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PObasic calculator android development failing
 

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  1. PObasic calculator android development failing
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    <p>I was following a tutorial on creating a temperature converter and it worked. Then I thought let me develop a calculator (basic edit text, text view and button manipulation) to practice further using these widgets.</p> <p>I wrote the code below but it is failing for some reason. I believe it is a NullPointerException when passing to result.setText() but I even hardcoded a string there, yet it doesn't work.First code is my code and the other code is the converter that worked fine with me:</p> <pre><code>public class MainActivity extends Activity { private EditText firstNumber; private EditText secondNumber; private TextView result; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } public void calculate(View view) { switch(view.getId()) { case R.id.additionButton: firstNumber = (EditText) findViewById(R.id.editText1); secondNumber = (EditText) findViewById(R.id.editText2); if(firstNumber.getText().length() != 0 &amp;&amp; secondNumber.getText().length() != 0) { float x = Float.parseFloat(firstNumber.getText().toString()); float y = Float.parseFloat(secondNumber.getText().toString()); result.setText(String.valueOf(addition(x, y))); } break; } } private float addition(float x, float y) { return x + y; } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } } </code></pre> <p>and the converter code:</p> <pre><code>public class MainActivity extends Activity { private EditText text; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); text = (EditText) findViewById(R.id.editText1); } // This method is called at button click because we assigned the name to the // "OnClick property" of the button public void Convert(View view) { switch (view.getId()) { case R.id.button1: RadioButton celsiusButton = (RadioButton) findViewById(R.id.radio0); RadioButton fahrenheitButton = (RadioButton) findViewById(R.id.radio1); if (text.getText().length() == 0) { Toast.makeText(this, "Please enter a valid number", Toast.LENGTH_LONG).show(); return; } float inputValue = Float.parseFloat(text.getText().toString()); if (celsiusButton.isChecked()) { text.setText(String .valueOf(convertFahrenheitToCelsius(inputValue))); celsiusButton.setChecked(false); fahrenheitButton.setChecked(true); } else { text.setText(String .valueOf(convertCelsiusToFahrenheit(inputValue))); fahrenheitButton.setChecked(false); celsiusButton.setChecked(true); } break; } } // Converts to celsius private float convertFahrenheitToCelsius(float fahrenheit) { return ((fahrenheit - 32) * 5 / 9); } // Converts to fahrenheit private float convertCelsiusToFahrenheit(float celsius) { return ((celsius * 9) / 5) + 32; } } </code></pre> <p>Please help me out as I am starting android development :) Thanks a bunch!</p> <p>NOTE: I said I believe because I am still getting used to debugger. This is the error msg it is showing:</p> <blockquote> <p>07-06 12:31:39.236: E/AndroidRuntime(28638): Caused by: java.lang.NullPointerException 07-06 12:31:39.236: E/AndroidRuntime(28638): at com.khalid.basiccalulator.MainActivity.calculate(MainActivity.java:34)</p> </blockquote>
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    1. CO_I believe it is a NullPointerException_ Jus't don't _believe_, you have a LogCat with all informations about exceptions, open it and see what is causing your app crash
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