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POHow to broadcast a parcelable object in an intent?
 

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  1. POHow to broadcast a parcelable object in an intent?
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    <p>I'm new to Java / Android and trying to develop an adroid application which communicates with a USB CAN Bus adapter. I receive messages from the adapter in a string via my CANBusController class and I have built a parcelable class, CANMessage, which converts the string received into a form I can use (int Id, int Length, byte[] data). Now I'm trying to display the message I have received. I have a Fragment, CANBusControlFragment, which declares a BroadcastReceiver. When a message is a received, I build my CANMessage, place it and its string into a bundle, place the bundle into an Intent, and use sendBroadcast(intent):</p> <pre><code>CANBusController { public void handleMessage(Message msg) { Bundle bundle = msg.getData(); CANMessage canMsg = bundle.getParcelable("CAN_MESSAGE"); if (canMsg != null) { Intent intent = new Intent(); intent.setAction(BroadcastActions.CAN_MESSAGE_RECEIVED); //intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); intent.putExtra("CAN_MESSAGE", canMsg); intent.putExtra("STRING_MESSAGE", canMsg.toString()); parentContext.sendBroadcast(intent); } } } CANBusControlFragment extends Fragment { private final BroadcastReceiver canMsgReceiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { String action = intent.getAction(); Bundle bundle = intent.getExtras(); try { if (BroadcastActions.CAN_MESSAGE_RECEIVED.equals(action)) { synchronized(this) { String str = bundle.getString("STRING_MESSAGE"); // &lt;-- Crash CANMessage canMsg = bundle.getParcelable("CAN_MESSAGE"); // Append(str); Append(canMsg.toString(); } } } catch (Exception ex) print exception } } } </code></pre> <p>If I add the CANMessage to the bundle, my application will crash in the onReceived method of the BroadcastReceiver with a Null Pointer Exception when I try to getString or getParcelable. If I do not include the CANMessage, then the application will work fine. I believe CANMessage implements Parcelable correctly, since I've tested it by performing all of the same steps except for broadcasting the message: Build CANMessage, putParcelable in Bundle, put Bundle in Intent, grab the Bundle out of the Intent, getParcelable out of the bundle.</p> <p>I appreciate any help. Thanks :)</p> <p>EDIT - LogCat information: It appears the error is in my parcel methods. Trying to readByteArray(byte[]) crashes the app.</p> <pre><code>11-12 09:17:44.568: E/AndroidRuntime(3087): FATAL EXCEPTION: main 11-12 09:17:44.568: E/AndroidRuntime(3087): java.lang.RuntimeException: Error receiving broadcast Intent { act=com.sb2tablet.CAN_MESSAGE_RECEIVED flg=0x10000010 (has extras) } in com.sb2tablet.CANBusControlFragment$1@9e8f6e00 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:768) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Handler.handleCallback(Handler.java:725) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Handler.dispatchMessage(Handler.java:92) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Looper.loop(Looper.java:137) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.app.ActivityThread.main(ActivityThread.java:5041) 11-12 09:17:44.568: E/AndroidRuntime(3087): at java.lang.reflect.Method.invokeNative(Native Method) 11-12 09:17:44.568: E/AndroidRuntime(3087): at java.lang.reflect.Method.invoke(Method.java:511) 11-12 09:17:44.568: E/AndroidRuntime(3087): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 11-12 09:17:44.568: E/AndroidRuntime(3087): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 11-12 09:17:44.568: E/AndroidRuntime(3087): at dalvik.system.NativeStart.main(Native Method) 11-12 09:17:44.568: E/AndroidRuntime(3087): Caused by: java.lang.NullPointerException 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Parcel.readByteArray(Parcel.java:1594) 11-12 09:17:44.568: E/AndroidRuntime(3087): at com.sb2tablet.models.CANMessage.&lt;init&gt;(CANMessage.java:93) 11-12 09:17:44.568: E/AndroidRuntime(3087): at com.sb2tablet.models.CANMessage$1.createFromParcel(CANMessage.java:18) 11-12 09:17:44.568: E/AndroidRuntime(3087): at com.sb2tablet.models.CANMessage$1.createFromParcel(CANMessage.java:1) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Parcel.readParcelable(Parcel.java:2103) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Parcel.readValue(Parcel.java:1965) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Parcel.readMapInternal(Parcel.java:2226) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Bundle.unparcel(Bundle.java:223) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.os.Bundle.containsKey(Bundle.java:271) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.content.Intent.hasExtra(Intent.java:4121) 11-12 09:17:44.568: E/AndroidRuntime(3087): at com.sb2tablet.CANBusControlFragment$1.onReceive(CANBusControlFragment.java:51) 11-12 09:17:44.568: E/AndroidRuntime(3087): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:758) </code></pre> <p>Edit - writeToParcel and Parcel in:</p> <pre><code>public void writeToParcel(Parcel out, int flags) { out.writeValue(id); // int out.writeValue(len); // int out.writevalue(data); // byteArray, the value is not null here //out.writeByArray(data); } public CANMessage(Parcel in) { id = in.readInt(); len = in.readInt(); in.readByteArray(data); // Actual crash is here } </code></pre> <p>EDIT - Test Case 1 - It seems extra data is added to my parcel, I'm not sure how.</p> <pre><code>public void writeToParcel(Parcel out, int flags) { out.writeValue(id); // int = 256 out.writeValue(len); // int = 2, length of byte array out.writevalue(data); // byte array = { 17, 51 } } public CANMessage(Parcel in) { len = in.readInt(); // 1 id = in.readInt(); // 256 len = in.readInt(); // 1 len = in.readInt(); // 2 int i = in.readInt(); // 13 if (data == null) data = new byte[len]; in.readByteArray(data); // data = { 17, 51 } } </code></pre> <p>EDIT - Test Case 2</p> <pre><code>public void writeToParcel(Parcel out, int flags) { out.writeValue(id); // int = 256 out.writeValue(len); // int = 2, length of byte array out.writeByteArray(data); // byte array = { 17, 51 } } public CANMessage(Parcel in) { len = in.readInt(); // 1 id = in.readInt(); // 256 len = in.readInt(); // 1 len = in.readInt(); // 2 len = in.readInt(); // 2 if (data == null) data = new byte[len]; // in.readByteArray(data); // Crashes int i = in.readInt(); // 13073 = 0x3311 = byte[] { 17, 51 } } </code></pre>
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      1. POHow to broadcast a parcelable object in an intent?
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      1. POHow to broadcast a parcelable object in an intent?
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    1. COPost the errors from the logcat. Are you getting a "class not found" exception?
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      1. POHow to broadcast a parcelable object in an intent?
      1. USDavid Wasser
    2. COJust posted the logcat errors. Seems I do not understand Parcels well :)
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      1. POHow to broadcast a parcelable object in an intent?
      1. USbergermeister
    3. COParcel is just a serialization technique. This is actually a pretty common problem. See my answer.
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      1. POHow to broadcast a parcelable object in an intent?
      1. USDavid Wasser
 

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