The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
/*
* Copyright (C) 2007 The Android开源工程
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.notepad;
import com.example.android.notepad.NotePad;
import android.content.ClipDescription;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;
import android.content.ContentProvider.PipeDataWriter;
import android.content.res.AssetFileDescriptor;
import android.content.res.Resources;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.os.Bundle;
import android.os.ParcelFileDescriptor;
import android.provider.LiveFolders;
import android.text.TextUtils;
import android.util.Log;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
/**
* Provides access to a database of notes. Each note has a title, the note
* itself, a creation date and a modified data.
*/
public class NotePadProvider extends ContentProvider implements PipeDataWriter<Cursor> {
// Used for debugging and logging
private static final String TAG = "NotePadProvider";
/**
* The database that the provider uses as its underlying data store
*/
private static final String DATABASE_NAME = "note_pad.db";
/**
* The database version
*/
private static final int DATABASE_VERSION = 2;
/**
* A projection map used to select columns from the database
*/
private static HashMap<String, String> sNotesProjectionMap;
/**
* A projection map used to select columns from the database
*/
private static HashMap<String, String> sLiveFolderProjectionMap;
/**
* Standard projection for the interesting columns of a normal note.
*/
private static final String[] READ_NOTE_PROJECTION = new String[] {
NotePad.Notes._ID, // Projection position 0, the note's id
NotePad.Notes.COLUMN_NAME_NOTE, // Projection position 1, the note's content
NotePad.Notes.COLUMN_NAME_TITLE, // Projection position 2, the note's title
};
private static final int READ_NOTE_NOTE_INDEX = 1;
private static final int READ_NOTE_TITLE_INDEX = 2;
/*
* Constants used by the Uri matcher to choose an action based on the pattern
* of the incoming URI
*/
// The incoming URI matches the Notes URI pattern
private static final int NOTES = 1;
// The incoming URI matches the Note ID URI pattern
private static final int NOTE_ID = 2;
// The incoming URI matches the Live Folder URI pattern
private static final int LIVE_FOLDER_NOTES = 3;
/**
* A UriMatcher instance
*/
private static final UriMatcher sUriMatcher;
// Handle to a new DatabaseHelper.
private DatabaseHelper mOpenHelper;
/**
* A block that instantiates and sets static objects
*/
static {
/*
* Creates and initializes the URI matcher
*/
// Create a new instance
sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
// Add a pattern that routes URIs terminated with "notes" to a NOTES operation
sUriMatcher.addURI(NotePad.AUTHORITY, "notes", NOTES);
// Add a pattern that routes URIs terminated with "notes" plus an integer
// to a note ID operation
sUriMatcher.addURI(NotePad.AUTHORITY, "notes/#", NOTE_ID);
// Add a pattern that routes URIs terminated with live_folders/notes to a
// live folder operation
sUriMatcher.addURI(NotePad.AUTHORITY, "live_folders/notes", LIVE_FOLDER_NOTES);
/*
* Creates and initializes a projection map that returns all columns
*/
// Creates a new projection map instance. The map returns a column name
// given a string. The two are usually equal.
sNotesProjectionMap = new HashMap<String, String>();
// Maps the string "_ID" to the column name "_ID"
sNotesProjectionMap.put(NotePad.Notes._ID, NotePad.Notes._ID);
// Maps "title" to "title"
sNotesProjectionMap.put(NotePad.Notes.COLUMN_NAME_TITLE, NotePad.Notes.COLUMN_NAME_TITLE);
// Maps "note" to "note"
sNotesProjectionMap.put(NotePad.Notes.COLUMN_NAME_NOTE, NotePad.Notes.COLUMN_NAME_NOTE);
// Maps "created" to "created"
sNotesProjectionMap.put(NotePad.Notes.COLUMN_NAME_CREATE_DATE,
NotePad.Notes.COLUMN_NAME_CREATE_DATE);
// Maps "modified" to "modified"
sNotesProjectionMap.put(
NotePad.Notes.COLUMN_NAME_MODIFICATION_DATE,
NotePad.Notes.COLUMN_NAME_MODIFICATION_DATE);
/*
* Creates an initializes a projection map for handling Live Folders
*/
// Creates a new projection map instance
sLiveFolderProjectionMap = new HashMap<String, String>();
// Maps "_ID" to "_ID AS _ID" for a live folder
sLiveFolderProjectionMap.put(LiveFolders._ID, NotePad.Notes._ID + " AS " + LiveFolders._ID);
// Maps "NAME" to "title AS NAME"
sLiveFolderProjectionMap.put(LiveFolders.NAME, NotePad.Notes.COLUMN_NAME_TITLE + " AS " +
LiveFolders.NAME);
}
/**
*
* This class helps open, create, and upgrade the database file. Set to package visibility
* for testing purposes.
*/
static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
// calls the super constructor, requesting the default cursor factory.
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
/**
*
* Creates the underlying database with table name and column names taken from the
* NotePad class.
*/
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE " + NotePad.Notes.TABLE_NAME + " ("
+ NotePad.Notes._ID + " INTEGER PRIMARY KEY,"
+ NotePad.Notes.COLUMN_NAME_TITLE + " TEXT,"
+ NotePad.Notes.COLUMN_NAME_NOTE + " TEXT,"
+ NotePad.Notes.COLUMN_NAME_CREATE_DATE + " INTEGER,"
+ NotePad.Notes.COLUMN_NAME_MODIFICATION_DATE + " INTEGER"
+ ");");
}
/**
*
* Demonstrates that the provider must consider what happens when the
* underlying datastore is changed. In this sample, the database is upgraded the database
* by destroying the existing data.
* A real application should upgrade the database in place.
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Logs that the database is being upgraded
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
// Kills the table and existing data
db.execSQL("DROP TABLE IF EXISTS notes");
// Recreates the database with a new version
onCreate(db);
}
}
/**
*
* Initializes the provider by creating a new DatabaseHelper. onCreate() is called
* automatically when Android creates the provider in response to a resolver request from a
* client.
*/
@Override
public boolean onCreate() {
// Creates a new helper object. Note that the database itself isn't opened until
// something tries to access it, and it's only created if it doesn't already exist.
mOpenHelper = new DatabaseHelper(getContext());
// Assumes that any failures will be reported by a thrown exception.
return true;
}
/**
* This method is called when a client calls
* {@link android.content.ContentResolver#query(Uri, String[], String, String[], String)}.
* Queries the database and returns a cursor containing the results.
*
* @return A cursor containing the results of the query. The cursor exists but is empty if
* the query returns no results or an exception occurs.
* @throws IllegalArgumentException if the incoming URI pattern is invalid.
*/
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
String sortOrder) {
// Constructs a new query builder and sets its table name
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
qb.setTables(NotePad.Notes.TABLE_NAME);
/**
* Choose the projection and adjust the "where" clause based on URI pattern-matching.
*/
switch (sUriMatcher.match(uri)) {
// If the incoming URI is for notes, chooses the Notes projection
case NOTES:
qb.setProjectionMap(sNotesProjectionMap);
break;
/* If the incoming URI is for a single note identified by its ID, chooses the
* note ID projection, and appends "_ID = <noteID>" to the where clause, so that
* it selects that single note
*/
case NOTE_ID:
qb.setProjectionMap(sNotesProjectionMap);
qb.appendWhere(
NotePad.Notes._ID + // the name of the ID column
"=" +
// the position of the note ID itself in the incoming URI
uri.getPathSegments().get(NotePad.Notes.NOTE_ID_PATH_POSITION));
break;
case LIVE_FOLDER_NOTES:
// If the incoming URI is from a live folder, chooses the live folder projection.
qb.setProjectionMap(sLiveFolderProjectionMap);
break;
default:
// If the URI doesn't match any of the known patterns, throw an exception.
throw new IllegalArgumentException("Unknown URI " + uri);
}
String orderBy;
// If no sort order is specified, uses the default
if (TextUtils.isEmpty(sortOrder)) {
orderBy = NotePad.Notes.DEFAULT_SORT_ORDER;
} else {
// otherwise, uses the incoming sort order
orderBy = sortOrder;
}
// Opens the database object in "read" mode, since no writes need to be done.
SQLiteDatabase db = mOpenHelper.getReadableDatabase();
/*
* Performs the query. If no problems occur trying to read the database, then a Cursor
* object is returned; otherwise, the cursor variable contains null. If no records were
* selected, then the Cursor object is empty, and Cursor.getCount() returns 0.
*/
Cursor c = qb.query(
db, // The database to query
projection, // The columns to return from the query
selection, // The columns for the where clause
selectionArgs, // The values for the where clause
null, // don't group the rows
null, // don't filter by row groups
orderBy // The sort order
);
// Tells the Cursor what URI to watch, so it knows when its source data changes
c.setNotificationUri(getContext().getContentResolver(), uri);
return c;
}
/**
* This is called when a client calls {@link android.content.ContentResolver#getType(Uri)}.
* Returns the MIME data type of the URI given as a parameter.
*
* @param uri The URI whose MIME type is desired.
* @return The MIME type of the URI.
* @throws IllegalArgumentException if the incoming URI pattern is invalid.
*/
@Override
public String getType(Uri uri) {
/**
* Chooses the MIME type based on the incoming URI pattern
*/
switch (sUriMatcher.match(uri)) {
// If the pattern is for notes or live folders, returns the general content type.
case NOTES:
case LIVE_FOLDER_NOTES:
return NotePad.Notes.CONTENT_TYPE;
// If the pattern is for note IDs, returns the note ID content type.
case NOTE_ID:
return NotePad.Notes.CONTENT_ITEM_TYPE;
// If the URI pattern doesn't match any permitted patterns, throws an exception.
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
}
/**
* This describes the MIME types that are supported for opening a note
* URI as a stream.
*/
static ClipDescription NOTE_STREAM_TYPES = new ClipDescription(null,
new String[] { ClipDescription.MIMETYPE_TEXT_PLAIN });
/**
* Returns the types of available data streams. URIs to specific notes are supported.
* The application can convert such a note to a plain text stream.
*
* @param uri the URI to analyze
* @param mimeTypeFilter The MIME type to check for. This method only returns a data stream
* type for MIME types that match the filter. Currently, only text/plain MIME types match.
* @return a data stream MIME type. Currently, only text/plan is returned.
* @throws IllegalArgumentException if the URI pattern doesn't match any supported patterns.
*/
@Override
public String[] getStreamTypes(Uri uri, String mimeTypeFilter) {
/**
* Chooses the data stream type based on the incoming URI pattern.
*/
switch (sUriMatcher.match(uri)) {
// If the pattern is for notes or live folders, return null. Data streams are not
// supported for this type of URI.
case NOTES:
case LIVE_FOLDER_NOTES:
return null;
// If the pattern is for note IDs and the MIME filter is text/plain, then return
// text/plain
case NOTE_ID:
return NOTE_STREAM_TYPES.filterMimeTypes(mimeTypeFilter);
// If the URI pattern doesn't match any permitted patterns, throws an exception.
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
}
/**
* Returns a stream of data for each supported stream type. This method does a query on the
* incoming URI, then uses
* {@link android.content.ContentProvider#openPipeHelper(Uri, String, Bundle, Object,
* PipeDataWriter)} to start another thread in which to convert the data into a stream.
*
* @param uri The URI pattern that points to the data stream
* @param mimeTypeFilter A String containing a MIME type. This method tries to get a stream of
* data with this MIME type.
* @param opts Additional options supplied by the caller. Can be interpreted as
* desired by the content provider.
* @return AssetFileDescriptor A handle to the file.
* @throws FileNotFoundException if there is no file associated with the incoming URI.
*/
@Override
public AssetFileDescriptor openTypedAssetFile(Uri uri, String mimeTypeFilter, Bundle opts)
throws FileNotFoundException {
// Checks to see if the MIME type filter matches a supported MIME type.
String[] mimeTypes = getStreamTypes(uri, mimeTypeFilter);
// If the MIME type is supported
if (mimeTypes != null) {
// Retrieves the note for this URI. Uses the query method defined for this provider,
// rather than using the database query method.
Cursor c = query(
uri, // The URI of a note
READ_NOTE_PROJECTION, // Gets a projection containing the note's ID, title,
// and contents
null, // No WHERE clause, get all matching records
null, // Since there is no WHERE clause, no selection criteria
null // Use the default sort order (modification date,
// descending
);
// If the query fails or the cursor is empty, stop
if (c == null || !c.moveToFirst()) {
// If the cursor is empty, simply close the cursor and return
if (c != null) {
c.close();
}
// If the cursor is null, throw an exception
throw new FileNotFoundException("Unable to query " + uri);
}
// Start a new thread that pipes the stream data back to the caller.
return new AssetFileDescriptor(
openPipeHelper(uri, mimeTypes[0], opts, c, this), 0,
AssetFileDescriptor.UNKNOWN_LENGTH);
}
// If the MIME type is not supported, return a read-only handle to the file.
return super.openTypedAssetFile(uri, mimeTypeFilter, opts);
}
/**
* Implementation of {@link android.content.ContentProvider.PipeDataWriter}
* to perform the actual work of converting the data in one of cursors to a
* stream of data for the client to read.
*/
@Override
public void writeDataToPipe(ParcelFileDescriptor output, Uri uri, String mimeType,
Bundle opts, Cursor c) {
// We currently only support conversion-to-text from a single note entry,
// so no need for cursor data type checking here.
FileOutputStream fout = new FileOutputStream(output.getFileDescriptor());
PrintWriter pw = null;
try {
pw = new PrintWriter(new OutputStreamWriter(fout, "UTF-8"));
pw.println(c.getString(READ_NOTE_TITLE_INDEX));
pw.println("");
pw.println(c.getString(READ_NOTE_NOTE_INDEX));
} catch (UnsupportedEncodingException e) {
Log.w(TAG, "Ooops", e);
} finally {
c.close();
if (pw != null) {
pw.flush();
}
try {
fout.close();
} catch (IOException e) {
}
}
}
/**
* This is called when a client calls
* {@link android.content.ContentResolver#insert(Uri, ContentValues)}.
* Inserts a new row into the database. This method sets up default values for any
* columns that are not included in the incoming map.
* If rows were inserted, then listeners are notified of the change.
* @return The row ID of the inserted row.
* @throws SQLException if the insertion fails.
*/
@Override
public Uri insert(Uri uri, ContentValues initialValues) {
// Validates the incoming URI. Only the full provider URI is allowed for inserts.
if (sUriMatcher.match(uri) != NOTES) {
throw new IllegalArgumentException("Unknown URI " + uri);
}
// A map to hold the new record's values.
ContentValues values;
// If the incoming values map is not null, uses it for the new values.
if (initialValues != null) {
values = new ContentValues(initialValues);
} else {
// Otherwise, create a new value map
values = new ContentValues();
}
// Gets the current system time in milliseconds
Long now = Long.valueOf(System.currentTimeMillis());
// If the values map doesn't contain the creation date, sets the value to the current time.
if (values.containsKey(NotePad.Notes.COLUMN_NAME_CREATE_DATE) == false) {
values.put(NotePad.Notes.COLUMN_NAME_CREATE_DATE, now);
}
// If the values map doesn't contain the modification date, sets the value to the current
// time.
if (values.containsKey(NotePad.Notes.COLUMN_NAME_MODIFICATION_DATE) == false) {
values.put(NotePad.Notes.COLUMN_NAME_MODIFICATION_DATE, now);
}
// If the values map doesn't contain a title, sets the value to the default title.
if (values.containsKey(NotePad.Notes.COLUMN_NAME_TITLE) == false) {
Resources r = Resources.getSystem();
values.put(NotePad.Notes.COLUMN_NAME_TITLE, r.getString(android.R.string.untitled));
}
// If the values map doesn't contain note text, sets the value to an empty string.
if (values.containsKey(NotePad.Notes.COLUMN_NAME_NOTE) == false) {
values.put(NotePad.Notes.COLUMN_NAME_NOTE, "");
}
// Opens the database object in "write" mode.
SQLiteDatabase db = mOpenHelper.getWritableDatabase();
// Performs the insert and returns the ID of the new note.
long rowId = db.insert(
NotePad.Notes.TABLE_NAME, // The table to insert into.
NotePad.Notes.COLUMN_NAME_NOTE, // A hack, SQLite sets this column value to null
// if values is empty.
values // A map of column names, and the values to insert
// into the columns.
);
// If the insert succeeded, the row ID exists.
if (rowId > 0) {
// Creates a URI with the note ID pattern and the new row ID appended to it.
Uri noteUri = ContentUris.withAppendedId(NotePad.Notes.CONTENT_ID_URI_BASE, rowId);
// Notifies observers registered against this provider that the data changed.
getContext().getContentResolver().notifyChange(noteUri, null);
return noteUri;
}
// If the insert didn't succeed, then the rowID is <= 0. Throws an exception.
throw new SQLException("Failed to insert row into " + uri);
}
/**
* This is called when a client calls
* {@link android.content.ContentResolver#delete(Uri, String, String[])}.
* Deletes records from the database. If the incoming URI matches the note ID URI pattern,
* this method deletes the one record specified by the ID in the URI. Otherwise, it deletes a
* a set of records. The record or records must also match the input selection criteria
* specified by where and whereArgs.
*
* If rows were deleted, then listeners are notified of the change.
* @return If a "where" clause is used, the number of rows affected is returned, otherwise
* 0 is returned. To delete all rows and get a row count, use "1" as the where clause.
* @throws IllegalArgumentException if the incoming URI pattern is invalid.
*/
@Override
public int delete(Uri uri, String where, String[] whereArgs) {
// Opens the database object in "write" mode.
SQLiteDatabase db = mOpenHelper.getWritableDatabase();
String finalWhere;
int count;
// Does the delete based on the incoming URI pattern.
switch (sUriMatcher.match(uri)) {
// If the incoming pattern matches the general pattern for notes, does a delete
// based on the incoming "where" columns and arguments.
case NOTES:
count = db.delete(
NotePad.Notes.TABLE_NAME, // The database table name
where, // The incoming where clause column names
whereArgs // The incoming where clause values
);
break;
// If the incoming URI matches a single note ID, does the delete based on the
// incoming data, but modifies the where clause to restrict it to the
// particular note ID.
case NOTE_ID:
/*
* Starts a final WHERE clause by restricting it to the
* desired note ID.
*/
finalWhere =
NotePad.Notes._ID + // The ID column name
" = " + // test for equality
uri.getPathSegments(). // the incoming note ID
get(NotePad.Notes.NOTE_ID_PATH_POSITION)
;
// If there were additional selection criteria, append them to the final
// WHERE clause
if (where != null) {
finalWhere = finalWhere + " AND " + where;
}
// Performs the delete.
count = db.delete(
NotePad.Notes.TABLE_NAME, // The database table name.
finalWhere, // The final WHERE clause
whereArgs // The incoming where clause values.
);
break;
// If the incoming pattern is invalid, throws an exception.
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
/*Gets a handle to the content resolver object for the current context, and notifies it
* that the incoming URI changed. The object passes this along to the resolver framework,
* and observers that have registered themselves for the provider are notified.
*/
getContext().getContentResolver().notifyChange(uri, null);
// Returns the number of rows deleted.
return count;
}
/**
* This is called when a client calls
* {@link android.content.ContentResolver#update(Uri,ContentValues,String,String[])}
* Updates records in the database. The column names specified by the keys in the values map
* are updated with new data specified by the values in the map. If the incoming URI matches the
* note ID URI pattern, then the method updates the one record specified by the ID in the URI;
* otherwise, it updates a set of records. The record or records must match the input
* selection criteria specified by where and whereArgs.
* If rows were updated, then listeners are notified of the change.
*
* @param uri The URI pattern to match and update.
* @param values A map of column names (keys) and new values (values).
* @param where An SQL "WHERE" clause that selects records based on their column values. If this
* is null, then all records that match the URI pattern are selected.
* @param whereArgs An array of selection criteria. If the "where" param contains value
* placeholders ("?"), then each placeholder is replaced by the corresponding element in the
* array.
* @return The number of rows updated.
* @throws IllegalArgumentException if the incoming URI pattern is invalid.
*/
@Override
public int update(Uri uri, ContentValues values, String where, String[] whereArgs) {
// Opens the database object in "write" mode.
SQLiteDatabase db = mOpenHelper.getWritableDatabase();
int count;
String finalWhere;
// Does the update based on the incoming URI pattern
switch (sUriMatcher.match(uri)) {
// If the incoming URI matches the general notes pattern, does the update based on
// the incoming data.
case NOTES:
// Does the update and returns the number of rows updated.
count = db.update(
NotePad.Notes.TABLE_NAME, // The database table name.
values, // A map of column names and new values to use.
where, // The where clause column names.
whereArgs // The where clause column values to select on.
);
break;
// If the incoming URI matches a single note ID, does the update based on the incoming
// data, but modifies the where clause to restrict it to the particular note ID.
case NOTE_ID:
// From the incoming URI, get the note ID
String noteId = uri.getPathSegments().get(NotePad.Notes.NOTE_ID_PATH_POSITION);
/*
* Starts creating the final WHERE clause by restricting it to the incoming
* note ID.
*/
finalWhere =
NotePad.Notes._ID + // The ID column name
" = " + // test for equality
uri.getPathSegments(). // the incoming note ID
get(NotePad.Notes.NOTE_ID_PATH_POSITION)
;
// If there were additional selection criteria, append them to the final WHERE
// clause
if (where !=null) {
finalWhere = finalWhere + " AND " + where;
}
// Does the update and returns the number of rows updated.
count = db.update(
NotePad.Notes.TABLE_NAME, // The database table name.
values, // A map of column names and new values to use.
finalWhere, // The final WHERE clause to use
// placeholders for whereArgs
whereArgs // The where clause column values to select on, or
// null if the values are in the where argument.
);
break;
// If the incoming pattern is invalid, throws an exception.
default:
throw new IllegalArgumentException("Unknown URI " + uri);
}
/*Gets a handle to the content resolver object for the current context, and notifies it
* that the incoming URI changed. The object passes this along to the resolver framework,
* and observers that have registered themselves for the provider are notified.
*/
getContext().getContentResolver().notifyChange(uri, null);
// Returns the number of rows updated.
return count;
}
/**
* A test package can call this to get a handle to the database underlying NotePadProvider,
* so it can insert test data into the database. The test case class is responsible for
* instantiating the provider in a test context; {@link android.test.ProviderTestCase2} does
* this during the call to setUp()
*
* @return a handle to the database helper object for the provider's data.
*/
DatabaseHelper getOpenHelperForTest() {
return mOpenHelper;
}
}