《第一行代码》学习笔记——第七章 内容提供器

《第一行代码》学习笔记——第七章 内容提供器

• 内容提供器简介
• 访问其他程序中的数据
• 创建自定义内容提供器

内容提供器简介

内容提供器主要用于在不用的应用程序之间实现数据共享的功能。

访问其他程序中的数据

读取系统联系人

	Cursor cursor = null;
	try {
	    cursor = getContentResolver().query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI,
	            null, null, null, null);
	    if (cursor != null) {
	        while (cursor.moveToNext()) {
	            String displayName = cursor.getString(
	                    cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
	            String number = cursor.getString(
	                    cursor.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));
	            contactsList.add(displayName + "\n" + number);
	        }
	        adapter.notifyDataSetChanged();
	    }
	} catch (Exception e) {
	    e.printStackTrace();
	} finally {
	    if (cursor != null)
	        cursor.close();
	}

创建自定义内容提供器

标准Uri写法：

	content://com.example.app.provider/table1/1

表示希望访问com.example.app这个应用的table表中id为1的数据

通配符	描述
*	表示匹配任意长度的任意字符
#	表示匹配任意长度的数字

匹配任意表内容：

	content://com.example.app.provider/*

匹配表table1中任意一行数据：

	content://com.example.app.provider/table1/#

使用UriMatcher类匹配URI

UriMatcher提供addURI()方法添加一个Uri和对应的自定义码：

	uriMatcher.addURI("com.example.app.provider", "table1", 0);

通过调用match()方法，匹配传入的Uri，返回匹配的自定义码：

	int code = uriMatcher.match(uri);

表的MIME类型

描述	值
类型部分	vnd
子类型部分，单个行	android.cursor.item/
子类型部分，多个行	android.cursor.dir/
提供程序特有部分	vnd.<name>.<type>

表table1的MIME：

	vnd.android.cursor.dir/vnd.com.example.app.provider.table1

表table1中id=1的数据的MIME：

	vnd.android.cursor.item/vnd.com.example.app.provider.table1

创建自定义内容提供器

1. 新建自定义内容提供器类继承ContentProvider，并实现其方法：

public class DatabaseProvider extends ContentProvider {

    private static final int BOOK_DIR = 0;
    private static final int BOOK_ITEM = 1;
    private static final int CATEGORY_DIR = 2;
    private static final int CATEGORY_ITEM = 3;

    private static final String AUTHORITY = "com.lhh.databasetest.provider";

    private static UriMatcher uriMatcher;

    private MyDatabaseHelper dbHelper;

    static {
        uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        uriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);
        uriMatcher.addURI(AUTHORITY, "book/#", BOOK_ITEM);
        uriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);
        uriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int deletedRows = 0;
        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
                deletedRows = db.delete("Book", selection, selectionArgs);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                deletedRows = db.delete("Book", "id=?", new String[]{bookId});
                break;
            case CATEGORY_DIR:
                deletedRows = db.delete("Category", selection, selectionArgs);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                deletedRows = db.delete("Category", "id=?", new String[]{categoryId});
                break;
            default:
                break;
        }
        return deletedRows;
    }

    @Override
    public String getType(Uri uri) {
        String type = null;
        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
                type = "vnd.android.cursor.dir/vnd.com.lhh.databasetest.provider.book";
                break;
            case BOOK_ITEM:
                type = "vnd.android.cursor.item/vnd.com.lhh.databasetest.provider.book";
                break;
            case CATEGORY_DIR:
                type = "vnd.android.cursor.dir/vnd.com.lhh.databasetest.provider.category";
                break;
            case CATEGORY_ITEM:
                type = "vnd.android.cursor.item/vnd.com.lhh.databasetest.provider.category";
                break;
            default:
                break;
        }
        return type;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        Uri uriReturn = null;
        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
            case BOOK_ITEM:
                long bookId = db.insert("Book", null, values);
                uriReturn = Uri.parse("content://" + AUTHORITY + "/book/" + bookId);
                break;
            case CATEGORY_DIR:
            case CATEGORY_ITEM:
                long categoryId = db.insert("Category", null, values);
                uriReturn = Uri.parse("content://" + AUTHORITY + "/category/" + categoryId);
                break;
            default:
                break;
        }
        return uriReturn;
    }

    @Override
    public boolean onCreate() {
        dbHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 2);
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        SQLiteDatabase db = dbHelper.getReadableDatabase();
        Cursor cursor = null;
        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
                cursor = db.query("Book", projection, selection, selectionArgs,
                        null, null, sortOrder);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                cursor = db.query("Book", projection, "id=?", new String[]{bookId},
                        null, null, sortOrder);
                break;
            case CATEGORY_DIR:
                cursor = db.query("Category", projection, selection, selectionArgs,
                        null, null, sortOrder);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                cursor = db.query("Category", projection, "id=?", new String[]{categoryId},
                        null, null, sortOrder);
                break;
            default:
                break;
        }
        return cursor;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection,
                      String[] selectionArgs) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();
        int updateRows = 0;
        switch (uriMatcher.match(uri)) {
            case BOOK_DIR:
                updateRows = db.update("Book", values, selection, selectionArgs);
                break;
            case BOOK_ITEM:
                String bookId = uri.getPathSegments().get(1);
                updateRows = db.update("Book", values, "id=?", new String[]{bookId});
                break;
            case CATEGORY_DIR:
                updateRows = db.update("Category", values, selection, selectionArgs);
                break;
            case CATEGORY_ITEM:
                String categoryId = uri.getPathSegments().get(1);
                updateRows = db.update("Category", values, "id=?", new String[]{categoryId});
                break;
            default:
                break;
        }
        return updateRows;
    }
}

2. 在AndroidManifest.xml中注册内容提供器：

	<provider
	    android:name=".DatabaseProvider"
	    android:authorities="com.lhh.databasetest.provider"
	    android:enabled="true"
	    android:exported="true"/>

android:name属性表示提供程序类名
android:authorities属性表示内容提供器的标识
android:enable属性表示是否启用
android:exported属性表示是否允许其他程序访问

3. 在其他程序中访问内容提供器

switch (v.getId()) {
	case R.id.add_data:
	    Uri uri = Uri.parse("content://com.lhh.databasetest.provider/book");
	    ContentValues values = new ContentValues();
	    values.put("name", "A * of Kings");
	    values.put("author", "George Martin");
	    values.put("pages", 1040);
	    values.put("price", 22.85);
	    Uri newUri = getContentResolver().insert(uri, values);
	    newId = newUri.getPathSegments().get(1);
	    break;
	case R.id.query_data:
	    Uri uri1 = Uri.parse("content://com.lhh.databasetest.provider/book");
	    Cursor cursor = getContentResolver().query(uri1, null, null, null, null, null);
	    if (cursor != null) {
	        while (cursor.moveToNext()) {
	            String name = cursor.getString(cursor.getColumnIndex("name"));
	            String author = cursor.getString(cursor.getColumnIndex("author"));
	            int pages = cursor.getInt(cursor.getColumnIndex("pages"));
	            double price = cursor.getDouble(cursor.getColumnIndex("price"));
	            Log.i(TAG, "onClick: name: " + name);
	            Log.i(TAG, "onClick: author: " + author);
	            Log.i(TAG, "onClick: pages: " + pages);
	            Log.i(TAG, "onClick: price: " + price);
	        }
	        cursor.close();
	    }
	    break;
	case R.id.update_data:
	    Uri uri2 = Uri.parse("content://com.lhh.databasetest.provider/book/" + newId);
	    ContentValues values2 = new ContentValues();
	    values2.put("name", "A Storm of Swords");
	    values2.put("pages", 1216);
	    values2.put("price", 24.05);
	    getContentResolver().update(uri2, values2, null, null);
	    break;
	case R.id.delete_data:
	    Uri uri3 = Uri.parse("content://com.lhh.databasetest.provider/book/" + newId);
	    getContentResolver().delete(uri3, null, null);
	    break;
	default:
	    break;
	}

本文地址：https://blog.csdn.net/qq_28673129/article/details/110502546