我正在尝试使用RandomAccessFile类从.json文件中读取和写入信息，该文件是从URL提取到Android应用程序的内部文件，但我有一些麻烦。我已确保将url.oponConnection();放入AsyncTask，因此无需在主要活动上运行，并且我已验证正在从.json读取信息文件。 （我把它输出到我的logcat）。
现在我的问题是我无法读取我创建的文件，因为即使在我使用RandomAccessFile.seek(0)之后，RandomAccessFile的指针也没有移动到文件的开头我希望如果可能，将此文件设为.txt文件。我知道这是很多要阅读的代码，但我到处寻找，我无法弄明白。任何帮助表示赞赏。
的AsyncTask
public class AsyncTaskActivity extends Activity {
public static class AsyncInfo extends AsyncTask<Void, Void, String>
{
protected void onPostExecute() {
}
@Override
protected void onPreExecute() {
}
@Override
protected String doInBackground(Void... params) {
try {
Log.i("AsyncTask", "Loading...");
// Make a URL to the web page
URL url = new URL("http://api.wunderground.com/api/0c0fcc3bf62ab910/conditions/q/IN/Fort_Wayne.json");
// Get the input stream through URL Connection
URLConnection con = url.openConnection();
InputStream is = con.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String line;
// read each line and write to text file
while ((line = br.readLine()) != null) {
Log.i("AsyncTask", line);
TextEditor.file = new File(MainActivity.path, "siteInfo.txt");
TextEditor.writeString(line);
}
TextEditor.saveAndClose();
} catch (IOException e) {
e.printStackTrace();
}
Log.i("AsyncTask", "DONE");
return "Executed";
}
}
}
这里的TestEditor类是我尝试读取和写入文件的地方
public class TextEditor {
public static File file;
private static RandomAccessFile in;
private static RandomAccessFile out;
private static String s;
/**
* Opens a file to be used for input (if not already open),
* reads a line from the file, and returns the entire line of data.
*
* @return a line of text from the input file
*/
public static String readString() {
if (in == null) {
try {
in = new RandomAccessFile(file, "rw");//new BufferedReader(new FileReader(file));
in.seek(0);
s = in.readLine();
Log.e("readString", "STRING S: " + s + ".");
return s;
} catch (Exception e) {
System.err.println("Cannot open file for input!");
e.printStackTrace();
}
}
return s;
}
/**
* Opens a file to be used for output (if not already open),
* writes a string to the file and wrties a newline.
*
* @param s The string text to be written. Follwing the string, a newline is added to the file.
*/
public static void writeString(String s) {
try {
out = new RandomAccessFile(file, "rw");
out.seek(0);
out.write(s.getBytes());
}
catch (IOException e) {
e.printStackTrace();
Log.e("writeString", "File Writer Failure");
}
}
/**
* Saves and closes the file (when opened for either input or output).
* <p/>
* Note: If the program terminates before the file is closed,
* no data will be saved or written to the file.
*/
public static void saveAndClose() {
if (in != null) {
try {
in.close();
in = null;
} catch (Exception e) {
System.err.println("Cannot close input file!");
e.printStackTrace();
}
}
if (out != null) {
try {
out.close();
out = null;
} catch (Exception e) {
System.err.println("Cannot close output file!");
e.printStackTrace();
}
}
}
这是.json文件
{
"response": {
"version":"0.1",
"termsofService":"http://www.wunderground.com/weather/api/d/terms.html",
"features": {
"conditions": 1
}
}
, "current_observation": {
"image": {
"url":"http://icons.wxug.com/graphics/wu2/logo_130x80.png",
"title":"Weather Underground",
"link":"http://www.wunderground.com"
},
"display_location": {
"full":"Fort Wayne, IN",
"city":"Fort Wayne",
"state":"IN",
"state_name":"Indiana",
"country":"US",
"country_iso3166":"US",
"zip":"46801",
"magic":"1",
"wmo":"99999",
"latitude":"41.13000107",
"longitude":"-85.12999725",
"elevation":"242.9"
},
"observation_location": {
"full":"Ludwig Park, Fort Wayne, Indiana",
"city":"Ludwig Park, Fort Wayne",
"state":"Indiana",
"country":"US",
"country_iso3166":"US",
"latitude":"41.135193",
"longitude":"-85.150581",
"elevation":"774 ft"
},
"estimated": {
},
"station_id":"KINFORTW73",
"observation_time":"Last Updated on December 14, 10:34 PM EST",
"observation_time_rfc822":"Wed, 14 Dec 2016 22:34:42 -0500",
"observation_epoch":"1481772882",
"local_time_rfc822":"Wed, 14 Dec 2016 22:34:50 -0500",
"local_epoch":"1481772890",
"local_tz_short":"EST",
"local_tz_long":"America/New_York",
"local_tz_offset":"-0500",
"weather":"Partly Cloudy",
"temperature_string":"11.3 F (-11.5 C)",
"temp_f":11.3,
"temp_c":-11.5,
"relative_humidity":"44%",
"wind_string":"From the WSW at 4.9 MPH Gusting to 7.4 MPH",
"wind_dir":"WSW",
"wind_degrees":243,
"wind_mph":4.9,
"wind_gust_mph":"7.4",
"wind_kph":7.9,
"wind_gust_kph":"11.9",
"pressure_mb":"1022",
"pressure_in":"30.17",
"pressure_trend":"+",
"dewpoint_string":"-6 F (-21 C)",
"dewpoint_f":-6,
"dewpoint_c":-21,
"heat_index_string":"NA",
"heat_index_f":"NA",
"heat_index_c":"NA",
"windchill_string":"3 F (-16 C)",
"windchill_f":"3",
"windchill_c":"-16",
"feelslike_string":"3 F (-16 C)",
"feelslike_f":"3",
"feelslike_c":"-16",
"visibility_mi":"10.0",
"visibility_km":"16.1",
"solarradiation":"0",
"UV":"0.0","precip_1hr_string":"0.00 in ( 0 mm)",
"precip_1hr_in":"0.00",
"precip_1hr_metric":" 0",
"precip_today_string":"0.00 in (0 mm)",
"precip_today_in":"0.00",
"precip_today_metric":"0",
"icon":"partlycloudy",
"icon_url":"http://icons.wxug.com/i/c/k/nt_partlycloudy.gif",
"forecast_url":"http://www.wunderground.com/US/IN/Fort_Wayne.html",
"history_url":"http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KINFORTW73",
"ob_url":"http://www.wunderground.com/cgi-bin/findweather/getForecast?query=41.135193,-85.150581",
"nowcast":""
}
}
答案 0 :(得分：0)
所以我想出了如何使用Scanner和BufferedWriter将数据读/写为字符串。这是经过编辑的TextEditor课程。
public class TextEditor {
public static File file;
private static Scanner in;
private static BufferedWriter out;
/**
* Opens a file to be used for input (if not already open),
* reads a line from the file, and returns the entire line of data.
*
* @return a line of text from the input file
*/
public static String readString() {
if (in == null) {
try {
in = new Scanner(file);
} catch (Exception e) {
System.err.println("Cannot open file for input!");
e.printStackTrace();
}
}
try {
if (in.hasNext()) {
String s = in.nextLine();
return s;
} else {
return null;
}
} catch (Exception e) {
System.err.println("Cannot read file!");
e.printStackTrace();
}
return null;
}
/**
* Opens a file to be used for output (if not already open),
* writes a string to the file and writes a newline.
*
* @param s The string text to be written. Following the string, a newline is added to the file.
*/
public static void writeString(String s) {
if (out == null) {
try {
out = new BufferedWriter(new FileWriter(file));
}
catch (Exception e) {
System.err.println("Cannot create file for output!");
e.printStackTrace();
}
}
try {
out.write(s);
out.newLine();
}
catch (Exception e) {
System.err.println("Cannot write file!");
e.printStackTrace();
}
}
/**
* Saves and closes the file (when opened for either input or output).
* <p/>
* Note: If the program terminates before the file is closed,
* no data will be saved or written to the file.
*/
public static void saveAndClose() {
if (in != null) {
try {
in.close();
in = null;
}
catch (Exception e) {
System.err.println("Cannot close input file!");
e.printStackTrace();
}
}
if (out != null) {
try {
out.close();
out = null;
}
catch (Exception e) {
System.err.println("Cannot close output file!");
e.printStackTrace();
}
}
}
}