想要在值为 NULL 或 VOID 时显示错误消息（如果 EditText 为空但应用程序不断崩溃）

Question

public void add(View v)
{

    EditText first=findViewById(R.id.first),second=findViewById(R.id.second);
    double f=Double.parseDouble(first.getText().toString());
    double s=Double.parseDouble(second.getText().toString());
    TextView result=findViewById(R.id.result);
    double r;
    if(TextUtils.isEmpty(first.getText().toString()))
    {
        first.setError("This field can't be empty");
    }
    else if(TextUtils.isEmpty(second.getText().toString()))
    {
        second.setError("This field can't be empty");
    }
    else {
        r = f + s;
        result.setText("" + r);
    }

}

我想从用户输入中添加两个数字，并在 editText 为空时显示错误消息。
但是在执行这段代码时，我的应用程序一直崩溃。

Answer 1

如果 Editext 值不为空，您需要将 Editext 值转换为 Double

试试这个

public void add(View v)
{

    EditText first=findViewById(R.id.first);
    EditText second=findViewById(R.id.second);      

    TextView result=findViewById(R.id.result);

    double r;

    if(TextUtils.isEmpty(first.getText().toString()))
    {
        first.setError("This field can't be empty");
    }
    else if(TextUtils.isEmpty(second.getText().toString()))
    {
        second.setError("This field can't be empty");
    }
    else {
        double s=Double.parseDouble(second.getText().toString());
        double f=Double.parseDouble(first.getText().toString());
        r = f + s;
        result.setText("" + r);
    }

}

Answer 2

添加"null"校验，空校验前

例如：

if((first.gettext().toString) == null ||
    TextUtils.isEmpty(first.getText().toString()))
        {
            first.setError("This field can't be empty");
        }
        else if((second.gettext().toString) == null || TextUtils.isEmpty(second.getText().toString()))
        {
            second.setError("This field can't be empty");
        }
        else {
            r = f + s;
            result.setText("" + r);
        }

Answer 3

全球第一，第二

public void add(View v) {
    first = findViewById(R.id.first);
    second = findViewById(R.id.second);
    TextView result = findViewById(R.id.result);
    double r;
    if (Validates()) {
        double s = Double.parseDouble(second.getText().toString());
        double f = Double.parseDouble(first.getText().toString());
        r = f + s;
        result.setText("" + r);
    }
}


public boolean Validates() {
    if (first.getText().toString().equalsIgnoreCase("")) {
        first.setError("This field can't be empty");
        return false;
    } else if (second.getText().toString().equalsIgnoreCase("")) {
        second.setError("This field can't be empty");
        return false;
    } else {
        return true;
    }
}

想要在值为 NULL 或 VOID 时显示错误消息（如果 EditText 为空但应用程序不断崩溃）

Want to display an error message if the value is NULL or VOID if EditText is empty but apps keeps crashing

java

crash

android