方法kpg.initializate中的Android NullPointer异常

我是Android中的新手，我正在尝试编写一个关于密码/解密应用程序的“简单”教程。我有下面的代码方法kpg.initializate中的Android NullPointer异常

public class MainActivity extends AppCompatActivity { 
    KeyPairGenerator kpg; 
    KeyPair kp; 
    PublicKey publicKey; 
    PrivateKey privateKey; 
    byte[] encryptedBytes, decryptedBytes; 
    Cipher cipher, cipher1; 
    String encrypted, decrypted; 

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

     try { 
      generateKey(); 
      TextView txtPuk = (TextView) findViewById(R.id.tViewPUK); 
      txtPuk.setText(kp.getPublic().toString()); 
     }catch(Exception e){ 
      e.printStackTrace(); 
      Toast.makeText(getBaseContext(), e.toString(),Toast.LENGTH_LONG).show(); 
     } 

     setContentView(R.layout.activity_main); 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getMenuInflater().inflate(R.menu.menu_main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 
    public void generateKey() throws NoSuchAlgorithmException, NoSuchPaddingException, 
      IllegalBlockSizeException,BadPaddingException,InvalidKeyException{ 
     try{ 
       kpg = KeyPairGenerator.getInstance("RSA"); 
      kpg.initialize(1024); //NULLPOINTER HERE 
      kp = kpg.genKeyPair(); 

     }catch(Exception e){ 
      e.printStackTrace(); 
      Toast.makeText(getBaseContext(), e.toString(),Toast.LENGTH_LONG).show(); 

     } 

    } 
    public byte[] RSAEncrypt(final String plain) throws NoSuchAlgorithmException, NoSuchPaddingException, 
      IllegalBlockSizeException, BadPaddingException, InvalidKeyException { 
     ; 
     publicKey = kp.getPublic(); 
     privateKey = kp.getPrivate(); 

     cipher = Cipher.getInstance("RSA"); 
     cipher.init(Cipher.ENCRYPT_MODE, publicKey); 
     encryptedBytes = cipher.doFinal(plain.getBytes()); 
     return encryptedBytes; 
    } 

    public String RSADecrypt(final byte[] encryptedBytes) throws NoSuchAlgorithmException, NoSuchPaddingException, 
      InvalidKeyException, IllegalBlockSizeException, BadPaddingException { 

     cipher1 = Cipher.getInstance("RSA"); 
     cipher1.init(Cipher.DECRYPT_MODE, privateKey); 
     decryptedBytes = cipher1.doFinal(encryptedBytes); 
     decrypted = new String(decryptedBytes); 
     return decrypted; 
    } 

}

但正如标题所说，我得到了一个kpg.initialize(1024)空指针。由于理论似乎是正确的，我觉得这可能是一个盲目的把戏，我没有遵循，所以这可能是什么原因发生

编辑：编辑代码以删除redudant代码，如sugested

来源

2015-06-02 Artur Peniche

尝试移动'kpg.initialize（1024）; kp = kpg.genKeyPair（）;'到前面的try catch块。 – siriscac

对不起，我做了这两个尝试/块，以找出哪一个正在给空指针 –

问题是在setContentView(R.layout.activity_main);之前拨打findViewById(R.id.tViewPUK)。

来源

2015-06-02 23:54:31 ESoares

正确的口袋里：^） –

方法kpg.initializate中的Android NullPointer异常

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