android中contentProvider及ContentResolver

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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。

 <provider android:name="com.hbk.hbk_provider.PersonProvider" android:authorities="com.hbk.hbk_provider.personprovider" android:exported="true"/>

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

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="insert"
        android:text="INSERT" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="delete"
        android:text="DELETE" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="update"
        android:text="UPDATE" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="query"
        android:text="QUERY" />

</LinearLayout>

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