如何解决存储库类将ViewModel中的空值返回到回收者视图列表
到目前为止，这是我的实现。扫描完成后，我试图获取蓝牙设备的列表。但是observer不会返回设备列表。
MainActivity.java
public class MainActivity extends AppCompatActivity {
private static final String TAG = MainActivity.class.getSimpleName();
private static final int REQUEST_CODE_OPEN_GPS = 1;
private static final int REQUEST_CODE_PERMISSION_LOCATION = 2;
BluetoothAdapter bluetoothAdapter;
private MutableLiveData<List<DataModel>> deviceLiveData;
public static List<BleDevice> bleDeviceList;
private List<BleDevice> deviceList = new ArrayList<>();
private RecyclerView rvDevices;
private MAdapter devicesAdapter;
private MainViewModel mainViewModel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bleDeviceList = new ArrayList<>();
rvDevices = findViewById(R.id.main_rv);
BleManager.getInstance().init(getApplication());
BleManager.getInstance()
.enableLog(true)
.setReConnectCount(5,5000)
.setConnectOverTime(20000)
.setOperateTimeout(5000);
checkPermissions();
}
private void checkPermissions() {
bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
if (!bluetoothAdapter.isEnabled()) {
Toast.makeText(this,getString(R.string.please_open_blue),Toast.LENGTH_LONG).show();
return;
}
String[] permissions = {Manifest.permission.ACCESS_FINE_LOCATION,Manifest.permission.ACCESS_COARSE_LOCATION};
List<String> permissionDeniedList = new ArrayList<>();
for (String permission : permissions) {
int permissionCheck = ContextCompat.checkSelfPermission(this,permission);
if (permissionCheck == PackageManager.PERMISSION_GRANTED) {
onPermissionGranted(permission);
} else {
permissionDeniedList.add(permission);
}
}
if (!permissionDeniedList.isEmpty()) {
String[] deniedPermissions = permissionDeniedList.toArray(new String[permissionDeniedList.size()]);
ActivityCompat.requestPermissions(this,deniedPermissions,REQUEST_CODE_PERMISSION_LOCATION);
}
}
Observer<List<BleDevice>> userListUpdateObserver = new Observer<List<BleDevice>>() {
@Override
public void onChanged(List<BleDevice> userArrayList) {
devicesAdapter = new MAdapter(MainActivity.this,userArrayList,new MAdapter.OnClick() {
@Override
public void onItemClick(View v) {
Toast.makeText(MainActivity.this,"Clicked",Toast.LENGTH_SHORT).show();
}
});
rvDevices.setLayoutManager(new LinearLayoutManager(MainActivity.this));
rvDevices.setAdapter(devicesAdapter);
devicesAdapter.notifyDataSetChanged();
}
};
private void onPermissionGranted(String permission) {
switch (permission) {
case Manifest.permission.ACCESS_FINE_LOCATION:
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && !checkGPSIsOpen()) {
new AlertDialog.Builder(this)
.setTitle("Prompt")
.setMessage(R.string.gpsNotifyMsg)
.setNegativeButton(R.string.cancel,new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,int which) {
finish();
}
})
.setPositiveButton(R.string.setting,int which) {
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivityForResult(intent,REQUEST_CODE_OPEN_GPS);
}
})
.setCancelable(false)
.show();
} else {
startScan();
mainViewModel = new ViewModelProvider(MainActivity.this).get(MainViewModel.class);
mainViewModel.getUserMutableLiveData().observe(this,userListUpdateObserver);
}
break;
}
}
private boolean checkGPSIsOpen() {
LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
if (locationManager == null)
return false;
return locationManager.isProviderEnabled(android.location.LocationManager.GPS_PROVIDER);
}
@Override
protected void onActivityResult(int requestCode,int resultCode,Intent data) {
super.onActivityResult(requestCode,resultCode,data);
if (requestCode == REQUEST_CODE_OPEN_GPS) {
if (checkGPSIsOpen()) {
startScan();
}
}
}
@Override
public final void onRequestPermissionsResult(int requestCode,@NonNull String[] permissions,@NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode,permissions,grantResults);
switch (requestCode) {
case REQUEST_CODE_PERMISSION_LOCATION:
if (grantResults.length > 0) {
for (int i = 0; i < grantResults.length; i++) {
if (grantResults[i] == PackageManager.PERMISSION_GRANTED) {
onPermissionGranted(permissions[i]);
}
}
}
break;
}
}
public static void startScan() {
BleManager.getInstance().scan(new BleScanCallback() {
@Override
public void onScanStarted(boolean success) {
}
@Override
public void onLeScan(BleDevice bleDevice) {
super.onLeScan(bleDevice);
}
@Override
public void onScanning(BleDevice bleDevice) {
}
@Override
public void onScanFinished(List<BleDevice> scanResultList) {
bleDeviceList.addAll(scanResultList);
}
});
}
public static void clearScanDevice() {
for (int i = 0; i < bleDeviceList.size(); i++) {
BleDevice device = bleDeviceList.get(i);
if (!BleManager.getInstance().isConnected(device)) {
bleDeviceList.remove(i);
}
}
}
public void addDevice(BleDevice bleDevice) {
removeDevice(bleDevice);
String newBleDeviceName = bleDevice.getMac();
if (newBleDeviceName == null) return;
}
public void removeDevice(BleDevice bleDevice) {
for (int i = 0; i < bleDeviceList.size(); i++) {
BleDevice device = bleDeviceList.get(i);
if (bleDevice.getKey().equals(device.getKey())) {
bleDeviceList.remove(i);
}
}
}
@Override
public void onBackPressed() {
AlertDialog.Builder builder1 = new AlertDialog.Builder(this);
builder1.setTitle("Exit?");
builder1.setMessage("Are you sure you want to disconnect?.");
builder1.setCancelable(true);
builder1.setPositiveButton(
"Yes",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id) {
BleManager.getInstance().disconnectAllDevice();
BleManager.getInstance().destroy();
Toast.makeText(MainActivity.this,"Disconnected",Toast.LENGTH_SHORT).show();
dialog.cancel();
finish();
}
});
builder1.setNegativeButton(
"No",int id) {
dialog.cancel();
}
});
AlertDialog alert11 = builder1.create();
alert11.show();
}
@Override
protected void onDestroy() {
super.onDestroy();
BleManager.getInstance().disconnectAllDevice();
BleManager.getInstance().destroy();
}
@Override
protected void onResume() {
super.onResume();
}
public void clearConnectedDevice() {
for (int i = 0; i < bleDeviceList.size(); i++) {
BleDevice device = bleDeviceList.get(i);
if (BleManager.getInstance().isConnected(device)) {
bleDeviceList.remove(i);
}
}
}
}
我在startScan()中使用了MainActivity.java方法。我可以在onScanFinished()中找到可发现的BleDevices列表。我正在尝试在存储库类 MainDataRepository.java 中实现相同的方法。我正在 MainViewModel.java 中从该类获取null数据。这是我所有类的实现。
MainDataRepository.java
public class MainDataRepository {
private static final String TAG = "MainDataRepository";
private static final MainDataRepository ourInstance = new MainDataRepository();
private MutableLiveData<List<BleDevice>> deviceListLiveData = new MutableLiveData<>();
public static MainDataRepository getInstance() {
return ourInstance;
}
public MutableLiveData<List<BleDevice>> getTodos() {
BleManager.getInstance().scan(new BleScanCallback() {
@Override
public void onScanStarted(boolean success) {
Log.d("View Model","scAN started");
}
@Override
public void onLeScan(BleDevice bleDevice) {
super.onLeScan(bleDevice);
Log.d("onLeScan","onLeScan: View Model");
}
@Override
public void onScanning(BleDevice bleDevice) {
Log.d("View Model","scannig");
}
@Override
public void onScanFinished(List<BleDevice> scanResultList) {
Log.d("View Model","onScanFinished: " + scanResultList.size());
for (int i = 0; i < scanResultList.size(); i++) {
Log.d("View Model","onScanFinished: " + scanResultList.get(i).getName() + " and " + scanResultList.get(i).getMac());
}
}
});
return deviceListLiveData;
}
}
MainViewModel.java
public class MainViewModel extends ViewModel {
private MutableLiveData<List<BleDevice>> userLiveData;
public static List<BleDevice> deviceArrayList = new ArrayList<>();
private MainDataRepository repository = MainDataRepository.getInstance();
public MainViewModel() {
super();
userLiveData = new MutableLiveData<>();
userLiveData = repository.getTodos();
Log.d("View Model","MainViewModel: " + userLiveData.getValue());
init();
}
public MutableLiveData<List<BleDevice>> getUserMutableLiveData() {
return userLiveData;
}
public void init() {
populateList();
userLiveData.setValue(deviceArrayList);
}
public void populateList() {
deviceArrayList = new ArrayList<>();
Log.d("Inside Populate","populateList: ");
}
}
MAdapter.java
public class MAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private Context mContext;
private List<BleDevice> bleDeviceList;
public OnClick click;
public MAdapter(Context mContext,List<BleDevice> bleDeviceList,OnClick click) {
this.mContext = mContext;
this.bleDeviceList = bleDeviceList;
this.click = click;
}
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent,int viewType) {
View rootView = LayoutInflater.from(mContext).inflate(R.layout.card_ll,parent,false);
return new MViewHolder(rootView);
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder,int position) {
BleDevice device = bleDeviceList.get(position);
((MViewHolder) holder).tvName.setText(device.getName());
((MViewHolder) holder).tvMac.setText(device.getMac());
((MViewHolder) holder).btnConnect.setText("Pair");
((MViewHolder) holder).btnConnect.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
click.onItemClick(v);
((MViewHolder) holder).btnConnect.setText("Paired");
((MViewHolder) holder).btnConnect.setClickable(false);
}
});
}
@Override
public int getItemCount() {
return bleDeviceList.size();
}
static class MViewHolder extends RecyclerView.ViewHolder {
private TextView tvName,tvMac;
private Button btnConnect;
public MViewHolder(@NonNull View itemView) {
super(itemView);
tvName = itemView.findViewById(R.id.device_name);
tvMac = itemView.findViewById(R.id.device_mac_address);
btnConnect = itemView.findViewById(R.id.btn_connect);
}
}
public interface OnClick {
public void onItemClick(View v);
}
}
谢谢。
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