我试图做一个平均值并保存最后添加到平均值的数字，但我的代码总是＆＃34;返回＆＃34;我在logcat：
07-06 08:14:44.646 9981-9981/com.example.emilio.notification E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.emilio.notification, PID: 9981
java.lang.NumberFormatException: Invalid double: ""
at java.lang.StringToReal.invalidReal(StringToReal.java:63)
at java.lang.StringToReal.parseDouble(StringToReal.java:267)
at java.lang.Double.parseDouble(Double.java:301)
at com.example.emilio.notification.MainActivity.stackmyArray(MainActivity.java:207)
at com.example.emilio.notification.MainActivity.writeMyArray(MainActivity.java:192)
at com.example.emilio.notification.MainActivity.access$100(MainActivity.java:47)
at com.example.emilio.notification.MainActivity$2.onClick(MainActivity.java:109)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
这是我的代码:(写入/读取文件是最后一个数字的代码，数组的写入/读取是平均值。我开始尝试做一个数组，但我无法追加，所以如果你的问题有一个数组，而不是我的＆＃34;逻辑＆＃34;，它的确定。堆栈代码是增量，所以如果我再添加一个数字到平均值，它将做正确的除法）
private void writeToFile(String data) {
try {
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput("estrela.txt", Context.MODE_PRIVATE));
outputStreamWriter.write(data);
outputStreamWriter.close();
} catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
}
private String readFromFile() {
String ret = "";
try {
InputStream inputStream = openFileInput("estrela.txt");
if (inputStream != null) {
InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String receiveString = "";
StringBuilder stringBuilder = new StringBuilder();
while ((receiveString = bufferedReader.readLine()) != null) {
stringBuilder.append(receiveString);
}
inputStream.close();
ret = stringBuilder.toString();
}
} catch (FileNotFoundException e) {
Log.e("login activity", "File not found: " + e.toString());
} catch (IOException e) {
Log.e("login activity", "Can not read file: " + e.toString());
}
return ret;
}
private void writeMyArray(double rate){
//PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("arraymedia.txt", true)));
//.println(rate);
Double ratex2 = rate + Double.parseDouble(readMyArray());
try {
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput("test3.txt", Context.MODE_PRIVATE));
if(readMyArray() == "")
{
outputStreamWriter.write(0);
}
outputStreamWriter.write(Double.toString(ratex2));
outputStreamWriter.close();
stackmyArray();
} catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
}
private void stackmyArray()
{
if(readMyArray() != "") {
try {
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput("test3count.txt", Context.MODE_PRIVATE));
if(stackread() == "")
{outputStreamWriter.write(0);}
Double stack = Double.parseDouble(stackread()) + 1;
outputStreamWriter.write(Double.toString(stack));
outputStreamWriter.close();
} catch (IOException e) {
Log.e("Exception", "File write failed: " + e.toString());
}
}
else
{
try {
OutputStreamWriter outputStreamWriter = new OutputStreamWriter(openFileOutput("test3count.txt", Context.MODE_PRIVATE));
outputStreamWriter.write(Integer.toString(1));
outputStreamWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
private String readMyArray(){
String ret = "";
try {
InputStream inputStream = openFileInput("test3.txt");
if (inputStream != null) {
InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String receiveString = "";
StringBuilder stringBuilder = new StringBuilder();
while ((receiveString = bufferedReader.readLine()) != null) {
stringBuilder.append(receiveString);
}
inputStream.close();
ret = stringBuilder.toString();
}
} catch (FileNotFoundException e) {
Log.e("login activity", "File not found: " + e.toString());
} catch (IOException e) {
Log.e("login activity", "Can not read file: " + e.toString());
}
return ret;
}
private String stackread(){
String ret = "";
try {
InputStream inputStream = openFileInput("test3count.txt");
InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String receiveString = "";
StringBuilder stringBuilder = new StringBuilder();
while ((receiveString = bufferedReader.readLine()) != null) {
stringBuilder.append(receiveString);
}
inputStream.close();
ret = stringBuilder.toString();
} catch (FileNotFoundException e) {
Log.e("login activity", "File not found: " + e.toString());
} catch (IOException e) {
Log.e("login activity", "Can not read file: " + e.toString());
}
return ret;
}
通过Keppil回答，我现在有了这个logcat：
07-06 08:38:25.223 18958-18958/com.example.emilio.notification E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.emilio.notification, PID: 18958
java.lang.NumberFormatException: Invalid int: "��"
at java.lang.Integer.invalidInt(Integer.java:138)
at java.lang.Integer.parse(Integer.java:410)
at java.lang.Integer.parseInt(Integer.java:367)
at java.lang.Integer.parseInt(Integer.java:334)
at com.example.emilio.notification.MainActivity$2.onClick(MainActivity.java:114)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
答案 0 :(得分：0)
您在转换前检查String是否为""，但您仍然尝试转换它：
if(stackread() == "")
{outputStreamWriter.write(0);}
Double stack = Double.parseDouble(stackread()) + 1;
outputStreamWriter.write(Double.toString(stack));
此外，两次调用stackread()可能会有问题，而您使用==来比较字符串。将其更改为：
String stackRead = stackread();
if (stackRead.equals("")) {
outputStreamWriter.write(0);
} else {
Double stack = Double.parseDouble(stackRead) + 1;
outputStreamWriter.write(Double.toString(stack));
}