【Android基础】内容提供者ContentProvider的使用详解_本应用内可以调用本应用的contentprovider吗

/**
 * 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);
		}
	}