android中contentProvider及ContentResolver

野性酷女 2023-01-05 05:28 182阅读 0赞

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这个技术是解决应用之间的一个调用，如常见的应用间数据库查询，内容提供者暴露接口，内容解析器ContentResolver通过调用相应CRUD接口，内容提供者需要在清单文件进行定义。  
案例：  
我们新建一个PersonProvider继承ContentProvider，并在CRUD实现上借助Sqlite工具类进行操作。  
这个同时需要理解一些理论性的知识，如URI的格式content://com.hbk.hbk\_provider.personprovider/person/3  
调用的URI是否合法，用到的相关API，有  
UriMatcher.addURI(String authority, String path, int code) // 添加合法URI  
int android.content.UriMatcher.match(Uri uri)// 判断Uri是否合法  
long android.content.ContentUris.parseId(Uri contentUri)// 提取uri的id  
Uri ContentUris.withAppendedId(Uri contentUri, long id)// 这个一般用在插入，使得插入后的Uri有id值

PersonProvider.java

package com.hbk.hbk_provider;
    
    import org.apache.http.client.utils.URIUtils;
    
    import android.content.ContentProvider;
    import android.content.ContentUris;
    import android.content.ContentValues;
    import android.content.UriMatcher;
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;
    import android.net.Uri;
    import android.util.Log;
    
    public class PersonProvider extends ContentProvider { 
    
    	private DbHelper dbHelper;
    	private static UriMatcher matchers = new UriMatcher(UriMatcher.NO_MATCH);
    	
    	static{ 
    		matchers.addURI("com.hbk.hbk_provider.personprovider", "/person", 1);
    		matchers.addURI("com.hbk.hbk_provider.personprovider", "/person/#", 2);//#匹配任意数字
    	}
    	
    	public PersonProvider() { 
    		Log.e("TAG", "PersonProvider()");
    	}
    	@Override
    	public boolean onCreate() { 
    		Log.e("TAG", "PersonProvider onCreate()");
    		dbHelper = new DbHelper(getContext());
    		return false;
    	}
    
    	/** * content://com.hbk.hbk_provider.personprovider/person 不根据id查询 * content://com.hbk.hbk_provider.personprovider/person/3 根据id查询 */
    	@Override
    	public Cursor query(Uri uri, String[] projection, String selection,
    			String[] selectionArgs, String sortOrder) { 
    		SQLiteDatabase database = dbHelper.getReadableDatabase();
    		// 根据
    		int code = matchers.match(uri);
    		if(code == 1){ //不根据id查询
    			// 
    			Cursor cursor = database.query("person", projection, selection, selectionArgs, null, null, null);
    			return cursor;
    		}else if(code == 2){ 
    			// 根据id查询
    			long id = ContentUris.parseId(uri);
    			Cursor cursor = database.query("person", projection, "_id=?", new String[]{ id+""}, null, null, null);
    			return cursor;
    		}else{ 
    			throw new RuntimeException("查询的uri不合法");
    		}
    	}
    
    	@Override
    	public String getType(Uri uri) { 
    		// TODO Auto-generated method stub
    		return null;
    	}
    
    	/** * content://com.hbk.hbk_provider.personprovider/person 插入 * content://com.hbk.hbk_provider.personprovider/person/3 根据id插入(没有) */
    	@Override
    	public Uri insert(Uri uri, ContentValues values) { 
    		SQLiteDatabase database = dbHelper.getReadableDatabase();
    		int code = matchers.match(uri);
    		if(code == 1){ //不根据id查询
    			// 
    			long id = database.insert("person", null, values);
    			uri = ContentUris.withAppendedId(uri, id);
    			database.close();
    			return uri;	
    		}else { 
    			database.close();
    			throw new RuntimeException("插入的uri不合法");
    		}
    	}
    
    	/** * content://com.hbk.hbk_provider.personprovider/person 不根据id删除 * content://com.hbk.hbk_provider.personprovider/person/3 根据id删除 */
    	@Override
    	public int delete(Uri uri, String selection, String[] selectionArgs) { 
    		SQLiteDatabase database = dbHelper.getReadableDatabase();
    		int code = matchers.match(uri);
    		int deleteCount = -1;
    		if(code == 1){ //不根据id删除
    			deleteCount = database.delete("person", selection, selectionArgs);
    		}else if(code == 2){ 
    			long id = ContentUris.parseId(uri);
    			deleteCount = database.delete("person", "_id="+id, null);
    		}else{ 
    			database.close();
    			throw new RuntimeException("删除的uri不合法");
    		}
    		database.close();
    		return deleteCount;
    	}
    
    
    	/** * content://com.hbk.hbk_provider.personprovider/person 不根据id更新 * content://com.hbk.hbk_provider.personprovider/person/3 根据id更新 */
    	@Override
    	public int update(Uri uri, ContentValues values, String selection,
    			String[] selectionArgs) { 
    		SQLiteDatabase database = dbHelper.getReadableDatabase();
    		int code = matchers.match(uri);
    		int updateCount = -1;
    		if(code == 1){ //不根据id更新
    			updateCount = database.update("person", values, selection, selectionArgs);
    		}else if(code == 2){ 
    			long id = ContentUris.parseId(uri);
    			updateCount = database.update("person", values, "_id="+id, null);
    		}else{ 
    			database.close();
    			throw new RuntimeException("更新的uri不合法");
    		}
    		database.close();
    		return updateCount;
    	}
    
    }

在清单文件中进行定义，exported为true表示允许其他营业进行调用，一般authorities的值为全类名小写，这个提供给内容解析器进行标识的字符串。

DbHelper.java常用的工具类

package com.hbk.hbk_provider;
    
    import android.content.Context;
    import android.database.sqlite.SQLiteDatabase;
    import android.database.sqlite.SQLiteOpenHelper;
    import android.util.Log;
    
    public class DbHelper extends SQLiteOpenHelper { 
    
    	public DbHelper(Context context) { 
    		super(context, "huangbaokang.db", null,1);
    	}
    
    	@Override
    	public void onCreate(SQLiteDatabase db) { 
    		Log.i("TAG","建表。。。");
    		db.execSQL("create table person(_id integer primary key autoincrement,name varchar)");
    		db.execSQL("insert into person(name) values('huangbaokang')");
    	}
    
    	@Override
    	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    
    	}
    
    }

内容解析调用方android工程  
布局  
![在这里插入图片描述][20210111211859334.png]

处理Activity

package com.hbk.hbk_resolver;
    
    import android.app.Activity;
    import android.content.ContentResolver;
    import android.content.ContentValues;
    import android.database.Cursor;
    import android.net.Uri;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Toast;
    
    public class MainActivity extends Activity { 
    
    	@Override
    	protected void onCreate(Bundle savedInstanceState) { 
    		super.onCreate(savedInstanceState);
    		setContentView(R.layout.activity_main);
    	}
    	
    	/* * 通过ContentResolver调用ContentProvider插入一条记录 */
    	public void insert(View v) { 
    		//1. 得到ContentResolver对象
    		ContentResolver resolver = getContentResolver();
    		//2. 调用其insert
    		Uri uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person");
    		//uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person/3");//将抛异常
    		ContentValues values = new ContentValues();
    		values.put("name", "JACK");
    		uri = resolver.insert(uri, values);
    		
    		Toast.makeText(this, uri.toString(), 1).show();
    	}
    
    	/* * 通过ContentResolver调用ContentProvider更新一条记录 */
    	public void update(View v) { 
    		//1. 得到ContentResolver对象
    		ContentResolver resolver = getContentResolver();
    		//2. 执行update
    		Uri uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person/2");
    		ContentValues values = new ContentValues();
    		values.put("name", "JACK2");
    		int updateCount = resolver.update(uri, values, null, null);
    		
    		Toast.makeText(this, "updateCount="+updateCount, 1).show();
    	}
    
    	/* * 通过ContentResolver调用ContentProvider删除一条记录 */
    	public void delete(View v) { 
    		//1. 得到ContentResolver对象
    		ContentResolver resolver = getContentResolver();
    		//2. 执行delete
    		Uri uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person/2");
    		int deleteCount = resolver.delete(uri, null, null);
    		Toast.makeText(this, "deleteCount="+deleteCount, 1).show();
    	}
    	public void query(View v){ 
    		ContentResolver contentResolver = getContentResolver();
    		//2. 调用其query, 得到cursor
    		Uri uri = Uri.parse("content://com.hbk.hbk_provider.personprovider/person");
    		Cursor cursor = contentResolver.query(uri, null, null, null, null);
    		while(cursor.moveToNext()){ 
    			int id = cursor.getInt(0);
    			String name = cursor.getString(1);
    			Toast.makeText(this, "id="+id+" name="+name, 0).show();
    		}
    		cursor.close();
    	}
    }

工程架构  
![在这里插入图片描述][20210111212027978.png]  
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![在这里插入图片描述][20210511091712437.png_pic_center]

[Link 1]: https://www.captainai.net/flyop007/
[20210111211859334.png]: /images/20221119/902b6ec347234cad86346f58918b56c4.png
[20210111212027978.png]: /images/20221119/e04fe2caaa194db5971aa7afd87d6b29.png
[20210511091712437.png_pic_center]: https://img-blog.csdnimg.cn/20210511091712437.png#pic_center