I'm currently working on a school project in Android Studio and so far I've written (with a little help from stackoverflow.com) an algorithm which generates a random equation everytime you press a button on the screen. The equation then shows up in a textview on the screen. I've added a second textview in which the result of the equation shows up. Here is my code so far:
String[] operationSet = new String[]{"+", "-", "/", "*"};
public void generate(View view) {
Random random = new Random();
int numOfOperations = random.nextInt(2) + 1;
List<String> operations = new ArrayList<>();
for (int i = 0; i < numOfOperations; i++) {
String operation = operationSet[random.nextInt(4)];
operations.add(operation);
}
int numOfNumbers = numOfOperations + 1;
List<Integer> numbers = new ArrayList<>();
for (int i = 0; i < numOfNumbers; i++) {
int number = random.nextInt(10)+1;
numbers.add(number);
}
String equation = "";
for (int i = 0; i < numOfOperations; i++) {
equation += numbers.get(i);
equation += operations.get(i);
}
equation += numbers.get(numbers.size() -1);
TextView TextEquation = (TextView)findViewById(R.id.textView);
TextEquation.setText(equation);
String stringResultOfEquation = String.valueOf(equation);
// Calculate the result of the equation
double doubleEquation = Double.parseDouble(equation);
double doubleResult = abs(doubleEquation);
String stringResult = String.valueOf(doubleResult);
TextView textResult = (TextView)findViewById(R.id.textView2);
textResult.setText(stringResult);
}
The problem now is, that when I launch the app in the emulator and I press the button on the screen, my app crashes and giving the error message: "unfortunately SolveIt has stopped" Everything worked perfectly fine until I've added the second textview2 with the result of the equation in it. So I guess there must be something wrong with it:
double doubleEquation = Double.parseDouble(equation);
double doubleResult = abs(doubleEquation);
String stringResult = String.valueOf(doubleResult);
TextView textResult = (TextView)findViewById(R.id.textView2);
textResult.setText(stringResult);
Maybe there is a problem with converting my string into a double but I really don't know.
Here is the logcat if someone is wondering:
10-12 22:41:23.646 14905-14905/mycompany.solveit E/AndroidRuntime: FATAL EXCEPTION: main
Process: mycompany.solveit, PID: 14905
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NumberFormatException: Invalid double: "3/1"
at java.lang.StringToReal.invalidReal(StringToReal.java:63)
at java.lang.StringToReal.initialParse(StringToReal.java:164)
at java.lang.StringToReal.parseDouble(StringToReal.java:282)
at java.lang.Double.parseDouble(Double.java:301)
at mycompany.solveit.FullscreenActivity.generate(FullscreenActivity.java:210)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
10-12 22:41:25.672 14905-14905/mycompany.solveit I/Process: Sending signal. PID: 14905 SIG: 9
If anything is unclear in my question, feel free to ask and I will try to clarify the problem :)
Thank you already in advance!
