android 玩转ContentProvider之三－－实现一个ContentProvider对多张表进行操作

来源：互联网发布：nike acg 知乎编辑：程序博客网时间：2024/05/09 08:22

本人原创作品，谢绝转载！

前一篇android 玩转ContentProvider之二－－实现多个ContentProvider对多张表进行操作中提到的是多个ContentProvider处理，一个ContentProvider对应一张表，下面说一下一个ContentProvider操作多张表的用法。

因为只有一个ContentProvider，所以在ContentProvider中就要区别多张表，很明确一下子就找到解决问题的切入点。下面的方法就是这样做的。也就是说authority只有一个，但Content_uri还是要有多个，因为要对应多张表。下面看代码：

直接操作数据类DatabaseHelper跟前面是一样的

DatabaseHelper.java

package com.jacp.database;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import com.jacp.demo.provider.Provider;/** * 直接操作数据库类 * @author jacp * */public class DatabaseHelper extends SQLiteOpenHelper {private static final String DATABASE_NAME = "jacp_demo.db";private static final int DATABASE_VERSION = 1;    public DatabaseHelper(Context context) {        super(context, DATABASE_NAME, null, DATABASE_VERSION);    }    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL("CREATE TABLE " + Provider.ProgrammerColumns.TABLE_NAME + " ("                + Provider.ProgrammerColumns._ID + " INTEGER PRIMARY KEY,"                + Provider.ProgrammerColumns.NAME + " TEXT,"                + Provider.ProgrammerColumns.AGE + " INTEGER"                + ");");                db.execSQL("CREATE TABLE " + Provider.LeaderColumns.TABLE_NAME + " ("        + Provider.LeaderColumns._ID + " INTEGER PRIMARY KEY,"        + Provider.LeaderColumns.NAME + " TEXT,"        + Provider.LeaderColumns.TITLE + " TEXT,"        + Provider.LeaderColumns.LEVEL + " INTEGER"        + ");");    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        db.execSQL("DROP TABLE IF EXISTS " + Provider.ProgrammerColumns.TABLE_NAME);        db.execSQL("DROP TABLE IF EXISTS " + Provider.LeaderColumns.TABLE_NAME);        onCreate(db);    }}

保存跟数据库及表有关的常量，里面只有一个authority：
Provider.java

package com.jacp.demo.provider;import android.net.Uri;import android.provider.BaseColumns;/** * 保存数据库中的常量 * @author jacp * */public class Provider {// 这里只有一个authoritypublic static final String AUTHORITY = "com.jacp.provider.demo.common";    public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.jacp.demo";    public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.jacp.demo";    /**     * 保存programmer表中用到的常量     * @author jacp     *     */public static final class ProgrammerColumns implements BaseColumns {// 注意这个地方和下面LeaderColumns类中CONTENT_URI一样，用的是同一个AUTHORITYpublic static final Uri CONTENT_URI = Uri.parse("content://"+ AUTHORITY +"/programmers");public static final String TABLE_NAME = "programmer";public static final String DEFAULT_SORT_ORDER = "age desc";public static final String NAME = "name";public static final String AGE = "age";}/** * 保存leader表中用到的常量 * @author mayliang * */public static final class LeaderColumns implements BaseColumns {public static final Uri CONTENT_URI = Uri.parse("content://"+ AUTHORITY +"/leaders");public static final String TABLE_NAME = "leader";public static final String DEFAULT_SORT_ORDER = "level desc";public static final String NAME = "name";public static final String TITLE = "title";public static final String LEVEL = "level";}}

对多张表数据进行增删改查操作的ContentProvider类：

CommonProvider.java

package com.jacp.demo.provider;import java.util.HashMap;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;import com.jacp.database.DatabaseHelper;/** * 对programmer和leader表进行操作的ContentProvider * @author jacp * */public class CommonProvider extends ContentProvider {    private static HashMap<String, String> sprogrammersProjectionMap;    private static final int PROGRAMMERS = 1;    private static final int PROGRAMMERS_ID = 2;        // 这里要增加匹配项    private static final int LEADERS = 3;    private static final int LEADERS_ID = 4;    private static final UriMatcher sUriMatcher;    private DatabaseHelper mOpenHelper;    @Override    public boolean onCreate() {        mOpenHelper = new DatabaseHelper(getContext());        return true;    }    @Override    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,            String sortOrder) {        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();        String orderBy;        switch (sUriMatcher.match(uri)) { // 这里要对不同表的匹配结果做不同处理        case LEADERS:        case LEADERS_ID:        qb.setTables(Provider.LeaderColumns.TABLE_NAME);        // If no sort order is specified use the default        if (TextUtils.isEmpty(sortOrder)) {        orderBy = Provider.LeaderColumns.DEFAULT_SORT_ORDER;        } else {        orderBy = sortOrder;        }        break;        case PROGRAMMERS:        case PROGRAMMERS_ID:        qb.setTables(Provider.ProgrammerColumns.TABLE_NAME);        // If no sort order is specified use the default        if (TextUtils.isEmpty(sortOrder)) {        orderBy = Provider.ProgrammerColumns.DEFAULT_SORT_ORDER;        } else {        orderBy = sortOrder;        }        break;        default:        throw new IllegalArgumentException("Unknown URI " + uri);        }        switch (sUriMatcher.match(uri)) {        case LEADERS:        case PROGRAMMERS:            qb.setProjectionMap(sprogrammersProjectionMap);            break;        case PROGRAMMERS_ID:            qb.setProjectionMap(sprogrammersProjectionMap);            qb.appendWhere(Provider.ProgrammerColumns._ID + "=" + uri.getPathSegments().get(1));            break;                    case LEADERS_ID:        qb.setProjectionMap(sprogrammersProjectionMap);        qb.appendWhere(Provider.LeaderColumns._ID + "=" + uri.getPathSegments().get(1));        break;        default:            throw new IllegalArgumentException("Unknown URI " + uri);        }        // Get the database and run the query        SQLiteDatabase db = mOpenHelper.getReadableDatabase();        Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, orderBy);        // Tell the cursor what uri to watch, so it knows when its source data changes        c.setNotificationUri(getContext().getContentResolver(), uri);        return c;    }    @Override    public String getType(Uri uri) {        switch (sUriMatcher.match(uri)) { // 这里也要增加匹配项        case LEADERS:        case PROGRAMMERS:            return Provider.CONTENT_TYPE;        case PROGRAMMERS_ID:        case LEADERS_ID:            return Provider.CONTENT_ITEM_TYPE;        default:            throw new IllegalArgumentException("Unknown URI " + uri);        }    }    @Override    public Uri insert(Uri uri, ContentValues initialValues) {    ContentValues values;    if (initialValues != null) {    values = new ContentValues(initialValues);    } else {    values = new ContentValues();    }        String tableName = "";    String nullColumn = "";    switch (sUriMatcher.match(uri)) { // 这里要对不同表的匹配结果做不同处理    case LEADERS:    tableName = Provider.LeaderColumns.TABLE_NAME;    nullColumn = Provider.LeaderColumns.NAME;    // Make sure that the fields are all set            if (values.containsKey(Provider.LeaderColumns.NAME) == false) {                values.put(Provider.LeaderColumns.NAME, "");            }            if (values.containsKey(Provider.LeaderColumns.TITLE) == false) {                values.put(Provider.LeaderColumns.TITLE, "");            }                        if (values.containsKey(Provider.LeaderColumns.LEVEL) == false) {            values.put(Provider.LeaderColumns.LEVEL, 0);            }    break;    case PROGRAMMERS:    tableName = Provider.ProgrammerColumns.TABLE_NAME;    nullColumn = Provider.ProgrammerColumns.NAME;    // Make sure that the fields are all set            if (values.containsKey(Provider.ProgrammerColumns.NAME) == false) {                values.put(Provider.ProgrammerColumns.NAME, "");            }            if (values.containsKey(Provider.ProgrammerColumns.AGE) == false) {                values.put(Provider.ProgrammerColumns.AGE, 0);            }    break;default:// Validate the requested urithrow new IllegalArgumentException("Unknown URI " + uri);        }        SQLiteDatabase db = mOpenHelper.getWritableDatabase();        long rowId = db.insert(tableName, nullColumn, values);        if (rowId > 0) {            Uri noteUri = ContentUris.withAppendedId(uri, rowId);            getContext().getContentResolver().notifyChange(noteUri, null);            return noteUri;        }        throw new SQLException("Failed to insert row into " + uri);    }    @Override    public int delete(Uri uri, String where, String[] whereArgs) {        SQLiteDatabase db = mOpenHelper.getWritableDatabase();        int count;        switch (sUriMatcher.match(uri)) { // 这里要对不同表的匹配结果做不同处理，注意下面用到的表名不要弄错了        case PROGRAMMERS:            count = db.delete(Provider.ProgrammerColumns.TABLE_NAME, where, whereArgs);            break;        case PROGRAMMERS_ID:            String programmerId = uri.getPathSegments().get(1);            count = db.delete(Provider.ProgrammerColumns.TABLE_NAME, Provider.ProgrammerColumns._ID + "=" + programmerId                    + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);            break;                    case LEADERS:        count = db.delete(Provider.LeaderColumns.TABLE_NAME, where, whereArgs);        break;                case LEADERS_ID:        String leaderId = uri.getPathSegments().get(1);        count = db.delete(Provider.LeaderColumns.TABLE_NAME, Provider.LeaderColumns._ID + "=" + leaderId        + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);        break;        default:            throw new IllegalArgumentException("Unknown URI " + uri);        }        getContext().getContentResolver().notifyChange(uri, null);        return count;    }    @Override    public int update(Uri uri, ContentValues values, String where, String[] whereArgs) {        SQLiteDatabase db = mOpenHelper.getWritableDatabase();        int count;        switch (sUriMatcher.match(uri)) { // 这里要对不同表的匹配结果做不同处理，注意下面用到的表名不要弄错了        case PROGRAMMERS:            count = db.update(Provider.ProgrammerColumns.TABLE_NAME, values, where, whereArgs);            break;        case PROGRAMMERS_ID:            String noteId = uri.getPathSegments().get(1);            count = db.update(Provider.ProgrammerColumns.TABLE_NAME, values, Provider.ProgrammerColumns._ID + "=" + noteId                    + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);            break;        case LEADERS:        count = db.update(Provider.LeaderColumns.TABLE_NAME, values, where, whereArgs);        break;                case LEADERS_ID:        String leaderId = uri.getPathSegments().get(1);        count = db.update(Provider.LeaderColumns.TABLE_NAME, values, Provider.LeaderColumns._ID + "=" + leaderId        + (!TextUtils.isEmpty(where) ? " AND (" + where + ')' : ""), whereArgs);        break;        default:            throw new IllegalArgumentException("Unknown URI " + uri);        }        getContext().getContentResolver().notifyChange(uri, null);        return count;    }    static {        sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);        sUriMatcher.addURI(Provider.AUTHORITY, "programmers", PROGRAMMERS);        sUriMatcher.addURI(Provider.AUTHORITY, "programmers/#", PROGRAMMERS_ID);                // 这里要增加另一张表的匹配项        sUriMatcher.addURI(Provider.AUTHORITY, "leaders", LEADERS);        sUriMatcher.addURI(Provider.AUTHORITY, "leaders/#", LEADERS_ID);        // 保存所有表用到的字段        sprogrammersProjectionMap = new HashMap<String, String>();        sprogrammersProjectionMap.put(Provider.ProgrammerColumns._ID, Provider.ProgrammerColumns._ID);        sprogrammersProjectionMap.put(Provider.ProgrammerColumns.NAME, Provider.ProgrammerColumns.NAME);        sprogrammersProjectionMap.put(Provider.ProgrammerColumns.AGE, Provider.ProgrammerColumns.AGE);                sprogrammersProjectionMap.put(Provider.ProgrammerColumns._ID, Provider.ProgrammerColumns._ID);        sprogrammersProjectionMap.put(Provider.ProgrammerColumns.NAME, Provider.ProgrammerColumns.NAME);        sprogrammersProjectionMap.put(Provider.LeaderColumns.TITLE, Provider.LeaderColumns.TITLE);        sprogrammersProjectionMap.put(Provider.LeaderColumns.LEVEL, Provider.LeaderColumns.LEVEL);    }}

leader表对应的数据对象：

Leader.java

package com.jacp.pojos;public class Leader {public String name;public String title;public int level;}

programmer表对应的数据对象：

Programmer.java

package com.jacp.pojos;public class Programmer {public String name;public int age;}

用Activity测试：

package com.jacp.demo;import android.app.Activity;import android.content.ContentValues;import android.database.Cursor;import android.net.Uri;import android.os.Bundle;import android.text.TextUtils;import android.util.Log;import com.jacp.demo.provider.Provider;import com.jacp.pojos.Leader;import com.jacp.pojos.Programmer;public class ContentProviderDemoActivity extends Activity {private static final String TAG = "ProviderActivity";    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);                testLeader();        testProgrammer();    }        private void testProgrammer() {    Programmer p = new Programmer();        p.name = "jacp";        p.age = 99;        int id = insertProgrammer(p);        queryProgrammer(id);    }        private int insertProgrammer(Programmer programmer) {    ContentValues values = new ContentValues();    values.put(Provider.ProgrammerColumns.NAME, programmer.name);    values.put(Provider.ProgrammerColumns.AGE, programmer.age);    Uri uri = getContentResolver().insert(Provider.ProgrammerColumns.CONTENT_URI, values);    Log.i(TAG, "insert uri="+uri);    String lastPath = uri.getPathSegments().get(1);    if (TextUtils.isEmpty(lastPath)) {    Log.i(TAG, "insert failure!");    } else {    Log.i(TAG, "insert success! the id is " + lastPath);    }        return Integer.parseInt(lastPath);    }        private void queryProgrammer(int id) {    Cursor c = getContentResolver().query(Provider.ProgrammerColumns.CONTENT_URI, new String[] { Provider.ProgrammerColumns.NAME, Provider.ProgrammerColumns.AGE }, Provider.ProgrammerColumns._ID + "=?", new String[] { id + "" }, null);    if (c != null && c.moveToFirst()) {    Programmer p = new Programmer();    p.name = c.getString(c.getColumnIndexOrThrow(Provider.ProgrammerColumns.NAME));    p.age = c.getInt(c.getColumnIndexOrThrow(Provider.ProgrammerColumns.AGE));    c.close(); // 用完Cursor要释放资源，如果Cursor没有关闭系统会打出Error级别的Log    Log.i(TAG, "programmer.name="+p.name+"---programmer.age="+p.age);    } else {    Log.i(TAG, "query failure!");    }    }        private void testLeader() {    Leader leader = new Leader();    leader.name = "jacky";    leader.title = "CTO";    leader.level = 30;    int id = insertLeader(leader);    queryLeader(id);    }        private int insertLeader(Leader leader) {    ContentValues values = new ContentValues();    values.put(Provider.LeaderColumns.NAME, leader.name);    values.put(Provider.LeaderColumns.TITLE, leader.title);    values.put(Provider.LeaderColumns.LEVEL, leader.level);    Uri uri = getContentResolver().insert(Provider.LeaderColumns.CONTENT_URI, values);    Log.i(TAG, "insert uri="+uri);    String lastPath = uri.getLastPathSegment();    if (TextUtils.isEmpty(lastPath)) {    Log.i(TAG, "insert failure!");    } else {    Log.i(TAG, "insert success! the id is " + lastPath);    }        return Integer.parseInt(lastPath);    }        private void queryLeader(int id) {    Cursor c = getContentResolver().query(Provider.LeaderColumns.CONTENT_URI, new String[] { Provider.LeaderColumns.NAME, Provider.LeaderColumns.TITLE, Provider.LeaderColumns.LEVEL }, Provider.LeaderColumns._ID + "=?", new String[] { id + "" }, null);    if (c != null && c.moveToFirst()) {    Leader leader = new Leader();    leader.name = c.getString(c.getColumnIndexOrThrow(Provider.LeaderColumns.NAME));    leader.title = c.getString(c.getColumnIndexOrThrow(Provider.LeaderColumns.TITLE));    leader.level = c.getInt(c.getColumnIndexOrThrow(Provider.LeaderColumns.LEVEL));    Log.i(TAG, "leader.name="+leader.name+"---leader.title="+leader.title+"---leader.level="+leader.level);    } else {    Log.i(TAG, "query failure!");    }    }}

Manifest.xml文件中的配置：

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.jacp.demo"    android:versionCode="1"    android:versionName="1.0" >    <uses-sdk android:minSdkVersion="8" />    <application        android:icon="@drawable/ic_launcher"        android:label="@string/app_name" >        <activity            android:label="@string/app_name"            android:name=".ContentProviderDemoActivity" >            <intent-filter >                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>                <!-- 这里只注册了一个ContentProvider，要注意的地方和前面一样 -->        <provider android:name=".provider.CommonProvider"            android:authorities="com.jacp.provider.demo.common" />            </application></manifest>

到此为止ContentProvider用法总结基本结束，有人会问了，什么时候用多个？什么时候用一个？我给的答案是看个人习惯及自己的需求，如果觉得以后这张表会被删除，那么最好是分开写，写多个ContentProvider，这样容易区分。有人又会问用ContentProvider不就是多余的，项目里面的数据不会跟外部共享，所以不需要ContentProvider，直接操作数据库得了。也没错，用了ContentProvider基本上是公开了数据，但个人感觉用ContentProvider的好处是在项目架构上面降低了类与类之间的耦合性，直接用Content_uri就可以对表进行操作，其它不管系统是怎么调用的，感觉这一点还是比较好，所以推荐。

OK，就写到这里了，睡觉 ^ _ ^

demo下载地址：http://download.csdn.net/detail/maylian7700/4150144

如有遗漏不当之处，欢迎批评指正！