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我想找到附近的蓝牙设备，所以我使用BroadcastReceiver。大多数时候它工作正常，但有时我得到这个错误。接收蓝牙发现的广播错误
04-30 09:50:15.277: E/AndroidRuntime(847): FATAL EXCEPTION: main
04-30 09:50:15.277: E/AndroidRuntime(847): java.lang.RuntimeException: Error receiving broadcast Intent { act=android.bluetooth.device.action.FOUND (has extras) } in [email protected]
04-30 09:50:15.277: E/AndroidRuntime(847): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:722)
04-30 09:50:15.277: E/AndroidRuntime(847): at android.os.Handler.handleCallback(Handler.java:587)
04-30 09:50:15.277: E/AndroidRuntime(847): at android.os.Handler.dispatchMessage(Handler.java:92)
04-30 09:50:15.277: E/AndroidRuntime(847): at android.os.Looper.loop(Looper.java:130)
04-30 09:50:15.277: E/AndroidRuntime(847): at android.app.ActivityThread.main(ActivityThread.java:3683)
04-30 09:50:15.277: E/AndroidRuntime(847): at java.lang.reflect.Method.invokeNative(Native Method)
04-30 09:50:15.277: E/AndroidRuntime(847): at java.lang.reflect.Method.invoke(Method.java:507)
04-30 09:50:15.277: E/AndroidRuntime(847): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-30 09:50:15.277: E/AndroidRuntime(847): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-30 09:50:15.277: E/AndroidRuntime(847): at dalvik.system.NativeStart.main(Native Method)
04-30 09:50:15.277: E/AndroidRuntime(847): Caused by: java.lang.NullPointerException
04-30 09:50:15.277: E/AndroidRuntime(847): at com.waratah.app.SetMachineActivity$2.onReceive(SetMachineActivity.java:532)
04-30 09:50:15.277: E/AndroidRuntime(847): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:709)
04-30 09:50:15.277: E/AndroidRuntime(847): ... 9 more
这表明NullPointerException异常，但我不明白怎么能发生这种错误，因为我检查变量，以避免例外。
// The BroadcastReceiver that listens for discovered devices and
// changes the title when discovery is finished
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
if (intent == null) {
return;
}
String action = intent.getAction();
int i;
Machine d;
if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
if (mBtAdapter.isEnabled()) {
if(D) Log.d(BroadcastReceiver.class.getName(), "Bluetooth is enabled");
pd.dismiss();
}
doDiscovery();
// when bluetooth device is found
} else if (BluetoothDevice.ACTION_FOUND.equals(action)) {
if(D) Log.d(BroadcastReceiver.class.getName(), "found");
// Get the BluetoothDevice object from the Intent
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if (device != null) {
// Check if the device has name
if ((device.getName() != null)||(device.getName().length() > 0)) { //LINE 532 HERE
d = new Machine(device);
if (d.getPairingState() != BluetoothDevice.BOND_BONDED) {
d.setBluetoothState(true);
addDevice(d);
} else {
for (i = 0; i < adapter.getCount(); i++) {
if (adapter.getItem(i).getAddress().equals(device.getAddress())) {
adapter.getItem(i).setBluetoothState(true);
}
}
}
}
}
// When discovery is finished, change the Activity title
} else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
scanButton.setVisibility(View.VISIBLE);
pb.setVisibility(View.GONE);
scanning.setVisibility(View.GONE);
}
}
};
我已经注册了我的所有操作并正确注册了我的接收器。此错误偶尔会发生。 onReceive（）函数在没有任何东西可以被接收时触发吗？
感谢您的帮助。
编辑：532 线是
if ((device.getName() != null)||(device.getName().length() > 0)) {
所以这意味着设备必须是空的，但这样做的前一行的检查。
if (device != null) {
顺便说一下，两个广播接收机同时运行会导致这种错误吗？广播接收器收到后是否为空？
啊，什么SPECIFIC行有NullPointerException？你真的可以突出显示第532行，这是发生异常的地方。 – Femi
@Femi我无法突出显示代码行，因此我添加了一条评论，并单独引用了532行。 – Mira