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我想找到附近的藍牙設備，所以我使用BroadcastReceiver。大多數時候它工作正常，但有時我得到這個錯誤。接收藍牙發現的廣播錯誤
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
這表明NullPointerException異常，但我不明白怎麼能發生這種錯誤，因爲我檢查變量，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);
}
}
};
我已經註冊了我的所有操作並正確註冊了我的接收器。此錯誤偶爾會發生。 onReceive（）函數在沒有任何東西可以被接收時觸發嗎？
感謝您的幫助。
編輯：532 線是
if ((device.getName() != null)||(device.getName().length() > 0)) {
所以這意味着設備必須是空的，但這樣做的前一行的檢查。
if (device != null) {
順便說一下，兩個廣播接收機同時運行會導致這種錯誤嗎？廣播接收器收到後是否爲空？
啊，什麼SPECIFIC行有NullPointerException？你真的可以突出顯示第532行，這是發生異常的地方。 – Femi
@Femi我無法突出顯示代碼行，因此我添加了一條評論，並單獨引用了532行。 – Mira