android 玩轉ContentProvider之三－－實現一個ContentProvider對多張表進行操作

原創 maylian7700 2018-09-01 09:39

本人原創作品，謝絕轉載！

    前一篇android 玩轉ContentProvider之二－－實現多個ContentProvider對多張表進行操作中提到的是多個ContentProvider處理，一個ContentProvider對應一張表，下面說一下一個ContentProvider操作多張表的用法。

    因爲只有一個ContentProvider，所以在ContentProvider中就要區別多張表，很明確一下子就找到解決問題的切入點。下面的方法就是這樣做的。也就是說authority只有一個，但Content_uri還是要有多個，因爲要對應多張表。下面看代碼：

直接操作數據類DatabaseHelper跟前面是一樣的

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;

/**
 * 直接操作數據庫類
 * @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);
    }
}
保存跟數據庫及表有關的常量，裏面只有一個authority：
Provider.java

package com.jacp.demo.provider;

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

/**
 * 保存數據庫中的常量
 * @author jacp
 *
 */
public class Provider {
	
	// 這裏只有一個authority
	public 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 {
		// 注意這個地方和下面LeaderColumns類中CONTENT_URI一樣，用的是同一個AUTHORITY
		public 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";
		
	}
	
}
對多張表數據進行增刪改查操作的ContentProvider類：

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;

/**
 * 對programmer和leader表進行操作的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;
    
    // 這裏要增加匹配項
    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)) { // 這裏要對不同表的匹配結果做不同處理
        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)) { // 這裏也要增加匹配項
        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)) { // 這裏要對不同表的匹配結果做不同處理
    	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 uri
			throw 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)) { // 這裏要對不同表的匹配結果做不同處理，注意下面用到的表名不要弄錯了
        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)) { // 這裏要對不同表的匹配結果做不同處理，注意下面用到的表名不要弄錯了
        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);
        
        // 這裏要增加另一張表的匹配項
        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表對應的數據對象：

Leader.java

package com.jacp.pojos;

public class Leader {

	public String name;
	public String title;
	public int level;
}
programmer表對應的數據對象：

Programmer.java

package com.jacp.pojos;

public class Programmer {

	public String name;
	public int age;
}

用Activity測試：

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要釋放資源，如果Cursor沒有關閉系統會打出Error級別的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>
        
        <!-- 這裏只註冊了一個ContentProvider，要注意的地方和前面一樣 -->
        <provider android:name=".provider.CommonProvider"
            android:authorities="com.jacp.provider.demo.common" />
        
    </application>

</manifest>
到此爲止ContentProvider用法總結基本結束，有人會問了，什麼時候用多個？什麼時候用一個？我給的答案是看個人習慣及自己的需求，如果覺得以後這張表會被刪除，那麼最好是分開寫，寫多個ContentProvider，這樣容易區分。有人又會問用ContentProvider不就是多餘的，項目裏面的數據不會跟外部共享，所以不需要ContentProvider，直接操作數據庫得了。也沒錯，用了ContentProvider基本上是公開了數據，但個人感覺用ContentProvider的好處是在項目架構上面降低了類與類之間的耦合性，直接用Content_uri就可以對錶進行操作，其它不管系統是怎麼調用的，感覺這一點還是比較好，所以推薦。

OK，就寫到這裏了，睡覺 ^ _ ^

demo下載地址：http://download.csdn.net/detail/maylian7700/4150144

如有遺漏不當之處，歡迎批評指正！
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