错误捕获错误

Question

正在尝试捕获null或0输入。如果输入的是null，应用程序就会崩溃，如果输入的是0，它就会通过错误并返回奇怪的数学结果！

case_cost = (EditText) findViewById(R.id.case_cost);
dilution = (EditText) findViewById(R.id.dilution);
answer =(TextView) findViewById(R.id.answer);
ounces_pc = (TextView) findViewById(R.id.ounces_pc);

Button finishBtn = (Button) findViewById(R.id.button3);
finishBtn.setOnClickListener (new View.OnClickListener() {
    @Override
        public void onClick(View v) {
        // TODO Method 
        if (((Float.valueOf(dilution.getText().toString())) == 0) ||   
                         (dilution.getText().equals(null)))   {

    String errMsg = "Missing Dilution";
        answer.setText(errMsg);

    }   else;

调试信息：

StringToReal.invalidReal(String, boolean) line: 63  
StringToReal.parseFloat(String) line: 289   
Float.parseFloat(String) line: 300  
Float.valueOf(String) line: 337 
UccActivity$1.onClick(View) line: 47    
Button(View).performClick() line: 4102  
View$PerformClick.run() line: 17063 
Handler.handleCallback(Message) line: 615   
ViewRootImpl$ViewRootHandler(Handler).dispatchMessage(Message) line: 92 
Looper.loop() line: 155 
ActivityThread.main(String[]) line: 5454    
Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not   
available [native method]   
Method.invoke(Object, Object...) line: 511  
ZygoteInit$MethodAndArgsCaller.run() line: 1029 
ZygoteInit.main(String[]) line: 796 
NativeStart.main(String[]) line: not available [native method]  
Thread [<10> Binder_2] (Running)    
Thread [<9> Binder_1] (Running)"

Answer 1

您应该将Null的检查放在值的检查之前。否则，当它检查0并且值为Null时，它将抛出异常。

Answer 2

这种方法将允许您输入无效的字符串(字母)，并且不会崩溃(您的将按原样)。此外，您的0检查不起作用，因为您正在比较一个整型和一个浮点型。您应该使用0f

String text = dilution.getText().toString();
if (TextUtils.isEmpty(text)) {
  answer.setText("Empty input");
  return;
}

try {
    Float value = Float.valueOf(text);

    if (value == null || value == 0f) {
        answer.setText("Zero");
    }
} catch (NumberFormatException e) {
    answer.setText("Invalid input");
}