Question

这是代码：如何将其显示为仅小数点后2位？我使用String.format("%.2f", maltRequiredString);

时我的应用崩溃了

public class MainActivity extends AppCompatActivity {

    EditText batchVolEditText;
    EditText ogEditText;
    EditText bheEditText;
    TextView maltRequiredTextView;


    public void calculate(View view) {

        String batchVolString = batchVolEditText.getText().toString();
        String ogString = ogEditText.getText().toString();
        String bheString = bheEditText.getText().toString();

        double batchVolDouble = Double.parseDouble(batchVolString);
        double ogDouble = Double.parseDouble(ogString);
        double bheDouble = Double.parseDouble(bheString);
        double specificGravity = 0.96;

        double maltRequired = (batchVolDouble * ogDouble * specificGravity) / bheDouble;


        String maltRequiredString = Double.toString(maltRequired);

        maltRequiredTextView.setText(maltRequiredString + "kg");


    }

Answer 1

请记住，您无法使用

 String.format("%.2f", maltRequiredString);

因为maltRequiredString是字符串。正确的编码是你必须在这个函数中使用float，为此你必须将你的字符串转换为float

float f = Float.valueOf(maltRequiredString);  
String test = String.format("%.02f", f);

您也可以使用此技术将其设为2十进制

DecimalFormat decimalFormat = new DecimalFormat("#.##");
float twoDigitsF = Float.valueOf(decimalFormat.format(f));

Answer 2

您可以使用DecimalFormat来解决此问题。

//Make a new instance df that has 2 decimal places pattern.
Decimalformat df = new DecimalFormat("#.##");

// converting maltRequired form double to string.
String maltRequiredString  = df.format(maltRequired);

// then set the value of maltRequiredString to the TextView.
maltRequiredTextView.setText(String.valueOf(maltRequiredString));

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