java - 弱参考回调不起作用android

问题描述

我正在尝试将我的数据（accountNumber）从 LoyaltyCardReader.java 传递给 HCEPayment.java，但不知何故 HCEPayment.java 没有收到呼叫。有人可以帮我做错什么。我能够在 LoyaltyCardReader 中接收数据并在发送到 HCEPayment 之前将其记录下来。

这里没有从 LoyaltyCardReader 调用 onAccountReceived。

忠诚读卡器

package com.example.try2;

import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.nfc.tech.IsoDep;
import android.os.SystemClock;
import android.util.Log;
import android.widget.Toast;

import java.io.IOException;
import java.lang.ref.WeakReference;
import java.util.Arrays;

/**
 * Callback class, invoked when an NFC card is scanned while the device is running in reader mode.
 *
 * Reader mode can be invoked by calling NfcAdapter
 */
public class LoyaltyCardReader implements NfcAdapter.ReaderCallback {
    private static final String TAG = "LoyaltyCardReader";
    // AID for our loyalty card service.
    private static final String SAMPLE_LOYALTY_CARD_AID = "F222222222";
    // ISO-DEP command HEADER for selecting an AID.
    // Format: [Class | Instruction | Parameter 1 | Parameter 2]
    private static final String SELECT_APDU_HEADER = "00A40400";
    // Format: [Class | Instruction | Parameter 1 | Parameter 2]
    private static final String GET_DATA_APDU_HEADER = "00CA0000";
    // "OK" status word sent in response to SELECT AID command (0x9000)
    private static final byte[] SELECT_OK_SW = {(byte) 0x90, (byte) 0x00};

    String gotData = "", finalGotData = "";

    long timeTaken = 0;

    // Weak reference to prevent retain loop. mAccountCallback is responsible for exiting
    // foreground mode before it becomes invalid (e.g. during onPause() or onStop()).
    private WeakReference<AccountCallback> mAccountCallback;

    public interface AccountCallback {
        public void onAccountReceived(String account);
    }

    public LoyaltyCardReader(AccountCallback accountCallback) {
        mAccountCallback = new WeakReference<AccountCallback>(accountCallback);
    }

    /**
     * Callback when a new tag is discovered by the system.
     *
     * <p>Communication with the card should take place here.
     *
     * @param tag Discovered tag
     */
    @Override
    public void onTagDiscovered(Tag tag) {

        Log.i(TAG, "New tag discovered");
        // Android's Host-based Card Emulation (HCE) feature implements the ISO-DEP (ISO 14443-4)
        // protocol.
        //
        // In order to communicate with a device using HCE, the discovered tag should be processed
        // using the IsoDep class.
        IsoDep isoDep = IsoDep.get(tag);
        if (isoDep != null) {
            try {
                // Connect to the remote NFC device
                isoDep.connect();
                Log.i(TAG, "Timeout = " + isoDep.getTimeout());
                isoDep.setTimeout(3600);
                Log.i(TAG, "Timeout = " + isoDep.getTimeout());
                Log.i(TAG, "MaxTransceiveLength = " + isoDep.getMaxTransceiveLength());

                // Build SELECT AID command for our loyalty card service.
                // This command tells the remote device which service we wish to communicate with.
                Log.i(TAG, "Requesting remote AID: " + SAMPLE_LOYALTY_CARD_AID);
                byte[] selCommand = BuildSelectApdu(SAMPLE_LOYALTY_CARD_AID);
                // Send command to remote device
                Log.i(TAG, "Sending: " + ByteArrayToHexString(selCommand));
                byte[] result = isoDep.transceive(selCommand);
                // If AID is successfully selected, 0x9000 is returned as the status word (last 2
                // bytes of the result) by convention. Everything before the status word is
                // optional payload, which is used here to hold the account number.
                int resultLength = result.length;
                byte[] statusWord = {result[resultLength-2], result[resultLength-1]};
                byte[] payload = Arrays.copyOf(result, resultLength-2);
                if (Arrays.equals(SELECT_OK_SW, statusWord)) {
                    // The remote NFC device will immediately respond with its stored account number
                    String accountNumber = new String(payload, "UTF-8");
                    Log.i(TAG, "Received: " + accountNumber);
                    // Inform CardReaderFragment of received account number
                    Log.d("Account",accountNumber);
                    mAccountCallback.get().onAccountReceived(accountNumber);
                }
            } catch (IOException e) {
                Log.e(TAG, "Error communicating with card: " + e.toString());
            }
        }
    }

    /**
     * Build APDU for SELECT AID command. This command indicates which service a reader is
     * interested in communicating with. See ISO 7816-4.
     *
     * @param aid Application ID (AID) to select
     * @return APDU for SELECT AID command
     */
    public static byte[] BuildSelectApdu(String aid) {
        // Format: [CLASS | INSTRUCTION | PARAMETER 1 | PARAMETER 2 | LENGTH | DATA]
        return HexStringToByteArray(SELECT_APDU_HEADER + String.format("%02X", aid.length() / 2) + aid);
    }

    /**
     * Build APDU for GET_DATA command. See ISO 7816-4.
     *
     * @return APDU for SELECT AID command
     */
    public static byte[] BuildGetDataApdu() {
        // Format: [CLASS | INSTRUCTION | PARAMETER 1 | PARAMETER 2 | LENGTH | DATA]
        return HexStringToByteArray(GET_DATA_APDU_HEADER + "0FFF");
    }

    /**
     * Utility class to convert a byte array to a hexadecimal string.
     *
     * @param bytes Bytes to convert
     * @return String, containing hexadecimal representation.
     */
    public static String ByteArrayToHexString(byte[] bytes) {
        final char[] hexArray = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
        char[] hexChars = new char[bytes.length * 2];
        int v;
        for ( int j = 0; j < bytes.length; j++ ) {
            v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }

    /**
     * Utility class to convert a hexadecimal string to a byte string.
     *
     * <p>Behavior with input strings containing non-hexadecimal characters is undefined.
     *
     * @param s String containing hexadecimal characters to convert
     * @return Byte array generated from input
     */
    public static byte[] HexStringToByteArray(String s) {
        int len = s.length();
        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
                    + Character.digit(s.charAt(i+1), 16));
        }
        return data;
    }

}

HCEPayment.java

package com.example.try2;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.nfc.NfcAdapter;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

public class HCEPayment extends AppCompatActivity implements LoyaltyCardReader.AccountCallback {

    public static final String TAG = "CardReaderFragment";
    public static int READER_FLAGS =
            NfcAdapter.FLAG_READER_NFC_A | NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK;
    public LoyaltyCardReader mLoyaltyCardReader;
    private TextView mAccountField;
    StringBuilder stringReceived;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_hcepayment);
        mAccountField = (TextView) findViewById(R.id.card_account_field);
        mAccountField.setText("Waiting...");
        mLoyaltyCardReader = new LoyaltyCardReader(this);
        enableReaderMode();
    }
    @Override
    public void onPause() {
        super.onPause();
        disableReaderMode();
    }

    @Override
    public void onResume() {
        super.onResume();
        enableReaderMode();
    }

    private void enableReaderMode() {
        Log.i(TAG, "Enabling reader mode");
        NfcAdapter nfc = NfcAdapter.getDefaultAdapter(this);
        if (nfc != null) {
            nfc.enableReaderMode(this, mLoyaltyCardReader, READER_FLAGS, null);
        }
    }
    private void disableReaderMode() {
        Log.i(TAG, "Disabling reader mode");
        NfcAdapter nfc = NfcAdapter.getDefaultAdapter(this);
        if (nfc != null) {
            nfc.disableReaderMode(this);
        }
    }

    @Override
    public void onAccountReceived(String account) {
        stringReceived.append(account);
        if (account.contains("END")) {

        }
        this.runOnUiThread(new Runnable() {
            @Override
            public void run() {
                mAccountField.setText(account);
            }
        });
    }
}

标签： javaandroidcallbackweak-references

java - 弱参考回调不起作用android

问题描述

解决方案

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