android ContentProvider解析使用

一.1.ContentProvider为存储数据提供了统一的接口，使用ContentProvider可以使应用程序实现数据的共享

    2.每隔ContentProvider都拥有一个公共的URI叫做CONTENT_URI;用于表示ContentProvider所提供的数据

    3.ContentProvider提供以下函数query(),    insert();    update();    delete();    getType();    onCreate();(oncreate()函数在ContentProvider启动的时候，进行启动)；

    4.实现ContentProvider的过程

        4.1定义一个CONTENT_URI常量，用于访问ContentProvider;

        4.2定义一个类，继承ContentProvider

        4.3实现其函数insert();update();delete();query();getType();onCreate();

        4.4不要忘记在AndroidManifest.xml中声明

下面这个类是对ContentProvider的一些定义

package net.androidla.contentprovider;import android.net.Uri;import android.provider.BaseColumns;public class MyContentProviderMetaData {public static final String AUTHORIY = "net.androidla.contentprovider.MyContentProvider";public static final String DATABASE_NAME = "androidla.db";public static final int DATABASE_VERSION = 1;public static final String USERS_TABLE_NAME = "users";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.mycontentprovider.user";public static final String CONTENT_TYPE_ITEM = "vnd.android.cursor.item/vnd.mycontentprovider.user";public static final String USER_NAME = "name";public static final String DEFAULT_SORT_ORDER = "_id desc";}}

5.URI类简介

Uri代表了要操作的数据，Uri主要包含两部分信息，1是需要操作的ContentProvider,2对ContentProvider的什么数据进行操作。一个Uri有以下几部分，5.1scheme：ContentProvider（内容提供者）的scheme已经由Android所规定为：content://

            5.2主机名（或Authority）：用于唯一标识这个ContentProvider，外部调用者可以根据这个标识来找到它。

            5.3路径（path）：可以用来表示我们要操作的数据，路径的构建应根据业务而定，如下：

        要操作contact表中id为10的记录，可以构建这样的路径:/contact/10
      要操作contact表中id为10的记录的name字段， contact/10/name
        要操作contact表中的所有记录，可以构建这样的路径:/contact

这个是ContentProvider

package net.androidla.contentprovider;import java.util.HashMap;import net.androidla.contentprovider.MyContentProviderMetaData.UserTableMetaData;import net.androidla.databasehelper.SqliteHelper;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 MyContentProvider extends ContentProvider {public static final UriMatcher uriMatcher;public static final int INCOMING_USER_COLLECTION = 1;public static final int INCOMING_USER_SINGLE = 2;private SqliteHelper sqliteHelper;static {uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);uriMatcher.addURI(MyContentProviderMetaData.AUTHORIY, "users", INCOMING_USER_COLLECTION);uriMatcher.addURI(MyContentProviderMetaData.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);}@Overridepublic int delete(Uri arg0, String arg1, String[] arg2) {return 0;}@Overridepublic String getType(Uri uri) {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) {SQLiteDatabase db = sqliteHelper.getWritableDatabase();long rowId = db.insert(UserTableMetaData.TABLE_NAME, null, values);if (rowId > 0) {Uri insertUserUri = ContentUris.withAppendedId(UserTableMetaData.CONTENT_URI, rowId);getContext().getContentResolver().notifyChange(insertUserUri, null);return insertUserUri;}throw new SQLException("failed insert row into " + uri);}@Overridepublic boolean onCreate() {sqliteHelper = new SqliteHelper(getContext(), MyContentProviderMetaData.DATABASE_NAME, null, MyContentProviderMetaData.DATABASE_VERSION);return true;}@Overridepublic Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {SQLiteQueryBuilder builder = new SQLiteQueryBuilder();switch (uriMatcher.match(uri)) {case INCOMING_USER_COLLECTION:builder.setTables(UserTableMetaData.TABLE_NAME);builder.setProjectionMap(userProjectionMap);break;case INCOMING_USER_SINGLE:builder.setTables(UserTableMetaData.TABLE_NAME);builder.setProjectionMap(userProjectionMap);builder.appendWhere(UserTableMetaData._ID + "=" + uri.getPathSegments().get(1));break;default :builder.setTables(UserTableMetaData.TABLE_NAME);builder.setProjectionMap(userProjectionMap);break;}String orderBy;if (TextUtils.isEmpty(sortOrder)) {orderBy = UserTableMetaData.DEFAULT_SORT_ORDER;} else {orderBy = sortOrder;}SQLiteDatabase db = sqliteHelper.getWritableDatabase();Cursor c = builder.query(db, projection, selection, selectionArgs, null, null, orderBy);c.setNotificationUri(getContext().getContentResolver(), uri);return c; }@Overridepublic int update(Uri arg0, ContentValues arg1, String arg2, String[] arg3) {return 0;}}

这个是Activity

package net.androidla.test;import net.androidla.contentprovider.MyContentProviderMetaData;import net.androidla.contentprovider.MyContentProviderMetaData.UserTableMetaData;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;import android.widget.Toast;public class ContentProviderActivity extends Activity {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        final Button btnInsert = (Button) findViewById(R.id.btnInsert);        final Button btnQuery = (Button) findViewById(R.id.btnQuery);        btnInsert.setOnClickListener(onClickListener);        btnQuery.setOnClickListener(onClickListener);    }    private OnClickListener onClickListener = new OnClickListener() {@Overridepublic void onClick(View v) {Button btn = (Button) v;switch (btn.getId()) {case R.id.btnInsert:ContentValues values = new ContentValues();values.put(MyContentProviderMetaData.UserTableMetaData.USER_NAME, "test");Uri uri = getContentResolver().insert(MyContentProviderMetaData.UserTableMetaData.CONTENT_URI, values);Toast.makeText(ContentProviderActivity.this, uri.toString(), Toast.LENGTH_SHORT).show();break;case R.id.btnQuery:Cursor c = getContentResolver().query(MyContentProviderMetaData.UserTableMetaData.CONTENT_URI, null, null, null, null);StringBuilder strSb = new StringBuilder();while(c.moveToNext()) {strSb.append(c.getString(c.getColumnIndex(UserTableMetaData.USER_NAME)));strSb.append("\r\n");}Toast.makeText(ContentProviderActivity.this, strSb.toString(), Toast.LENGTH_LONG).show();break;}}};}

还有一个是连接SQLiteDatabase的

package net.androidla.databasehelper;import net.androidla.contentprovider.MyContentProviderMetaData;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;public class SqliteHelper extends SQLiteOpenHelper {public SqliteHelper(Context context, String name, CursorFactory factory, int version) {super(context, name, factory, version);}@Overridepublic void onCreate(SQLiteDatabase db) {String sql = "create table " + MyContentProviderMetaData.USERS_TABLE_NAME+ "(" + MyContentProviderMetaData.UserTableMetaData._ID+ " INTEGER PRIMARY KEY AUTOINCREMENT," + MyContentProviderMetaData.UserTableMetaData.USER_NAME+ " varchar(20));";db.execSQL(sql);}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}}