如何以编程方式在Android中读取/写入数据字典

Question

I want to read/write data dictionary in file which is in android internal/external memory. In WP7, they have used IsolatedStorage for storing the dictionary directly. In IOS, they can write NSDictionary directly to the file. Please anyone tell me the way to write DataDictionary into file.

Note: I have the keys and values in the Map variable. how to store this Map directly to file

Answer 1

I would suggest putting your words into a database for the following reasons

DB lookups on android with SQLite are "fast enough" (~1ms) for even
the most impatient of users

Reading large files into memory is a dangerous practice in memory-limited environments such as android.

Trying to read entries out of a file "in place" rather than "in
memory" is effectively trying to solve all the problems that SQLite
already solves for you.

Embed a database in the .apk of a distributed application [Android]

You can find more detailed examples by searching object serialization

[EDIT 1]

Map map = new HashMap();
map.put("1",new Integer(1));
map.put("2",new Integer(2));
map.put("3",new Integer(3));
FileOutputStream fos = new FileOutputStream("map.ser");
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(map);
oos.close();

FileInputStream fis = new FileInputStream("map.ser");
ObjectInputStream ois = new ObjectInputStream(fis);
Map anotherMap = (Map) ois.readObject();
ois.close();

System.out.println(anotherMap);

[EDIT 2]

try {

        File file = new File(getFilesDir() + "/map.ser");

        Map map = new HashMap();
        map.put("1", new Integer(1));
        map.put("2", new Integer(2));
        map.put("3", new Integer(3));
        Map anotherMap = null;

        if (!file.exists()) {
            FileOutputStream fos = new FileOutputStream(file);
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(map);
            oos.close();

            System.out.println("added");                
        } else {
            FileInputStream fis = new FileInputStream(file);
            ObjectInputStream ois = new ObjectInputStream(fis);
            anotherMap = (Map) ois.readObject();
            ois.close();

            System.out.println(anotherMap);
        }



    } catch (Exception e) {

    }

[EDIT 3]

Iterator myVeryOwnIterator = meMap.keySet().iterator();
while(myVeryOwnIterator.hasNext()) {
    String key=(String)myVeryOwnIterator.next();
    String value=(String)meMap.get(key);

     // check for value

}

Answer 2

I'm unsure if using SharedPreferences ( link ) is something that is suitable for your usecase.

You store via a key-value pair, and can have multiple SharedPreferences per application. While both are stored as String objects, the value can be automatically cast to other primitives using built in methods.

Mark Murphy has written a library, cwac-loaderex ( link ), to facilitate access of SharedPreferences via the use of the Loader pattern ( link ), which offsets some of the work you need to do to keep IO off the main thread.