Question

I’m using setVisibility() to hide some UI components at onStart(), with the aim of making them reappear under certain conditions at onActivityResult().

I have set variables as global variable, and assigned to the component at onCreate().

Code to make the component invisible works correctly, such as auth_btn.setVisibility(View.INVISIBLE);

However, at onActivityResult(), auth_btn.setVisibility(View.VISIBLE); does not make the button reappear.

Code (from pastebin in the comments):

private Button auth_btn = null;
private Button newAcc_btn = null;
private EditText mEdit = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Set up the window layout
    setContentView(R.layout.main);

    //instance of database adapter
    db = new DBAdapter(this);

    // Get local Bluetooth adapter
    mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

    // If the adapter is null, then Bluetooth is not supported
    if (mBluetoothAdapter == null) {
        Toast.makeText(this, "Bluetooth is not available", Toast.LENGTH_LONG).show();
        finish();
        return;
    }

    auth_btn = (Button) findViewById(R.id.btn_auth);
    mEdit = (EditText)findViewById(R.id.text_username);
    newAcc_btn = (Button) findViewById(R.id.btn_newAcc);

    //read every entry from database
    db.load();
}

@Override
public void onStart() {
    super.onStart();

    // If BT is not on, request that it be enabled.
    if (!mBluetoothAdapter.isEnabled()) {
        Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
        // Otherwise, setup the session
    } else {
        setupSession();
    }
}

private void setupSession () {
    //Authenticate
    auth_btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            try {
                out.write(AUTHENTICATE);
                out.flush();
            } catch (IOException e) {
                e.printStackTrace();
            }
            authenticate();
        }
    });

    //Create new account
    newAcc_btn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            try{
                out.write(NEWACCOUNT);
                out.flush();
            } catch (IOException e) {
                e.printStackTrace();
            }
            newAccount();
        }
    });

    //Scan QR Code
    Button scan = (Button) findViewById(R.id.btn_scan);
    scan.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent("com.google.zxing.client.android.SCAN");
            intent.putExtra("SCAN_MODE", "QR_CODE_MODE");
            startActivityForResult(intent, SCAN_QR_CODE);
        }
    });

    auth_btn.setVisibility(View.INVISIBLE);
    newAcc_btn.setVisibility(View.INVISIBLE);
    mEdit.setVisibility(View.INVISIBLE);

}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent intent) {
    if (requestCode == SCAN_QR_CODE) {
        if (resultCode == RESULT_OK) {
            //Successful scan
            processQR(intent.getStringExtra("SCAN_RESULT"));
            //String format = intent.getStringExtra("SCAN_RESULT_FORMAT"); //format of the code

            //Toast.makeText(this, contents, Toast.LENGTH_LONG).show();
        } else if (resultCode == RESULT_CANCELED) {
            Toast.makeText(this, "Scan failed!", Toast.LENGTH_SHORT).show();
        }
    }
    if (requestCode == REQUEST_ENABLE_BT) {
        // When the request to enable Bluetooth returns
        if (resultCode == Activity.RESULT_OK) {
            // Bluetooth is now enabled, so set up a chat session
            setupSession();
        } else {
            // User did not enable Bluetooth or an error occurred
            Log.d(TAG, "BT not enabled");
            Toast.makeText(this, "Bluetooth cannot be enabled", Toast.LENGTH_SHORT).show();
            finish();
        }
    }

}

public void processQR (String content) {
    String[] contents = content.split(" ");
    if (contents.length != 3) {
        Log.e(TAG, "Not well formed QR Code");
    }
    else {
        appKey = contents[APPKEY];
        macAdd = contents[MACADR];
        my_uuid = UUID.fromString(contents[UUID_STR]);
        Log.d(TAG, macAdd);
        String appName = db.getAppName(appKey);
        Log.d(TAG, appName);
        if (appName == null)
            return;
        Toast.makeText(this, appName, Toast.LENGTH_SHORT).show();
        BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(macAdd);
        try {
            bt = device.createInsecureRfcommSocketToServiceRecord(my_uuid);
            bt.connect();
            in = bt.getInputStream();
            out = bt.getOutputStream();
        } catch (IOException e) {
            e.printStackTrace();
        }
        Log.d(TAG, "Set new acc visible");
        mEdit = (EditText)findViewById(R.id.text_username);
        mEdit.setVisibility(View.VISIBLE);
        newAcc_btn.setVisibility(View.VISIBLE);

        if (db.appAccounts(appKey).getCount() > 0)
            auth_btn.setVisibility(View.VISIBLE);
    }
}

Answer 1

onStart() is called each time the activity is visible. After pressing the scan button, the intent is executed, then the buttons are set to VISIBLE at onActivityResult().

After which, the activity is visible again, causing onStart() to be executed, therefore making the buttons INVISIBLE again.