Android中ContentProvider和ContentResolver使用入门
在Android中，我们的应用有的时候需要对外提供数据接口，可以有如下几种方法：1）AIDL 2）Broadcast 3）ContentProvider。
使用AIDL需要我们编写AIDL接口以及实现，而且对方也要有相应的接口描述，有点麻烦；使用Broadcast，我们不需要任何接口描述，只要协议文档就可以了，但是有点不好就是，这种方式不直接而且是异步的；使用ContentProvider我们不需要接口描述，只需要知道协议，同时这种方式是同步的，使用方便。下面是ContentProvider实现：
/**
*
*/
package com.backgroundservice;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.util.Log;
/**
* TODO
*
* @author tianlu
* @version 1.0 Create At : 2010-2-18 下午01:58:39
*/
public class TestContentProvider extends ContentProvider {
private SQLiteDatabase mDb;
private DatabaseHelper mDbHelper = null;
private static final String DATABASE_NAME = "rssitems.db";
private static final String DATABASE_TABLE_NAME = "rssItems";
private static final int DB_VERSION = 1;
private static final int ALL_MESSAGES = 1;
private static final int SPECIFIC_MESSAGE = 2;
// Set up our URL matchers to help us determine what an
// incoming URI parameter is.
private static final UriMatcher URI_MATCHER;
static {
URI_MATCHER = new UriMatcher(UriMatcher.NO_MATCH);
URI_MATCHER.addURI("test", "item", ALL_MESSAGES);
URI_MATCHER.addURI("test", "item/#", SPECIFIC_MESSAGE);
}
// Here's the public URI used to query for RSS items.
public static final Uri CONTENT_URI = Uri
.parse("content://test/item");
// Here are our column name constants, used to query for field values.
public static final String ID = "_id";
public static final String NAME = "NAME";
public static final String VALUE = "VALUE";
public static final String DEFAULT_SORT_ORDER = ID + " DESC";
private static class DatabaseHelper extends AbstractDatabaseHelper {
@Override
protected String[] createDBTables() {
// TODO Auto-generated method stub
String sql = "CREATE TABLE " + DATABASE_TABLE_NAME + "(" + ID
+ " INTEGER PRIMARY KEY AUTOINCREMENT, " + NAME + " TEXT,"
+ VALUE + " TEXT);";
return new String[] { sql };
}
@Override
protected String[] dropDBTables() {
// TODO Auto-generated method stub
return null;
}
@Override
protected String getDatabaseName() {
// TODO Auto-generated method stub
return DATABASE_NAME;
}
@Override
protected int getDatabaseVersion() {
// TODO Auto-generated method stub
return DB_VERSION;
}
@Override
protected String getTag() {
// TODO Auto-generated method stub
return TestContentProvider.class.getSimpleName();
}
}
/**
*
*/
public TestContentProvider() {
// TODO Auto-generated constructor stub
}
/*
* (non-Javadoc)
*
* @see android.content.ContentProvider#delete(android.net.Uri,
* java.lang.String, java.lang.String[])
*/
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// NOTE Argument checking code omitted. Check your parameters!
int rowCount = mDb.delete(DATABASE_TABLE_NAME, selection, selectionArgs);
// Notify any listeners and return the deleted row count.
getContext().getContentResolver().notifyChange(uri, null);
return rowCount;
}
/*
* (non-Javadoc)
*
* @see android.content.ContentProvider#getType(android.net.Uri)
*/
@Override
public String getType(Uri uri) {
switch (URI_MATCHER.match(uri)) {
case ALL_MESSAGES:
return "vnd.android.cursor.dir/rssitem"; // List of items.
case SPECIFIC_MESSAGE:
return "vnd.android.cursor.item/rssitem"; // Specific item.
default:
return null;
}
}
/*
* (non-Javadoc)
*
* @see android.content.ContentProvider#insert(android.net.Uri,
* android.content.ContentValues)
*/
@Override
public Uri insert(Uri uri, ContentValues values) {
// NOTE Argument checking code omitted. Check your parameters! Check that
// your row addition request succeeded!
long rowId = -1;
rowId = mDb.insert(DATABASE_TABLE_NAME, NAME, values);
Uri newUri = Uri.withAppendedPath(CONTENT_URI, ""+rowId);
Log.i("TestContentProvider", "saved a record " + rowId + " " + newUri);
// Notify any listeners and return the URI of the new row.
getContext().getContentResolver().notifyChange(CONTENT_URI, null);
return newUri;
}
/*
* (non-Javadoc)
*
* @see android.content.ContentProvider#onCreate()
*/
@Override
public boolean onCreate() {
// TODO Auto-generated method stub
try
{
mDbHelper = new DatabaseHelper();
mDbHelper.open(getContext());
mDb = mDbHelper.getMDb();
}catch(Exception e){
e.printStackTrace();
}
return true;
}
/*
* (non-Javadoc)
*
* @see android.content.ContentProvider#query(android.net.Uri,
* java.lang.String[], java.lang.String, java.lang.String[],
* java.lang.String)
*/
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// We won't bother checking the validity of params here, but you should!
// SQLiteQueryBuilder is the helper class that creates the
// proper SQL syntax for us.
SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder();
// Set the table we're querying.
qBuilder.setTables(DATABASE_TABLE_NAME);
// If the query ends in a specific record number, we're
// being asked for a specific record, so set the
// WHERE clause in our query.
if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){
qBuilder.appendWhere("_id=" + uri.getLastPathSegment());
Log.i("TestContentProvider", "_id=" + uri.getLastPathSegment());
}
// Make the query.
Cursor c = qBuilder.query(mDb,
projection,
selection,
selectionArgs,
null,
null,
sortOrder);
Log.i("TestContentProvider", "get records");
c.setNotificationUri(getContext().getContentResolver(), uri);
return c;
}
/*
* (non-Javadoc)
*
* @see android.content.ContentProvider#update(android.net.Uri,
* android.content.ContentValues, java.lang.String, java.lang.String[])
*/
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// NOTE Argument checking code omitted. Check your parameters!
int updateCount = mDb.update(DATABASE_TABLE_NAME, values, selection, selectionArgs);
// Notify any listeners and return the updated row count.
getContext().getContentResolver().notifyChange(uri, null);
return updateCount;
}
}
配置文件如下：
<provider android:name="TestContentProvider"
android:authorities="test">
</provider>在客户端中可以使用如下方法进行调用：
ContentValues values = new ContentValues();
values.put(TestContentProvider.NAME, "testname1");
values.put(TestContentProvider.VALUE, "testvalu1e");
Uri newAddUri = TestActivity.this.getContentResolver().insert(TestContentProvider.CONTENT_URI, values);
Cursor c = TestActivity.this.managedQuery(newAddUri, new String[]{TestContentProvider.NAME}, null, null, null);
Log.i("TestActivity", "" + c.getCount());
if(c.moveToNext())
{
Log.i("TestActivity", c.getString(0));
}
使用AIDL需要我们编写AIDL接口以及实现，而且对方也要有相应的接口描述，有点麻烦；使用Broadcast，我们不需要任何接口描述，只要协议文档就可以了，但是有点不好就是，这种方式不直接而且是异步的；使用ContentProvider我们不需要接口描述，只需要知道协议，同时这种方式是同步的，使用方便。下面是ContentProvider实现：
/**
* */package com.backgroundservice;import android.content.ContentProvider;import android.content.ContentValues;import android.content.UriMatcher;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteQueryBuilder;import android.net.Uri;import android.util.Log;/** * TODO * * @author tianlu * @version 1.0 Create At : 2010-2-18 下午01:58:39 */public class TestContentProvider extends ContentProvider {
private SQLiteDatabase mDb; private DatabaseHelper mDbHelper = null; private static final String DATABASE_NAME = "rssitems.db"; private static final String DATABASE_TABLE_NAME = "rssItems"; private static final int DB_VERSION = 1; private static final int ALL_MESSAGES = 1; private static final int SPECIFIC_MESSAGE = 2; // Set up our URL matchers to help us determine what an // incoming URI parameter is. private static final UriMatcher URI_MATCHER; static {
URI_MATCHER = new UriMatcher(UriMatcher.NO_MATCH); URI_MATCHER.addURI("test", "item", ALL_MESSAGES); URI_MATCHER.addURI("test", "item/#", SPECIFIC_MESSAGE); } // Here's the public URI used to query for RSS items. public static final Uri CONTENT_URI = Uri .parse("content://test/item"); // Here are our column name constants, used to query for field values. public static final String ID = "_id"; public static final String NAME = "NAME"; public static final String VALUE = "VALUE"; public static final String DEFAULT_SORT_ORDER = ID + " DESC"; private static class DatabaseHelper extends AbstractDatabaseHelper { @Override protected String[] createDBTables() { // TODO Auto-generated method stub String sql = "CREATE TABLE " + DATABASE_TABLE_NAME + "(" + ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + NAME + " TEXT," + VALUE + " TEXT);"; return new String[] { sql }; } @Override protected String[] dropDBTables() { // TODO Auto-generated method stub return null; } @Override protected String getDatabaseName() { // TODO Auto-generated method stub return DATABASE_NAME; } @Override protected int getDatabaseVersion() { // TODO Auto-generated method stub return DB_VERSION; } @Override protected String getTag() { // TODO Auto-generated method stub return TestContentProvider.class.getSimpleName(); } } /** * */ public TestContentProvider() { // TODO Auto-generated constructor stub } /* * (non-Javadoc) * * @see android.content.ContentProvider#delete(android.net.Uri, * java.lang.String, java.lang.String[]) */ @Override public int delete(Uri uri, String selection, String[] selectionArgs) { // NOTE Argument checking code omitted. Check your parameters! int rowCount = mDb.delete(DATABASE_TABLE_NAME, selection, selectionArgs); // Notify any listeners and return the deleted row count. getContext().getContentResolver().notifyChange(uri, null); return rowCount; } /* * (non-Javadoc) * * @see android.content.ContentProvider#getType(android.net.Uri) */ @Override public String getType(Uri uri) { switch (URI_MATCHER.match(uri)) { case ALL_MESSAGES: return "vnd.android.cursor.dir/rssitem"; // List of items. case SPECIFIC_MESSAGE: return "vnd.android.cursor.item/rssitem"; // Specific item. default: return null; } } /* * (non-Javadoc) * * @see android.content.ContentProvider#insert(android.net.Uri, * android.content.ContentValues) */ @Override public Uri insert(Uri uri, ContentValues values) { // NOTE Argument checking code omitted. Check your parameters! Check that // your row addition request succeeded! long rowId = -1; rowId = mDb.insert(DATABASE_TABLE_NAME, NAME, values); Uri newUri = Uri.withAppendedPath(CONTENT_URI, ""+rowId); Log.i("TestContentProvider", "saved a record " + rowId + " " + newUri); // Notify any listeners and return the URI of the new row. getContext().getContentResolver().notifyChange(CONTENT_URI, null); return newUri; } /* * (non-Javadoc) * * @see android.content.ContentProvider#onCreate() */ @Override public boolean onCreate() { // TODO Auto-generated method stub try { mDbHelper = new DatabaseHelper(); mDbHelper.open(getContext()); mDb = mDbHelper.getMDb(); }catch(Exception e){ e.printStackTrace(); } return true; } /* * (non-Javadoc) * * @see android.content.ContentProvider#query(android.net.Uri, * java.lang.String[], java.lang.String, java.lang.String[], * java.lang.String) */ public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { // We won't bother checking the validity of params here, but you should! // SQLiteQueryBuilder is the helper class that creates the // proper SQL syntax for us. SQLiteQueryBuilder qBuilder = new SQLiteQueryBuilder(); // Set the table we're querying. qBuilder.setTables(DATABASE_TABLE_NAME); // If the query ends in a specific record number, we're // being asked for a specific record, so set the // WHERE clause in our query. if((URI_MATCHER.match(uri)) == SPECIFIC_MESSAGE){ qBuilder.appendWhere("_id=" + uri.getLastPathSegment()); Log.i("TestContentProvider", "_id=" + uri.getLastPathSegment()); } // Make the query. Cursor c = qBuilder.query(mDb, projection, selection, selectionArgs, null, null, sortOrder); Log.i("TestContentProvider", "get records"); c.setNotificationUri(getContext().getContentResolver(), uri); return c; } /* * (non-Javadoc) * * @see android.content.ContentProvider#update(android.net.Uri, * android.content.ContentValues, java.lang.String, java.lang.String[]) */ @Override public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) { // NOTE Argument checking code omitted. Check your parameters! int updateCount = mDb.update(DATABASE_TABLE_NAME, values, selection, selectionArgs); // Notify any listeners and return the updated row count. getContext().getContentResolver().notifyChange(uri, null); return updateCount; }} <provider android:name="TestContentProvider" android:authorities="test"> </provider> ContentValues values = new ContentValues(); values.put(TestContentProvider.NAME, "testname1"); values.put(TestContentProvider.VALUE, "testvalu1e"); Uri newAddUri = TestActivity.this.getContentResolver().insert(TestContentProvider.CONTENT_URI, values); Cursor c = TestActivity.this.managedQuery(newAddUri, new String[]{TestContentProvider.NAME}, null, null, null); Log.i("TestActivity", "" + c.getCount()); if(c.moveToNext()) { Log.i("TestActivity", c.getString(0)); }上面的代码是先进行插入，然后进行查询并打印。就是如此简单，所有的应用如果需要都可以对外方便的提供数据接口，同时其他应用也可以很方便的进行调用。
TrackBack：http://www.blogjava.net/TiGERTiAN/archive/2010/02/18/313403.html
