Question

我希望我的EditText为数字值，而不是以0开头，例如：

如果我输入123，则确定
如果我输入0123错误。

这就是我所做的：

if(editText.getText().toString().charAt(0) == '0' ) {
    Toast.makeText(getApplicationContext(), "Sorry firs charset must be not 0", Toast.LENGTH_SHORT).show();
}

但只有当我点击按钮（setOnClickListener）时它才有效。

如何在点击按钮之前检查此内容？

Answer 1

您可以在yourEditText.addTextChangedListener(new TextWatcher() { public void afterTextChanged(Editable s) { if( (s.length()> 0) && (s.toString().charAt(0) == '0') ) { Toast.makeText(getApplicationContext(), "Sorry first charset must be not 0", Toast.LENGTH_SHORT).show(); } } public void beforeTextChanged(CharSequence s, int start, int count, int after) {} public void onTextChanged(CharSequence s, int start, int before, int count) {} });

中添加TextWatcher

{{1}}

Answer 2

   youredittext.addTextChangedListener(new TextWatcher()
    {
    @Override
    public void afterTextChanged(Editable mEdit) 
    {
        text = mEdit.toString();
         if(text.charAt(0) == '0' ) {
                    Toast.makeText(getApplicationContext(), "Sorry firs charset must be not 0", Toast.LENGTH_SHORT).show();
                }
    }

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

    public void onTextChanged(CharSequence s, int start, int before, int count){}
});

Answer 3

请试试这个：

 editText.addTextChangedListener(new TextWatcher() {
            @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 && s.charAt(0) == '0') {
                    Toast.makeText(getApplicationContext(), "Sorry firs charset must be not 0", Toast.LENGTH_SHORT).show();
                }
            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });

Answer 4

您需要添加TextChangedListener。

TextChangedListener向TextWatcher添加EditText，并在每次EditText's文字发生变化时致电。

您希望您的edittext不以“0”开头。所以将TextChangedListener分配给EditText，然后检查键入字符的事件。

editText.addTextChangedListener(new TextWatcher()
    {
    @Override
    public void afterTextChanged(Editable mEdit) {
         if(mEdit.toString().length() > 0&& mEdit.toString().charAt(0) == '0' ) {
              Toast.makeText(getApplicationContext(), "First letter must not be 0", Toast.LENGTH_SHORT).show();
         }
    }

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

    public void onTextChanged(CharSequence s, int start, int before, int count){}
});

Answer 5

使用android.text.TextWatcher

实现您的活动

editText.addTextChangedListener(this);

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

}

@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {

}

@Override
public void afterTextChanged(Editable s) {
   if(editText.getText().toString().charAt(0) == '0' ) { 
Toast.makeText(getApplicationContext(), "Sorry firs charset must be not 0", Toast.LENGTH_SHORT).show();
        } 
    } 
}

Answer 6

onTextChanged 方法用于立即对文本执行更改。它有三个参数。第一个参数是 Charequence s，它是在文本字段中输入的字符串 。接下来的三个int参数适用于Start, Before, Count。

 Your_EditText.addTextChangedListener(new TextWatcher()
        {
        @Override
        public void afterTextChanged(Editable mEdit) 
        {

        }

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

        public void onTextChanged(CharSequence s, int start, int before, int count){

           if (s.length()>0 && s.charAt(0) == '0') 
            {
           Toast.makeText(getApplicationContext(), "Sorry First Charset must be not 0", Toast.LENGTH_SHORT).show();

                }
            });

EditText第一个charset必须不是0

6 个答案: