AndroidContentProvider——13

ContentProvider
1.ContentProvider为存储和获取数据提供了统一的接口

2.使用ContentProvider可以在不同的应用程序之间共享数据

URI
1.每一个ContentProvider都拥有一个公共的URI,这个URI用于表示这个ContentProvider所提供的数据。

2.Android所提供的ContentProvider都存放在android.provider包当中。

ContentProvider所提供的函数
1.query()：查询
2.insert()：插入
3.update()：更新
4.delete()：删除
5.getType()：得到数据类型

6.onCreate()：创建时的回调函数

实现ContentProvider的过程
1.定义一个CONTENT_URI常量
2.定义一个类，继承ContentProvider
3.实现query,insert,update,delete,getType和onCreate方法

4.在AndroidManifest.xml当中进行声明

package com.example.contentprovider;import com.example.contentprovider.FirstProviderMetaData.UserTableMetaData;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;public class DBHelper extends SQLiteOpenHelper{public static final String DATABASE_NAME = "FirstProvider.db";public static final int DATABASE_VERSION = 1;public DBHelper(Context context) {super(context, DATABASE_NAME, null, DATABASE_VERSION);}@Overridepublic void onCreate(SQLiteDatabase db) {System.out.println("create a Database");String sql = "create table " + UserTableMetaData.TABLE_NAME + "(" + UserTableMetaData._ID + " integer," + UserTableMetaData.USER_NAME + " varchar(20))";db.execSQL(sql);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {System.out.println("update a Database");}}

package com.example.contentprovider;import android.net.Uri;import android.provider.BaseColumns;public class FirstProviderMetaData {public static final String AUTHORIY = "com.example.contentprovider.FirstContentProvider";public static final class UserTableMetaData implements BaseColumns{public static final String TABLE_NAME = "users";public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORIY + "/users");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";public static final String USER_NAME = "name";public static final String DEFAULT_SORT_ORDER = "_id desc";}}

package com.example.contentprovider;import java.util.HashMap;import com.example.contentprovider.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 DBHelper dh;static{uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);//把繁琐的地址变成一个标识符uriMatcher.addURI(FirstProviderMetaData.AUTHORIY, "users", INCOMING_USER_COLLECTION);uriMatcher.addURI(FirstProviderMetaData.AUTHORIY, "users/#", INCOMING_USER_SINGLE);}public static HashMap<String, String> userProjectMap;static{userProjectMap = new HashMap<String, String>();userProjectMap.put(UserTableMetaData._ID, UserTableMetaData._ID);userProjectMap.put(UserTableMetaData.USER_NAME, UserTableMetaData.USER_NAME);}@Overridepublic int delete(Uri arg0, String arg1, String[] arg2) {return 0;}@Overridepublic String getType(Uri uri) {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("Unknown URI" + uri);}}@Overridepublic Uri insert(Uri uri, ContentValues values) {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);getContext().getContentResolver().notifyChange(insertedUserUri, null);return insertedUserUri;}throw new SQLException("Failed to insert row into" + uri);}@Overridepublic boolean onCreate() {dh = new DBHelper(getContext());System.out.println("onCreate");return false;}@Overridepublic 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(userProjectMap);break;case INCOMING_USER_SINGLE:qb.setTables(UserTableMetaData.TABLE_NAME);qb.setProjectionMap(userProjectMap);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, sortOrder);c.setNotificationUri(getContext().getContentResolver(), uri);System.out.println("query");return c;}@Overridepublic int update(Uri arg0, ContentValues arg1, String arg2, String[] arg3) {return 0;}}

package com.example.contentprovider;import com.example.contentprovider.FirstProviderMetaData.UserTableMetaData;import android.net.Uri;import android.os.Bundle;import android.app.Activity;import android.content.ContentValues;import android.database.Cursor;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class MainActivity extends Activity {Button insertButton;Button queryButton;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);insertButton = (Button) findViewById(R.id.insertButton);queryButton = (Button) findViewById(R.id.queryButton);insertButton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {ContentValues values = new ContentValues();values.put(UserTableMetaData.USER_NAME, "zhangsan");Uri uri = getContentResolver().insert(UserTableMetaData.CONTENT_URI, values);System.out.println("uri--->" + uri.toString());}});queryButton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {Cursor c = getContentResolver().query(UserTableMetaData.CONTENT_URI, null, null, null, null);while(c.moveToNext()){System.out.println(c.getString(c.getColumnIndex(UserTableMetaData.USER_NAME)));}}});}}

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.example.contentprovider"    android:versionCode="1"    android:versionName="1.0" >    <uses-sdk        android:minSdkVersion="10"        android:targetSdkVersion="10" />    <application        android:allowBackup="true"        android:icon="@drawable/ic_launcher"        android:label="@string/app_name"        android:theme="@style/AppTheme" >        <activity            android:name="com.example.contentprovider.MainActivity"            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.example.contentprovider.FirstContentProvider"            android:authorities="com.example.contentprovider.FirstContentProvider"/>    </application></manifest>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <Button         android:id="@+id/insertButton"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:text="插入"/>        <Button         android:id="@+id/queryButton"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:text="查询"/></LinearLayout>