ContentProvider
ContentProvider 是Android的四大组件之一,对于许多比较复杂的数据的处理,许多APP都是采用ContentProvider,来创建一个DB数据库,从而可以统一对DB数据进行处理。
下面的这个样例,是创建一个员工管理的DB数据库,员工信息包括姓名,年龄,性别。我们可以对这个DB数据库进行基本的增,删,查,改操作。
用户界面如下图:
关键的代码:
1.Employees.java
public class Employees {
public static final String AUTHORITY = "com.konka.provider.Employees";
private Employees() {}
// 内部类
public static final class Employee implements BaseColumns {
// 构造方法
private Employee() {}
// 访问Uri
public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/employee");
// 内容类型
public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.amaker.employees";
public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.amaker.employees";
// 默认排序常量
public static final String DEFAULT_SORT_ORDER = "name DESC";// 按姓名排序
// 表字段常量
public static final String NAME = "name"; // 姓名
public static final String GENDER= "gender"; // 性别
public static final String AGE = "age"; // 年龄
}
}
2.DBHelper.java
/**
*
* 数据库工具类
*/
public class DBHelper extends SQLiteOpenHelper{
// 数据库名称常量
private static final String DATABASE_NAME = "Employees.db";
// 数据库版本常量
private static final int DATABASE_VERSION = 1;
// 表名称常量
public static final String EMPLOYEES_TABLE_NAME = "employee";
// 构造方法
public DBHelper(Context context) {
// 创建数据库
super(context, DATABASE_NAME,null, DATABASE_VERSION);
}
// 创建时调用
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE " + EMPLOYEES_TABLE_NAME + " ("
+ Employee._ID + " INTEGER PRIMARY KEY,"
+ Employee.NAME + " TEXT,"
+ Employee.GENDER + " TEXT,"
+ Employee.AGE + " INTEGER"
+ ");");
}
// 版本更新时调用
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// 删除表
db.execSQL("DROP TABLE IF EXISTS employee");
onCreate(db);
}
}
3.EmployeeProvider.java
public class EmployeeProvider extends ContentProvider{
// 数据库帮助类
private DBHelper dbHelper = null;
// Uri工具类
private static final UriMatcher sUriMatcher;
// 查询、更新条件
private static final int EMPLOYEE = 1;
private static final int EMPLOYEE_ID = 2;
// 查询列集合
private static HashMap<String, String> empProjectionMap;
static {
// Uri匹配工具类
sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
sUriMatcher.addURI(Employees.AUTHORITY, "employee", EMPLOYEE);
sUriMatcher.addURI(Employees.AUTHORITY, "employee/#", EMPLOYEE_ID);
// 实例化查询列集合
empProjectionMap = new HashMap<String, String>();
// 添加查询列
empProjectionMap.put(Employee._ID, Employee._ID);
empProjectionMap.put(Employee.NAME, Employee.NAME);
empProjectionMap.put(Employee.GENDER, Employee.GENDER);
empProjectionMap.put(Employee.AGE, Employee.AGE);
}
// 创建是调用
public boolean onCreate() {
// 实例化数据库帮助类
dbHelper = new DBHelper(getContext());
return true;
}
// 添加方法
public Uri insert(Uri uri, ContentValues values) {
// 获得数据库实例
SQLiteDatabase db = dbHelper.getWritableDatabase();
// 插入数据,返回行ID
long rowId = db.insert(DBHelper.EMPLOYEES_TABLE_NAME, Employee.NAME, values);
// 如果插入成功返回uri
if (rowId > 0) {
Uri empUri = ContentUris.withAppendedId(Employee.CONTENT_URI, rowId);
getContext().getContentResolver().notifyChange(empUri, null);
return empUri;
}
return null;
}
// 删除方法
public int delete(Uri uri, String selection, String[] selectionArgs) {
// 获得数据库实例
SQLiteDatabase db = dbHelper.getWritableDatabase();
// 获得数据库实例
int count;
switch (sUriMatcher.match(uri)) {
// 根据指定条件删除
case EMPLOYEE:
count = db.delete(DBHelper.EMPLOYEES_TABLE_NAME, selection, selectionArgs);
break;
// 根据指定条件和ID删除
case EMPLOYEE_ID:
String noteId = uri.getPathSegments().get(1);
count = db.delete(DBHelper.EMPLOYEES_TABLE_NAME, Employee._ID + "=" + noteId
+ (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""), selectionArgs);
break;
default:
throw new IllegalArgumentException("错误的 URI " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}
// 获得类型
public String getType(Uri uri) {
return null;
}
// 查询方法
public Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder) {
SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
switch (sUriMatcher.match(uri)) {
// 查询所有
case EMPLOYEE:
qb.setTables(DBHelper.EMPLOYEES_TABLE_NAME);
qb.setProjectionMap(empProjectionMap);
break;
// 根据ID查询
case EMPLOYEE_ID:
qb.setTables(DBHelper.EMPLOYEES_TABLE_NAME);
qb.setProjectionMap(empProjectionMap);
qb.appendWhere(Employee._ID + "=" + uri.getPathSegments().get(1));
break;
default:
throw new IllegalArgumentException("Uri错误! " + uri);
}
// 使用默认排序
String orderBy;
if (TextUtils.isEmpty(sortOrder)) {
orderBy = Employee.DEFAULT_SORT_ORDER;
} else {
orderBy = sortOrder;
}
// 获得数据库实例
SQLiteDatabase db = dbHelper.getReadableDatabase();
// 返回游标集合
Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);
c.setNotificationUri(getContext().getContentResolver(), uri);
return c;
}
// 更新方法
public int update(Uri uri, ContentValues values, String selection,String[] selectionArgs) {
// 获得数据库实例
SQLiteDatabase db = dbHelper.getWritableDatabase();
int count;
switch (sUriMatcher.match(uri)) {
// 根据指定条件更新
case EMPLOYEE:
count = db.update(DBHelper.EMPLOYEES_TABLE_NAME, values, selection, selectionArgs);
break;
// 根据指定条件和ID更新
case EMPLOYEE_ID:
String noteId = uri.getPathSegments().get(1);
count = db.update(DBHelper.EMPLOYEES_TABLE_NAME, values, Employee._ID + "=" + noteId
+ (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""), selectionArgs);
break;
default:
throw new IllegalArgumentException("错误的 URI " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}
}
4.ContentProviderFullDemoActivity.java
public class ContentProviderFullDemoActivity extends Activity implements OnClickListener {
public static String TAG = "ContentProviderFullDemoActivity";
public Uri uri = Employee.CONTENT_URI;
private Button insertData = null;
private Button queryData = null;
private Button deleteData = null;
private Button updateData = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
insertData = (Button) findViewById(R.id.insertData);
insertData.setOnClickListener(ContentProviderFullDemoActivity.this);
queryData = (Button) findViewById(R.id.queryData);
queryData.setOnClickListener(ContentProviderFullDemoActivity.this);
deleteData = (Button) findViewById(R.id.deleteData);
deleteData.setOnClickListener(ContentProviderFullDemoActivity.this);
updateData = (Button) findViewById(R.id.updateData);
updateData.setOnClickListener(ContentProviderFullDemoActivity.this);
}
@Override
public void onClick(View view) {
// TODO Auto-generated method stub
if(view == insertData){
ContentValues values = new ContentValues();
values.put(Employee.NAME, "amaker");
values.put(Employee.GENDER, "male");
values.put(Employee.AGE,30);
// 插入
insert(uri,values);
Log.i(TAG, "insert");
}else if(view == queryData){
// 查询
query();
Log.i(TAG, "query");
}else if(view == deleteData){
//这是删除名字为:amaker的数据的方法:
String[] deleteValue = {"amaker"};
String where = "name";
// 删除
del(uri,where,deleteValue);
Log.i(TAG, "del");
}else if(view == updateData){
ContentValues values = new ContentValues();
values.put(Employee.NAME, "testUpdate");
values.put(Employee.GENDER, "female");
values.put(Employee.AGE,39);
String where = "name";
String[] selectValue = {"amaker"};
// 更新
update(uri,values,where,selectValue);
Log.i(TAG, "update");
}
}
// 插入
private void insert(Uri uri, ContentValues values){
getContentResolver().insert(uri, values);
}
// 查询
private void query(){
// 查询列数组
String[] PROJECTION = new String[] {
Employee._ID, // 0
Employee.NAME, // 1
Employee.GENDER, // 2
Employee.AGE // 3
};
// 查询所有备忘录信息
Cursor cursor = getContentResolver().query(Employee.CONTENT_URI,PROJECTION, null, null,Employee.DEFAULT_SORT_ORDER);
//Cursor c = managedQuery(Employee.CONTENT_URI, PROJECTION, null,null, Employee.DEFAULT_SORT_ORDER);
if (cursor.moveToFirst()) {
// 遍历游标
for (int i = 0; i < cursor.getCount(); i++) {
cursor.moveToPosition(i);
String name = cursor.getString(1);
String gender = cursor.getString(2);
int age = cursor.getInt(3);
Log.i(TAG, "db第"+i+"个数据:"+"--name:"+name+"--gender:"+gender+"--age:"+age);
}
}
cursor.close();
}
// 删除方法
private void del(Uri uri,String where, String[] deleteValue){
/**** 删除ID为1的记录的方法:
// 删除ID为1的记录
Uri uri = ContentUris.withAppendedId(Employee.CONTENT_URI, 1);
// 获得ContentResolver,并删除
getContentResolver().delete(uri, null, null);
****/
getContentResolver().delete(uri, where+"=?", deleteValue);
}
// 更新
private void update(Uri uri, ContentValues values, String where, String[] selectValue){
/**************************************************************
// 更新ID为1的记录
Uri uri = ContentUris.withAppendedId(Employee.CONTENT_URI, 1);
ContentValues values = new ContentValues();
// 添加员工信息
values.put(Employee.NAME, "hz.guo");
values.put(Employee.GENDER, "male");
values.put(Employee.AGE,31);
// 获得ContentResolver,并更新
getContentResolver().update(uri, values, null, null);
*************************************************************/
//getContentResolver().update(uri, values, "name"+"=?", selectValue);
getContentResolver().update(uri, values, where+"=?", selectValue);
}
}
源码下载地址:
http://download.youkuaiyun.com/detail/hfreeman2011/5041208