How to clear text when entering new number

Question

I am working on a calculator. If i dont enter any numbers and click on the operator the app crashes as you can see below why.

public void setOperator(String operatorCharacter){
    if (operatorState == false){
        displayHandler.clearRecorder();

    if (operatorState == true){
        calculate();*

Is there any workaround for this?

Edit If the display is empty and I press on a operator button it crashes because i have written

  if (operatorState == true){
        calculate();*

Here is my calculate code.

public void calculate() {
        seOp = Float.parseFloat(displayHandler.getDisplay().getText().toString());
        secondPacket = buttonManager.getExtSpinner().getSelectedItem().toString();
        ansPacket = buttonManager.getAnsSpinner().getSelectedItem().toString();

        try {
            double targetPacket = conversion.getPacketSize(ansPacket);
            double fiOpInTarget = 0d;

            if (firstPacket != null) {
                double firstOperandConversion = conversion.getPacketSize(firstPacket);
                fiOpInTarget = (fiOp * targetPacket) / firstOperandConversion;

            }
            double secondOperandConversion = conversion.getPacketSize(secondPacket);
            double seOpinTarget = (seOp * targetPacket) / secondOperandConversion;

            if (operator.equals("+")) {
                answerInTarget = fiOpInTarget + seOpinTarget;
            }
            else if (operator.equals("-")) {
                answerInTarget = fiOpInTarget - seOpinTarget;

            } else if (operator.equals("/")) {
                answerInTarget = (fiOpInTarget / seOpinTarget);

            } else if (operator.equals("x")) {
                answerInTarget = fiOpInTarget * seOpinTarget;

            } else {
                answerInTarget = seOpinTarget;
                displayHandler.addSingleValue(seOp, secondPacket);
            }
            displayHandler.setDisplay(String.format("%.2f", answerInTarget));
        }
            catch (Exception e) {
                e.printStackTrace();
                displayHandler.setDisplay("beep boop no internet. Please relaunch");
            }
        operatorState = false;


    }

The error

03-13 00:47:09.465 5467-5467/com.zeus.vibin.conv E/AndroidRuntime: FATAL EXCEPTION: main
                                                               Process: com.zeus.vibin.conv, PID: 5467
                                                               java.lang.IllegalStateException: Could not execute method for android:onClick
                                                                   at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
                                                                   at android.view.View.performClick(View.java:5198)
                                                                   at android.view.View$PerformClick.run(View.java:21147)
                                                                   at android.os.Handler.handleCallback(Handler.java:739)
                                                                   at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                   at android.os.Looper.loop(Looper.java:148)
                                                                   at android.app.ActivityThread.main(ActivityThread.java:5417)
                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                                                                Caused by: java.lang.reflect.InvocationTargetException
                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                   at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
                                                                   at android.view.View.performClick(View.java:5198) 
                                                                   at android.view.View$PerformClick.run(View.java:21147) 
                                                                   at android.os.Handler.handleCallback(Handler.java:739) 
                                                                   at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                                   at android.os.Looper.loop(Looper.java:148) 
                                                                   at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                                   at java.lang.reflect.Method.invoke(Native Method) 
                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
                                                                Caused by: java.lang.NumberFormatException: Invalid float: ""
                                                                   at java.lang.StringToReal.invalidReal(StringToReal.java:63)
                                                                   at java.lang.StringToReal.parseFloat(StringToReal.java:308)
                                                                   at java.lang.Float.parseFloat(Float.java:306)
                                                                   at com.zeus.vibin.conv.button.math.Maths.setOperator(Maths.java:45)
                                                                   at com.zeus.vibin.conv.button.buttons.ButtonManager.operatorClick(ButtonManager.java:57)
                                                                   at com.zeus.vibin.conv.button.main.Convert.operatorClicked(Convert.java:33)
                                                                   at java.lang.reflect.Method.invoke(Native Method) 
                                                                   at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
                                                                   at android.view.View.performClick(View.java:5198) 
                                                                   at android.view.View$PerformClick.run(View.java:21147) 
                                                                   at android.os.Handler.handleCallback(Handler.java:739) 
                                                                   at android.os.Handler.dispatchMessage(Handler.java:95) 
                                                                   at android.os.Looper.loop(Looper.java:148) 
                                                                   at android.app.ActivityThread.main(ActivityThread.java:5417) 
                                                                   at java.lang.reflect.Method.invoke(Native Method) 
                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Maths.java:45

 displayHandler.addToRecorder(buttonManager.getExtSpinner().getSelectedItem().toString(),
            Float.parseFloat(displayHandler.getDisplay().getText().toString()),operatorCharacter);

ButtonManager.java:57

  maths.setOperator(buttonText);

Convert.java:33

buttonManager.operatorClick(v.getId());

The [logcat will tell you what reason your app has stopped](http://stackoverflow.com/questions/23353173/unfortunately-myapp-has-stopped-how-can-i-solve-this). Please [edit] your question with it. — OneCricketeer, Mar 12 '17 at 19:25
Also, please show a [mcve]. None of this code makes sense out of context. — OneCricketeer, Mar 12 '17 at 19:25
@cricket_007 It crashes on if (operatorState == true){ calculate(); — vibin thomas, Mar 12 '17 at 19:26
@cricket_007 I am sorry i have uploaded the code in the edit. — vibin thomas, Mar 12 '17 at 19:29
We also need to know the exact and complete error message you get and what line numbers mentioned in it refer to which lines of your code example. — Timothy Truckle, Mar 12 '17 at 19:31
Possible duplicate of [What is a NumberFormatException and how can I fix it?](http://stackoverflow.com/questions/39849984/what-is-a-numberformatexception-and-how-can-i-fix-it) — xenteros, Apr 10 '17 at 09:36

OneCricketeer · Answer 1 · 2017-03-12T19:45:01.780

If the display is empty and I press on a operator button it crashes

Because Float.parseFloat doesn't like empty strings.

Caused by: java.lang.NumberFormatException: Invalid float: ""

That first method call can / will fail.

public void calculate() {
    seOp = Float.parseFloat(displayHandler.getDisplay().getText().toString());

You simply need to check if the string is empty first and handle that appropriately

public void calculate() {
    String op = displayHandler.getDisplay().getText().toString();
    if (!op.isEmpty()) {
        try {
            seOp = Float.parseFloat(op); 
        } catch (NumberFormatException e) {
            seOp = 0.0; // some default value
        }
    }
    secondPacket = buttonManager.getExtSpinner().getSelectedItem().toString();
    ansPacket = buttonManager.getAnsSpinner().getSelectedItem().toString();

You could also move the try { statement above Float.parseFloat if you did want to just catch the exception.

Then read the logcat again and read the message like I pointed to. — OneCricketeer, Mar 12 '17 at 19:43

score 0 · Answer 2 · answered Mar 12 '17 at 19:47

0

You can disable your operator buttons until click any numbers,

or you can check your first and second numbers for created or not.

if(fiOpInTarget != null && seOpinTarget!= null) {
  //do your calculations
   if (operator.equals("+")) {
     answerInTarget = fiOpInTarget + seOpinTarget;
   }
//so on
}

answered Mar 12 '17 at 19:47

Hard_Coder

718
6
13

operator != cannot be applied to null /double. – vibin thomas Mar 13 '17 at 11:25

How to clear text when entering new number

2 Answers2