Question

我正在执行扫描附近蓝牙设备的任务，但我不知道它在哪里出错，因为有时候它会顺利运行但有时会出现错误，如图所示

09-09 16:46:49.574    5577-5577/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: aiyaz.conceptioni.ticket, PID: 5577
    java.lang.NullPointerException
            at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
            at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
            at android.widget.AbsListView.obtainView(AbsListView.java:2341)
            at android.widget.ListView.measureHeightOfChildren(ListView.java:1273)
            at android.widget.ListView.onMeasure(ListView.java:1182)
            at android.view.View.measure(View.java:16845)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
            at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1621)
            at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1199)
            at android.widget.LinearLayout.onMeasure(LinearLayout.java:609)
            at android.view.View.measure(View.java:16845)
            at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:824)
            at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:500)
            at android.view.View.measure(View.java:16845)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
            at android.view.View.measure(View.java:16845)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
            at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1621)
            at android.widget.LinearLayout.measureVertical(LinearLayout.java:742)
            at android.widget.LinearLayout.onMeasure(LinearLayout.java:607)
            at android.view.View.measure(View.java:16845)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5374)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:340)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2368)
            at android.view.View.measure(View.java:16845)
            at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2289)
            at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1355)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1552)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1232)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6271)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:788)
            at android.view.Choreographer.doCallbacks(Choreographer.java:591)
            at android.view.Choreographer.doFrame(Choreographer.java:560)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:774)
            at android.os.Handler.handleCallback(Handler.java:808)
            at android.os.Handler.dispatchMessage(Handler.java:103)
            at android.os.Looper.loop(Looper.java:193)
            at android.app.ActivityThread.main(ActivityThread.java:5347)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:835)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:651)
            at dalvik.system.NativeStart.main(Native Method)

我不知道它在哪里获得NullPointerException。我一直在寻找一整天，但无法找到它。这是我的代码

public class AppSettings extends Activity {

    Button btnLogout;
    ImageView imgBlutoothOnOff,homeIcon;
    boolean isBluetoothOn;
    BluetoothAdapter bluetoothAdapter;
    DatabaseHelper databaseHelper;
    SQLiteDatabase sqLiteDatabase;
    SharedPreferences sharedPreferences;
    ListView bluetoothDeviceList;
    ArrayList<String> bluetoothDeviceName=new ArrayList<>();
    ArrayList<String> bluetoothDeviceId=new ArrayList<>();
    ArrayAdapter<String> arrayAdapter;
    BluetoothDevices getBluetoothDevices;
    CustomProgressDialog customProgressDialog;
    private BroadcastReceiver broadcastReceiver;

@Override
    protected void onCreate(Bundle savedInstance){
        super.onCreate(savedInstance);
        setContentView(R.layout.activity_app_settings);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        bluetoothAdapter=BluetoothAdapter.getDefaultAdapter();
        registerReceiver(mReceiver, new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED));

    initialize();

    imgBlutoothOnOff.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if(isBluetoothOn){
                bluetoothAdapter.disable();
                isBluetoothOn=false;
                imgBlutoothOnOff.setImageResource(R.drawable.bluetooth_key_off);
            }else{
                bluetoothAdapter.enable();
                isBluetoothOn=true;
                imgBlutoothOnOff.setImageResource(R.drawable.bluetooth_key_on);
            }
        }
    });


}
public void initialize(){
    btnLogout=(Button)findViewById(R.id.setting_logout_btn);
    imgBlutoothOnOff=(ImageView)findViewById(R.id.settings_bluetooth_on_off);
    databaseHelper=new DatabaseHelper(AppSettings.this);
    sqLiteDatabase=databaseHelper.getWritableDatabase();
    sharedPreferences=getSharedPreferences(ReferenceStrings.SharedPref,MODE_PRIVATE);

 customProgressDialog=new CustomProgressDialog(AppSettings.this);
    customProgressDialog.setCancelable(true);


    bluetoothDeviceList=(ListView)findViewById(R.id.app_settings_bluetooth_list);
    if(bluetoothAdapter.isEnabled()){
        isBluetoothOn=true;
        imgBlutoothOnOff.setImageResource(R.drawable.bluetooth_key_on);
        IntentFilter filter = new IntentFilter();
        filter.addAction(BluetoothDevice.ACTION_FOUND);
        filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
        filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        this.registerReceiver(mReceiver_search, filter);
        startDiscovery();
    }
    else {
        isBluetoothOn = false;
        imgBlutoothOnOff.setImageResource(R.drawable.bluetooth_key_off);
    }

}

private void getPairedDevices(){

    BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();

    List<String> s = new ArrayList<String>();

    for(BluetoothDevice bt : pairedDevices) {
        s.add(bt.getName());
    }
    startDiscovery();
}


private void startDiscovery(){
    arrayAdapter=new ArrayAdapter<String>(getBaseContext(),android.R.layout.simple_list_item_1,bluetoothDeviceName);
    arrayAdapter.setNotifyOnChange(true);
    bluetoothDeviceList.setAdapter(arrayAdapter);
    bluetoothAdapter.startDiscovery();
}

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    public void onReceive (Context context, Intent intent) {
        String action = intent.getAction();
        if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {
            final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,
                    BluetoothAdapter.ERROR);
            switch (state) {
                case BluetoothAdapter.STATE_OFF:
                    arrayAdapter.clear();
                    arrayAdapter.notifyDataSetChanged();
                    Toast.makeText(context, "Bluetooth is off", Toast.LENGTH_LONG).show();
                    break;
                case BluetoothAdapter.STATE_TURNING_OFF:
                    break;
                case BluetoothAdapter.STATE_ON:
                    Toast.makeText(context, "Bluetooth is on", Toast.LENGTH_LONG).show();
                    startDiscovery();
                    break;
                case BluetoothAdapter.STATE_TURNING_ON:
                    break;
            }
        }
    }
};

final BroadcastReceiver mReceiver_search = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();

        if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
              customProgressDialog.show();
        } else if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
            customProgressDialog.cancel();

        } else if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            //bluetooth device found

    BluetoothDevice device = (BluetoothDevice) intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            bluetoothDeviceName.add(device.getName());
            bluetoothDeviceId.add(device.getAddress());
            arrayAdapter.notifyDataSetChanged();
        }
    }
};

@Override
protected void onPause() {
    super.onPause();
    try {
        if(mReceiver!=null) {
            unregisterReceiver(mReceiver);
        }
    }catch (Exception e){

    }
}
}

请忽略未使用的变量。如果我做错了，请告诉我。谢谢。：）

Answer 1

小心，找到的蓝牙设备可以有一个空名称。因此，如果您在适配器中使用bluetoothDeviceName.add(device.getName());，请检查它。

扫描蓝牙设备时出错

1 个答案: