如何检测Android中未插入SIM卡？

Question

我想在每次手机启动时检查手机中是否存在SIM卡。如果没有插入SIM卡，应用程序将删除所有SMS消息，删除所有帐户凭据，删除所有电话联系人，并自动擦除外部存储上的所有数据。但是当我启动手机时，应用程序被强行关闭......我配置的Toast也没有出现......我能知道怎样才能检查SIM卡的缺失情况？我已经尝试过simSerial.equals（“”）和simSerial.equals（null），但是失败了...需要有人帮忙...谢谢

if (simSerial.equals(null)){
            Toast.makeText(testContext.getApplicationContext(), "No SIM card detected!!!", Toast.LENGTH_LONG).show();
            Log.d("Message", "No SIM card");

            ContentResolver cr = context.getContentResolver();
            Cursor cursor = cr.query(ContactsContract.Contacts.CONTENT_URI, null, null, null, null);

            while(cursor.moveToNext()){
                String lookupKey = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.LOOKUP_KEY));   
                Uri uri = Uri.withAppendedPath(ContactsContract.Contacts.CONTENT_LOOKUP_URI, lookupKey);
                cr.delete(uri, null, null);
            }

            accManager = AccountManager.get(context);
            Account [] acc = accManager.getAccounts();
            if (acc.length > 0){            
                for (int j=0; j<acc.length; j++){
                    Account accountToRemove = acc[j];
                    accManager.removeAccount(accountToRemove, null, null);
                }
            }

            ContentResolver cr1 = context.getContentResolver();
            Cursor cursor1 = cr1.query(Uri.parse("content://sms/"), null, null, null,null);
            try {
                  while (cursor1.moveToNext()) {
                     int id = cursor1.getInt(0);
                     cr1.delete(Uri.parse("content://sms/" + id), null, null);
                  }
                } finally {
                  cursor.close();
                }

            //Wipe data on SD card
            wipeSdCard();
        }