我试过做一个分析xml文件的应用程序。在模拟器中它工作正常，但当我在真实设备，Android手机和Android平板电脑上运行它，它崩溃...
这是MainActivity.java
public class MainActivity extends ActionBarActivity {
public List<UnitModel> model = null;
private String filename = "ModelInfo.txt";
UnitModelParser parser = new UnitModelParser();
public List<Gps> coordinate = new ArrayList<Gps>();
private String fName;
GpsXmlParser gpsParser = new GpsXmlParser();
ArrayList<Gps> coorList = gpsParser.getItemsList();
String TAG = "Test";
private static final String FOLDER_PATH = Environment.getExternalStorageDirectory() + "/Gps/";
File dir = new File (FOLDER_PATH);
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new LoadModelTask().execute();
Button btnModel = (Button) findViewById(R.id.btnModel);
btnModel.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// write on SD card file data in the text box
if (isWritable()) {
ArrayList<UnitModel> modelList = parser.getItemsList();
UnitModel modd = modelList.get(0);
StringBuilder locationStrBuilder = new StringBuilder();
locationStrBuilder.append(modd);
String locationStrModel = locationStrBuilder.toString();
fName = locationStrModel + ".txt";
try {
File sdCard = Environment.getExternalStorageDirectory();
File directory = new File(sdCard.getAbsolutePath()+"/GpsOutput");
directory.mkdirs();
File myFile = new File(directory, filename);
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile, true);
OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
myOutWriter.append(locationStrModel + "\n");
myOutWriter.close();
fOut.close();
Toast.makeText(getBaseContext(),"Successfully acquired the unit information.",Toast.LENGTH_SHORT).show();
System.out.println("Model ID : " + locationStrModel);
}
catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_SHORT).show();
}
}
else
{
Toast.makeText(getBaseContext(),"SD Card Not Available",Toast.LENGTH_SHORT).show();
}
}
});
new LoadGpsTask().execute();
Button btnGps = (Button) findViewById(R.id.btnGps);
btnGps.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
StringBuilder locationStrBuilder = new StringBuilder();
int s = 0;
for (Gps c : coordinate)
{
locationStrBuilder.append(c.toString());
System.out.println(++s + c.toString());
}
if (isWritable()) {
try {
File sdCard = Environment.getExternalStorageDirectory();
File directory = new File(sdCard.getAbsolutePath()+"/GpsOutput");
directory.mkdirs();
File myFile = new File(directory, fName);
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile, false);
OutputStreamWriter myOutWriter = new OutputStreamWriter(fOut);
myOutWriter.append(locationStrBuilder);
myOutWriter.close();
fOut.close();
Toast.makeText(getBaseContext(),"Successfully downloaded gps coordinate.",Toast.LENGTH_SHORT).show();
}
catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_SHORT).show();
} }
else
{
Toast.makeText(getBaseContext(),"SD Card Not Available",Toast.LENGTH_SHORT).show();
}
}
});
}// onCreate
private class LoadModelTask extends AsyncTask<String, Void, List<UnitModel>> {
@Override
protected List<UnitModel> doInBackground(String... args) {
// CALL XMLPULLPARSER & RETURN A LIST
model = parser.parse(getBaseContext());
return model;
}
}
//filenamefilter method
public FilenameFilter xmlFilter = new FilenameFilter() {
@Override
public boolean accept(File dir, String name) {
return name.endsWith(".xml") || name.endsWith(".XML");
}
};
private class LoadGpsTask extends AsyncTask<String, Void, List<Gps>> {
@Override
protected List<Gps> doInBackground(String... args) {
// CALL XMLPULLPARSER & RETURN A LIST
String files[] = dir.list(xmlFilter);
for (String filename : files) {
String path = dir.getAbsolutePath() + "/" + filename;
Log.i(TAG, path);
System.out.println("PARSING : " + path);
coordinate.addAll(gpsParser.parse(path));
Log.i(TAG,"message");
Log.i(TAG,coordinate.size() + "");
}
Log.i(TAG,coordinate.size() + "");
return coordinate;
}
}
public boolean isWritable() {
String status = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(status))
{
return true;
}
return false;
} //isWritable
}
这是logcat的输出：
05-15 14:03:35.016: E/AndroidRuntime(2942): FATAL EXCEPTION: AsyncTask #2
05-15 14:03:35.016: E/AndroidRuntime(2942): java.lang.RuntimeException: An error occured while executing doInBackground()
05-15 14:03:35.016: E/AndroidRuntime(2942): at android.os.AsyncTask$3.done(AsyncTask.java:299)
05-15 14:03:35.016: E/AndroidRuntime(2942): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
05-15 14:03:35.016: E/AndroidRuntime(2942): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
05-15 14:03:35.016: E/AndroidRuntime(2942): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
05-15 14:03:35.016: E/AndroidRuntime(2942): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
05-15 14:03:35.016: E/AndroidRuntime(2942): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
05-15 14:03:35.016: E/AndroidRuntime(2942): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
05-15 14:03:35.016: E/AndroidRuntime(2942): at java.lang.Thread.run(Thread.java:838)
05-15 14:03:35.016: E/AndroidRuntime(2942): Caused by: java.lang.NullPointerException
05-15 14:03:35.016: E/AndroidRuntime(2942): at asp.xmlreader.MainActivity$LoadGpsTask.doInBackground(MainActivity.java:152)
05-15 14:03:35.016: E/AndroidRuntime(2942): at asp.xmlreader.MainActivity$LoadGpsTask.doInBackground(MainActivity.java:1)
05-15 14:03:35.016: E/AndroidRuntime(2942): at android.os.AsyncTask$2.call(AsyncTask.java:287)
05-15 14:03:35.016: E/AndroidRuntime(2942): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
05-15 14:03:35.016: E/AndroidRuntime(2942): ... 4 more
05-15 14:03:35.041: V/InputMethodManager(2942): onWindowFocus: null softInputMode=288 first=true flags=#1810100
05-15 14:03:35.042: V/InputMethodManager(2942): START INPUT: com.android.internal.policy.impl.PhoneWindow$DecorView{41377878 V.E..... R.....ID 0,0-768,976} ic=null tba=android.view.inputmethod.EditorInfo@413a1d28 controlFlags=#104
05-15 14:03:35.044: V/InputMethodManager(2942): Starting input: Bind result=InputBindResult{com.android.internal.view.IInputMethodSession$Stub$Proxy@413a2678 com.google.android.inputmethod.latin/com.android.inputmethod.latin.LatinIME #16}
05-15 14:03:36.076: D/OpenGLRenderer(2942): Flushing caches (mode 0)
05-15 14:03:36.174: D/OpenGLRenderer(2942): Flushing caches (mode 0)
05-15 14:03:36.178: D/OpenGLRenderer(2942): Flushing caches (mode 1)
05-15 14:03:36.183: D/OpenGLRenderer(2942): Flushing caches (mode 0)
05-15 14:03:38.085: I/Process(2942): Sending signal. PID: 2942 SIG: 9
谁能告诉我为什么会这样？感谢你不要抨击，因为我是新手。
答案 0 :(得分：0)
在不同的设备和Android版本上有很多问题，找到外部存储的真实路径（如果可用）看起来你遇到其中一个，请看这个question，希望它能帮到你找到适合您的任务的解决方法。
答案 1 :(得分：0)
也许你需要在新设备上创建文件夹
private static final String FOLDER_PATH = Environment.getExternalStorageDirectory（）+“/ Gps /”;
文件目录=新文件（FOLDER_PATH）;
private class LoadGpsTask extends AsyncTask<String, Void, List<Gps>> {
@Override
protected List<Gps> doInBackground(String... args) {
//create folder if not exist
boolean success = true;
if (!dir.exists()) {
success = dir.mkdir();
}
if (!success) {
// Do something else on failure
}
// CALL XMLPULLPARSER & RETURN A LIST
String files[] = dir.list(xmlFilter);