android - 不幸的是，应用程序已停止

Question

com.example.converter.MainActivity在控制台中的此评论之后在设备 emulator-5554 上启动活动它在运行时向我显示错误，不幸的是转换器已停止。

请建议我该怎么做？

public class mainactivity extends Activity {

private EditText text;

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        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.main, menu);
        return true;
    }

  // This method is called at button click because we assigned the name to the
  // "OnClick property" of the button
  public void onClick(View view) {
    switch (view.getId()) {
    case R.id.button1:
      RadioButton celsiusButton = (RadioButton) findViewById(R.id.radioButton1);
      RadioButton fahrenheitButton = (RadioButton) findViewById(R.id.radioButton2);
      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;
  }
} 

Answer 1

您忘记初始化textEditText。

我认为你在这里是 NullPointerExceptionif (text.getText().length() == 0) {

所以在使用前像这样初始化。

text = (EditText)findViewById(R.id.yourTextViewId);