【Content Provider】一个完整的ContentProvider框架

/** * Listing 8-14: A skeleton Content Provider implementation */package com.paad.DatabaseSkeleton;import android.content.ContentProvider;import android.content.ContentUris;import android.content.ContentValues;import android.content.Context;import android.content.UriMatcher;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteException;import android.database.sqlite.SQLiteOpenHelper;import android.database.sqlite.SQLiteQueryBuilder;import android.net.Uri;import android.text.TextUtils;import android.util.Log;public class MyContentProvider extends ContentProvider {    public static final Uri CONTENT_URI = Uri            .parse("content://com.paad.skeletondatabaseprovider/elements");    /**     * Listing 8-8: Defining a UriMatcher to determine if a request is for all     * elements or a single row     */    // Create the constants used to differentiate between the different URI    // requests.    private static final int ALLROWS = 1;    private static final int SINGLE_ROW = 2;    private static final UriMatcher uriMatcher;    // Populate the UriMatcher object, where a URI ending in    // 'elements' will correspond to a request for all items,    // and 'elements/[rowID]' represents a single row.    static {        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);        uriMatcher.addURI("com.paad.skeletondatabaseprovider", "elements",                ALLROWS);        uriMatcher.addURI("com.paad.skeletondatabaseprovider", "elements/#",                SINGLE_ROW);    }    /** */    // The index (key) column name for use in where clauses.    public static final String KEY_ID = "_id";    // The name and column index of each column in your database.    // These should be descriptive.    public static final String KEY_COLUMN_1_NAME = "KEY_COLUMN_1_NAME";    // TODO: Create public field for each column in your table.    /**     * Listing 8-9: Creating the Content Provider�s database     */    private MySQLiteOpenHelper myOpenHelper;    @Override    public boolean onCreate() {        // Construct the underlying database.        // Defer opening the database until you need to perform        // a query or transaction.        myOpenHelper = new MySQLiteOpenHelper(getContext(),                MySQLiteOpenHelper.DATABASE_NAME, null,                MySQLiteOpenHelper.DATABASE_VERSION);        return true;    }    /**     * Listing 8-10: Implementing queries and transactions within a Content     * Provider     */    @Override    public Cursor query(Uri uri, String[] projection, String selection,            String[] selectionArgs, String sortOrder) {        // Open thedatabase.        SQLiteDatabase db;        try {            db = myOpenHelper.getWritableDatabase();        } catch (SQLiteException ex) {            db = myOpenHelper.getReadableDatabase();        }        // Replace these with valid SQL statements if necessary.        String groupBy = null;        String having = null;        // Use an SQLite Query Builder to simplify constructing the        // database query.        SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();        // If this is a row query, limit the result set to the passed in row.        switch (uriMatcher.match(uri)) {        case SINGLE_ROW:            String rowID = uri.getPathSegments().get(1);            queryBuilder.appendWhere(KEY_ID + "=" + rowID);        default:            break;        }        // Specify the table on which to perform the query. This can        // be a specific table or a join as required.        queryBuilder.setTables(MySQLiteOpenHelper.DATABASE_TABLE);        // Execute the query.        Cursor cursor = queryBuilder.query(db, projection, selection,                selectionArgs, groupBy, having, sortOrder);        // Return the result Cursor.        return cursor;    }    /**     * Listing 8-11: Returning a Content Provider MIME type     */    @Override    public String getType(Uri uri) {        // Return a string that identifies the MIME type        // for a Content Provider URI        switch (uriMatcher.match(uri)) {        case ALLROWS:            return "vnd.android.cursor.dir/vnd.paad.elemental";        case SINGLE_ROW:            return "vnd.android.cursor.item/vnd.paad.elemental";        default:            throw new IllegalArgumentException("Unsupported URI: " + uri);        }    }    /**     * Listing 8-12: Typical Content Provider transaction implementations     */    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        // Open a read / write database to support the transaction.        SQLiteDatabase db = myOpenHelper.getWritableDatabase();        // If this is a row URI, limit the deletion to the specified row.        switch (uriMatcher.match(uri)) {        case SINGLE_ROW:            String rowID = uri.getPathSegments().get(1);            selection = KEY_ID                    + "="                    + rowID                    + (!TextUtils.isEmpty(selection) ? " AND (" + selection                            + ')' : "");        default:            break;        }        // To return the number of deleted items you must specify a where        // clause. To delete all rows and return a value pass in "1".        if (selection == null)            selection = "1";        // Perform the deletion.        int deleteCount = db.delete(MySQLiteOpenHelper.DATABASE_TABLE,                selection, selectionArgs);        // Notify any observers of the change in the data set.        getContext().getContentResolver().notifyChange(uri, null);        // Return the number of deleted items.        return deleteCount;    }    @Override    public Uri insert(Uri uri, ContentValues values) {        // Open a read / write database to support the transaction.        SQLiteDatabase db = myOpenHelper.getWritableDatabase();        // To add empty rows to your database by passing in an empty        // Content Values object you must use the null column hack        // parameter to specify the name of the column that can be        // set to null.        String nullColumnHack = null;        // Insert the values into the table        long id = db.insert(MySQLiteOpenHelper.DATABASE_TABLE, nullColumnHack,                values);        // Construct and return the URI of the newly inserted row.        if (id > -1) {            // Construct and return the URI of the newly inserted row.            Uri insertedId = ContentUris.withAppendedId(CONTENT_URI, id);            // Notify any observers of the change in the data set.            getContext().getContentResolver().notifyChange(insertedId, null);            return insertedId;        } else            return null;    }    @Override    public int update(Uri uri, ContentValues values, String selection,            String[] selectionArgs) {        // Open a read / write database to support the transaction.        SQLiteDatabase db = myOpenHelper.getWritableDatabase();        // If this is a row URI, limit the deletion to the specified row.        switch (uriMatcher.match(uri)) {        case SINGLE_ROW:            String rowID = uri.getPathSegments().get(1);            selection = KEY_ID                    + "="                    + rowID                    + (!TextUtils.isEmpty(selection) ? " AND (" + selection                            + ')' : "");        default:            break;        }        // Perform the update.        int updateCount = db.update(MySQLiteOpenHelper.DATABASE_TABLE, values,                selection, selectionArgs);        // Notify any observers of the change in the data set.        getContext().getContentResolver().notifyChange(uri, null);        return updateCount;    }    private static class MySQLiteOpenHelper extends SQLiteOpenHelper {        // Database name, version, and table names.        private static final String DATABASE_NAME = "myDatabase.db";        private static final int DATABASE_VERSION = 1;        private static final String DATABASE_TABLE = "mainTable";        // SQL Statement to create a new database.        private static final String DATABASE_CREATE = "create table "                + DATABASE_TABLE + " (" + KEY_ID                + " integer primary key autoincrement, " + KEY_COLUMN_1_NAME                + " text not null);";        public MySQLiteOpenHelper(Context context, String name,                CursorFactory factory, int version) {            super(context, name, factory, version);        }        // Called when no database exists in disk and the helper class needs        // to create a new one.        @Override        public void onCreate(SQLiteDatabase _db) {            _db.execSQL(DATABASE_CREATE);        }        // Called when there is a database version mismatch meaning that the        // version        // of the database on disk needs to be upgraded to the current version.        @Override        public void onUpgrade(SQLiteDatabase _db, int _oldVersion,                int _newVersion) {            // Log the version upgrade.            Log.w("TaskDBAdapter", "Upgrading from version " + _oldVersion                    + " to " + _newVersion                    + ", which will destroy all old data");            // Upgrade the existing database to conform to the new version.            // Multiple            // previous versions can be handled by comparing _oldVersion and            // _newVersion            // values.            // The simplest case is to drop the old table and create a new one.            _db.execSQL("DROP TABLE IF IT EXISTS " + DATABASE_TABLE);            // Create a new one.            onCreate(_db);        }    }}