Question

我有2个字段和一个按钮。我想在字段为空时禁用该按钮。我尝试了很多解决方案，但仍然无效。这是我的代码：

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

btnCount.setOnClickListener(new View.OnClickListener() {   

@Override
        public void onClick(View view) {
            String p1 =
                    edtP.getText().toString().trim();
            String l2 =
                    edtL.getText().toString().trim();

            double dp = Double.parseDouble(p1);
            double dl = Double.parseDouble(l2);

            double total = dp * dl;

            txtT.setText("equals: " +total);

            if (  ( !p1.trim().isEmpty()) && ( !l2.trim().isEmpty()) ) {

                btnCount.setEnabled(false);
            }

        }
    }); }

每次运行项目时，我总是会收到此错误：

java.lang.NumberFormatException: Invalid double: ""
     at java.lang.StringToReal.invalidReal(StringToReal.java:63)
     at java.lang.StringToReal.parseDouble(StringToReal.java:267)

Answer 1

将textChange侦听器添加到两个字段和两个字段的onTextChanged方法中，检查提供的文本是否为空。如果为空则禁用按钮，否则启用按钮。

Field1.addTextChangedListener(new TextWatcher() {

   @Override
   public void afterTextChanged(Editable s) {}

   @Override    
   public void beforeTextChanged(CharSequence s, int start,
     int count, int after) {
   }

   @Override    
   public void onTextChanged(CharSequence s, int start,
     int before, int count) {
      if(s.length() != 0 && Field2.getText().toString.length()!=0){
        // enable the button
      }else{
        // disable the button
      }
   }
  });

Field2.addTextChangedListener(new TextWatcher() {

   @Override
   public void afterTextChanged(Editable s) {}

   @Override
   public void beforeTextChanged(CharSequence s, int start,
     int count, int after) {
   }

   @Override
   public void onTextChanged(CharSequence s, int start,
     int before, int count) {
      if(s.length() != 0 && Field1.getText().toString.length()!=0){
        // enable the button
      }else{
        // disable the button
      }
   }
  });

Answer 2

试试这个：

btnCount.setOnClickListener(new View.OnClickListener() {   

@Override
        public void onClick(View view) {
if(edtP.getText().toString().length()>0 &&  edtL.getText().toString().length()>0){
            String p1 =
                    edtP.getText().toString().trim();
            String l2 =
                    edtL.getText().toString().trim();

            double dp = Double.parseDouble(p1);
            double dl = Double.parseDouble(l2);

            double total = dp * dl;

            txtT.setText("equals: " +total);

           if (  !(p1.trim().isEmpty()) && ( !l2.trim().isEmpty()) ) {

                    btnCount.setEnabled(true);
                }
    else{
    btnCount.setEnabled(false);
    }
}
else{
 Toast.makeText(getApplicationContext(),"Edittexts are empty",Toast.LENGTH_LONG).show();
}
        }
    }); }

Answer 3

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

btnCount.setOnClickListener(new View.OnClickListener() {   

@Override
        public void onClick(View view) {
            String p1 =  edtP.getText().toString().trim();
            String l2 =  edtL.getText().toString().trim();
            double dp = 0, dl = 0, total = 0;
            try{
              dp = Double.parseDouble(p1);
              dl = Double.parseDouble(l2);
              total = dp * dl;
              txtT.setText("equals: " +total);
            }catch(Exception e){
              dp = -1;
              dl = -1;
              btnCount.setEnabled(false);
            }
        }
    }); 
}

编辑文本时禁用Android按钮（解析值）清空

3 个答案: