如果任何编辑文本为空，如何禁用按钮?

Question

我尝试使用TextWatcher，但是如果我创建多个TextWatcher(每个EditText一个(，当我开始填写任何EditText时，该按钮就会启用。

例：

public class MainActivity extends AppCompatActivity {
EditText numberOneEditText;
EditText numberTwoEditText;
EditText numberThreeEditText;
TextView sumTextView;
public void calculate(View view) {

String numberOneString = numberOneEditText.getText().toString();
String numberTwoString = numberTwoEditText.getText().toString();
String numberThreeString = numberThreeEditText.getText().toString();
double numberOneDouble = Double.parseDouble(numberOneString);
double numberTwoDouble = Double.parseDouble(numberTwoString);
double numberThreeDouble = Double.parseDouble(numberThreeString);
double sum = numberOneDouble + numberTwoDouble + numberThreeDouble;
sumTextView.setText(sum.getText().toString())
}

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
numberOneEditText = findViewById(R.id.numberOneEditText);
numberTwoEditText = findViewById(R.id.numberTwoEditText);
numberThreeEditText = findViewById(R.id.numberThreeEditText);
sumTextView = findViewById(R.id.sumTextView);
}
}

Answer 1

使用 TextWatcher。它将解决您的问题：

editText.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
if(s.toString().trim().length()==0){
btn.setEnabled(false);
} else {
btn.setEnabled(true);
}
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count,
int after) {
// TODO Auto-generated method stub
}
@Override
public void afterTextChanged(Editable s) {
// TODO Auto-generated method stub
}
});

Answer 2

这必须解决您的问题：

public class AppActivity extends Activity {
private EditText editText1;
private EditText editText2;
private TextWatcher textWatcher = new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence charSequence, int i, int i2, int i3) {
}
@Override
public void onTextChanged(CharSequence charSequence, int i, int i2, int i3) {
checkFieldsForEmptyValues();
}
@Override
public void afterTextChanged(Editable editable) {
}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.register_activity);
editText1 = (EditText) findViewById(R.id.reg_password);
editText2 = (EditText) findViewById(R.id.reg_password2);
editText1.addTextChangedListener(textWatcher);
editText2.addTextChangedListener(textWatcher);
checkFieldsForEmptyValues();
}
private  void checkFieldsForEmptyValues(){
Button btn = (Button) findViewById(R.id.btnId);
String s1 = editText1.getText().toString();
String s2 = editText2.getText().toString();
if (s1.length() > 0 && s2.length() > 0) {
btn.setEnabled(true);
} else {
btn.setEnabled(false);
}
}
}

谢谢。

Answer 3

文本观察器应检查所有三个 EditText 是否都有数据(最好还要确保它们是双精度的，如果不是，则显示带有错误消息的标签(

像这样：

TextWatcher watcher = 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) {
}
@Override
public void afterTextChanged(Editable s) {
for (EditText et  : new EditText[] {numberOneEditText, 
numberTwoEditText, numberThreeEditText}) {
try {
Double.parseDouble(et.getText());
} catch (NumberFormatException e) {
// Disable button, show error label, etc.
button.setEnabld(false);
return;
}
}
//Enable buttton, hide error label if available
button.setEnabled(true);
}
};
}
numberOneEditText.addTextChangedListener(watcher);
numberTwoEditText.addTextChangedListener(watcher);
numberThreeEditText.addTextChangedListener(watcher);

Answer 4

你只需要声明一个分配给所有编辑文本的文本观察器。然后：

btn.setEnabled(!(str1.isEmpty || str2.isEmpty() || str3.isEmpty));

您也可以直接检查它是否是有效的双精度，如果不是，则不启用。

Answer 5

EditText numberOneEditText;
EditText numberTwoEditText;
EditText numberThreeEditText;
TextView sumTextView;
public void calculate(View view) {
boolean isValid = true;
String numberOneString = numberOneEditText.getText().toString();
String numberTwoString = numberTwoEditText.getText().toString();
String numberThreeString = numberThreeEditText.getText().toString();
if(numberOneString.trim().isEmpty ||numberTwoString.trim().isEmpty() 
|| numberThreeString.trim().isEmpty()){
isValid = false;}
if(isValid){
double numberOneDouble = Double.parseDouble(numberOneString);
double numberTwoDouble = Double.parseDouble(numberTwoString);
double numberThreeDouble = Double.parseDouble(numberThreeString);
double sum = numberOneDouble + numberTwoDouble + numberThreeDouble;
sumTextView.setText(sum.getText().toString())
}  
}