您好我正在使用GCMListener服务来收听传入的消息。我正在TinyDB的帮助下尝试在服务中访问我的共享偏好设置。
尝试访问共享首选项时出现以下错误。
java.lang.RuntimeException: Unable to instantiate service com.artqueen.aahaan.GCM.MyGcmListenerService: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
at android.app.ActivityThread.handleCreateService(ActivityThread.java:3271)
at android.app.ActivityThread.access$1900(ActivityThread.java:182)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1558)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6141)
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:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:184)
at android.preference.PreferenceManager.getDefaultSharedPreferences(PreferenceManager.java:369)
at com.artqueen.aahaan.Helper.TinyDB.<init>(TinyDB.java:31)
at com.artqueen.aahaan.GCM.MyGcmListenerService.<init>(MyGcmListenerService.java:40)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1650)
at android.app.ActivityThread.handleCreateService(ActivityThread.java:3268)
at android.app.ActivityThread.access$1900(ActivityThread.java:182)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1558)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6141)
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:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
我正在使用 GCMListenerService ，就像这样
public class MyGcmListenerService extends GcmListenerService {
private static final String TAG = "MyGcmListenerService";
TinyDB tinyDB = new TinyDB(MyGcmListenerService.this);
@Override
public void onMessageReceived(String from, Bundle data) {
String message = data.getString("message");
String user = data.getString("user","");
Log.e("user = "," "+user);
ArrayList<String> blockList = tinyDB.getListString("blockList");
if(blockList.contains(user)){
//dont show notification
}else {
//show notification
sendNotification(user);
}
}
供您参考， TinyDB 类看起来像这样
public class TinyDB {
private SharedPreferences preferences;
private String DEFAULT_APP_IMAGEDATA_DIRECTORY;
private String lastImagePath = "";
public TinyDB(Context appContext) {
preferences = PreferenceManager.getDefaultSharedPreferences(appContext);
}
/**
* Decodes the Bitmap from 'path' and returns it
* @param path image path
* @return the Bitmap from 'path'
*/
public Bitmap getImage(String path) {
Bitmap bitmapFromPath = null;
try {
bitmapFromPath = BitmapFactory.decodeFile(path);
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
return bitmapFromPath;
}
/**
* Returns the String path of the last saved image
* @return string path of the last saved image
*/
public String getSavedImagePath() {
return lastImagePath;
}
/**
* Saves 'theBitmap' into folder 'theFolder' with the name 'theImageName'
* @param theFolder the folder path dir you want to save it to e.g "DropBox/WorkImages"
* @param theImageName the name you want to assign to the image file e.g "MeAtLunch.png"
* @param theBitmap the image you want to save as a Bitmap
* @return true if image was saved, false otherwise
*/
public boolean putImage(String theFolder, String theImageName, Bitmap theBitmap) {
if (theFolder == null || theImageName == null || theBitmap == null)
return false;
this.DEFAULT_APP_IMAGEDATA_DIRECTORY = theFolder;
String mFullPath = setupFullPath(theImageName);
if (!mFullPath.equals("")) {
lastImagePath = mFullPath;
return saveBitmap(mFullPath, theBitmap);
}
return false;
}
/**
* Saves 'theBitmap' into 'fullPath'
* @param fullPath full path of the image file e.g. "Images/MeAtLunch.png"
* @param theBitmap the image you want to save as a Bitmap
* @return true if image was saved, false otherwise
*/
public boolean putImageWithFullPath(String fullPath, Bitmap theBitmap) {
return !(fullPath == null || theBitmap == null) && saveBitmap(fullPath, theBitmap);
}
/**
* Creates the path for the image with name 'imageName' in DEFAULT_APP.. directory
* @param imageName name of the image
* @return the full path of the image. If it failed to create directory, return empty string
*/
private String setupFullPath(String imageName) {
File mFolder = new File(Environment.getExternalStorageDirectory(), DEFAULT_APP_IMAGEDATA_DIRECTORY);
if (isExternalStorageReadable() && isExternalStorageWritable() && !mFolder.exists()) {
if (!mFolder.mkdirs()) {
Log.e("ERROR", "Failed to setup folder");
return "";
}
}
return mFolder.getPath() + '/' + imageName;
}
/**
* Saves the Bitmap as a PNG file at path 'fullPath'
* @param fullPath path of the image file
* @param bitmap the image as a Bitmap
* @return true if it successfully saved, false otherwise
*/
private boolean saveBitmap(String fullPath, Bitmap bitmap) {
if (fullPath == null || bitmap == null)
return false;
boolean fileCreated = false;
boolean bitmapCompressed = false;
boolean streamClosed = false;
File imageFile = new File(fullPath);
if (imageFile.exists())
if (!imageFile.delete())
return false;
try {
fileCreated = imageFile.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
FileOutputStream out = null;
try {
out = new FileOutputStream(imageFile);
bitmapCompressed = bitmap.compress(CompressFormat.PNG, 100, out);
} catch (Exception e) {
e.printStackTrace();
bitmapCompressed = false;
} finally {
if (out != null) {
try {
out.flush();
out.close();
streamClosed = true;
} catch (IOException e) {
e.printStackTrace();
streamClosed = false;
}
}
}
return (fileCreated && bitmapCompressed && streamClosed);
}
// Getters
/**
* Get int value from SharedPreferences at 'key'. If key not found, return 'defaultValue'
* @param key SharedPreferences key
* @param defaultValue int value returned if key was not found
* @return int value at 'key' or 'defaultValue' if key not found
*/
public int getInt(String key, int defaultValue) {
return preferences.getInt(key, defaultValue);
}
/**
* Get parsed ArrayList of Integers from SharedPreferences at 'key'
* @param key SharedPreferences key
* @return ArrayList of Integers
*/
public ArrayList<Integer> getListInt(String key) {
String[] myList = TextUtils.split(preferences.getString(key, ""), "‚‗‚");
ArrayList<String> arrayToList = new ArrayList<String>(Arrays.asList(myList));
ArrayList<Integer> newList = new ArrayList<Integer>();
for (String item : arrayToList)
newList.add(Integer.parseInt(item));
return newList;
}
/**
* Get long value from SharedPreferences at 'key'. If key not found, return 'defaultValue'
* @param key SharedPreferences key
* @param defaultValue long value returned if key was not found
* @return long value at 'key' or 'defaultValue' if key not found
*/
public long getLong(String key, long defaultValue) {
return preferences.getLong(key, defaultValue);
}
/**
* Get float value from SharedPreferences at 'key'. If key not found, return 'defaultValue'
* @param key SharedPreferences key
* @param defaultValue float value returned if key was not found
* @return float value at 'key' or 'defaultValue' if key not found
*/
public float getFloat(String key, float defaultValue) {
return preferences.getFloat(key, defaultValue);
}
/**
* Get double value from SharedPreferences at 'key'. If exception thrown, return 'defaultValue'
* @param key SharedPreferences key
* @param defaultValue double value returned if exception is thrown
* @return double value at 'key' or 'defaultValue' if exception is thrown
*/
public double getDouble(String key, double defaultValue) {
String number = getString(key);
try {
return Double.parseDouble(number);
} catch (NumberFormatException e) {
return defaultValue;
}
}
/**
* Get parsed ArrayList of Double from SharedPreferences at 'key'
* @param key SharedPreferences key
* @return ArrayList of Double
*/
public ArrayList<Double> getListDouble(String key) {
String[] myList = TextUtils.split(preferences.getString(key, ""), "‚‗‚");
ArrayList<String> arrayToList = new ArrayList<String>(Arrays.asList(myList));
ArrayList<Double> newList = new ArrayList<Double>();
for (String item : arrayToList)
newList.add(Double.parseDouble(item));
return newList;
}
/**
* Get String value from SharedPreferences at 'key'. If key not found, return ""
* @param key SharedPreferences key
* @return String value at 'key' or "" (empty String) if key not found
*/
public String getString(String key) {
return preferences.getString(key, "");
}
/**
* Get parsed ArrayList of String from SharedPreferences at 'key'
* @param key SharedPreferences key
* @return ArrayList of String
*/
public ArrayList<String> getListString(String key) {
return new ArrayList<String>(Arrays.asList(TextUtils.split(preferences.getString(key, ""), "‚‗‚")));
}
/**
* Get boolean value from SharedPreferences at 'key'. If key not found, return 'defaultValue'
* @param key SharedPreferences key
* @param defaultValue boolean value returned if key was not found
* @return boolean value at 'key' or 'defaultValue' if key not found
*/
public boolean getBoolean(String key, boolean defaultValue) {
return preferences.getBoolean(key, defaultValue);
}
/**
* Get parsed ArrayList of Boolean from SharedPreferences at 'key'
* @param key SharedPreferences key
* @return ArrayList of Boolean
*/
public ArrayList<Boolean> getListBoolean(String key) {
ArrayList<String> myList = getListString(key);
ArrayList<Boolean> newList = new ArrayList<Boolean>();
for (String item : myList) {
if (item.equals("true")) {
newList.add(true);
} else {
newList.add(false);
}
}
return newList;
}
// Put methods
/**
* Put int value into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param value int value to be added
*/
public void putInt(String key, int value) {
preferences.edit().putInt(key, value).apply();
}
/**
* Put ArrayList of Integer into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param intList ArrayList of Integer to be added
*/
public void putListInt(String key, ArrayList<Integer> intList) {
Integer[] myIntList = intList.toArray(new Integer[intList.size()]);
preferences.edit().putString(key, TextUtils.join("‚‗‚", myIntList)).apply();
}
/**
* Put long value into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param value long value to be added
*/
public void putLong(String key, long value) {
preferences.edit().putLong(key, value).apply();
}
/**
* Put float value into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param value float value to be added
*/
public void putFloat(String key, float value) {
preferences.edit().putFloat(key, value).apply();
}
/**
* Put double value into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param value double value to be added
*/
public void putDouble(String key, double value) {
putString(key, String.valueOf(value));
}
/**
* Put ArrayList of Double into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param doubleList ArrayList of Double to be added
*/
public void putListDouble(String key, ArrayList<Double> doubleList) {
Double[] myDoubleList = doubleList.toArray(new Double[doubleList.size()]);
preferences.edit().putString(key, TextUtils.join("‚‗‚", myDoubleList)).apply();
}
/**
* Put String value into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param value String value to be added
*/
public void putString(String key, String value) {
preferences.edit().putString(key, value).apply();
}
/**
* Put ArrayList of String into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param stringList ArrayList of String to be added
*/
public void putListString(String key, ArrayList<String> stringList) {
String[] myStringList = stringList.toArray(new String[stringList.size()]);
preferences.edit().putString(key, TextUtils.join("‚‗‚", myStringList)).apply();
}
/**
* Put boolean value into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param value boolean value to be added
*/
public void putBoolean(String key, boolean value) {
preferences.edit().putBoolean(key, value).apply();
}
/**
* Put ArrayList of Boolean into SharedPreferences with 'key' and save
* @param key SharedPreferences key
* @param boolList ArrayList of Boolean to be added
*/
public void putListBoolean(String key, ArrayList<Boolean> boolList) {
ArrayList<String> newList = new ArrayList<String>();
for (Boolean item : boolList) {
if (item) {
newList.add("true");
} else {
newList.add("false");
}
}
putListString(key, newList);
}
/**
* Remove SharedPreferences item with 'key'
* @param key SharedPreferences key
*/
public void remove(String key) {
preferences.edit().remove(key).apply();
}
/**
* Delete image file at 'path'
* @param path path of image file
* @return true if it successfully deleted, false otherwise
*/
public boolean deleteImage(String path) {
return new File(path).delete();
}
/**
* Clear SharedPreferences (remove everything)
*/
public void clear() {
preferences.edit().clear().apply();
}
/**
* Retrieve all values from SharedPreferences. Do not modify collection return by method
* @return a Map representing a list of key/value pairs from SharedPreferences
*/
public Map<String, ?> getAll() {
return preferences.getAll();
}
/**
* Register SharedPreferences change listener
* @param listener listener object of OnSharedPreferenceChangeListener
*/
public void registerOnSharedPreferenceChangeListener(
SharedPreferences.OnSharedPreferenceChangeListener listener) {
preferences.registerOnSharedPreferenceChangeListener(listener);
}
/**
* Unregister SharedPreferences change listener
* @param listener listener object of OnSharedPreferenceChangeListener to be unregistered
*/
public void unregisterOnSharedPreferenceChangeListener(
SharedPreferences.OnSharedPreferenceChangeListener listener) {
preferences.unregisterOnSharedPreferenceChangeListener(listener);
}
/**
* Check if external storage is writable or not
* @return true if writable, false otherwise
*/
public static boolean isExternalStorageWritable() {
return Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState());
}
/**
* Check if external storage is readable or not
* @return true if readable, false otherwise
*/
public static boolean isExternalStorageReadable() {
String state = Environment.getExternalStorageState();
return Environment.MEDIA_MOUNTED.equals(state) ||
Environment.MEDIA_MOUNTED_READ_ONLY.equals(state);
}
}
我无法弄清楚为什么我无法在服务中访问我的共享首选项。请帮帮我。提前谢谢。
答案 0 :(得分：2)
已使用getApplicationContext()
TinyDB tinyDB = new TinyDB(getApplicationContext());
用于访问上下文
答案 1 :(得分：0)
最有可能的问题不是在正确的位置调用SharedPreferences。如果我们使用run线程（在我们的Service类中），我们应该在它内部调用它，或者如果你需要在onCreate（）中，那么在你的Service类的onCreate（）方法中调用它
SharedPreferences shp = getApplicationContext().getSharedPreferences("sam", Context.MODE_PRIVATE);
SharedPreferences.Editor editor = shp.edit();