编辑文本未正确更改

Question

我是Stackoverflow的新手。

我正在尝试制作一个单位转换器，其中函数"计算货币"返回结果的双精度值。但是 TextView "outputNumber" 的值总是根据之前的输入而变化。

例如 - 如果我输入 1，则输出数字更改为"null"，但是当我在 1 之后输入另一个数字时，输出数字将更改为应该在 1 上更改的值。但是 Toast 显示正确的值，即在 1 上，它显示 1，因此 myInputNumber 的值根据输入是正确的。

谁能帮我？

inputNumber.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) {
}
@Override
public void afterTextChanged(Editable s) {
try {
myInputNumber = Double.parseDouble(s.toString());
Double myText = calculations.calculateCurrency(myInputNumber, convertFrom, convertTo);
Toast.makeText(MainActivity.this, myInputNumber+"", Toast.LENGTH_SHORT).show();
outputNumber.setText(myText+"");
} catch (ExecutionException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (Exception e){
e.printStackTrace();
}
}
}
);

计算代码.calculateCurrency是：

public Double calculateCurrency(Double input, String convertFrom, String convertTo) throws ExecutionException, InterruptedException {
myCurrencyFetcher fetchCurrency = new myCurrencyFetcher();
fetchCurrency.execute(Double.toString(input), convertFrom, convertTo);
return myText;
}

class myCurrencyFetcher extends AsyncTask<String, Double, Double>{
URL url;
StringBuffer stringBuffer;
@Override
protected Double doInBackground(String... params) {
try{
Double myInputNumber = Double.parseDouble(params[0]);
String convertFrom = params[1];
String convertTo = params[2];
url = new URL("http://api.fixer.io/latest?base="+convertFrom+"&symbols="+convertTo);
HttpURLConnection connection;
connection = (HttpURLConnection) url.openConnection();
connection.connect();
InputStream inputStream = connection.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
stringBuffer = new StringBuffer();
String line = "";
while((line = reader.readLine()) != null){
stringBuffer.append(line);
}
String finalJSON = stringBuffer.toString();
JSONObject parentObject = new JSONObject(finalJSON);
JSONObject finalObject = parentObject.getJSONObject("rates");
String rate = finalObject.getString(convertTo);
//String year = finalObject.getString("year");
Double myRate = Double.parseDouble(rate);
return myInputNumber*myRate;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Double result) {
super.onPostExecute(result);
Calculations.myText = result;
}
}

Answer 1

你必须改变你的代码。

@Override
public void afterTextChanged(Editable s) {
try {
myInputNumber = Double.parseDouble(s.toString());
Double myText = calculations.calculateCurrency(myInputNumber, convertFrom, convertTo);
Toast.makeText(MainActivity.this, myInputNumber+"", Toast.LENGTH_SHORT).show();
//outputNumber.setText(myText+""); // Remove this line
} catch (ExecutionException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (Exception e){
e.printStackTrace();
}
}

将 TextView (outputNumber) 作为参数添加到构造函数。 myCurrencyFetcher fetchCurrency = new myCurrencyFetcher(outputNumber);

class myCurrencyFetcher extends AsyncTask<String, Double, Double>{
private WeakReference<TextView> weakOutputNumber; 
public myCurrencyFetcher (TextView outputNumber) {
weakOutputNumber= new WeakReference<TextView>(outputNumber);
} 
/* ... Other methods are the same */
@Override
protected void onPostExecute(Double result) {
super.onPostExecute(result);
//Calculations.myText = result;
if (weakOutputNumber != null) {
TextView outputNumber = weakOutputNumber.get();
if (outputNumber != null) {
outputNumber.setText(new String(result));
}
}
}
}

Answer 2

在方法calculations.calculateCurrency(myInputNumber, convertFrom, convertTo);处重试添加synchronized