The old library zxing is not running in my app

The old library zxing is not running in my app - java

What's wrong with this code? I am running the following code in MainActivity but I get only an empty app:
package com.example.testbar;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import com.google.zxing.Result;
import android.util.Log;
import me.dm7.barcodescanner.zxing.ZXingScannerView;
public class MainActivity extends AppCompatActivity implements ZXingScannerView.ResultHandler {
private ZXingScannerView mScannerView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_main);
// Programmatically initialize the scanner view
mScannerView = new ZXingScannerView(this);
setContentView(mScannerView);
}
#Override
public void handleResult(Result rawResult) {
// Do something with the result here
Log.v("TAG", rawResult.getText()); // Prints scan results
// Prints the scan format (qrcode, pdf417 etc.)
Log.v("TAG", rawResult.getBarcodeFormat().toString());
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Scan Result");
builder.setMessage(rawResult.getText());
AlertDialog alert1 = builder.create();
alert1.show();
// If you would like to resume scanning, call this method below:
mScannerView.resumeCameraPreview(this);
}
#Override
public void onResume() {
super.onResume();
// Register ourselves as a handler for scan results.
mScannerView.setResultHandler(this);
// Start camera on resume
mScannerView.startCamera();
}
#Override
public void onPause() {
super.onPause();
// Stop camera on pause
mScannerView.stopCamera();
}
}
I've added the permissions in the AndroidManifest.xml file:
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera"/>
<uses-feature android:name="android.hardware.camera.autofocus"/>
The code builds without errors in Android Studio but I only get an empty app... and no camera when the app runs.

You should follow Android's documentation for checking and requesting permissions.
https://developer.android.com/training/permissions/requesting
I have modified your code and this should be a working sample.
public class MainActivity extends AppCompatActivity implements ZXingScannerView.ResultHandler {
private ZXingScannerView mScannerView;
private static final int MY_PERMISSIONS_REQUEST_CAMERA = 101;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setContentView(R.layout.activity_main);
// Programmatically initialize the scanner view
mScannerView = new ZXingScannerView(this);
setContentView(mScannerView);
}
#Override
public void handleResult(Result rawResult) {
// Do something with the result here
Log.v("TAG", rawResult.getText()); // Prints scan results
// Prints the scan format (qrcode, pdf417 etc.)
Log.v("TAG", rawResult.getBarcodeFormat().toString());
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Scan Result");
builder.setMessage(rawResult.getText());
AlertDialog alert1 = builder.create();
alert1.show();
// If you would like to resume scanning, call this method below:
mScannerView.resumeCameraPreview(this);
}
#Override
public void onResume() {
super.onResume();
// Register ourselves as a handler for scan results.
mScannerView.setResultHandler(this);
// Start camera on resume
if (hasPermission(Manifest.permission.CAMERA)) {
startCamera();
}
}
#Override
public void onPause() {
super.onPause();
// Stop camera on pause
mScannerView.stopCamera();
}
private void startCamera() {
mScannerView.startCamera();
}
private Boolean hasPermission(String permission) {
if (ContextCompat.checkSelfPermission(this, permission) != PackageManager.PERMISSION_GRANTED) {
// you need to request the permission
Log.d("TAG", "User hasn't granted permission.");
// No explanation needed for camera. request the permission
ActivityCompat.requestPermissions(this,
new String[]{permission},
MY_PERMISSIONS_REQUEST_CAMERA);
}
else {
Log.d("TAG", "User already granted permission.");
return true;
}
return false;
}
#Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_CAMERA:
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
startCamera();
} else {
Log.d("TAG", "Permission denied by user...");
}
break;
}
}
}

Related

App crashes after clicking scan button for the first time but the app works after i reopen it

I'm trying to create an indoor location services app in android studio.There is a scan button which start the discovery of BLE devices. When i click on the scan button,the app crashes. But when i reopen the app and click on the scan button again,it works.
i tried this taken from one of the projects from stackoverflow.
Class variable:
private BluetoothAdapter mBtAdapter = null;
final BluetoothManager btManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBtAdapter = btManager.getAdapter();
if (mBtAdapter == null || !mBtAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
}
public void onScanButton(){
if (mBtAdapter.isEnabled()){
scanLeDevice(true);
}
}
this is my code
BluetoothManager btManager; //field 'btManager' is never used
private BluetoothAdapter btAdapter = null;
BluetoothLeScanner btScanner;
Button startScanningButton;
Button stopScanningButton;
TextView peripheralTextView;
private final static int REQUEST_ENABLE_BT = 1;
private static final int PERMISSION_REQUEST_COARSE_LOCATION = 1;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
peripheralTextView = (TextView) findViewById(R.id.peripheralTextView);
peripheralTextView.setMovementMethod(new ScrollingMovementMethod());
startScanningButton = (Button) findViewById(R.id.StartScanButton);
startScanningButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
startScanning();
}
});
stopScanningButton = (Button) findViewById(R.id.StopScanButton);
stopScanningButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
stopScanning();
}
});
stopScanningButton.setVisibility(View.INVISIBLE);
final BluetoothManager btManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
btAdapter = btManager.getAdapter();
btScanner = btAdapter.getBluetoothLeScanner();
if (btAdapter != null && !btAdapter.isEnabled()) {
Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableIntent,REQUEST_ENABLE_BT);
}
// Make sure we have access coarse location enabled, if not, prompt the user to enable it
if (this.checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
final AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("This app needs location access");
builder.setMessage("Please grant location access so this app can detect peripherals.");
builder.setPositiveButton(android.R.string.ok, null);
builder.setOnDismissListener(new DialogInterface.OnDismissListener() {
#Override
public void onDismiss(DialogInterface dialog) {
requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, PERMISSION_REQUEST_COARSE_LOCATION);
}
});
builder.show();
}
}
// Device scan callback.
private ScanCallback leScanCallback = new ScanCallback() {
#Override
public void onScanResult(int callbackType, ScanResult result) {
peripheralTextView.append("MAC address: " + result.getDevice().getAddress() + " rssi: " + result.getRssi() + "TxPower:" + result.getTxPower() + "\n");
// auto scroll for text view
final int scrollAmount = peripheralTextView.getLayout().getLineTop(peripheralTextView.getLineCount()) - peripheralTextView.getHeight();
// if there is no need to scroll, scrollAmount will be <=0
if (scrollAmount > 0)
peripheralTextView.scrollTo(0, scrollAmount);
}
};
#Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults) {
switch (requestCode) {
case PERMISSION_REQUEST_COARSE_LOCATION: {
if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
System.out.println("coarse location permission granted");
} else {
final AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Functionality limited");
builder.setMessage("Since location access has not been granted, this app will not be able to discover beacons when in the background.");
builder.setPositiveButton(android.R.string.ok, null);
builder.setOnDismissListener(new DialogInterface.OnDismissListener() {
#Override
public void onDismiss(DialogInterface dialog) {
}
});
builder.show();
}
}
}
}
public void startScanning() {
System.out.println("start scanning");
peripheralTextView.setText("");
startScanningButton.setVisibility(View.INVISIBLE);
stopScanningButton.setVisibility(View.VISIBLE);
AsyncTask.execute(new Runnable() {
#Override
public void run() {
btScanner.startScan(leScanCallback);
}
});
}
public void stopScanning() {
System.out.println("stopping scanning");
peripheralTextView.append("Stopped Scanning");
startScanningButton.setVisibility(View.VISIBLE);
stopScanningButton.setVisibility(View.INVISIBLE);
AsyncTask.execute(new Runnable() {
#Override
public void run() {
btScanner.stopScan(leScanCallback);
}
});
}
}
The logcat shows
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.bluetooth.le.BluetoothLeScanner.startScan(android.bluetooth.le.ScanCallback)' on a null object reference
at com.example.myapplication.MainActivity$6.run(MainActivity.java:137)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:764)

Before i click the Scan button,a prompt will be display asking to turn
on the bluetooth.So bluetooth will be turned on
You are wrong about that part. You ask the user to enable it, but it might not have happened yet. At least you need to get the Scanner later on.
Currently you set the Scanner reference before the permission requesting has been initiated.
This also explains why it works after your App has crashed for the first time, because the 2nd time you come here the Permission has been enabled.
From the Javadoc of BluetoothAdapter#getBluetoothLeScanner():
Will return null if Bluetooth is turned off or if Bluetooth LE
Advertising is not supported on this device.
You can change your code to:
public void startScanning() {
btScanner = btAdapter.getBluetoothLeScanner();
if (btScanner == null) {
// not enabled yet or not supported
return;
}
System.out.println("start scanning");
peripheralTextView.setText("");
startScanningButton.setVisibility(View.INVISIBLE);
stopScanningButton.setVisibility(View.VISIBLE);
AsyncTask.execute(new Runnable() {
#Override
public void run() {
btScanner.startScan(leScanCallback);
}
});
}

How to change the location manager into fused location provider api?

I'm very new to android studio, and I'm working with an app that demands more of accuracy of location, first i used location manager but it provides not so accurate location of the user now i want to change it to fused location api but im confused with it, i don't know how to put it in my activity,I already search the net but nothing seems to have sense to me.
here is my Main Activity
public class MainActivity extends AppCompatActivity {
ContactDbAdapter contactDbAdapter;
private GoogleApiClient client;
EditText messageText;
UserDbAdapter userDbAdapter;
Cursor cursor;
TextView locationText;
#Override
public int checkUriPermission(Uri uri, int pid, int uid, int modeFlags) {
return super.checkUriPermission(uri, pid, uid, modeFlags);
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
userDbAdapter = new UserDbAdapter(this);
messageText = (EditText) findViewById(R.id.messageText);
locationText = (TextView) findViewById(R.id.locationTextView);
try {
userDbAdapter.open();
} catch (SQLException error) {
Log.e("mytag", "Error open userDbAdapter\n");
}
contactDbAdapter = new ContactDbAdapter(this);
try {
contactDbAdapter.open();
} catch (SQLException error) {
Log.e("mytag", "Error open contactDbAdapter\n");
}
cursor = contactDbAdapter.getContacts();
final Button sos = (Button) findViewById(R.id.redbutton);
final Button finish = (Button) findViewById(R.id.greenbutton);
final CountDownTimer timer = new CountDownTimer(3999, 100) {
public void onTick(long millisUntilFinished) {
sos.setText("" + ((int) (millisUntilFinished) / 1000));
}
public void onFinish() {
sos.setVisibility(View.GONE);
finish.setVisibility(View.VISIBLE);
finish.setText("finish");
SmsManager smsManager = SmsManager.getDefault();
cursor = contactDbAdapter.getContacts();
String msg = messageText.getText().toString() + "#" + locationText.getText().toString();
Log.e("mytag", msg);
if(cursor.moveToFirst()){
do{
String number=cursor.getString(cursor.getColumnIndex(contactDbAdapter.PHONE_NUM));
smsManager.sendTextMessage(number, null, msg, null, null);
}while(cursor.moveToNext());
}
}
};
sos.setTag(1);
sos.setOnClickListener(
new Button.OnClickListener() {
public void onClick(View v) {
final int status = (Integer) v.getTag();
if (status != 1) {
sos.setText("sos");
sos.setTag(1);
timer.cancel();
} else {
sos.setTag(0);
timer.start();
}
}
}
);
finish.setOnClickListener(
new Button.OnClickListener() {
public void onClick(View v) {
sos.setVisibility(View.VISIBLE);
finish.setVisibility(View.GONE);
sos.callOnClick();
}
}
);
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
switch (id) {
case R.id.contact:
Intent contactIntent = new Intent(getApplicationContext(), LogInActivity.class);
startActivity(contactIntent);
return true;
case R.id.message:
Intent messageIntent = new Intent(getApplicationContext(), DisplayMessageActivity.class);
startActivity(messageIntent);
default:
break;
}
return super.onOptionsItemSelected(item);
}
#Override
public void onStart() {
super.onStart();
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client.connect();
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Main Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app deep link URI is correct.
Uri.parse("android-app://com.cse4471.osu.sos_osu/http/host/path")
);
AppIndex.AppIndexApi.start(client, viewAction);
}
#Override
public void onResume() {
super.onResume();
// refresh user message
cursor = userDbAdapter.getUsers();
if (cursor.moveToFirst()) {
messageText.setText(cursor.getString(cursor.getColumnIndex(userDbAdapter.MESSAGE)));
}
// Acquire a reference to the system Location Manager
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
ActivityCompat.requestPermissions(this, new String[]{
Manifest.permission.ACCESS_FINE_LOCATION, Manifest.permission.ACCESS_COARSE_LOCATION, Manifest.permission.INTERNET}, 10);
return;
}
LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);
LocationListener locationListener = new LocationListener() {
public void onLocationChanged(Location location) {
// Called when a new location is found by the network location provider.
locationText.setText("Latitude:" + location.getLatitude() + ", Longitude:" + location.getLongitude());
}
public void onStatusChanged(String provider, int status, Bundle extras) {
}
public void onProviderEnabled(String provider) {
}
public void onProviderDisabled(String provider) {
}
};
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 3000, 0, locationListener);
Location loc = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if(loc != null) {
// messageText.setText("Latitude:" + loc.getLatitude() + ", Longitude:" + loc.getLongitude());
locationText.setText("Latitude:" + loc.getLatitude() + ", Longitude:" + loc.getLongitude());
}
}
#Override
public void onStop() {
super.onStop();
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
Action viewAction = Action.newAction(
Action.TYPE_VIEW, // TODO: choose an action type.
"Main Page", // TODO: Define a title for the content shown.
// TODO: If you have web page content that matches this app activity's content,
// make sure this auto-generated web page URL is correct.
// Otherwise, set the URL to null.
Uri.parse("http://host/path"),
// TODO: Make sure this auto-generated app deep link URI is correct.
Uri.parse("android-app://com.cse4471.osu.sos_osu/http/host/path")
);
AppIndex.AppIndexApi.end(client, viewAction);
client.disconnect();
}
#Override
public void onDestroy() {
super.onDestroy();
if (cursor != null) {
cursor.close();
}
}
I already put in my manifest the permissions and I also added the 'com.google.android.gms:play-services-location:10.0.0' in my gradle file. The issue now is i want to change the location manager into fused location provider api.

Since location provider is deprecated with LocationProviderClient in latest play services version but if you want to continue with the location provider here is the sample working activity code for location provider in activity
public class LocationActivity extends AppCompatActivity implements
GoogleApiClient.OnConnectionFailedListener, GoogleApiClient.ConnectionCallbacks,
LocationListener, GetAddressFromLatLng.LocationAddressResponse {
private LocationRequest mLocationRequest;
public static final int PLAY_SERVICES_RESOLUTION_REQUEST = 1000;
private static final int MILLISECONDS_PER_SECOND = 1000;
private FusedLocationProviderApi locationProvider = LocationServices.FusedLocationApi;
private GoogleApiClient mGoogleApiClient;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// create GoogleClient
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addApi(LocationServices.API)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this).build();
mGoogleApiClient.connect();
}
#Override
public void onConnected(#Nullable Bundle bundle) {
if (mGoogleApiClient != null && mGoogleApiClient.isConnected()) {
requestLocationUpdates();
}
}
public void requestLocationUpdates() {
if (ActivityCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
// runtime permissions
return;
}
locationProvider.requestLocationUpdates(mGoogleApiClient, mLocationRequest, this);
}
#Override
public void onRequestPermissionsResult(int requestCode, #NonNull String[] permissions,
#NonNull int[] grantResults) {
switch (requestCode) {
case LOCATION_PERMISSION_REQUEST_CODE:
if (grantResults.length > 0) {
if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
requestLocationUpdates();
}
}
break;
}
}
#Override
public void onConnectionSuspended(int i) {
}
#Override
public void onConnectionFailed(#NonNull ConnectionResult connectionResult) {
}
#Override
public void onLocationChanged(Location location) {
// every time location changed it calls itself
}
#Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
switch (requestCode) {
case PLAY_SERVICES_RESOLUTION_REQUEST:
switch (resultCode) {
case Activity.RESULT_OK:
requestLocationUpdates();
break;
case Activity.RESULT_CANCELED:
// Do failure task
break;
}
break;
}
}
#Override
protected void onStop() {
super.onStop();
if (mGoogleApiClient != null && mGoogleApiClient.isConnected())
mGoogleApiClient.disconnect();
}
#Override
protected void onResume() {
super.onResume();
if (mGoogleApiClient != null && mGoogleApiClient.isConnected()) {
requestLocationUpdates();
}
}
}

barcode scanner result twice

hello i try to develop an app which i should be able to scan in main activity and with intent i get the result in a textbox. My only problem is that when i scan the barcode SOMETIMES it opens the result activity 2-3 times.. Maybe someone could help me i dont know what to do
i dont know how i should help you
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (ContextCompat.checkSelfPermission(this, Manifest.permission.INTERNET) != PackageManager.PERMISSION_GRANTED){
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.INTERNET}, 200);
}
if (ContextCompat.checkSelfPermission(this, android.Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED)
{
ActivityCompat.requestPermissions(this, new String[]{android.Manifest.permission.CAMERA}, 200);
}
cameraPreview = (SurfaceView) findViewById(R.id.cameraPreview);
cameraPreview.setZOrderMediaOverlay(true);
barcodeDetector = new BarcodeDetector.Builder(this)
.setBarcodeFormats(Barcode.ALL_FORMATS)
.build();
cameraSource = new CameraSource
.Builder(this, barcodeDetector)
.setFacing(CameraSource.CAMERA_FACING_BACK)
.setRequestedFps(24)
.setRequestedPreviewSize(1600, 1024)
.setAutoFocusEnabled(true)
.build();
cameraPreview.getHolder().addCallback(new SurfaceHolder.Callback() {
#Override
public void surfaceCreated(SurfaceHolder holder) {
try{
if(ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED){
cameraSource.start(cameraPreview.getHolder());
}
}
catch (IOException e){
e.printStackTrace();
}
}
#Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
#Override
public void surfaceDestroyed(SurfaceHolder holder) {
cameraSource.stop();
}
});
barcodeDetector.setProcessor(new Detector.Processor<Barcode>() {
#Override
public void release() {
}
#Override
public void receiveDetections(Detector.Detections<Barcode> detections) {
final SparseArray<Barcode> barcodes = detections.getDetectedItems();
if (barcodes.size() != 0)
{
Intent intent = new Intent(MainActivity.this, finish.class);
intent.putExtra("barcode", barcodes.valueAt(0));
startActivityForResult(intent, 100);
finish();
}
}
});
}
#Override
protected void onDestroy() {
super.onDestroy();
cameraSource.release();
barcodeDetector.release();
}
FINISH ACTIVITY
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.finish);
result = (TextView) findViewById(R.id.editText1);
final Barcode barcode = getIntent().getParcelableExtra("barcode");
result.setText(barcode.displayValue);

You probably don't want to setup in onCreate and teardown in onDestroy. If you do, the camera will still be active and scanning even after your activity has moved to the background. Use onResume and onPause instead.
The other issue you may be experiencing is that receiveDetections is called every time it detects a barcode (even if it's the same barcode). If the barcode detector can detect barcodes faster than the system can start an activity, the callback will be called multiple times before you release the camera and barcode detector. To prevent this, you can use a flag to prevent startActivity from being called more than once or you can release the barcode detector (and camera) from inside receiveDetections

What you can do is release barcode detector immediately after your barcode data is received.
barcodeDetector.setProcessor(new Detector.Processor<Barcode>() {
#Override
public void release() {
}
#Override
public void receiveDetections(Detector.Detections<Barcode> detections) {
final SparseArray<Barcode> barcode = detections.getDetectedItems();
if (barcode.size() != 0) {
barcodeDetector.release();
//......put your code here.....//
}
}
});

App Crashes instantly after asking for location permission

I have looked for question similar to this and all of them did not include the catlog so nobody could really help them. I have made sure to include it here so I hope you can help! Basically as soon as I Open the app it prompts me with a location permission saying will I allow it. As soon as i hit yes, the app crashes!
package com.worden.jason.sample;
import android.Manifest;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
public class MainActivity extends AppCompatActivity implements LocationListener {
LocationManager locationManager;
public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
String provider;
public void Analysis(View view) {
Intent intent = new Intent(MainActivity.this,Analysis.class);
startActivity(intent);
finish();
}
public void Tips(View view) {
Intent intent = new Intent(MainActivity.this,Tips.class);
startActivity(intent);
finish();
}
public boolean checkLocationPermission() {
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_FINE_LOCATION)) {
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
new AlertDialog.Builder(this)
.setTitle(R.string.TileLocation)
.setMessage(R.string.TextLocation)
.setPositiveButton(R.string.Positive, new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
}
})
.create()
.show();
} else {
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
}
return false;
} else {
return true;
}
}
#Override
public void onRequestPermissionsResult(int requestCode,
#NonNull String permissions[], #NonNull int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_LOCATION: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// location-related task you need to do.
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
locationManager.requestLocationUpdates(provider, 400, 1, this);
}
} else {
// permission denied, boo! Disable the
}
return;
}
}
}
#Override
public void onLocationChanged(Location location) {
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
#Override
public void onProviderEnabled(String provider) {
}
#Override
public void onProviderDisabled(String provider) {
}
#Override
protected void onResume() {
super.onResume();
if (checkLocationPermission()) {
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
//Request location updates:
locationManager.requestLocationUpdates(provider, 400, 1, this);
}
}
}
}
log for crash
EDIT
public class MainActivity extends AppCompatActivity implements LocationListener {
LocationManager locationManager;
public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
**String GPS_PROVIDER;**
public void Analysis(View view) {
Intent intent = new Intent(MainActivity.this,Analysis.class);
startActivity(intent);
finish();
}
public void Tips(View view) {
Intent intent = new Intent(MainActivity.this,Tips.class);
startActivity(intent);
finish();
}
**#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);**
}
public boolean checkLocationPermission() {
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(this,
Manifest.permission.ACCESS_FINE_LOCATION)) {
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
new AlertDialog.Builder(this)
.setTitle(R.string.TileLocation)
.setMessage(R.string.TextLocation)
.setPositiveButton(R.string.Positive, new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialogInterface, int i) {
//Prompt the user once explanation has been shown
ActivityCompat.requestPermissions(MainActivity.this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
}
})
.create()
.show();
} else {
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.ACCESS_FINE_LOCATION},
MY_PERMISSIONS_REQUEST_LOCATION);
}
return false;
} else {
return true;
}
}
#Override
public void onRequestPermissionsResult(int requestCode,
#NonNull String permissions[], #NonNull int[] grantResults) {
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_LOCATION: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
// location-related task you need to do.
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
locationManager.requestLocationUpdates(GPS_PROVIDER, 400, 1, this);
}
} else {
// permission denied, boo! Disable the
}
return;
}
}
}
#Override
public void onLocationChanged(Location location) {
}
#Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
#Override
public void onProviderEnabled(String provider) {
}
#Override
public void onProviderDisabled(String provider) {
}
#Override
protected void onResume() {
super.onResume();
if (checkLocationPermission()) {
if (ContextCompat.checkSelfPermission(this,
Manifest.permission.ACCESS_FINE_LOCATION)
== PackageManager.PERMISSION_GRANTED) {
//Request location updates:
locationManager.requestLocationUpdates(GPS_PROVIDER, 400, 1, this);
}
}
}
}

Two problems here:
You do not initialize the locationManager field. Your call to locationManager.requestLocationUpdates results in a NullPointerException.
You do not initialize the provider field. Your call to locationManager.requestLocationUpdates does not like this.
To fix the first problem, add this override:
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
}
To fix the second problem, throw out your provider field and use LocationManager.GPS_PROVIDER (or one of the other providers defined in LocationManager) instead. Or initialize the provider field.
Setting breakpoints and running the program under a debugger is a good way to find such problems. Another approach is to look at logs – I'll bet there's a relevant stack trace in there somewhere.
Also ensure that your manifest mentions the requisite permission:
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

Android App Architecture: Implements user permission in lifecycle

I have a LocationListener which is extended LiveData Class. From the Android 6.0, the permission is requested in runtime. Now , when I tried to implements the LiveData Class and it required the permission checking in onActive() function. I have to make the boilerplate code in each activity for the permission requested and result received. Is there any way to move such
onRequestPermissionsResult() and checkSelfPermission() functions to the LocationListener ?
LocationFragment.java
public class LocationFragment extends LifecycleFragment {
private FragmentLocationBinding binding;
public LocationFragment() {
// Required empty public constructor
}
#Override
public void onActivityCreated(#Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (ContextCompat.checkSelfPermission(getActivity(),
permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
// Should we show an explanation?
if (ActivityCompat.shouldShowRequestPermissionRationale(getActivity(),
Manifest.permission.ACCESS_COARSE_LOCATION)) {
// Show an explanation to the user *asynchronously* -- don't block
// this thread waiting for the user's response! After the user
// sees the explanation, try again to request the permission.
} else {
// No explanation needed, we can request the permission.
ActivityCompat.requestPermissions(getActivity(),
new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
200);
// MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
// app-defined int constant. The callback method gets the
// result of the request.
}
}
//get the viewmodel from activity
LastLocationViewModel lastLocationViewModel = ViewModelProviders.of(getActivity())
.get(LastLocationViewModel.class);
lastLocationViewModel.getLastKnowLocation().observe(this, location -> {
binding.setLocation(location);
});
}
#Override
public void onRequestPermissionsResult(int requestCode,
String permissions[], int[] grantResults) {
switch (requestCode) {
case 200: {
// If request is cancelled, the result arrays are empty.
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
Toast.makeText(getActivity(), "Rights Granted", Toast.LENGTH_SHORT).show();
// permission was granted, yay! Do the
// contacts-related task you need to do.
} else {
// permission denied, boo! Disable the
// functionality that depends on this permission.
}
return;
}
// other 'case' lines to check for other
// permissions this app might request
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
binding = DataBindingUtil
.inflate(LayoutInflater.from(getActivity()), R.layout.fragment_location, null, false);
return binding.getRoot();
}
}
LastLocationListener.java
public class LastLocationListener extends LiveData<Location> {
private LocationManager locationManager;
private Context context;
private LocationListener listener = new LocationListener() {
#Override
public void onLocationChanged(Location location) {
Log.d("Location Msg", location.toString());
setValue(location);
}
#Override
public void onStatusChanged(String s, int i, Bundle bundle) {
}
#Override
public void onProviderEnabled(String s) {
}
#Override
public void onProviderDisabled(String s) {
}
};
public LastLocationListener(Context context) {
this.context = context;
locationManager = (LocationManager) context.getSystemService(
Context.LOCATION_SERVICE);
}
#Override
protected void onActive() {
if (ActivityCompat.checkSelfPermission(context, permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED
&& ActivityCompat.checkSelfPermission(context, permission.ACCESS_COARSE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
// TODO: Consider calling
// ActivityCompat#requestPermissions
// here to request the missing permissions, and then overriding
// public void onRequestPermissionsResult(int requestCode, String[] permissions,
// int[] grantResults)
// to handle the case where the user grants the permission. See the documentation
// for ActivityCompat#requestPermissions for more details.
return;
}
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, listener);
}
#Override
protected void onInactive() {
locationManager.removeUpdates(listener);
}
}

when I tried to implements the LiveData Class and it required the permission checking in onActive() function
No, it does not. What you are seeing is a Lint warning, which you can suppress.
What is required is that you hold the permission before attempting to use this particular bit of LiveData.
Is there any way to move such onRequestPermissionsResult() and checkSelfPermission() functions to the LocationListener ?
No.

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