如果 EditText 字段为空或输入的值等于 0，如何使 Toast 弹出？

Question

首先，我是 Android Studio 的新手。 我目前正在尝试制作一个 BMI 计算器应用程序，用户必须输入他们的体重和身高以及 select 用于两者的测量单位。 在以下情况下，单击按钮时应弹出 Toast 消息 (R.string.toastError)：(1-2) 重量和高度的 EditText 字段为空，以及 (3) 如果 HeightInput 的值小于或等于零； 否则，应继续计算。

当我测试它时，整个数学部分运行良好，但是当我将字段留空时，应用程序就会崩溃。 虽然当 HeightInput = 0 时会弹出 Toast，但不会在 Weight 的 EditText 字段同时留空时弹出。 我认为这是我写“if”语句的方式给我带来了问题。

 // if edit text is empty
            if (editTextWeightInput.getText().toString().length() == 0 || editTextHeightInput.getText().toString().length() == 0 || HeightInput <= 0) {
                Toast.makeText(getApplicationContext(), R.string.toastError, Toast.LENGTH_SHORT).show();
            } else {
                    double finalheight = Math.pow((HeightInput * constantHeight), 2.00);
                    double BodyMassIndex = (WeightInput * constantWeight) / finalheight;
                    DecimalFormat BodyMassIndexFormat = new DecimalFormat("##.##");
                    TextView textViewResult = (TextView) findViewById(R.id.textViewBmiResult);
                    textViewResult.setText(BodyMassIndexFormat.format(BodyMassIndex));
                }

这是整个代码供参考：

public class MainActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    
    // weight units spinner
    final Spinner spinWeightUnit = (Spinner) findViewById(R.id.spinnerWeightUnit);
    spinWeightUnit.setOnItemSelectedListener(this);
    ArrayAdapter <CharSequence> WeightList = ArrayAdapter.createFromResource(this, R.array.WeightUnits, android.R.layout.simple_spinner_item);
    WeightList.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinWeightUnit.setAdapter(WeightList);
    
    // height units spinner
    final Spinner spinHeightUnit = (Spinner) findViewById(R.id.spinnerHeightUnit);
    spinHeightUnit.setOnItemSelectedListener(this);
    ArrayAdapter <CharSequence> HeightList = ArrayAdapter.createFromResource(this, R.array.HeightUnits, android.R.layout.simple_spinner_item);
    HeightList.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinHeightUnit.setAdapter(HeightList);
    
    // calculate button
    Button buttonCalculate = (Button) findViewById(R.id.buttonCalculate);
    buttonCalculate.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            
            // declaration
            EditText editTextWeightInput = (EditText) findViewById(R.id.editTextWeightInput);
            EditText editTextHeightInput = (EditText) findViewById(R.id.editTextHeightInput);
            double WeightInput = Double.valueOf(editTextWeightInput.getText().toString());
            double HeightInput = Double.valueOf(editTextHeightInput.getText().toString());
            String finalWeightUnit = String.valueOf(spinWeightUnit.getSelectedItem());
            String finalHeightUnit = String.valueOf(spinHeightUnit.getSelectedItem());
            double constantWeight;
            double constantHeight;
            
            // weight conversion constant
            if (finalWeightUnit.equals("kilograms")) {
                constantWeight = 1.00;
            } else {
                constantWeight = 1 / 2.204623;
            }
            
            // height conversion constant
            switch (finalHeightUnit) {
                case "inches":
                    constantHeight = 0.0254;
                    break;
                case "centimeters":
                    constantHeight = 0.01;
                    break;
                case "feet":
                    constantHeight = 1 / 3.2808;
                    break;
                default:
                    constantHeight = 1.00;
                    break;
            }
            
            // if edit text is empty
            if (editTextWeightInput.getText().toString().length() == 0 || editTextHeightInput.getText().toString().length() == 0 || HeightInput <= 0) {
                Toast.makeText(getApplicationContext(), R.string.toastError, Toast.LENGTH_SHORT).show();
            } else {
                    double finalheight = Math.pow((HeightInput * constantHeight), 2.00);
                    double BodyMassIndex = (WeightInput * constantWeight) / finalheight;
                    DecimalFormat BodyMassIndexFormat = new DecimalFormat("##.##");
                    TextView textViewResult = (TextView) findViewById(R.id.textViewBmiResult);
                    textViewResult.setText(BodyMassIndexFormat.format(BodyMassIndex));
                }
            }
        });
    }

@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {

}



  @Override
    public void onNothingSelected(AdapterView<?> adapterView) {

    }
}

我会很感激任何帮助！ 谢谢！

Answer 1

在 if 语句中尝试下面

if (editTextWeightInput.getText().toString().trim().isEmpty() || editTextHeightInput.getText().toString().trim().isEmpty() || HeightInput <= 0)

Answer 2

您还需要验证您的声明代码。

     // declaration
 EditText editTextWeightInput = (EditText) findViewById(R.id.editTextWeightInput);
        EditText editTextHeightInput = (EditText) findViewById(R.id.editTextHeightInput);

      if(TextUtil.isEmpty(editTextWeightInput.getText().toString())||TextUtil.isEmpty(editTextHeightInput.getText().toString())){
            Toast.makeText(getApplicationContext(), R.string.toastError, 
                Toast.LENGTH_SHORT).show();
    
       }else{

            
        double WeightInput = Double.valueOf(editTextWeightInput.getText().toString());
        double HeightInput = Double.valueOf(editTextHeightInput.getText().toString());
        String finalWeightUnit = String.valueOf(spinWeightUnit.getSelectedItem());
        String finalHeightUnit = String.valueOf(spinHeightUnit.getSelectedItem());
        double constantWeight;
        double constantHeight;

}

Answer 3

当您将 EditText 留空时，getString() function 返回 null 值。 首先，您需要在 if 条件下检查 null。

if (editTextWeightInput.getText() == null || editTextWeightInput.getText().toString().length() == 0 || HeightInput <= 0)