My music app is referencing persistently stored data. All are currently stored as text files:
Favorites - single text file array. App starts, reads the text file, stores in memory. Array is checked when ListView is expanded. If array changes text file is rewritten.
Last Played - single text file array list. Updated every 5 seconds. Retains the history of the played songs to allow the user to return to any album and resume position.
Playlists - currently individual text files, one for each list. List of playlists generated from file names when required. Each playlist text file has array list inside it. Read Write when required.
Most Played - single text file array list. Updated once per song played.
I am wondering whether this data would warrant the need to change to a database, or whether I have taken the right approach. I don't foresee the need for adding additional data so this should be the most I would need.
Advice please!
You can store the text files in SharedPreference and it should work well.
Database if preferable if a lot of data needs to be stored. Using a database is more optimal than parsing a string.
The correct approach is to create a class for each of the things you want to represent, e.g. favourites. Each class has a save() and reload() method. The point is that you can change the underlying storage mechanism in the save() and reload() methods without having to change the rest of your code. Imagine in the future, you want to enable saving to Dropbox. You would simply change these methods and your app would just work (OK, you'd need to add stuff to get Dropbox account details but you get the idea).
You could go further and define Interfaces for loading and saving. That interface can use a single class responsible for nothing except saving and loading. As long as any consumer and provider classes adhere to the interface, you can mix and match, and even implement storage approaches yet to be invented, without recoding your app. You only have one class to work with if, and whenever, you change your storage approach.
class StorageManager(){
enum DataType {Favourites, MostPlayed, PlayList };
...
public save(DataType dataType){
if (dataType == DataType.Favourites){
saveFavouritesToDB();
...
...
}
This approach gives you maximum flexibility, maximum future proofing and better maintainability.
I think it would be better to go with Database.
The database should provide you with some optimizations, performance improvements and basically you don't have to reinvent the wheel (doing read / write operations on the disk, use some buffers before rewriting, and the like).
Plus, I think you will love the way all code will be organized and split into its own layers once you start using this way.
Related
My firebase contains different data trees like Users, hobbies, class, scores etc. I want to get values from two sets of data “Users” and “hobbies”.
What is the best way to get values from the two tables?
Should I use firebaseDatabase.getReference() and then
dataSnapshot.child("Users").child(“name”).getValue().toString();
dataSnapshot.child("hobbies ").child(“track”).getValue().toString();
Or do I have to firebaseDatabase.getReference(“Users”) and firebaseDatabase.getReference(“hobbies”);
Since I noticed that firebaseDatabase.getReference() seem to refer to all data including the ones that are not needed(class, scores etc). Will this cause the app to slow down or does it have any implications?
If you attach a listener to a DatabaseReference, it will download/read all data under that reference. So if you attach a listener to FirebaseDatabase.getInstance().getReference(), you are reading all data in your database.
If you only need a subset of all data in your app, it's more efficient to only load that data. This means that you'll need to attach a separate listener to each branch of data that you need.
I am new to Android App development, working on an android app which populate a list of numbers, in a listview dynamically, depending on the choice of the user, but, the moment user closes the App, the items in the listview are lost. How can I maintain the state of the listview?
Examples with code would be highly appreciated.
When I open Activity A, it allows users to add friends, and this friend list is shown in the form of items of listview in the same Activity, however, when I move to Activity B, and then come back to Activity A, this friend list disappears. I need to make sure that this friend list should not be lost while moving between activities. Please help.
I think that for your purpose there are 3 main methods, i'll explain them from the easier to the most difficult (in my opinion).
Text File
A way to do this is to create two methods in a class:
one has to create the text file in the storage if it isn't created before and read that, the other has to append a String to a StringBuilder and write it on the previous text file.
For this method you need the uses-permission of reading and writing to storage.
This link can help you: http://developer.android.com/training/basics/data-storage/files.html
JSON (also XML)
With JSON file you can create a list of objects with your data that you can serialize when you update the list and deserialize when you want to read it. For this purpose you have to study JavaScript syntax or, at least, JSON one.
SQLite Database
Android SDK incorporate a class named SQLiteOpenHelper that you can extend to create a database inside your app.
This link can help you: http://developer.android.com/training/basics/data-storage/databases.html
There are also references saving methods but i think that aren't right for your purpose, they work betters to save something like preferences or single data like last login informations.
I went through your comment. I would personally suggest using SQLiteOpenHelper
You might need to understand the use of SQLite, hence the tutorial
Simple Flow. On your Activity 1 where person Add Friends save it to DB
Then refresh the List from the DB. So when you move to Activity 2 and come back again to Activity 1 your List will refresh from DB. Hence no loss of data as you want.
EDIT
As user wanted to know how to use the ListView with DB.
Following are my suggestion
Sai Geetha
Youtube
I am working on an Android app, where media(audio/video/images) could be stored either internally/externally. I would be facing the following scenarios
Case I
Setting dynamically images from the random value broadcasted by the app.
Right now, I am managing it as
if(rowData.strName.equals("football")){
imageView.setImageResource(R.drawable.football);
}else if(rowData.strName.equals("chess")){
imageView.setImageResource(R.drawable.chess);
Problem As of now, I am having few records so managing else if loop in not big headache, but later it could turn out to be one.
Case II
Downloading a media from internet, saving it in external storage and loading it on an imageview as an when required
Problem Incase, the image has already been downloaded(app keeps track of downloaded image), the user ejects the card, then I plan to use
try{
}catch(FileNotFoundException e){
imageView.setImageResource(R.drawable.no_media);//media from the app
}
Case III
I will be having a listView of a category.Each Category contains certain sub-category names,their images(inbuilt & to be downloaded externally) & their description.Each sub-category has sub records with each record having its own one or image(inbuilt & to be downloaded externally),description and media files(both audio and video).
I am confused on what Collection class shall I use for this case and how to begin with? For data that is to be retrieved from the server(online), I plan to use XMLParsing. Please suggest me the best way to achieve the problem.
Wow! This is really three questions. If only I could get three times the rep :)
Case I
Use a Map to store and retrieve stuff. Saves you writing lots of if/else statements.
Map<String,Integer> drawableMap = new HashMap<String,Integer>();
drawableMap.put("football", R.drawable.football);
// Then later to retrieve...
imageView.setImageResource(drawableMap.get("football"));
Case II
OK, this seems fine. Though for most of my image loading I use existing libraries like Universal Image Loader or Volley. These may do what you need, I'm not sure.
Case III
I would take an OO approach and model the data appropriately. You don't have to choose "a" Collection class to use. Create a Category class. Create a SubCategory class. Have the Category class "have" SubCategories, etc. Take it from there.
XML parsing is fine, I'm not sure what you're expecting to be suggested. You may also like to consider JSON, a popular data format.
I'm making an app that has a listview with a child listview for each parent listview item. The children have a few children items as well. You can add/delete an element from any of these lists. I'm concerned that using MODE_APPEND will be a difficulty because I'm assuming it just appends to the end of the file and I actually want the elements to be grouped together in the file. I'm doing all of this to make sure that the data is available upon the application being destroyed and reopened. I'm also worried that MODE_APPPEND isn't private like MODE_PRIVATE is.
http://developer.android.com/reference/android/content/Context.html#MODE_APPEND
I wouldn't use MODE_APPEND. There shouldn't be no security concerns about that, but it should be easier to handle (group by datatypes, ...) the data by reading and writing the file each time.
Another possibility could be using SQLite as database for storing these values.
I am creating an android application in which I am parsing so much XML data (XML data comes from a server) which contains Strings and image url's also.I need to use this data in many part of application. So for saving all these data I have used ArrayList and HashMap.I have declared ArrayList's and HashMap's variables in a single class as public static variables so I can access this data through a single class whenever I need.
And for images I have created ArrayList and placed in same single class same as other data(public static).Once I download a image through image url's I save those image drawables to these ArrayList variables so whenever I need any image again so I use these variables to get it.
Now my doubt is whether this approach is right or not. Please suggest me the right way.
Thank you
You should actually take a look at: http://developer.android.com/guide/topics/data/data-storage.html
It all depends on how you use the data, does it need to be updated all the time when the user opens the app you could take a look at this answer: How to declare global variables in Android? where you declare a global application and have the variables there.
Otherwise I would actually advice to use an sqlite database. http://developer.android.com/guide/topics/data/data-storage.html#db One good example is here: http://www.vogella.de/articles/AndroidSQLite/article.html