Casting 'findViewById(R.id.)' to 'Button' is redundant

Question

So I'm trying to build a scanner and generator for QR Code.

Here's my code for the scanner:

 private Button scan_btn;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_reader);
    scan_btn = (Button) findViewById(R.id.scan_btn);
    final Activity activity = this;
    scan_btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            IntentIntegrator integrator = new IntentIntegrator(activity);
            integrator.setDesiredBarcodeFormats(IntentIntegrator.QR_CODE_TYPES);
            integrator.setPrompt("Scan");
            integrator.setCameraId(0);
            integrator.setBeepEnabled(false);
            integrator.setBarcodeImageEnabled(false);
            integrator.initiateScan();
        }
    });
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    IntentResult result = IntentIntegrator.parseActivityResult(requestCode, resultCode, data);
    if(result != null){
        if(result.getContents()==null){
            Toast.makeText(this, "You cancelled the scanning", Toast.LENGTH_LONG).show();
        }
        else {
            Toast.makeText(this, result.getContents(),Toast.LENGTH_LONG).show();
        }
    }
    else {
        super.onActivityResult(requestCode, resultCode, data);
    }
}}

I got a warning like this: Casting 'findViewById(R.id.scan_btn)' to 'Button' is redundant

Is gonna affect my app? cause when I tried to open my app, it suddenly crash.

UPDATE:

Here's my Generator code:

public class GeneratorActivity extends AppCompatActivity {

EditText text;
Button gen_btn;
ImageView image;
String text2Qr;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_generator);
    text = findViewById(R.id.text);
    gen_btn = findViewById(R.id.gen_btn);
    image = findViewById(R.id.image);
    gen_btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            text2Qr = text.getText().toString().trim();
            MultiFormatWriter multiFormatWriter = new MultiFormatWriter();
            try{
                BitMatrix bitMatrix = multiFormatWriter.encode(text2Qr, BarcodeFormat.QR_CODE,200,200);
                BarcodeEncoder barcodeEncoder = new BarcodeEncoder();
                Bitmap bitmap = barcodeEncoder.createBitmap(bitMatrix);
                image.setImageBitmap(bitmap);
            }
            catch (WriterException e){
                e.printStackTrace();
            }
        }
    });
}}

My MainActivity for the 'buttons' code:

public class MainActivity extends AppCompatActivity {

Button gen, scan;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    gen = findViewById(R.id.gen);
    scan = findViewById(R.id.scan);
    gen.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent gIntent = new Intent(MainActivity.this, GeneratorActivity.class);
            startActivity(gIntent);
        }
    });
    scan.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent rIntent = new Intent(MainActivity.this, ReaderActivity.class);
            startActivity(rIntent);
        }
    });
}}

UPDATE: There's nothing wrong with the redundant problem. This case is solved on xml code typo mistake. So its already answered on one of my questions. Thanks. Please looking forward on my others questions. I really need it to get done for my project soon.

The redundant cast warning is just a warning and does not have anything to deal with crashes. To start debugging a crash, have a look at stacktrace in logcat. https://stackoverflow.com/questions/23353173/unfortunately-myapp-has-stopped-how-can-i-solve-this — laalto, Feb 02 '18 at 18:22

score 0 · Answer 1 · answered Feb 02 '18 at 16:54

0

Try out this, Change your code as below :

scan_btn = findViewById(R.id.scan_btn);

answered Feb 02 '18 at 16:54

Abhishek kumar

4,347
8
29
44

I already change it, but still my app got crash when I tried to open it – Ricardo F. Seikka Feb 02 '18 at 18:03

score 0 · Accepted Answer · answered Feb 02 '18 at 18:24

0

It does not affect your code. This is a new feature of Android studio that directly maps the widget from your XML to Java code. Your app may crash for any other reason

answered Feb 02 '18 at 18:24

Arpit todewale

153
12

So it mean no harm then? Could you please help me with another questions that I just post? Its almost the same case but different problem. I really need to get this project done soon. – Ricardo F. Seikka Feb 02 '18 at 18:30
Sure. Happy to help – Arpit todewale Feb 02 '18 at 18:39
Thank you so much. Please look into it sir :) – Ricardo F. Seikka Feb 02 '18 at 18:40

score 0 · Answer 3 · answered Apr 27 '18 at 04:44

Starting with API 26, findViewById uses inference for its return type, so you no longer have to cast.

Old definition:

Button btn = (Button) findViewById(R.id.btn)

New definition:

<T extends View> T findViewById(R.id.value)

So if your compile Sdk is at least 26, it means that you can make use of this. No need casting.

Casting 'findViewById(R.id.)' to 'Button' is redundant

3 Answers3