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POAndroid bluetooth connection fails on the first try
 

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  1. POAndroid bluetooth connection fails on the first try
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    <p>I'm developing two bluetooth apps, both are based on the bluetoothChat sample but one of them is also able to send/receive data from a microcontroller using the USB Accessory mode. These apps run on two different devices, a Nexus 4 and a V301 (a chinese phone). In general everything works fine, the problem is just that on the first try the two devices are not able to make a bluetooth connection. The bluetoothChat app is simply not able to make a connection, the other app (BT+USB) stops and crashes if I try to make a connection. The thing is though, after this crash, everything works fine and I'm able to eventually make a connection from both the two apps. Here are the two android manifest and the error that comes out when the BT+USB app crashes. </p> <p>The error displayed by the Eclipse console:</p> <pre><code>06-24 12:40:10.090: W/dalvikvm(5886): threadid=1: thread exiting with uncaught exception (group=0x40a98390) 06-24 12:40:10.110: E/AndroidRuntime(5886): FATAL EXCEPTION: main 06-24 12:40:10.110: E/AndroidRuntime(5886): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { (has extras) }} to activity {com.example.bluetoothx10y/com.example.bluetoothx10y.BluetoothChat}: java.lang.NullPointerException 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.app.ActivityThread.deliverResults(ActivityThread.java:2988) 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.app.ActivityThread.handleSendResult(ActivityThread.java:3031) 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.app.ActivityThread.access$1100(ActivityThread.java:126) 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1185) 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.os.Handler.dispatchMessage(Handler.java:99) 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.os.Looper.loop(Looper.java:137) 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.app.ActivityThread.main(ActivityThread.java:4482) 06-24 12:40:10.110: E/AndroidRuntime(5886): at java.lang.reflect.Method.invokeNative(Native Method) 06-24 12:40:10.110: E/AndroidRuntime(5886): at java.lang.reflect.Method.invoke(Method.java:511) 06-24 12:40:10.110: E/AndroidRuntime(5886): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787) 06-24 12:40:10.110: E/AndroidRuntime(5886): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554) 06-24 12:40:10.110: E/AndroidRuntime(5886): at dalvik.system.NativeStart.main(Native Method) 06-24 12:40:10.110: E/AndroidRuntime(5886): Caused by: java.lang.NullPointerException 06-24 12:40:10.110: E/AndroidRuntime(5886): at com.example.bluetoothx10y.BluetoothChat.onActivityResult(BluetoothChat.java:537) 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.app.Activity.dispatchActivityResult(Activity.java:4649) 06-24 12:40:10.110: E/AndroidRuntime(5886): at android.app.ActivityThread.deliverResults(ActivityThread.java:2984) 06-24 12:40:10.110: E/AndroidRuntime(5886): ... 11 more </code></pre> <p>The android manifest of the BT+USB app (called bluetoothx10y):</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.bluetoothx10y" android:versionCode="1" android:versionName="1.0" &gt; &lt;uses-sdk android:minSdkVersion="9" android:targetSdkVersion="15" /&gt; &lt;uses-feature android:name="android.hardware.usb.accessory"/&gt; &lt;uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" /&gt; &lt;uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /&gt; &lt;uses-permission android:name="android.permission.BLUETOOTH"/&gt; &lt;uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/&gt; &lt;application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" &gt; &lt;activity android:name="com.example.bluetoothx10y.BluetoothChat" android:label="@string/app_name" android:screenOrientation="landscape" &gt; &lt;intent-filter&gt; &lt;action android:name="android.intent.action.MAIN" /&gt; &lt;category android:name="android.intent.category.LAUNCHER" /&gt; &lt;/intent-filter&gt; &lt;intent-filter&gt; &lt;action android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED"/&gt; &lt;/intent-filter&gt; &lt;meta-data android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED" android:resource="@xml/accessory_filter"&gt; &lt;/meta-data&gt; &lt;/activity&gt; &lt;activity android:name=".DeviceListActivity" android:label="@string/app_name" android:theme="@android:style/Theme.Dialog" android:screenOrientation="landscape" /&gt; &lt;/application&gt; &lt;/manifest&gt; </code></pre> <p>The android manifest of the BT app (called BluetoothChat):</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.android.BluetoothChat" android:versionCode="1" android:versionName="1.0"&gt; &lt;uses-sdk android:minSdkVersion="6" android:targetSdkVersion="9" /&gt; &lt;uses-permission android:name="android.permission.BLUETOOTH_ADMIN" /&gt; &lt;uses-permission android:name="android.permission.BLUETOOTH" /&gt; &lt;application android:label="@string/app_name" android:icon="@drawable/app_icon" &gt; &lt;activity android:name=".BluetoothChat" android:label="@string/app_name"&gt; &lt;intent-filter&gt; &lt;action android:name="android.intent.action.MAIN" /&gt; &lt;category android:name="android.intent.category.LAUNCHER" /&gt; &lt;/intent-filter&gt; &lt;/activity&gt; &lt;activity android:name=".DeviceListActivity" android:label="@string/select_device" android:theme="@android:style/Theme.Dialog" /&gt; &lt;/application&gt; &lt;/manifest&gt; </code></pre> <p>At line 536 and 537 I have:</p> <pre><code>mBluetoothAdapter.getRemoteDevice(address); // Attempt to connect to the device mChatService.connect(device); </code></pre> <p>mChatService is an object of the class responsible for setting up and managing the Bluetooth connection</p> <pre><code>public synchronized void connect(BluetoothDevice device) { if (D) Log.d(TAG, "connect to: " + device); // Cancel any thread attempting to make a connection if (mState == STATE_CONNECTING) { if (mConnectThread != null) {mConnectThread.cancel(); mConnectThread = null;} } // Cancel any thread currently running a connection if (mConnectedThread != null) {mConnectedThread.cancel(); mConnectedThread = null;} // Start the thread to connect with the given device mConnectThread = new ConnectThread(device); mConnectThread.start(); setState(STATE_CONNECTING); } </code></pre>
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    1. COWhat is in BluetoothChat.java line 537. You have a NullPointerException there. Examine the stack trace you posted, it tells a lot!
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      1. USallprog
    2. COThis is what I have at line 536 and 537: BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address); // Attempt to connect to the device mChatService.connect(device); mChatService is an object of the class responsible for setting up and managing the Bluetooth connection.
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    3. COIs the address of your remote device being identified? If it's returned as a Null, you'll see that error.
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      1. POAndroid bluetooth connection fails on the first try
      1. USDave Moore
 

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