Content Provider使用

 

1、Content Provider基本概念

一、Content Provider提供爲存儲和獲取數據提供了統一的接口

二、使用Content Provider能夠再不一樣的應用程序間共享數據

三、Android爲常見的一些數據提供了ContentPrivater（包括音頻、視頻、圖片和通信錄等等）

數據模型

ContentProider使用表的形式來組織數據

URI

一、每個ContentProvider都擁有一個公共的URI，這個URI用於表示這個ContentProvider所提供的數據。

二、Android所提供的ContentProvider存存放在android.provider

ContentProvider 所提供的函數

一、query() 查詢

二、insert() 插入

三、update() 更新

四、delete() 刪除

五、getType() 獲得數據類型

六、onCreate() 建立時回調函數

實現ContentProvider的過程

一、定義一個CONTENT_URI常量

二、定義一個類，繼承ContentProvider

三、實現query，insert，update，delete，getType，onCreate方法

四、在AndroidManifest.xml當中進行聲明

package com.zyf.testcp;

import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class CPActivity extends Activity {
	
	Button insertButton;
	Button queryButton;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.mian);
		insertButton = (Button) findViewById(R.id.insetButton);
		queryButton = (Button) findViewById(R.id.queryButton);
		insertButton.setOnClickListener(new InsertListener());
		queryButton.setOnClickListener(new QueryListener());
	}
	
	class InsertListener implements OnClickListener{

		@Override
		public void onClick(View v) {
			ContentValues values = new ContentValues();
			values.put(FirstProviderMetaData.UserTableMetaData.USER_NAME, 
					"張三");
			Uri uri = getContentResolver().insert(
					FirstProviderMetaData.UserTableMetaData.CONTENT_URI,
					values);
			System.out.println("uri--->"+uri.toString());
		}
		
	}
	class QueryListener implements OnClickListener{
		
		@Override
		public void onClick(View v) {
			Cursor c = getContentResolver().query(
					FirstProviderMetaData.UserTableMetaData.CONTENT_URI, 
					null, null, null, null);
			while(c.moveToNext()){
				System.out.println(c);
				
				int id = c.getInt(c.getColumnIndex(FirstProviderMetaData.UserTableMetaData._ID));
				String name = c.getString(c.getColumnIndex(FirstProviderMetaData.UserTableMetaData.USER_NAME));
				System.out.println("ID==>"+id+";NAME->"+name);
			}
			
		}
		
	}
	
}

package com.zyf.testcp;

import android.net.Uri;
import android.provider.BaseColumns;

public class FirstProviderMetaData {
	public static final String AUTHORIY = "com.zyf.testcp.FirstContentProvider";
	//數據庫名稱
	public static final String DATABASE_NAME = "FirstProvider.db";
	//數據庫的版本
	public static final int DATABASE_VERSION = 1;
	//表名
	public static final String USERS_TABLE_NAME = "users";
	
	public static final class UserTableMetaData implements BaseColumns{
		//表名
		public static final String TABLE_NAME = "users";
		//訪問該ContentProvider的Uri
		public static final Uri CONTENT_URI = Uri.parse("content://"+AUTHORIY+"/users");
		//該ContentProvider所返回的數據類型的定義
		public static final String CONTENT_TYPE ="vnd.android.cursor.dir/vnd.firstprovider.user";
		public static final String CONTENT_TYPE_ITEM ="vnd.android.cursor.item/vnd.firstprovider.user";
		//列名
		public static final String USER_NAME = "name";
		//默認排序方法
		public static final String DEFAULT_SORT_ORDER = "_id desc";
	}
}

package com.zyf.testcp;

import java.util.HashMap;

import com.zyf.db.DatabaseHelper;
import com.zyf.testcp.FirstProviderMetaData.UserTableMetaData;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.text.TextUtils;

public class FirstContentProvider extends ContentProvider{
	
	public static final UriMatcher uriMatcher;
	public static final int INCOMING_USER_COLLECTION = 1;
	public static final int INCOMING_USER_SINGLE = 2;
	private DatabaseHelper dh;
	
	static{
		uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
		uriMatcher.addURI(FirstProviderMetaData.AUTHORIY, "users", 
				INCOMING_USER_COLLECTION);
		uriMatcher.addURI(FirstProviderMetaData.AUTHORIY, "users/#", 
				INCOMING_USER_SINGLE);
	}
	
	public static HashMap<String, String> userProjectionMap;
	static{
		userProjectionMap = new HashMap<String, String>();
		userProjectionMap.put(UserTableMetaData._ID, UserTableMetaData._ID);
		userProjectionMap.put(UserTableMetaData.USER_NAME, UserTableMetaData.USER_NAME);
	}
	
	@Override
	public int delete(Uri arg0, String arg1, String[] arg2) {
		System.out.println("delete");
		return 0;
	}
	
	/**
	 * 根據傳入的Uri，返回該Uri所表示的數據類型
	 */
	@Override
	public String getType(Uri uri) {
		// TODO Auto-generated method stub
		System.out.println("getType");
		switch(uriMatcher.match(uri)){
			case INCOMING_USER_COLLECTION:
				return UserTableMetaData.CONTENT_TYPE;
			case INCOMING_USER_SINGLE:
				return UserTableMetaData.CONTENT_TYPE_ITEM;
			default:
				throw new IllegalArgumentException("Unknow URI"+uri);
		}
	}
	
	/**
	 * 該函數的返回值是一個Uri，這個Uri表示的是剛剛使用這個函數所插入的數據
	 * content://com.zyf.cp.FirstContentProvider/users/1
	 */
	@Override
	public Uri insert(Uri uri, ContentValues values) {
		// TODO Auto-generated method stub
		System.out.println("insert");
		SQLiteDatabase db = dh.getWritableDatabase();
		long rowId = db.insert(UserTableMetaData.TABLE_NAME, null, values);
		if(rowId>0){
			Uri insertedUserUri = ContentUris.withAppendedId(UserTableMetaData.CONTENT_URI, rowId);
			//通知監聽器，數據已經改變
			getContext().getContentResolver().notifyChange(insertedUserUri, null);
			System.out.println(insertedUserUri);
			return insertedUserUri;
		}
		throw new SQLException("Failed to insert row into"+uri);
	}

	@Override
	public boolean onCreate() {
		dh = new DatabaseHelper(getContext(), FirstProviderMetaData.DATABASE_NAME);
		System.out.println("onCreate");
		return true;
	}

	@Override
	public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
			String sortOrder) {
		SQLiteQueryBuilder qb = new SQLiteQueryBuilder();
		switch (uriMatcher.match(uri)) {
		case INCOMING_USER_COLLECTION:
			qb.setTables(UserTableMetaData.TABLE_NAME);
			qb.setProjectionMap(userProjectionMap);
			break;
		case INCOMING_USER_SINGLE:
			qb.setTables(UserTableMetaData.TABLE_NAME);
			qb.setProjectionMap(userProjectionMap);
			qb.appendWhere(UserTableMetaData._ID + "=" + uri.getPathSegments().get(1));
			break; 
		}
		String orderBy;
		if(TextUtils.isEmpty(sortOrder)){
			orderBy = UserTableMetaData.DEFAULT_SORT_ORDER;
		}else{
			orderBy = sortOrder;
		}
		SQLiteDatabase db = dh.getWritableDatabase();
		Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);
		c.setNotificationUri(getContext().getContentResolver(),uri);
		System.out.println("query");
		return c;
	}

	@Override
	public int update(Uri arg0, ContentValues values, String whereClause, String[] whereArgs) {
		// TODO Auto-generated method stub
		System.out.println("insert");
		SQLiteDatabase db = dh.getWritableDatabase();
		long rowId = db.update(UserTableMetaData.TABLE_NAME, values, whereClause, whereArgs);
		Uri insertedUserUri = ContentUris.withAppendedId(UserTableMetaData.CONTENT_URI, rowId);
		getContext().getContentResolver().notifyChange(insertedUserUri, null);
		
		return 0;
	}

}

package com.zyf.db;

import com.zyf.testcp.FirstProviderMetaData;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

//DatabaseHelper做爲一個訪問SQLite的助手類，提供兩個方面的功能
//第一，getReadableDatabase(),getWriteableDatabase()能夠得到SQLiteDatabase對象，經過對象能夠對數據庫進行
//第二，提供了onCreate()和onUpdate()兩個回調函數,容許咱們在建立和升級數據庫的時候，進行本身的操做
public class DatabaseHelper extends SQLiteOpenHelper{
	
	private static final int VERSION = 1;
	
	public DatabaseHelper(Context context, String name, CursorFactory factory,
			int version) {
		super(context, name, factory, version);
		// TODO Auto-generated constructor stub
	}
	public DatabaseHelper(Context context, String name){
		this(context, name, VERSION);
	}
	

	public DatabaseHelper(Context context, String name, int version) {
		this(context, name, null,version);
	}
	//該函數在第一次建立數據庫的時候執行，其實是在第一次獲得SQLiteDatabase對象的時候，纔會調用這個方法
	@Override
	public void onCreate(SQLiteDatabase db) {
		// TODO Auto-generated method stub
		System.out.println("create a Database");
		db.execSQL("create table " + FirstProviderMetaData.USERS_TABLE_NAME+
				"("+FirstProviderMetaData.UserTableMetaData._ID+" " +
				"INTEGER PRIMARY KEY AUTOINCREMENT," +
				FirstProviderMetaData.UserTableMetaData.USER_NAME+" varchar(20));");
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		// TODO Auto-generated method stub
		System.out.println("update a Database");
	}

}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.zyf.testcp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".CPActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <provider 
            android:name="com.zyf.testcp.FirstContentProvider"
            android:authorities="com.zyf.testcp.FirstContentProvider"></provider>
    </application>

</manifest>

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

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
    <Button
        android:id="@+id/insetButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="插入數據" />
    <Button
        android:id="@+id/queryButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="查詢數據" />

</LinearLayout>