[ヘルプ]致命的な例外：メインのjava.lang.NullPointerException

Question

public class MainActivity extends Activity { 
    private static final String TAG = "MainActivity"; 
    ProductDatabase.ProductDatabaseHelper controller = new ProductDatabase.ProductDatabaseHelper(this); 
    EditText mBarcodeEdit; 
    EditText mFormatEdit; 
    EditText mTitleEdit; 
    EditText mPriceEdit; 
    private static final int ZBAR_SCANNER_REQUEST = 0; 
    private static final int ZBAR_QR_SCANNER_REQUEST = 1; 
    private static final ProductData mProductData = new ProductData(); 
    Button mScanButton; 
    Button mAddButton; 
    Button mSelectButton; 
    Button mExportButton; 
    Button btnimport; 
    ProductDatabase mProductDb; 
    ListView ls; 
    TextView infotext; 
    File file = null; 
// DatabaseHelper dbhelper = null; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     ls = (ListView) findViewById(R.id.placeslist); 
     mBarcodeEdit = (EditText) findViewById(R.id.barcodeEdit); 
     mFormatEdit = (EditText) findViewById(R.id.codeFormatEdit); 
     mTitleEdit = (EditText) findViewById(R.id.titleEdit); 
     mPriceEdit = (EditText) findViewById(R.id.priceEdit); 
     mScanButton = (Button) findViewById(R.id.scan_btn); 
     mAddButton = (Button) findViewById(R.id.addButton); 
     mSelectButton = (Button) findViewById(R.id.selelctButton); 
     mProductDb = new ProductDatabase(this); // not yet shown 
     infotext = (TextView) findViewById(R.id.txtresulttext); 
     mExportButton = (Button) findViewById(R.id.exportbtn); 



     mSelectButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       Intent i = new Intent(MainActivity.this, product_list.class); 
       startActivity(i); 
      } 

     }); 
     mAddButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       String barcode = mBarcodeEdit.getText().toString(); 
       String format = mFormatEdit.getText().toString(); 
       String title = mTitleEdit.getText().toString(); 
       String price = mPriceEdit.getText().toString(); 

       String errors = validateFields(barcode, format, title, price); 
       if (errors.length() > 0) { 
        showInfoDialog(MainActivity.this, "Please fix errors", errors); 
       } else { 
        mProductData.barcode = barcode; 
        mProductData.format = format; 
        mProductData.title = title; 
        mProductData.price = new BigDecimal(price); 

        mProductDb.insert(mProductData); 
        showInfoDialog(MainActivity.this, "Success", "Product saved successfully"); 
        resetForm(); 
       } 

      } 
     }); 


     mExportButton.setOnClickListener(new View.OnClickListener() { 
      SQLiteDatabase sqldb = controller.getReadableDatabase(); //My Database class 
      Cursor c =null; 
      @Override 
      public void onClick(View view) { //main code begins here 
       try { 
        c = sqldb.rawQuery("select * from spot_pay.db", null); 

        int rowcount = 0; 
        int colcount = 0; 
        File sdCardDir = Environment.getExternalStorageDirectory(); 
        String filename = "MyBackUp.csv"; 
        // the name of the file to export with 
        File saveFile = new File(sdCardDir, filename); 
        FileWriter fw = new FileWriter(saveFile); 

        BufferedWriter bw = new BufferedWriter(fw); 
        rowcount = c.getCount(); 
        colcount = c.getColumnCount(); 
        if (rowcount > 0) { 
         c.moveToFirst(); 

         for (int i = 0; i < colcount; i++) { 
          if (i != colcount - 1) { 

           bw.write(c.getColumnName(i) + ","); 

          } else { 

           bw.write(c.getColumnName(i)); 

          } 
         } 
         bw.newLine(); 

         for (int i = 0; i < rowcount; i++) { 
          c.moveToPosition(i); 

          for (int j = 0; j < colcount; j++) { 
           if (j != colcount - 1) 
            bw.write(c.getString(j) + ","); 
           else 
            bw.write(c.getString(j)); 
          } 
          bw.newLine(); 
         } 
         bw.flush(); 
         infotext.setText("Exported Successfully."); 
        } 
       } catch (Exception ex) { 
        if (sqldb.isOpen()) { 
         sqldb.close(); 
         infotext.setText(ex.getMessage().toString()); 
        } 

       } finally { 

       } 

      } 
     }); 
    } 

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





    private void showInfoDialog(Context context, String title, String information) { 
     new AlertDialog.Builder(context) 
       .setMessage(information) 
       .setTitle(title) 
       .setPositiveButton("OK", new DialogInterface.OnClickListener() { 
        public void onClick(DialogInterface dialog, int which) { 
         dialog.dismiss(); 

        } 
       }).show(); 
    } 

    private void resetForm() { 
     // TODO Auto-generated method stub 
     mBarcodeEdit.getText().clear(); 
     mFormatEdit.getText().clear(); 
     mTitleEdit.getText().clear(); 
     mPriceEdit.getText().clear(); 
    } 


    public void launchScanner(View v) { 
     if (isCameraAvailable()) { 
      Intent intent = new Intent(this, ZBarScannerActivity.class); 
      startActivityForResult(intent, ZBAR_SCANNER_REQUEST); 
     } else { 
      Toast.makeText(this, "Rear Facing Camera Unavailable", Toast.LENGTH_SHORT).show(); 
     } 
    } 

    public void launchQRScanner(View v) { 
     if (isCameraAvailable()) { 
      Intent intent = new Intent(this, ZBarScannerActivity.class); 
      intent.putExtra(ZBarConstants.SCAN_MODES, new int[]{Symbol.QRCODE}); 
      startActivityForResult(intent, ZBAR_SCANNER_REQUEST); 
     } else { 
      Toast.makeText(this, "Rear Facing Camera Unavailable", Toast.LENGTH_SHORT).show(); 
     } 
    } 

    public boolean isCameraAvailable() { 
     PackageManager pm = getPackageManager(); 
     return pm.hasSystemFeature(PackageManager.FEATURE_CAMERA); 
    } 

    @Override 
    protected void onActivityResult(int requestCode, int resultCode, Intent data) { 
     switch (requestCode) { 
      case ZBAR_SCANNER_REQUEST: 
      case ZBAR_QR_SCANNER_REQUEST: 
       if (resultCode == RESULT_OK) { 
        mBarcodeEdit.setText(data.getStringExtra(ZBarConstants.SCAN_RESULT)); 
//     Toast.makeText(this, "Scan Result = " + data.getStringExtra(ZBarConstants.SCAN_RESULT), Toast.LENGTH_SHORT).show(); 
       } else if (resultCode == RESULT_CANCELED && data != null) { 
        String error = data.getStringExtra(ZBarConstants.ERROR_INFO); 
        if (!TextUtils.isEmpty(error)) { 
         Toast.makeText(this, error, Toast.LENGTH_SHORT).show(); 
        } 
       } 
       break; 
     } 
    } 

    private static String validateFields(String barcode, String format, 
             String title, String price) { 
     StringBuilder errors = new StringBuilder(); 

     if (barcode.matches("^\\s*$")) { 
      errors.append("Barcode required\n"); 
     } 

     if (format.matches("^\\s*$")) { 
      errors.append("Format required\n"); 
     } 

     if (title.matches("^\\s*$")) { 
      errors.append("Title required\n"); 
     } 

     if (!price.matches("^-?\\d+(.\\d+)?$")) { 
      errors.append("Need numeric price\n"); 
     } 

     return errors.toString(); 
    } 

} 

Answer 1

私は文字列がどこかでnullかもしれないと思う。テキストフィールドに何かを入力するか、ヌル文字列を確認してください。