标签：cursor sqlite contentprovider 内容提供者
/**
* 内容提供者
*
* @author ZhaoKaiQiang
* @time 2014年6月6日
*/
public class StudentProvider extends ContentProvider {
// 数据库操作类，用于获取SQLiteDatabase
private MyDbOpenHelper dbHelper;
private static final int STUDENT = 1;
private static final int STUDENTS = 2;
// UriMatcher类是一个很重要的类，因为我们需要根据传入的uri，来判断执行相对应的操作
private static final UriMatcher MATCHER = new UriMatcher(UriMatcher.NO_MATCH);
// 静态代码块用于初始化MATCHER需要匹配的uri
static {
// MATCHER.addURI(主机名(用于唯一标示一个ContentProvider,这个需要和清单文件中的authorities属性相同),路径(可以用来表示我们要操作的数据，路径的构建应根据业务而定),返回值(用于匹配uri的时候，作为匹配的返回值));
MATCHER.addURI("com.example.mydbdemo.StudentProvider", "student", STUDENTS);
MATCHER.addURI("com.example.mydbdemo.StudentProvider", "student/#", STUDENT);
}
// 进行数据的初始化操作
@Override
public boolean onCreate() {
dbHelper = new MyDbOpenHelper(getContext());
return false;
}
// 查询
// 如果uri为 content://com.example.mydbdemo.StudentProvider/student
// 则代表查询所有的student表内的数据
// 如果uri为 content://com.example.mydbdemo.StudentProvider/student/6
// 则代表查询student表内id=6的数据
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
SQLiteDatabase db = dbHelper.getReadableDatabase();
//判断传入的uri到底匹配哪一个，从而实现不同的业务需求
switch (MATCHER.match(uri)) {
//查询全部的学生信息
case STUDENTS:
//db.query(表明, 要查询的列(是一个String数组), where条件, where条件中的参数, groupBy, having, sortOrder);
return db.query("student", projection, selection, selectionArgs, null, null, sortOrder);
//查询某一个id对应的学生的信息
case STUDENT:
//取出我们要查询的数据的id
long id = ContentUris.parseId(uri);
String where = "id=" + id;
//将selection查询信息拼接到我们的where条件中
if (selection != null && !"".equals(selection)) {
where = selection + " and " + where;
}
return db.query("student", projection, where, selectionArgs, null, null, sortOrder);
//如uri不匹配，抛出不合法参数的异常
default:
throw new IllegalArgumentException("Unkwon Uri:" + uri.toString());
}
}
// 插入
@Override
public Uri insert(Uri uri, ContentValues values) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
switch (MATCHER.match(uri)) {
case STUDENTS:
long id = db.insert("student", "name", values);
return ContentUris.withAppendedId(uri, id);
default:
throw new IllegalArgumentException("Uri不匹配");
}
}
//删除数据
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
int count = 0;
switch (MATCHER.match(uri)) {
case STUDENTS:
count = db.delete("student", selection, selectionArgs);
return count;
case STUDENT:
long id = ContentUris.parseId(uri);
String where = "id=" + id;
if (selection != null && !"".equals(selection)) {
where = selection + " and " + where;
}
count = db.delete("student", where, selectionArgs);
return count;
default:
throw new IllegalArgumentException("Unkwon Uri:" + uri.toString());
}
}
//更新数据
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
int count = 0;
switch (MATCHER.match(uri)) {
case STUDENTS:
count = db.update("student", values, selection, selectionArgs);
return count;
case STUDENT:
long id = ContentUris.parseId(uri);
String where = "id=" + id;
if (selection != null && !"".equals(selection)) {
where = selection + " and " + where;
}
count = db.update("student", values, where, selectionArgs);
return count;
default:
throw new IllegalArgumentException("Unkwon Uri:" + uri.toString());
}
}
// 用于获取MIME Type
@Override
public String getType(Uri uri) {
switch (MATCHER.match(uri)) {
case STUDENT:
return "vnd.android.cursor.item/student";
case STUDENTS:
return "vnd.android.cursor.dir/student";
default:
throw new IllegalArgumentException("Unkwon Uri:" + uri.toString());
}
}
}<!-- 不要忘记exported这个属性，如果不加，可能会导致外部程序访问失败，错误信息为权限拒绝 -->
<!-- authorities这个属性就是我们在ContentProvider中使用的addURI方法时的第一个参数的取值 -->
<provider
android:name="com.example.mydbdemo.StudentProvider"
android:exported="true"
android:authorities="com.example.mydbdemo.StudentProvider" >
</provider>//使用ContentProvider添加数据的测试
public void testadd() throws Throwable {
//获取ContentResolver对象，完成对ContentProvider的调用
ContentResolver contentResolver = this.getContext().getContentResolver();
//构建我们的uir，这个uri
Uri insertUri = Uri.parse("content://com.example.mydbdemo.StudentProvider/student");
ContentValues values = new ContentValues();
values.put("name", "zhaokaikai");
values.put("age", 91);
values.put("school", "bbbb");
//返回值为我们刚插入进入的数据的uri地址
Uri uri = contentResolver.insert(insertUri, values);
Log.i(TAG, uri.toString());
}//使用ContentProvider删除数据的测试
public void testDelete() throws Throwable {
ContentResolver contentResolver = this.getContext().getContentResolver();
//删除id为6的学生信息
Uri deleteUri = Uri.parse("content://com.example.mydbdemo.StudentProvider/student/6");
contentResolver.delete(deleteUri, null, null);
}//使用ContentProvider更新数据的测试
public void testUpdate() throws Throwable {
ContentResolver contentResolver = this.getContext().getContentResolver();
//更新id = 6 的学生信息
Uri updateUri = Uri.parse("content://com.example.mydbdemo.StudentProvider/student/6");
ContentValues values = new ContentValues();
values.put("name", "testUp");
values.put("age", "101");
values.put("school", "ccccc");
contentResolver.update(updateUri, values, null, null);
}//使用ContentProvider查询数据的测试
public void testFind() throws Throwable {
ContentResolver contentResolver = this.getContext().getContentResolver();
//这个uri用于查询所有的数据，若查询某个id的数据，则构建下面的uri
//Uri selectUri = Uri.parse("content://com.example.mydbdemo.StudentProvider/student/要查询的id");
Uri selectUri = Uri.parse("content://com.example.mydbdemo.StudentProvider/student");
Cursor cursor = contentResolver.query(selectUri, null, null, null, "id desc");
while (cursor.moveToNext()) {
int id = cursor.getInt(cursor.getColumnIndex("id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
int age = cursor.getInt(cursor.getColumnIndex("age"));
String school = cursor.getString(cursor.getColumnIndex("school"));
Log.i(TAG, "id=" + id + ",name=" + name + ",age=" + age +",school="+school);
}
}【Android基础】内容提供者ContentProvider的使用详解,布布扣,bubuko.com
【Android基础】内容提供者ContentProvider的使用详解
标签：cursor sqlite contentprovider 内容提供者
原文地址：http://blog.csdn.net/zhaokaiqiang1992/article/details/28881287
