我正在研究一个计算器。如果我没有输入任何数字并点击操作员，应用程序崩溃，你可以在下面看到原因。
public void setOperator(String operatorCharacter){
if (operatorState == false){
displayHandler.clearRecorder();
if (operatorState == true){
calculate();*
有没有解决方法呢？
编辑 如果显示屏为空，我按下操作员按钮就会崩溃，因为我写了
if (operatorState == true){
calculate();*
这是我的计算代码。
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;
}
错误
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());
答案 0 :(得分：0)
如果显示屏为空，我按下操作员按钮就会崩溃
因为Float.parseFloat不喜欢空字符串。
Caused by: java.lang.NumberFormatException: Invalid float: ""第一个方法调用可以/将失败。
public void calculate() {
seOp = Float.parseFloat(displayHandler.getDisplay().getText().toString());
您只需要先检查字符串是否为空并正确处理
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();
如果你只想try {例外，你也可以将Float.parseFloat语句移到catch之上。
答案 1 :(得分：0)
您可以禁用操作员按钮，直到点击任何数字
或者您可以检查您创建的第一个和第二个数字。
if(fiOpInTarget != null && seOpinTarget!= null) {
//do your calculations
if (operator.equals("+")) {
answerInTarget = fiOpInTarget + seOpinTarget;
}
//so on
}