自定义ContentProvider

最新推荐文章于 2025-08-22 11:10:38 发布

HelloAndroid

最新推荐文章于 2025-08-22 11:10:38 发布

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分类专栏：数据存储文章标签： string null table database 数据库 class

本文链接：https://blog.youkuaiyun.com/csqyhmnc/article/details/6595338

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本文介绍了一个自定义的ContentProvider组件——NotePad，用于管理和提供笔记数据。NotePad通过定义特定的URI、MIME类型和数据库表结构来实现数据的增删改查功能，并在AndroidManifest.xml中进行了声明。

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工程1自定义ContentProvider：

NotePad.java:

public class NotePad 
{
	//ContentProvider的uri
	public static final String	AUTHORITY	= "com.google.provider.csqNotePad";
	
	//BaseColumns是一个常量接口，里面有一个"_id和"_count"字符串常量
	public static class Notes implements BaseColumns
	{
		//访问URI
		public static final Uri	 CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/notes");
		
		// 内容类型，新的MIME类型-多个
		public static final String	CONTENT_TYPE		= "vnd.android.cursor.dir/vnd.google.note";
		// 新的MIME类型-单个
		public static final String	CONTENT_ITEM_TYPE	= "vnd.android.cursor.item/vnd.google.note";

		//默认排序常量，按id排序
		public static final String	DEFAULT_SORT_ORDER	= "_id DESC";
		
		//字段
		public static final String	TITLE	 = "title";
		public static final String	NOTE	 = "note";
	}
}

MyProvider.java:

public class MyProvider extends ContentProvider
{
	private DatabaseHelper mOpenHelper = null;
	
	private static final UriMatcher sUriMatcher;
	private static HashMap<String, String> sNotesProjectionMap;
	static {
		sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
		sUriMatcher.addURI(NotePad.AUTHORITY, "notes", 1);
		sUriMatcher.addURI(NotePad.AUTHORITY, "notes/#", 2);
		
		sNotesProjectionMap = new HashMap<String, String>();
		sNotesProjectionMap.put(NotePad.Notes._ID, NotePad.Notes._ID);
		sNotesProjectionMap.put(NotePad.Notes.TITLE, NotePad.Notes.TITLE);
		sNotesProjectionMap.put(NotePad.Notes.NOTE, NotePad.Notes.NOTE);
	}
	
	
	
	// 数据库名
	private static final String DATABASE_NAME = "cptest.db";
	private static final int DATABASE_VERSION = 2;
	// 表名
	private static final String NOTES_TABLE_NAME = "notes";
	// 创建表SQL语句
	private static final String
	CREATE_TABLE = "CREATE TABLE " + NOTES_TABLE_NAME + " (" + NotePad.Notes._ID
			+ " INTEGER PRIMARY KEY," + NotePad.Notes.TITLE + " TEXT," + NotePad.Notes.NOTE
			+ " TEXT" + ");";
	//内部类SQLiteOpenHelper
	private static class DatabaseHelper extends SQLiteOpenHelper 
	{
		public DatabaseHelper(Context context) 
		{
			super(context, DATABASE_NAME, null, DATABASE_VERSION);
		}

		public void onCreate(SQLiteDatabase db) 
		{
			db.execSQL(CREATE_TABLE);
		}

		public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
		{
			db.execSQL("DROP TABLE IF EXISTS notes");
			onCreate(db);
		}
	}
	
	
	
	
	//创建
	public boolean onCreate() 
	{
		mOpenHelper = new DatabaseHelper(getContext());
		return true;
	}
	
	// 查询操作
	public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
			String sortOrder) 
	{
		SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
		
		switch (sUriMatcher.match(uri)) 
		{
		case 1://notes，所有
			qb.setTables(NOTES_TABLE_NAME);	
			qb.setProjectionMap(sNotesProjectionMap);
			break;
		case 2://notes/#，根据id查询
			qb.setTables(NOTES_TABLE_NAME);
			qb.setProjectionMap(sNotesProjectionMap);
			qb.appendWhere(NotePad.Notes._ID + "=" + uri.getPathSegments().get(1));
			break;
		default:
			throw new IllegalArgumentException("Unknown URI " + uri);
		}
		
		//排序方式
		String orderBy;
		if (sortOrder == null) {
			orderBy = NotePad.Notes.DEFAULT_SORT_ORDER;
		} else {
			orderBy = sortOrder;
		}
		
		//获取数据库实例
		SQLiteDatabase db = mOpenHelper.getWritableDatabase();
		
		//返回游标集合
		Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);
		c.setNotificationUri(getContext().getContentResolver(), uri);
		return c;
	}
	
	// 插入数据库
	public Uri insert(Uri uri, ContentValues initialValues) 
	{
		if (sUriMatcher.match(uri) != 1) 
		{
			throw new IllegalArgumentException("Unknown URI " + uri);
		}
		
		ContentValues cv;
		if (initialValues != null) 
		{
			cv = new ContentValues(initialValues);
		} else {
			cv = new ContentValues();
		}
		
		if (cv.containsKey(NotePad.Notes.TITLE) == false) 
		{
			Resources r = Resources.getSystem();
			cv.put(NotePad.Notes.TITLE,
					r.getString(android.R.string.untitled));
		}
		if (cv.containsKey(NotePad.Notes.NOTE) == false) 
		{
			cv.put(NotePad.Notes.NOTE, "");
		}
		
		//获取数据库实例
		SQLiteDatabase db = mOpenHelper.getWritableDatabase();
		//插入数据，返回id
		long rowId = db.insert(NOTES_TABLE_NAME, NotePad.Notes.NOTE, cv);
		//如果成功插入返回uri
		if (rowId > 0) 
		{
			Uri noteUri = ContentUris.withAppendedId(NotePad.Notes.CONTENT_URI,rowId);
			getContext().getContentResolver().notifyChange(noteUri, null);
			return noteUri;
		}
		return null;
	}
	
	//删除数据
	public int delete(Uri uri, String where, String[] whereArgs) 
	{
		//获取数据库实例
		SQLiteDatabase db = mOpenHelper.getWritableDatabase();
		
		int count;
		//根据指定条件删除
		switch (sUriMatcher.match(uri)) 
		{
		case 1:
			count = db.delete(NOTES_TABLE_NAME, where, whereArgs);
			break;
		case 2:
			String noteId = uri.getPathSegments().get(1);
			count = db.delete(NOTES_TABLE_NAME,
				NotePad.Notes._ID + "=" + noteId + (!where.isEmpty() ? " AND (" + where+ ")" : ""), 
				whereArgs);
			break;
		default:
			throw new IllegalArgumentException("Unknown URI " + uri);
		}
		
		getContext().getContentResolver().notifyChange(uri, null);
		
		return count;
	}

	// 更新数据
	public int update(Uri uri, ContentValues values, String where, String[] whereArgs) 
	{
		//获取数据库实例
		SQLiteDatabase db = mOpenHelper.getWritableDatabase();
		
		int count;
		//根据指定条件更新
		switch (sUriMatcher.match(uri)) 
		{
		case 1:
			count = db.update(NOTES_TABLE_NAME, values, where, whereArgs);
			break;
		case 2:
			String noteId = uri.getPathSegments().get(1);
			count = db.update(NOTES_TABLE_NAME, values,
					NotePad.Notes._ID + "=" + noteId + (!where.isEmpty() ? " AND (" + where
									+ ")" : ""), 
					whereArgs);
			break;
		default:
			throw new IllegalArgumentException("Unknown URI " + uri);
		}

		getContext().getContentResolver().notifyChange(uri, null);
		return count;
	}
	
	// 如果有自定义类型，必须实现该方法
	public String getType(Uri uri) 
	{
		switch (sUriMatcher.match(uri)) 
		{
		case 1:
			return NotePad.Notes.CONTENT_TYPE;

		case 2:
			return NotePad.Notes.CONTENT_ITEM_TYPE;

		default:
			throw new IllegalArgumentException("Unknown URI " + uri);
		}
	}
	
}

在AndroidMainfest.xml中声明：

在此工程Activity中测试：

public class MainActivity extends Activity 
{
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        /* 插入数据 */
		ContentValues values = new ContentValues();
        values.put(NotePad.Notes.TITLE, "title1");
        values.put(NotePad.Notes.NOTE, "note1");
		getContentResolver().insert(NotePad.Notes.CONTENT_URI, values);

		values.clear();
        values.put(NotePad.Notes.TITLE, "title2");
        values.put(NotePad.Notes.NOTE, "note2");
		getContentResolver().insert(NotePad.Notes.CONTENT_URI, values);
		
		/* 显示 */
		displayNote();
		Log.i("displayNote", "****************************************");
		updateFirst();
		displayNote();
		Log.i("displayNote", "****************************************");
		deleteFirst();
		displayNote();
		Log.i("displayNote", "****************************************");
    }
    
    private void displayNote()
	{
		String[] columns = new String[] { NotePad.Notes._ID, 
										  NotePad.Notes.TITLE, 
										  NotePad.Notes.NOTE, 
										};
		
		Uri myUri = NotePad.Notes.CONTENT_URI;
		
		Cursor cur = managedQuery(myUri, columns, null, null, null);
		
		for(cur.moveToFirst();!cur.isAfterLast();cur.moveToNext())
		{
			String id = cur.getString(cur.getColumnIndex(NotePad.Notes._ID));
			String title = cur.getString(cur.getColumnIndex(NotePad.Notes.TITLE));
			String note = cur.getString(cur.getColumnIndex(NotePad.Notes.NOTE));
			Log.i("displayNote", "id="+id+", title="+title+", note="+note);
		}
	}
    
    private void updateFirst()
	{
		ContentValues values = new ContentValues();
        values.put(NotePad.Notes.TITLE, "update1");
        values.put(NotePad.Notes.NOTE, "updatenote1");
        
    	getContentResolver().update(NotePad.Notes.CONTENT_URI, values, NotePad.Notes._ID +"=1", null);
	}
    
    private void deleteFirst()
	{
		ContentValues values = new ContentValues();
        values.put(NotePad.Notes.TITLE, "update1");
        values.put(NotePad.Notes.NOTE, "updatenote1");
        
    	getContentResolver().delete(NotePad.Notes.CONTENT_URI, NotePad.Notes._ID +"=1", null);
	}
    
}

新建一工程，在工程外调用：
需要权限：

<uses-permission android:name="android.permission.WRITE_CONTACTS"></uses-permission>
<uses-permission android:name="android.permission.READ_CONTACTS"></uses-permission>
测试程序：

public class MainActivity extends Activity 
{
	Uri uri = Uri.parse("content://com.google.provider.csqNotePad/notes");
	
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        /* 插入数据 */
		ContentValues values = new ContentValues();
        values.put("title", "title1");
        values.put("note", "note1");
		getContentResolver().insert(uri, values);
		values.clear();
        values.put("title", "title2");
        values.put("note", "note2");
		getContentResolver().insert(uri, values);
		
		/* 显示 */
		displayNote();
		Log.i("displayNote", "****************************************");
		updateFirst();
		displayNote();
		Log.i("displayNote", "****************************************");
		deleteFirst();
		displayNote();
		Log.i("displayNote", "****************************************");
    }
    
    
    private void displayNote()
	{
		String[] columns = new String[] { "_id", "title",  "note"};
		
		Cursor cur = managedQuery(uri, columns, null, null, null);
		
		for(cur.moveToFirst();!cur.isAfterLast();cur.moveToNext())
		{
			String id = cur.getString(cur.getColumnIndex("_id"));
			String title = cur.getString(cur.getColumnIndex("title"));
			String note = cur.getString(cur.getColumnIndex("note"));
			Log.i("displayNote", "id="+id+", title="+title+", note="+note);
		}
	}
    
    private void updateFirst()
	{
		ContentValues values = new ContentValues();
        values.put("title", "update1");
        values.put("note", "updatenote1");
        
    	getContentResolver().update(uri, values, "title = 'title1'", null);
	}
    
    private void deleteFirst()
	{
    	getContentResolver().delete(uri, "title = 'update1'", null);
	}
    
    
}