The Arca Core package provides all the groundwork for caching data within a ContentProvider and interacting with a remote store using a Service (i.e. outside the context of your Fragments/Activities). This means your application can use less battery, less bandwidth and provide a much more responsive user experience.
The Arca Broadcaster package adds the ability to send local broadcasts. This package is used by various other Arca packages in order to communicate errors and/or results.
The Arca Provider package builds off of the ContentProvider construct but delegates all the heavy lifting to a variety of different Dataset classes. Datasets are class representations for various storage types. This includes SQLiteTables, SQLiteViews or any custom implementation you create.
The Arca Service package lets you offload long running operations away from the lifecycle of your Activities and Fragments. It provides a Service implementation which accepts Operations, where each Operation is designed to encapsulate all the networking and storage required by an individual Dataset (see Arca-Provider).
The Arca Threading package provides a scheduler for background threads that allows for highly customizable, high-performance task scheduling. Developers can use this library to optimize tasks such as precaching, assigning/reassigning priorities, cancelling requests, and more.
The Arca Utils package contains a set of useful helper classes used by a variety of other Arca packages. It also contains convenience classes that may be useful when implementing your own ContentProvider.
Below we define our ContentProvider, which includes a definition of each Dataset that we are exposing to our application.
public class MyAppContentProvider extends DatabaseProvider {
private static final String AUTHORITY = MyAppContentProvider.class.getName();
private static final Uri BASE_URI = Uri.parse("content://" + AUTHORITY);
public static final class Uris {
public static final Uri POSTS = Uri.withAppendedPath(BASE_URI, Paths.POSTS);
public static final Uri USERS = Uri.withAppendedPath(BASE_URI, Paths.USERS);
public static final Uri USER_POSTS = Uri.withAppendedPath(BASE_URI, Paths.USER_POSTS);
}
private static final class Paths {
public static final String POSTS = "posts";
public static final String USERS = "users";
public static final String USER_POSTS = "user_posts";
}
@Override
public boolean onCreate() {
registerDataset(AUTHORITY, Paths.POSTS, PostTable.class);
registerDataset(AUTHORITY, Paths.USERS, UserTable.class);
registerDataset(AUTHORITY, Paths.USER_POSTS, UserPostView.class);
return true;
}
public static class PostTable extends SQLiteTable {
public interface Columns extends SQLiteTable.Columns {
@Unique(Unique.OnConflict.REPLACE)
@Column(Column.Type.INTEGER) String ID = "id";
@Column(Column.Type.TEXT) String TEXT = "text";
@Column(Column.Type.INTEGER) String USER_ID = "user_id";
@Column(Column.Type.INTEGER) String DATE = "date";
}
}
public static class UserTable extends SQLiteTable {
public interface Columns extends SQLiteTable.Columns {
@Unique(Unique.OnConflict.REPLACE)
@Column(Column.Type.INTEGER) String ID = "id";
@Column(Column.Type.TEXT) String NAME = "name";
@Column(Column.Type.INTEGER) String AGE = "age";
}
}
public static final class UserPostView extends SQLiteView {
@SelectFrom("PostTable as posts")
@Joins({
"LEFT JOIN UserTable as users ON posts.user_id = users.id"
})
@OrderBy("posts.date")
public interface Columns {
@Select("posts.id") String _ID = "_id";
@Select("posts.text") String TEXT = "text";
@Select("posts.date") String DATE = "date";
@Select("users.id") String USER_ID = "user_id";
@Select("users.name") String USER_NAME = "user_name";
}
}
}Now in order to populate our ContentProvider we can use the OperationService to make asynchronous requests to our server. To do this we invoke the OperationService.start(context, operation) method by passing it a new instance of an Operation. In this case we define an Operation for Users and Posts as shown below. The main advantage to delegating this responsibility to a Service is that the lifecycle of the network request is not tied to an Fragment or Activity.
public class GetPostListOperation extends SimpleOperation {
public GetPostListOperation() {
super(MyAppContentProvider.Uris.POSTS);
}
public GetPostListOperation(final Parcel in) {
super(in);
}
@Override
public ContentValues[] onExecute(final Context context) throws Exception {
final List<Post> response = MyAppApi.getPosts();
return DataUtils.getContentValues(response);
}
public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {
@Override
public GetPostListOperation createFromParcel(final Parcel in) {
return new GetPostListOperation(in);
}
@Override
public GetPostListOperation[] newArray(final int size) {
return new GetPostListOperation[size];
}
};
}public class GetUserListOperation extends SimpleOperation {
public GetUserListOperation() {
super(MyAppContentProvider.Uris.USERS);
}
public GetUserListOperation(final Parcel in) {
super(in);
}
@Override
public ContentValues[] onExecute(final Context context) throws Exception {
final List<User> response = MyAppApi.getUsers();
return DataUtils.getContentValues(response);
}
public static final Parcelable.Creator CREATOR = new Parcelable.Creator() {
@Override
public GetUserListOperation createFromParcel(final Parcel in) {
return new GetUserListOperation(in);
}
@Override
public GetUserListOperation[] newArray(final int size) {
return new GetUserListOperation[size];
}
};
}The Post and User models are defined below. In order for the DataUtils.getContentValues() method to be able to convert your model into a ContentValues object you will need to include a @ColumnName annotation on each field you want persisted in the database.
public static class Post {
@ColumnName(PostTable.Columns.ID)
private long mId;
@ColumnName(PostTable.Columns.TEXT)
private String mText;
@ColumnName(PostTable.Columns.USER_ID)
private long mUserId;
@ColumnName(PostTable.Columns.DATE)
private long mDate;
}public static class User {
@ColumnName(UserTable.Columns.ID)
private long mId;
private String mName;
@ColumnName(UserTable.Columns.NAME)
public String getName() {
return mName != null ? mName : "Anonymous";
}
@ColumnName(UserTable.Columns.AGE)
private int mAge;
}