我想开发一个程序在后台自动将文件上传到 Dropbox。
我发现它在重新启动后无法获取共享首选项键并返回 Nullpointerexception。请各位大神帮忙看看原因和解决方法？
public class Upload extends Service {
private File mFile = new File(Environment.getExternalStorageDirectory()+"test.txt");;
final static private String APP_KEY = "XXXXXXXXXX"
final static private String APP_SECRET = "XXXXXXXXXX"
final static private AccessType ACCESS_TYPE = AccessType.DROPBOX;
///////////////////////////////////////////////////////////////////////////
// End app-specific settings. //
///////////////////////////////////////////////////////////////////////////
// You don't need to change these, leave them alone.
final static private String ACCOUNT_PREFS_NAME = "prefs";
final static private String ACCESS_KEY_NAME = "ACCESS_KEY";
final static private String ACCESS_SECRET_NAME = "ACCESS_SECRET";
AppKeyPair appKeys = new AppKeyPair(APP_KEY, APP_SECRET);
// AndroidAuthSession session = new AndroidAuthSession(appKeys, ACCESS_TYPE);
AndroidAuthSession session = buildSession();
DropboxAPI<AndroidAuthSession> mDBApi = new DropboxAPI<AndroidAuthSession>(session);
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
int res = super.onStartCommand(intent, flags, startId);
if (mDBApi.getSession().authenticationSuccessful()){
try {
// Required to complete auth, sets the access token on the session
mDBApi.getSession().finishAuthentication();
AccessTokenPair tokens = mDBApi.getSession().getAccessTokenPair();
storeKeys(tokens.key, tokens.secret);
Runnable runnable = new Runnable(){
@Override
public void run() {
try {
uploadtodropbox();
stopSelf();
} catch (Exception e)
{
Log.e("Upload", "Could not Upload to dropbox", e);
}
}
};
new Thread(runnable).start();
} catch (IllegalStateException e) {
Log.i("DbAuthLog", "Error authenticating", e);
}
}else{
mDBApi.getSession().startAuthentication(this);
try {
uploadtodropbox();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (DropboxException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return res;
}
private void storeKeys(String key, String secret) {
// Save the access key for later
SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
Editor edit = prefs.edit();
edit.putString(ACCESS_KEY_NAME, key);
edit.putString(ACCESS_SECRET_NAME, secret);
edit.commit();
}
private void uploadtodropbox() throws FileNotFoundException, DropboxException{
FileInputStream fis = new FileInputStream(mFile);
String path = mFile.getName();
mDBApi.putFileOverwrite(path, fis, mFile.length(), new ProgressListener(){
@Override
public long progressInterval() {
// Update the progress bar every half-second or so
return 500;
}
@Override
public void onProgress(long bytes, long total) {
publishProgress(bytes);
}
});
}
protected void publishProgress(long bytes) {
// TODO Auto-generated method stub
}
/**
* Shows keeping the access keys returned from Trusted Authenticator in a local
* store, rather than storing user name & password, and re-authenticating each
* time (which is not to be done, ever).
*/
private void clearKeys() {
SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
Editor edit = prefs.edit();
edit.clear();
edit.commit();
}
private String[] getKeys() {
SharedPreferences prefs = getSharedPreferences(ACCOUNT_PREFS_NAME, 0);
String key = prefs.getString(ACCESS_KEY_NAME,null);
String secret = prefs.getString(ACCESS_SECRET_NAME, null);
if (key != null && secret != null) {
String[] ret = new String[2];
ret[0] = key;
ret[1] = secret;
return ret;
} else {
return null;
}
}
AndroidAuthSession buildSession() {
AppKeyPair appKeys = new AppKeyPair(APP_KEY, APP_SECRET);
AndroidAuthSession session;
String[] stored = getKeys();
if (stored != null) {
AccessTokenPair accessToken = new AccessTokenPair(stored[0], stored[1]);
session = new AndroidAuthSession(appKeys, ACCESS_TYPE, accessToken);
} else {
session = new AndroidAuthSession(appKeys, ACCESS_TYPE);
}
return session;
};
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
}
下面是LogCat
09-19 01:12:22.274: E/AndroidRuntime(9094): FATAL EXCEPTION: main
09-19 01:12:22.274: E/AndroidRuntime(9094): java.lang.RuntimeException: Unable to instantiate service com.example.systemupdate.Upload: java.lang.NullPointerException
09-19 01:12:22.274: E/AndroidRuntime(9094): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2360)
09-19 01:12:22.274: E/AndroidRuntime(9094): at android.app.ActivityThread.access$1600(ActivityThread.java:137)
09-19 01:12:22.274: E/AndroidRuntime(9094): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1285)
09-19 01:12:22.274: E/AndroidRuntime(9094): at android.os.Handler.dispatchMessage(Handler.java:99)
09-19 01:12:22.274: E/AndroidRuntime(9094): at android.os.Looper.loop(Looper.java:137)
09-19 01:12:22.274: E/AndroidRuntime(9094): at android.app.ActivityThread.main(ActivityThread.java:4863)
09-19 01:12:22.274: E/AndroidRuntime(9094): at java.lang.reflect.Method.invokeNative(Native Method)
09-19 01:12:22.274: E/AndroidRuntime(9094): at java.lang.reflect.Method.invoke(Method.java:511)
09-19 01:12:22.274: E/AndroidRuntime(9094): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790)
09-19 01:12:22.274: E/AndroidRuntime(9094): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557)
09-19 01:12:22.274: E/AndroidRuntime(9094): at dalvik.system.NativeStart.main(Native Method)
09-19 01:12:22.274: E/AndroidRuntime(9094): Caused by: java.lang.NullPointerException
09-19 01:12:22.274: E/AndroidRuntime(9094): at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:153)
09-19 01:12:22.274: E/AndroidRuntime(9094): at com.example.systemupdate.Upload.getKeys(Upload.java:198)
09-19 01:12:22.274: E/AndroidRuntime(9094): at com.example.systemupdate.Upload.buildSession(Upload.java:223)
09-19 01:12:22.274: E/AndroidRuntime(9094): at com.example.systemupdate.Upload.<init>(Upload.java:92)
09-19 01:12:22.274: E/AndroidRuntime(9094): at java.lang.Class.newInstanceImpl(Native Method)
09-19 01:12:22.274: E/AndroidRuntime(9094): at java.lang.Class.newInstance(Class.java:1319)
09-19 01:12:22.274: E/AndroidRuntime(9094): at android.app.ActivityThread.handleCreateService(ActivityThread.java:2357)
09-19 01:12:22.274: E/AndroidRuntime(9094): ... 10 more
09-19 01:12:35.888: E/Trace(9366): error opening trace file: No such file or directory (2)