我正在尝试创建一个简单的美元、英镑和欧元货币转换器，方法是在字段中输入金额，在微调器中选择从货币，然后选择货币 在另一个微调器中。然后，我在文本字段中输出转换后的金额。
但由于某种原因，我无法通过 onClick 方法，我不知道为什么。这可能很简单，但我看不到。
这是我的代码:
public class Calculate extends Activity implements OnItemSelectedListener,
OnClickListener {
Button Calculate;
String stringAmount;
double exchangeRate, E, D, Answer;
EditText Amount;
Spinner spinner, spinner1;
int ConvertFrom, ConvertTo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.calculate);
Initilise();
// this is calling the method initilise.
// listens for the button to be clicked
Calculate.setOnClickListener(this);
}
private void Initilise() {
// Method initilise.
/* Button */Calculate = (Button) findViewById(R.id.cal);
/* EditText */Amount = (EditText) findViewById(R.id.amount);
spinner = (Spinner) findViewById(R.id.Currency);
spinner1 = (Spinner) findViewById(R.id.Currency1);
}
public void format() {
ConvertFrom = 0;
ConvertTo = 0;
stringAmount = Amount.getText().toString();
E = 0; // set it to 0 as the default
try {
E = Integer.parseInt(stringAmount);
} catch (NumberFormatException e) {
}
}
@SuppressWarnings("deprecation")
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
spinner();
switch (v.getId()) {
case R.id.cal:
if (ConvertFrom == 0) {
FromEuro();
} else if (ConvertFrom == 1) {
FromUsd();
} else if (ConvertFrom == 2) {
FromGbp();
} else {
// Amount.setText("Invalid Input");
AlertDialog alertDialog = new AlertDialog.Builder(this)
.create();
alertDialog.setTitle("Input");
alertDialog.setMessage("Please Input a amount");
alertDialog.setButton("OK",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int which) {
// here you can add functions
}
});
alertDialog.setIcon(R.drawable.ic_launcher);
alertDialog.show();
}
}
}
public void spinner() {
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_spinner_item, R.array.Currencies);
spinner = (Spinner) findViewById(R.id.Currency);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(this);
spinner1 = (Spinner) findViewById(R.id.Currency1);
spinner1.setAdapter(adapter);
spinner1.setOnItemSelectedListener(this);
}
@Override
public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
// TODO Auto-generated method stub
int posistion = spinner.getSelectedItemPosition();
ConvertFrom = posistion;
int posistion1 = spinner1.getSelectedItemPosition();
ConvertTo = posistion1;
}
@Override
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
@SuppressWarnings("deprecation")
private void FromEuro() {
// TODO Auto-generated method stub
if (ConvertTo == 1) {
exchangeRate = 1.336891;
Answer = E * exchangeRate;
String Final = Double.toString(Answer);
Amount.setText(Final);
} else if (ConvertTo == 2) {
exchangeRate = 1.336891;
Answer = E * exchangeRate;
String Final = Double.toString(Answer);
Amount.setText(Final);
} else if (ConvertTo == 0) {
AlertDialog alertDialog = new AlertDialog.Builder(null).create();
alertDialog.setTitle("Input");
alertDialog.setMessage("Please Select a gender");
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
// here you can add functions
}
});
alertDialog.setIcon(R.drawable.ic_launcher);
alertDialog.show();
}
}
@SuppressWarnings("deprecation")
private void FromUsd() {
// TODO Auto-generated method stub
if (ConvertTo == 0) {
exchangeRate = 1.336891;
Answer = E * exchangeRate;
String Final = Double.toString(Answer);
Amount.setText(Final);
} else if (ConvertTo == 1) {
exchangeRate = 1.336891;
Answer = E * exchangeRate;
String Final = Double.toString(Answer);
Amount.setText(Final);
} else {
if (ConvertTo == 2) {
AlertDialog alertDialog = new AlertDialog.Builder(null)
.create();
alertDialog.setTitle("Input");
alertDialog.setMessage("Please Select a gender");
alertDialog.setButton("OK",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int which) {
// here you can add functions
}
});
alertDialog.setIcon(R.drawable.ic_launcher);
alertDialog.show();
}
}
}
private void FromGbp() {
// TODO Auto-generated method stub
if (ConvertTo == 2) {
exchangeRate = 1.336891;
Answer = E * exchangeRate;
String Final = Double.toString(Answer);
Amount.setText(Final);
} else if (ConvertTo == 0) {
exchangeRate = 1.336891;
Answer = E * exchangeRate;
String Final = Double.toString(Answer);
Amount.setText(Final);
} else {
if (ConvertTo == 1) {
Builder alertDialog = new AlertDialog.Builder(this);
alertDialog.setTitle("Input");
alertDialog.setMessage("Please Select a gender");
alertDialog.setPositiveButton("OK",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int which) {
// here you can add functions
}
});
alertDialog.setIcon(R.drawable.ic_launcher);
alertDialog.show();
}
}
}`
}
但我现在正在接收
02-19 16:55:01.514: E/AndroidRuntime(28638): 在 android.app.AlertDialog.resolveDialogTheme(AlertDialog.java:142)
上述错误。
<小时/>之前这个问题有以下错误:
想知道是否有人可以帮忙。我收到这些错误:
FATAL EXCEPTION: main
java.lang.NullPointerException
at com.travelcurrencyconverter.Calculate.onClick(Calculate.java:64)
at android.view.View.performClick(View.java:4222)
at android.view.View$PerformClick.run(View.java:17273)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4895)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:994)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:761)
at dalvik.system.NativeStart.main(Native Method)
最佳答案
您正在尝试访问第 64 行为 null 的引用成员(点之前的部分)。
此外，当您发布代码时，请将所有代码缩进四个空格，以使所有语法都着色。
此外，在执行此操作之前，请确保在 IDE 中自动设置代码格式。
关于Java 空指针异常(单击时)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14958277/