ContentProvider

野性酷女 2022-05-28 11:22 131阅读 0赞

import android.content.ContentProvider;
    import android.content.ContentResolver;
    import android.content.ContentUris;
    import android.content.ContentValues;
    import android.content.Context;
    import android.content.UriMatcher;
    import android.database.Cursor;
    import android.database.sqlite.SQLiteDatabase;
    import android.database.sqlite.SQLiteException;
    import android.database.sqlite.SQLiteOpenHelper;
    import android.database.sqlite.SQLiteQueryBuilder;
    import android.net.Uri;
    import android.support.annotation.Nullable;
    import android.text.TextUtils;
    
    import java.util.HashMap;
     public class GeneralCP extends ContentProvider {
        private static final String DB_NAME = "general.db";
        private static final String DB_TABLE = "paramsTable";
        private static final int DB_VERSION = 1;
        private static final String DB_CREATE = "create table if not exists " + DB_TABLE +
                " (" + GeneralCPConstants.ID + " integer primary key autoincrement, " +//主键，自增长.
                GeneralCPConstants.NAME + " text unique on conflict replace," +//参数名称
                GeneralCPConstants.VALUE + " text);";//参数值
        public static final UriMatcher uriMatcher;
    
        //初始化UriMatcher.
        static {
            uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);//不匹配任何路径的返回码.
            uriMatcher.addURI(GeneralCPConstants.AUTHORITY, "item", GeneralCPConstants.ITEM_ALL);
            uriMatcher.addURI(GeneralCPConstants.AUTHORITY, "item/#", GeneralCPConstants.ITEM_ONE);
        }
    
    
        private DBHelper dbHelper;
        private ContentResolver resolver;
        private SQLiteDatabase db;
    
        @Override
        public boolean onCreate() {
            Context context = getContext();
            resolver = context.getContentResolver();
            dbHelper = new DBHelper(context, DB_NAME, null, DB_VERSION);
            db = dbHelper.getWritableDatabase();
            return true;
        }
    
        @Nullable
        @Override
        public String getType(Uri uri) {
            switch (uriMatcher.match(uri)) {
                case GeneralCPConstants.ITEM_ALL:
                    return GeneralCPConstants.CONTENT_TYPE;
                case GeneralCPConstants.ITEM_ONE:
                    return GeneralCPConstants.CONTENT_ITEM_TYPE;
                default:
                    throw new IllegalArgumentException("Error Uri: " + uri);
            }
    
        }
    
        @Nullable
        @Override
        public Uri insert(Uri uri, ContentValues values) {
            if (uriMatcher.match(uri) != GeneralCPConstants.ITEM_ALL) {
                throw new IllegalArgumentException("Error Uri: " + uri);
            }
            if (db == null) {
                db = dbHelper.getWritableDatabase();
            }
            long id = db.insert(DB_TABLE, GeneralCPConstants.ID, values);
            if (id < 0) {
                throw new SQLiteException("Unable to insert " + values + " for " + uri);
            }
            Uri newUri = ContentUris.withAppendedId(uri, id);
            resolver.notifyChange(newUri, null);
            return newUri;
        }
    
        @Override
        public int delete(Uri uri, String selection, String[] selectionArgs) {
            if (db == null) {
                db = dbHelper.getWritableDatabase();
            }
            int count;
            switch (uriMatcher.match(uri)) {
                case GeneralCPConstants.ITEM_ALL: {
                    count = db.delete(DB_TABLE, selection, selectionArgs);
                    break;
                }
                case GeneralCPConstants.ITEM_ONE: {
                    String id = uri.getPathSegments().get(1);
                    count = db.delete(DB_TABLE, GeneralCPConstants.ID + "=" + id + (!TextUtils.isEmpty(selection) ? " and (" + selection + ')' : ""), selectionArgs);
                    break;
                }
                default:
                    throw new IllegalArgumentException("Error Uri: " + uri);
            }
            resolver.notifyChange(uri, null);
            return count;
        }
    
        @Override
        public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
            if (db == null) {
                db = dbHelper.getWritableDatabase();
            }
            int count;
            switch (uriMatcher.match(uri)) {
                case GeneralCPConstants.ITEM_ALL: {
                    count = db.update(DB_TABLE, values, selection, selectionArgs);
                    break;
                }
                case GeneralCPConstants.ITEM_ONE: {
                    String id = uri.getPathSegments().get(1);
                    count = db.update(DB_TABLE, values, GeneralCPConstants.ID + "=" + id
                            + (!TextUtils.isEmpty(selection) ? " and (" + selection + ')' : ""), selectionArgs);
                    break;
                }
                default:
                    throw new IllegalArgumentException("Error Uri: " + uri);
            }
            resolver.notifyChange(uri, null);
            return count;
        }
    
        /** * 为查询操作创建projection映射，可防SQL注入攻击。 */ private static final HashMap<String, String> vrcProjectionMap;
    
        static {
            vrcProjectionMap = new HashMap<String, String>();
            vrcProjectionMap.put(GeneralCPConstants.ID, GeneralCPConstants.ID);
            vrcProjectionMap.put(GeneralCPConstants.NAME, GeneralCPConstants.NAME);
            vrcProjectionMap.put(GeneralCPConstants.VALUE, GeneralCPConstants.VALUE);
        }
    
        @Nullable
        @Override
        public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
            if (db == null) {
                db = dbHelper.getWritableDatabase();
            }
            SQLiteQueryBuilder sqlBuilder = new SQLiteQueryBuilder();
            String limit = null;
            switch (uriMatcher.match(uri)) {
                case GeneralCPConstants.ITEM_ALL: {
                    sqlBuilder.setTables(DB_TABLE);
                    sqlBuilder.setProjectionMap(vrcProjectionMap);
                    break;
                }
                case GeneralCPConstants.ITEM_ONE: {
                    String id = uri.getPathSegments().get(1);
                    sqlBuilder.setTables(DB_TABLE);
                    sqlBuilder.setProjectionMap(vrcProjectionMap);
                    sqlBuilder.appendWhere(GeneralCPConstants.ID + "=" + id);
                    break;
                }
                default:
                    throw new IllegalArgumentException("Error Uri: " + uri);
            }
            Cursor cursor = sqlBuilder.query(db, projection, selection, selectionArgs, null, null, TextUtils.isEmpty(sortOrder) ? GeneralCPConstants.DEFAULT_SORT_ORDER : sortOrder, limit);
            cursor.setNotificationUri(resolver, uri);
            return cursor;
        }
    
    
        /** * 数据库辅助类 */ private static class DBHelper extends SQLiteOpenHelper {
            public DBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
                super(context, name, factory, version);
            }
    
            @Override
            public void onCreate(SQLiteDatabase db) {
                db.execSQL(DB_CREATE);
            }
    
            @Override
            public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
                db.execSQL("DROP TABLE IF EXISTS " + DB_TABLE);
                onCreate(db);
            }
        }
    }

查询时使用SQLiteQueryBuilder的原因： 
    为查询操作创建projection映射。该映射将用户传入到query方法中的列名和实际数据库中的列名建立起映射关系。这对重命名列名和消除连接（joins）时的二义性很有帮助。例如你可以将"name"映射到"people.name"。一旦一个projection映射建立，你必须包含用户可能请求的所有列名，即使键和值可能是相同的。
    
    如果不需要对列名进行映射，可以不调用这个函数。但是如果调用，必须对所有列都进行映射，映射中key和value可以完全相同。

多表查询

如果A表中存了用户名和密码，B表中存了用户名和其他具体信息，使用SQLiteQueryBuilder多表查询。  SQL语句：

代码如下:

SELECT A.name，A.password，B.age，B.sex FROM A,B WHERE A.name=B.name AND A.name=“bob”

多表查询步骤：

[?][Link 1]

<table style="width:1870px;background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;"> 
 <tbody style="background:none;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;"> 
  <tr style="background:none;border-top:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;"> 
   <td style="background:none;border-width:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:rgb(175,175,175);"> 
    <div style="background-image:none;border-width:0px 3px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);float:none;height:auto;line-height:1.1em;margin:0px;padding:0px .5em 0px 1em;text-align:right;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;white-space:pre;">
      1 
    </div> 
    <div style="background-image:none;border-width:0px 3px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);float:none;height:auto;line-height:1.1em;margin:0px;padding:0px .5em 0px 1em;text-align:right;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;white-space:pre;">
      2 
    </div> 
    <div style="background-image:none;border-width:0px 3px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);float:none;height:auto;line-height:1.1em;margin:0px;padding:0px .5em 0px 1em;text-align:right;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;white-space:pre;">
      3 
    </div> 
    <div style="background-image:none;border-width:0px 3px 0px 0px;border-right-style:solid;border-right-color:rgb(108,226,108);float:none;height:auto;line-height:1.1em;margin:0px;padding:0px .5em 0px 1em;text-align:right;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;white-space:pre;">
      4 
    </div></td> 
   <td style="width:1834px;background:none;border-width:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;"> 
    <div style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;"> 
     <div style="background-image:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px 1em;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;white-space:pre;"> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">SQLiteQueryBuilder builder=</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-weight:bold;font-size:1em;min-height:auto;color:rgb(0,102,153);">new</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">SQLiteQueryBuilder();</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:rgb(0,130,0);">//获得对象</code> 
     </div> 
     <div style="background-image:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px 1em;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;white-space:pre;"> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">builder.setTables(TABLENAME_A,TABLENAME_B);</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:rgb(0,130,0);">//设置需要查询的表，可多个</code> 
     </div> 
     <div style="background-image:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px 1em;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;white-space:pre;"> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">builder.appendWhere(TABLENAME_A+</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#0000FF;">"."</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">+NAME+</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#0000FF;">"="</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">TABLENAME_B+</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#0000FF;">"."</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">+NAME);</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:rgb(0,130,0);">//设置关联属性，表与属性间.隔开，属性以=连接</code> 
     </div> 
     <div style="background-image:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px 1em;vertical-align:baseline;width:auto;font-size:1em;min-height:auto;white-space:pre;"> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">cursor=builder.query(</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:rgb(0,153,0);">7</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:#000000;">个属性）;</code> 
      <code style="background:none;border:0px;float:none;height:auto;line-height:1.1em;margin:0px;padding:0px;vertical-align:baseline;width:auto;font-family:Consolas, 'Bitstream Vera Sans Mono', 'Courier New', Courier, monospace;font-size:1em;min-height:auto;color:rgb(0,130,0);">//7属性同单表查询</code> 
     </div> 
    </div></td> 
  </tr> 
 </tbody> 
</table>

[Link 1]: http://www.jb51.net/article/107637.htm#