java - 当我单击“计算”按钮以显示我的结果时应用程序崩溃

Question

在 BMI 计算器上工作，该计算器有一个旋转器，可以计算英尺/英寸以及用户的体重。

问题:当我点击计算我的应用崩溃时，我不确定发生了什么。我知道 logtcat 提到了一些关于 onclick 的事情，即使我已经在 oncreatview 上声明了按钮。

日志猫:

 04-08 13:02:27.486 12353-12353/com.example.treycoco.calorietracker
 E/AndroidRuntime: FATAL EXCEPTION: main
 Process: com.example.treycoco.calorietracker, PID: 12353
 java.lang.NullPointerException
 at com.example.treycoco.calorietracker.BmiFrag.onClick(BmiFrag.java:98)
 at android.view.View.performClick(View.java:4438)
 at android.view.View$PerformClick.run(View.java:18422)
 at android.os.Handler.handleCallback(Handler.java:733)
 at android.os.Handler.dispatchMessage(Handler.java:95)
 at android.os.Looper.loop(Looper.java:136)
 at android.app.ActivityThread.main(ActivityThread.java:5045)
 at java.lang.reflect.Method.invokeNative(Native Method)
 at java.lang.reflect.Method.invoke(Method.java:515)
 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
 at dalvik.system.NativeStart.main(Native Method)

BmiFrag.java

     public class BmiFrag extends Fragment implements View.OnClickListener {
     Button BmiButton;

    public static EditText heightFT;
    public static EditText heightIn;
    public static EditText weightIn;

    //adaptors spinners

    ArrayAdapter<String> HeightFeetAdapter;
    ArrayAdapter<String> WeightLBSAdapter;

    //references UI elements

    Spinner weightSpinner;
    Spinner heightSpinner;


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


    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {


    View myView = inflater.inflate(R.layout.fragment_bmi, container, false);

    heightSpinner= (Spinner) myView.findViewById(R.id.HeightSpin);

    weightSpinner= (Spinner)myView.findViewById(R.id.WeightSpin);


    BmiButton = (Button) myView.findViewById(R.id.CalculateBmi);
    BmiButton.setOnClickListener(this);


    initializeSpinnerAdapters();
    loadLBVal();
    loadFTVal();

    return myView;
   }

       @Override
       public void onClick(View v) {
       switch (v.getId()) {

       case R.id.CalculateBmi:


            final TextView tv4 = (TextView)
       getActivity().findViewById(R.id.TFDisplayBmi);

           /* str1*/
            String getWeightIN = weightIn.getText().toString();



             /* str2*/
            String  getHeightIN = heightIn.getText().toString();

            String getHeightFT = heightFT.getText().toString();



            if (TextUtils.isEmpty(getWeightIN)) {



                weightIn.setError("Please enter your weight");
                weightIn.requestFocus();
                return;
            }

            else if (TextUtils.isEmpty(getHeightIN)) {
                heightIn.setError("Please enter your height in Inches");
                heightIn.requestFocus();
                return;
            }

            else if (TextUtils.isEmpty(getHeightFT)) {
                heightFT.setError("Please enter your height in Feet");
                heightFT.requestFocus();
                return;
            }


            else {

               float weight = getSelectedWeight();
                float height = getSelectedHeight();


                float bmiValue = calculateBMI(weight,height);

                String bmiInterpretation = interpretBMI(bmiValue);

                tv4.setText(String.valueOf(bmiValue + "-" +
                bmiInterpretation));


            }



            break;

    }
    }

     // retrieve the weight from the spinner control converted to kg
          public float getSelectedWeight() {
          String selectedWeightValue =
          (String)weightSpinner.getSelectedItem();

          return (float) (Float.parseFloat(selectedWeightValue) * 
          0.45359237);
      }


          public float getSelectedHeight() {
          String selectedHeightValue = 
          (String)heightSpinner.getSelectedItem();

         // the position is feets and inches, so convert to meters andreturn
        String feets = selectedHeightValue.substring(0, 1);
        String inches = selectedHeightValue.substring(2, 4);
        return (float) (Float.parseFloat(feets) * 0.3048) +
                (float) (Float.parseFloat(inches) * 0.0254);

     }


       private float calculateBMI(float weight, float height ) {

       //weight * 703f / (float)Math.pow(heightIN+12f*v,2);
       float bmi=  (weight / (height * height));

        float total= Math.round(bmi);



          return  total;
    }


        private String interpretBMI(float bmiValue) {

          if (bmiValue < 16) {
          return "Severely underweight";
          } else if (bmiValue < 18.5) {

           return "Underweight";
         } else if (bmiValue < 25) {

           return "Normal";
        } else if (bmiValue < 30) {

           return "Overweight";
            } else {
           return "Obese";
        }
    }



         public void loadLBVal() {
         weightSpinner.setAdapter(WeightLBSAdapter);
         // set the default lib value
        weightSpinner.setSelection(WeightLBSAdapter.getPosition("170"));
        }


        // load the feets value range to the height spinner
       public void loadFTVal() {
       heightSpinner.setAdapter(HeightFeetAdapter);
       // set the default value to feets
      heightSpinner.setSelection(HeightFeetAdapter.getPosition("5\"05'"));
    }

         public void initializeSpinnerAdapters() {

         String[] weightLibs = new String[300];

               for (int i = 1; i <= 300; i ++) {
             weightLibs[k--] = String.format("%3d", i);
             }
        // initialize the weightLibsAdapter with the weightLibs values
        WeightLBSAdapter = new ArrayAdapter<String>(getContext(), 
        android.R.layout.simple_list_item_activated_1 , weightLibs);




        String[] heightFeets = new String[60];
       // loading 3"0' to 7"11' to the height in feet/inch
          k = 59;
          for (int i = 3; i < 8; i ++) {
          for (int j = 0; j < 12; j ++) {
            heightFeets[k--] = i + "\"" + String.format("%02d", j) + "'";
         }
        }
        // initialize the heightFeetAdapter with the heightFeets values
       HeightFeetAdapter = new ArrayAdapter<String>(getContext(), 
       android.R.layout.simple_list_item_activated_1, heightFeets);

      }


             @Override
           public void onActivityCreated(Bundle savedInstanceState) {
           super.onActivityCreated(savedInstanceState);
       }

            @Override
            public void onDestroy() {
            super.onDestroy();

           }

            @Override
            public void onDetach() {
            super.onDetach();
           }
         }

再次感谢。我仍在学习 Android Studio 和 Java，这是我第一次开发应用程序。另外，如果数学看起来不对，我深表歉意。我正在研究不同的公式。

Answer 1

您还没有初始化您的任何edittext 因此在您执行此操作时点击按钮

String getWeightIN = weightIn.getText().toString();

您收到空指针异常。像对按钮所做的那样初始化您的编辑文本，一切都会好起来的