java - 空字段导致错误 "stopped unexpectedly"

Question

是否有任何方法可以预定义字符串值，以便在任何字段为空时不会出现错误？所有比例1、2和3都是可选的，因此并不是要求用户输入一些数据，而是预先定义值以便不具有这些值。初学者问题。

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    cpc_inicial = (EditText) findViewById(R.id.cpc_inicial);
    porcentagem1 = (EditText) findViewById(R.id.porcentagem1);
    porcentagem2 = (EditText) findViewById(R.id.porcentagem2);
    porcentagem3 = (EditText) findViewById(R.id.porcentagem3);
    cpc_final = (TextView) findViewById(R.id.cpc_final);
    botao1 = (Button) findViewById(R.id.botao1);

    cpc_inicial.setInputType(InputType.TYPE_CLASS_NUMBER);
    porcentagem1.setInputType(InputType.TYPE_CLASS_NUMBER);
    porcentagem2.setInputType(InputType.TYPE_CLASS_NUMBER);
    porcentagem3.setInputType(InputType.TYPE_CLASS_NUMBER);

    botao1.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {

            if(porcentagem3 != null ) {             

            float cpc = Float.parseFloat(cpc_inicial.getText().toString());
            float v1 = Float.parseFloat(porcentagem1.getText().toString());
            float v2 = Float.parseFloat(porcentagem2.getText().toString());
            float v3 = Float.parseFloat(porcentagem3.getText().toString());
            TextView cpcfinal = cpc_final;

            if(cpc > 0.0 && v1 != 0.0 && v2 != 0.0 && v3 != 0.0 )
            {
            soma = (cpc*v1/100)+cpc;
            soma = soma*(v2/100)+soma;
            soma = soma*(v3/100)+soma;

            String sum = Float.toString(soma);
            cpcfinal.setText(sum);

            }
            } else  
            {
            TextView cpcfinal = cpc_final;
            soma = 0; 
            cpcfinal.setText("ops!"); }
        }
    });
}

谢谢

Answer 1

每次提交表单时，您都应该检查每个字段是否有正确的值。例如，如果您想检查可选字段是否有值，您应该这样做:

String optionalText = optionalFieldName.getText().toString();
if (optionalText.equals("some expected value")) {
    //Do something with the value here.
}

当然，您需要对每个可选字段执行类似的操作，并且实际上还应该对不是安全选项的字段执行相反的操作，并且可能警告用户该字段是必需的，例如:

String text = fieldName.getText().toString();
if (text.equals("")) {
    //field is empty, so warn the user that it is required.
}

如果您正在寻找的值本质上应该是数字，那么您应该这样做:

String text = field.getText().toString();
if (!text.equals("")) {
    //Field has at least some text in it.
    try {
        float val = Float.parseFloat(text);
    }catch (NumberFormatException ex) {
    //Enterered text was not a float value, so you should do something
    // here to let the user know that their input was invalid and what you expect
    }

    //Do something with the value
}