我在指紋演示中有一些錯誤

Question

我正在嘗試進行指紋演示。 但是，發生了以下異常。 我單擊按鈕時得到NullPointerException

01-04 11:35:18.647 3295-3295/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.letsnurture.fingerprint, PID: 3295
java.lang.NullPointerException: Attempt to invoke virtual method 'void javax.crypto.Cipher.init(int, java.security.Key)' on a null object reference
  at com.letsnurture.fingerprint.MainActivity.initCipher(MainActivity.java:179)
  at com.letsnurture.fingerprint.MainActivity.access$000(MainActivity.java:45)
  at com.letsnurture.fingerprint.MainActivity$1.onClick(MainActivity.java:131)
  at android.view.View.performClick(View.java:5198)
  at android.view.View$PerformClick.run(View.java:21147)
  at android.os.Handler.handleCallback(Handler.java:739)
  at android.os.Handler.dispatchMessage(Handler.java:95)
  at android.os.Looper.loop(Looper.java:148)
  at android.app.ActivityThread.main(ActivityThread.java:5417)
  at java.lang.reflect.Method.invoke(Native Method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

  01-04 12:08:55.382 1836-2383/? E/MDM: [83] b.run: Couldn't connect to Google API client: ConnectionResult{statusCode=API_UNAVAILABLE, resolution=null, message=null}

我的代碼如下：

import android.Manifest;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.app.KeyguardManager;
import android.content.Intent;
import android.content.SharedPreferences;
import android.hardware.fingerprint.FingerprintManager;
import android.security.keystore.KeyGenParameterSpec;
import android.security.keystore.KeyPermanentlyInvalidatedException;
import android.security.keystore.KeyProperties;
import android.util.Base64;
import android.util.Log;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;


import java.io.IOException;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.UnrecoverableKeyException;
import java.security.cert.CertificateException;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.KeyGenerator;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.inject.Inject;


public class MainActivity extends AppCompatActivity {


    private static final String TAG = MainActivity.class.getSimpleName();

    private static final String DIALOG_FRAGMENT_TAG = "myFragment";
    private static final String SECRET_MESSAGE = "Very secret message";
    /** Alias for our key in the Android Key Store */
    private static final String KEY_NAME = "my_key";

    @Inject
    KeyguardManager mKeyguardManager;
    @Inject
    FingerprintManager mFingerprintManager;
    @Inject
    FingerprintAuthenticationDialogFragment mFragment;
    @Inject
    KeyStore mKeyStore;
    @Inject
    KeyGenerator mKeyGenerator;
    @Inject
    Cipher mCipher;
    @Inject
    SharedPreferences mSharedPreferences;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        Button purchaseButton = (Button) findViewById(R.id.purchase_button);
        mKeyguardManager = (KeyguardManager) getSystemService(KEYGUARD_SERVICE);
        if (!mKeyguardManager.isKeyguardSecure()) {
            // Show a message that the user hasn't set up a fingerprint or lock screen.
            Toast.makeText(this,
                    "Secure lock screen hasn't set up.\n"
                            + "Go to 'Settings -> Security -> Fingerprint' to set up a fingerprint",
                    Toast.LENGTH_LONG).show();
            purchaseButton.setEnabled(false);
            return;
        }

        //noinspection ResourceType
        mFingerprintManager = (FingerprintManager) getSystemService(FINGERPRINT_SERVICE);
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.USE_FINGERPRINT) != 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;
        }
        if (!mFingerprintManager.hasEnrolledFingerprints()) {
            purchaseButton.setEnabled(false);
            // This happens when no fingerprints are registered.
            Toast.makeText(this,
                    "Go to 'Settings -> Security -> Fingerprint' and register at least one fingerprint",
                    Toast.LENGTH_LONG).show();
            return;
        }
        try {
            try {
                createKey();
            } catch (NoSuchProviderException e) {
                e.printStackTrace();
            }
        } catch (KeyStoreException e) {
            e.printStackTrace();
        }
        purchaseButton.setEnabled(true);
        purchaseButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                findViewById(R.id.confirmation_message).setVisibility(View.GONE);
                findViewById(R.id.encrypted_message).setVisibility(View.GONE);



                // Set up the crypto object for later. The object will be authenticated by use
                // of the fingerprint.
                try {
                    if (initCipher()) {

                        // Show the fingerprint dialog. The user has the option to use the fingerprint with
                        // crypto, or you can fall back to using a server-side verified password.
                        mFragment.setCryptoObject(new FingerprintManager.CryptoObject(mCipher));
                        boolean useFingerprintPreference = mSharedPreferences
                                .getBoolean(getString(R.string.use_fingerprint_to_authenticate_key),
                                        true);
                        if (useFingerprintPreference) {
                            mFragment.setStage(
                                    FingerprintAuthenticationDialogFragment.Stage.FINGERPRINT);
                        } else {
                            mFragment.setStage(
                                    FingerprintAuthenticationDialogFragment.Stage.PASSWORD);
                        }
                        mFragment.show(getFragmentManager(), DIALOG_FRAGMENT_TAG);
                    } else {
                        // This happens if the lock screen has been disabled or or a fingerprint got
                        // enrolled. Thus show the dialog to authenticate with their password first
                        // and ask the user if they want to authenticate with fingerprints in the
                        // future
                        mFragment.setCryptoObject(new FingerprintManager.CryptoObject(mCipher));
                        mFragment.setStage(
                                FingerprintAuthenticationDialogFragment.Stage.NEW_FINGERPRINT_ENROLLED);
                        mFragment.show(getFragmentManager(), DIALOG_FRAGMENT_TAG);
                    }
                } catch (NoSuchPaddingException e) {
                    e.printStackTrace();
                }
            }
        });

    }

    /**
     * Initialize the {@link Cipher} instance with the created key in the {@link #createKey()}
     * method.
     *
     * @return {@code true} if initialization is successful, {@code false} if the lock screen has
     * been disabled or reset after the key was generated, or if a fingerprint got enrolled after
     * the key was generated.
     */

    private boolean initCipher() throws NoSuchPaddingException {
        try {
            mKeyStore.load(null);
            SecretKey key = (SecretKey) mKeyStore.getKey(KEY_NAME, null);
           // mCipher = Cipher.getInstance("DES/CBC");
            mCipher.init(Cipher.ENCRYPT_MODE, key);
            return true;
        } catch (KeyPermanentlyInvalidatedException e) {
            return false;
        } catch (KeyStoreException | CertificateException | UnrecoverableKeyException | IOException
                | NoSuchAlgorithmException | InvalidKeyException e) {
            throw new RuntimeException("Failed to init Cipher", e);
        }
    }

    public void onPurchased(boolean withFingerprint) {
        if (withFingerprint) {
            // If the user has authenticated with fingerprint, verify that using cryptography and
            // then show the confirmation message.
            tryEncrypt();
        } else {
            // Authentication happened with backup password. Just show the confirmation message.
            showConfirmation(null);
        }
    }

    // Show confirmation, if fingerprint was used show crypto information.
    private void showConfirmation(byte[] encrypted) {
        findViewById(R.id.confirmation_message).setVisibility(View.VISIBLE);
        if (encrypted != null) {
            TextView v = (TextView) findViewById(R.id.encrypted_message);
            v.setVisibility(View.VISIBLE);
            v.setText(Base64.encodeToString(encrypted, 0 /* flags */));
        }
    }

    /**
     * Tries to encrypt some data with the generated key in {@link #createKey} which is
     * only works if the user has just authenticated via fingerprint.
     */
    private void tryEncrypt() {
        try {
            byte[] encrypted = mCipher.doFinal(SECRET_MESSAGE.getBytes());
            showConfirmation(encrypted);
        } catch (BadPaddingException | IllegalBlockSizeException e) {
            Toast.makeText(this, "Failed to encrypt the data with the generated key. "
                    + "Retry the purchase", Toast.LENGTH_LONG).show();
            Log.e(TAG, "Failed to encrypt the data with the generated key." + e.getMessage());
        }
    }

    /**
     * Creates a symmetric key in the Android Key Store which can only be used after the user has
     * authenticated with fingerprint.
     */
    public void createKey() throws KeyStoreException, NoSuchProviderException {
        // The enrolling flow for fingerprint. This is where you ask the user to set up fingerprint
        // for your flow. Use of keys is necessary if you need to know if the set of
        // enrolled fingerprints has changed.

      //  mKeyStore=(KeyStore)getSystemService(Context);
        mKeyStore = KeyStore.getInstance(KeyStore.getDefaultType());

        try {

            mKeyStore.load(null);
            // Set the alias of the entry in Android KeyStore where the key will appear
            // and the constrains (purposes) in the constructor of the Builder
             mKeyGenerator = mKeyGenerator.getInstance("AES", "BC");
            mKeyGenerator.init(new KeyGenParameterSpec.Builder(KEY_NAME,
                    KeyProperties.PURPOSE_ENCRYPT |
                            KeyProperties.PURPOSE_DECRYPT)
                    .setBlockModes(KeyProperties.BLOCK_MODE_CBC)
                    // Require the user to authenticate with a fingerprint to authorize every use
                    // of the key
                    .setUserAuthenticationRequired(true)
                    .setEncryptionPaddings(KeyProperties.ENCRYPTION_PADDING_PKCS7)
                    .build());
            mKeyGenerator.generateKey();
        } catch (NoSuchAlgorithmException | InvalidAlgorithmParameterException
                | CertificateException | IOException e) {

        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.action_settings) {
            Intent intent = new Intent(this, SettingsActivity.class);
            startActivity(intent);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}                                                                                                                         

Answer 1

我嘗試了相同的演示，它對我有用。

我認為您應該考慮這些注入注釋是否對您有用。 如果它們不起作用，則必須使用“ new”后跟構造函數自行初始化這些實例。 否則，您將收到該空對象引用錯誤。