“看看这个，我相信你会喜欢的。”

log_in.setOnClickListener(new OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        username=user_name.getText().toString();
        password=pass_word.getText().toString();
        if(username.equals(""))
        {
            user_name.setError("Enter username");
        }
        else if(password.equals(""))
        {
            pass_word.setError("Enter your password");
        }
        else
        {
            Intent intent=new Intent(MainActivity.this,Scan_QRActivity.class);
            startActivity(intent);
        }
    }
});

if ( (usernameEditText.getText()+"").equals("") ) { 
    // Really just another way
}

我曾经做过类似的事情;

EditText usernameEditText = (EditText) findViewById(R.id.editUsername);
sUsername = usernameEditText.getText().toString();
if (sUsername.matches("")) {
    Toast.makeText(this, "You did not enter a username", Toast.LENGTH_SHORT).show();
    return;
}

这里的派对已经晚了，但我只需要添加Android自己的TextUtils。isEmpty (CharSequence进行str)

如果字符串为null或0-length则返回true

所以如果你把你的五个edittext放在一个列表中，完整的代码将是:

for(EditText edit : editTextList){
    if(TextUtils.isEmpty(edit.getText()){
        // EditText was empty
        // Do something fancy
    }
}

你可以使用setOnFocusChangeListener，当焦点改变时，它会检查

        txt_membername.setOnFocusChangeListener(new OnFocusChangeListener() {

        @Override
        public void onFocusChange(View arg0, boolean arg1) {
            if (arg1) {
                //do something
            } else {
                if (txt_membername.getText().toString().length() == 0) {
                    txt_membername
                            .setError("Member name is not empty, Plz!");
                }
            }
        }
    });

使用这段简短的代码，您可以删除字符串开头和结尾的空白。如果字符串是“”，则返回消息“error”，否则就是字符串

EditText user = findViewById(R.id.user); 
userString = user.getText().toString().trim(); 
if (userString.matches("")) {
    Toast.makeText(this, "Error", Toast.LENGTH_SHORT).show();
    return; 
}else{
     Toast.makeText(this, "Ok", Toast.LENGTH_SHORT).show();
}