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我試圖做指紋演示。但是，發生以下異常。我得到NullPointerException我的按鈕點擊以下我在指紋演示中遇到了一些錯誤
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：
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);
}
}
你試過調試你的代碼嗎？ –
你有解決方案 – user1767260