Android四大组件——ContentProvider的增删改查和优化
前言
ContentProvider步骤：创数据库，写规则匹配，配置manifests，另一个应用使用
其实ContentProvider就是：在一个匹配器中写入自己写好的匹配规则，并对外提供写好的匹配规则供使用，剩下的就是增删改查的处理
细节处理：
在增删改查中的查询中，是没有cursor.getBoolean这个方法的，所以要对数据库中获取布尔值进行处理：
msg.setFlag(cursor.getInt(cursor.getColumnIndex("flag")) != 0);ContentProvider的增删改查
一、创建一个类继承SQLiteOpenHelper，并用SQL语句创建一个SQLite
public class CommonOpenHelper extends SQLiteOpenHelper {
private static CommonOpenHelper helper;
public static CommonOpenHelper getInstance(Context context) {
if (helper == null) {
helper = new CommonOpenHelper(context, "common.db", null, 1);
}
return helper;
}
private CommonOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table message(" +
"id integer primary key autoincrement, " +
"content varchar, " +
"date varchar " +
")");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
public class MyMessageProvider extends ContentProvider {
//数据库名
public final static String DB_MESSAGE = "message";
//放置一个数据库
CommonOpenHelper helper;
SQLiteDatabase db;
//空白匹配器
UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
//自身的匹配规则
final static int CODE_MESSAGE_INSERT = 0;
final static int CODE_MESSAGE_QUERY = 1;
final static int CODE_MESSAGE_DELETE = 2;
final static int CODE_MESSAGE_UPDATE = 3;
//主机名
final static String authority = "com.handsome.nfcc";
final static Uri BASE_URI = Uri.parse("content://com.handsome.nfcc");
//写入该主机名的匹配规则
{
matcher.addURI(authority, "message/insert", CODE_MESSAGE_INSERT);
matcher.addURI(authority, "message/query", CODE_MESSAGE_QUERY);
matcher.addURI(authority, "message/delete", CODE_MESSAGE_DELETE);
matcher.addURI(authority, "message/update", CODE_MESSAGE_UPDATE);
}
//对外提供的URI
public interface URI {
Uri CODE_MESSAGE_INSERT = Uri.parse("content://" + authority + "/message/insert");
Uri CODE_MESSAGE_QUERY = Uri.parse("content://" + authority + "/message/query");
Uri CODE_MESSAGE_DELETE = Uri.parse("content://" + authority + "/message/delete");
Uri CODE_MESSAGE_UPDATE = Uri.parse("content://" + authority + "/message/update");
}
@Override
public boolean onCreate() {
helper = CommonOpenHelper.getInstance(getContext());
db = helper.getWritableDatabase();
return false;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
switch (matcher.match(uri)) {
case CODE_MESSAGE_QUERY:
Cursor cursor = db.query(DB_MESSAGE, projection, selection, selectionArgs, null, null, sortOrder);
//注册内容观察者，观察数据变化
cursor.setNotificationUri(getContext().getContentResolver(), BASE_URI);
return cursor;
default:
throw new IllegalArgumentException("未识别的uri" + uri);
}
}
@Override
public String getType(Uri uri) {
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
switch (matcher.match(uri)) {
case CODE_MESSAGE_INSERT:
long rowId = db.insert(DB_MESSAGE, null, values);
if (rowId == -1) {
//添加失败
return null;
} else {
//发送内容广播
getContext().getContentResolver().notifyChange(BASE_URI, null);
//添加成功
return ContentUris.withAppendedId(uri, rowId);
}
default:
throw new IllegalArgumentException("未识别的uri" + uri);
}
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
switch (matcher.match(uri)) {
case CODE_MESSAGE_DELETE:
int number = db.delete(DB_MESSAGE, selection, selectionArgs);
//发送内容广播
getContext().getContentResolver().notifyChange(BASE_URI, null);
return number;
default:
throw new IllegalArgumentException("未识别的uri" + uri);
}
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
switch (matcher.match(uri)) {
case CODE_MESSAGE_UPDATE:
int number = db.update(DB_MESSAGE, values, selection, selectionArgs);
//发送内容广播
getContext().getContentResolver().notifyChange(BASE_URI, null);
return number;
default:
throw new IllegalArgumentException("未识别的uri" + uri);
}
}
}
public class MessageDao {
/**
* 添加数据
*/
public static boolean insert(ContentResolver resolver, Message msg) {
ContentValues values = new ContentValues();
values.put("content", msg.getContent());
values.put("date", DateUtils.showDate());
resolver.insert(MyMessageProvider.URI.CODE_MESSAGE_INSERT, values);
return true;
}
/**
* 删除数据
*/
public static void delete(ContentResolver resolver, int id) {
resolver.delete(MyMessageProvider.URI.CODE_MESSAGE_DELETE, "id = " + id, null);
}
/**
* 删除全部数据
*/
public static void deleteAll(ContentResolver resolver) {
resolver.delete(MyMessageProvider.URI.CODE_MESSAGE_DELETE, null, null);
}
/**
* 查询数据
*
* @param resolver
* @return
*/
public static List query(ContentResolver resolver) {
List list = new ArrayList<>();
Cursor cursor = resolver.query(MyMessageProvider.URI.CODE_MESSAGE_QUERY, null, null, null, null);
while (cursor.moveToNext()) {
Message msg = new Message();
msg.setDate(cursor.getString(cursor.getColumnIndex("date")));
msg.setContent(cursor.getString(cursor.getColumnIndex("content")));
msg.setId(cursor.getInt(cursor.getColumnIndex("id")));
list.add(0, msg);
}
return list;
}
} ContentProvider的优化
往往在一个项目中有很多的数据库，这个时候并不是重复的写ContentProvider代码，而是将所有数据库中放在一个ContentProvider中，提供一个查询表名的方法，并对其相应的表进行操作
一、ContentProvider的代码优化（一套代码适用多个数据库）
public class MyDataProvider extends ContentProvider {
//数据库名
public final static String DB_DATA = "data";
public final static String DB_FETCH = "fetch";
public final static String DB_MESSAGE = "message";
//放置一个数据库
CommonOpenHelper helper;
SQLiteDatabase db;
UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);
//自身的匹配规则
final static int CODE_DATA = 0;
final static int CODE_FETCH = 1;
final static int CODE_MESSAGE = 2;
//主机名
final static String authority = "com.handsome.nfc";
final static Uri BASE_URI = Uri.parse("content://com.handsome.nfc");
//写入该主机名的匹配规则
{
matcher.addURI(authority, "data", CODE_DATA);
matcher.addURI(authority, "fetch", CODE_FETCH);
matcher.addURI(authority, "message", CODE_MESSAGE);
}
//对外提供的URI
public interface URI {
Uri DATA_CONTENT_URI = Uri.parse(BASE_URI + "/data");
Uri FETCH_CONTENT_URI = Uri.parse(BASE_URI + "/fetch");
Uri MESSAGE_CONTENT_URI = Uri.parse(BASE_URI + "/message");
}
/**
* 获取数据库表名
*
* @param uri
* @return
*/
private String getTableName(Uri uri) {
String tableName = null;
switch (matcher.match(uri)) {
case CODE_DATA:
tableName = DB_DATA;
break;
case CODE_FETCH:
tableName = DB_FETCH;
break;
case CODE_MESSAGE:
tableName = DB_MESSAGE;
break;
default:
break;
}
return tableName;
}
@Override
public boolean onCreate() {
helper = CommonOpenHelper.getInstance(getContext());
db = helper.getWritableDatabase();
return false;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
String tableName = getTableName(uri);
if (tableName == null) {
throw new IllegalArgumentException("非法Uri：" + uri);
}
Cursor cursor = db.query(tableName, projection, selection, selectionArgs, null, null, sortOrder);
//注册内容观察者，观察数据变化
cursor.setNotificationUri(getContext().getContentResolver(), BASE_URI);
return cursor;
}
@Override
public String getType(Uri uri) {
return null;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
String tableName = getTableName(uri);
if (tableName == null) {
throw new IllegalArgumentException("非法Uri：" + uri);
}
long rowId = db.insert(tableName, null, values);
if (rowId == -1) {
return null;
} else {
//发送内容广播
getContext().getContentResolver().notifyChange(BASE_URI, null);
return ContentUris.withAppendedId(uri, rowId);
}
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
String tableName = getTableName(uri);
if (tableName == null) {
throw new IllegalArgumentException("非法Uri：" + uri);
}
int number = db.delete(tableName, selection, selectionArgs);
//发送内容广播
getContext().getContentResolver().notifyChange(BASE_URI, null);
return number;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
String tableName = getTableName(uri);
if (tableName == null) {
throw new IllegalArgumentException("非法Uri：" + uri);
}
int number = db.update(tableName, values, selection, selectionArgs);
//发送内容广播
getContext().getContentResolver().notifyChange(BASE_URI, null);
return number;
}
}二、在各个不同的数据库中的使用
Data数据库通过名字查询示例
private static boolean queryDataByName(ContentResolver resolver, String tag_id) {
Cursor cursor = resolver.query(MyDataProvider.URI.DATA_CONTENT_URI, null, "tag_id = '" + tag_id + "'", null, null);
if (cursor.moveToFirst()) {
return true;
}
return false;
}public static boolean insert(ContentResolver resolver, Fetch fetch) {
ContentValues values = new ContentValues();
values.put("fetch_num", fetch.getFetch_num());
values.put("username", fetch.getUsername());
values.put("installationId", fetch.getInstallationId());
values.put("created", fetch.getCreated());
values.put("date", System.currentTimeMillis());
resolver.insert(MyDataProvider.URI.FETCH_CONTENT_URI, values);
return true;
} public static List query(ContentResolver resolver) {
List list = new ArrayList<>();
Cursor cursor = resolver.query(MyDataProvider.URI.MESSAGE_CONTENT_URI, null, null, null, null);
while (cursor.moveToNext()) {
Message msg = new Message();
msg.setDate(cursor.getString(cursor.getColumnIndex("date")));
msg.setContent(cursor.getString(cursor.getColumnIndex("content")));
msg.setId(cursor.getInt(cursor.getColumnIndex("id")));
list.add(0, msg);
}
return list;
}