
07-18 08:53:28.583: E/AndroidRuntime(2345): at android.app.ActivityThread.main(ActivityThread.java:5392)
07-18 08:53:28.583: E/AndroidRuntime(2345): at java.lang.reflect.Method.invokeNative(Native Method)
07-18 08:53:28.583: E/AndroidRuntime(2345): at java.lang.reflect.Method.invoke(Method.java:525)
07-18 08:53:28.583: E/AndroidRuntime(2345): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
07-18 08:53:28.583: E/AndroidRuntime(2345): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
07-18 08:53:28.583: E/AndroidRuntime(2345): at dalvik.system.NativeStart.main(Native Method)
07-18 08:53:28.583: E/AndroidRuntime(2345): Caused by: java.lang.NullPointerException
07-18 08:53:28.583: E/AndroidRuntime(2345): at com.example.plugin.Scan$1.onReceive(Scan.java:74)
07-18 08:53:28.583: E/AndroidRuntime(2345): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:788)
07-18 08:53:28.583: E/AndroidRuntime(2345): ... 9 more
07-18 08:53:28.608: E/AppErrorDialog(586): Failed to get ILowStorageHandle instance
07-18 08:53:28.640: E/jdwp(2401): Failed sending reply to debugger: Success
07-18 08:53:29.221: E/AEE/DUMPSTATE(2424): copy_file: Copy /data/anr/2345.hprof to PROCESS_OOME_HPROF failed(2), No such file or directory
07-18 08:53:30.547: E/AEE/DUMPSTATE(2424): copy_file: Copy /proc/gpulog to SYS_GPU_INFO failed(2), No such file or directory
07-18 08:53:33.084: E/AEE/DUMPSTATE(2446): copy_process: execv /system/xbin/proc_mem failed(2), No such file or directory
07-18 08:53:33.097: E/AEE/DUMPSTATE(2447): copy_process: execv /system/bin/dmlog failed(2), No such file or directory
07-18 08:53:34.130: E/jdwp(2401): Failed sending reply to debugger: Success
第74行(該日志指示該錯誤導致了錯誤)是我在其中調用callbackContext.success
方法的行。 我確定strBarcode
存在,因為我可以將其記錄在onReceive
函數中。
您只是為CallbackContext
創建一個對象,但沒有通過調用該類的默認構造函數來對其進行初始化。那就是y發生了null pointer exception
所以這樣子
public void scan(CallbackContext context) {
this.callbackContext = context;
IntentFilter filter = new IntentFilter();
filter.addAction("action_barcode_broadcast");
if (this.receiver == null) {
this.receiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
if(intent.getAction().equals("action_barcode_broadcast")) {
strBarcode = intent.getExtras().getString("key_barcode_string");
callbackContext.success(strBarcode);
}
}
};
cordova.getActivity().startService(intentService);
cordova.getActivity().registerReceiver(this.receiver, filter);
}
}
這將修復Null pointer Exception
編輯
問題是返回的callbackContext
和您創建的callbackContext
具有相同的名稱。因此,請修改scan()
這樣看起來會像這樣
scan(callbackContext);
在函數內部
public void scan(CallbackContext clBackCtxt) {
this.callbackContext = clBackCtxt;
// your rest code
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