android 玩转ContentProvider之一－－实现ContentProvider操作数据库

时间：2021-11-04 09:26:11

本人原创作品，谢绝转载！

作为android四大组件之一，今天总结一下它的用法。

ContentProvider官方有很多地方提到，其中一个是在API文档上（http://developer.android.com/guide/topics/providers/content-providers.html）面有介绍，有兴趣去看一下，虽然是英文的，对了解ContentProvider很有用；还有一个地方是android SDK中的%android_home%/samples/android-x/下面的一个NotePad的demo，代码架构可以参考该demo。本文来自此demo，并做相关修改。

代码：

SQLite数据库直接操作类：

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;

/**
 * 操作数据库
 * @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.PersonColumns.TABLE_NAME + " ("
                + Provider.PersonColumns._ID + " INTEGER PRIMARY KEY,"
                + Provider.PersonColumns.NAME + " TEXT,"
                + Provider.PersonColumns.AGE + " INTEGER"
                + ");");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + Provider.PersonColumns.TABLE_NAME);
        onCreate(db);
    }
}
保存跟数据库及表有关的常量：
Provider.java 

package com.jacp.demo.provider;

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

/**
 * 存放跟数据库有关的常量
 * @author jacp
 *
 */
public class Provider {

// 这个是每个Provider的标识，在Manifest中使用
public static final String AUTHORITY = "com.jacp.provider.demo.person";

    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";

    /**
     * 跟Person表相关的常量
     * @author jacp
     *
     */
public static final class PersonColumns implements BaseColumns {
// CONTENT_URI跟数据库的表关联，最后根据CONTENT_URI来查询对应的表
public static final Uri CONTENT_URI = Uri.parse("content://"+ AUTHORITY +"/persons");
public static final String TABLE_NAME = "person";
public static final String DEFAULT_SORT_ORDER = "age desc";

public static final String NAME = "name";
public static final String AGE = "age";

}

}

对数据增删改查操作的类：

PersonProvider.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;

/**
 * 操作数据库Person表的ContentProvider
 * @author jacp
 *
 */
public class PersonProvider extends ContentProvider {

    private static HashMap<String, String> sPersonsProjectionMap;

    private static final int PERSONS = 1;
    private static final int PERSONS_ID = 2;

    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();
        qb.setTables(Provider.PersonColumns.TABLE_NAME);

        switch (sUriMatcher.match(uri)) {
        case PERSONS:
            qb.setProjectionMap(sPersonsProjectionMap);
            break;

        case PERSONS_ID:
            qb.setProjectionMap(sPersonsProjectionMap);
            qb.appendWhere(Provider.PersonColumns._ID + "=" + uri.getPathSegments().get(1));
            break;

        default:
            throw new IllegalArgumentException("Unknown URI " + uri);
        }

        // If no sort order is specified use the default
        String orderBy;
        if (TextUtils.isEmpty(sortOrder)) {
            orderBy = Provider.PersonColumns.DEFAULT_SORT_ORDER;
        } else {
            orderBy = sortOrder;
        }

        // 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)) {
        case PERSONS:
            return Provider.CONTENT_TYPE;
        case PERSONS_ID:
            return Provider.CONTENT_ITEM_TYPE;
        default:
            throw new IllegalArgumentException("Unknown URI " + uri);
        }
    }

    @Override
    public Uri insert(Uri uri, ContentValues initialValues) {
        // Validate the requested uri
        if (sUriMatcher.match(uri) != PERSONS) {
            throw new IllegalArgumentException("Unknown URI " + uri);
        }

        ContentValues values;
        if (initialValues != null) {
            values = new ContentValues(initialValues);
        } else {
            values = new ContentValues();
        }

        // Make sure that the fields are all set
        if (values.containsKey(Provider.PersonColumns.NAME) == false) {
            values.put(Provider.PersonColumns.NAME, "");
        }

        if (values.containsKey(Provider.PersonColumns.AGE) == false) {
            values.put(Provider.PersonColumns.AGE, 0);
        }

        SQLiteDatabase db = mOpenHelper.getWritableDatabase();
        long rowId = db.insert(Provider.PersonColumns.TABLE_NAME, Provider.PersonColumns.NAME, values);
        if (rowId > 0) {
            Uri noteUri = ContentUris.withAppendedId(Provider.PersonColumns.CONTENT_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)) {
        case PERSONS:
            count = db.delete(Provider.PersonColumns.TABLE_NAME, where, whereArgs);
            break;

        case PERSONS_ID:
            String noteId = uri.getPathSegments().get(1);
            count = db.delete(Provider.PersonColumns.TABLE_NAME, Provider.PersonColumns._ID + "=" + noteId
                    + (!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)) {
        case PERSONS:
            count = db.update(Provider.PersonColumns.TABLE_NAME, values, where, whereArgs);
            break;

        case PERSONS_ID:
            String noteId = uri.getPathSegments().get(1);
            count = db.update(Provider.PersonColumns.TABLE_NAME, values, Provider.PersonColumns._ID + "=" + noteId
                    + (!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);
        // 这个地方的persons要和PersonColumns.CONTENT_URI中最后面的一个Segment一致
        sUriMatcher.addURI(Provider.AUTHORITY, "persons", PERSONS);
        sUriMatcher.addURI(Provider.AUTHORITY, "persons/#", PERSONS_ID);

        sPersonsProjectionMap = new HashMap<String, String>();
        sPersonsProjectionMap.put(Provider.PersonColumns._ID, Provider.PersonColumns._ID);
        sPersonsProjectionMap.put(Provider.PersonColumns.NAME, Provider.PersonColumns.NAME);
        sPersonsProjectionMap.put(Provider.PersonColumns.AGE, Provider.PersonColumns.AGE);
    }
}


表对应的数据对象：
Person.java 

package com.jacp.pojos;

public class Person {

public String name;
public int age;
}


Activity测试：
ContentProviderDemoActivity.java 

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.Person;

public class ContentProviderDemoActivity extends Activity {

private static final String TAG = "ProviderActivity";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        test();
    }

    private void test() {
    Person p = new Person();
        p.name = "jacp";
        p.age = 99;
        int id = insert(p);
        query(id);
    }

    private int insert(Person person) {
    ContentValues values = new ContentValues();
    values.put(Provider.PersonColumns.NAME, person.name);
    values.put(Provider.PersonColumns.AGE, person.age);
    Uri uri = getContentResolver().insert(Provider.PersonColumns.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 query(int id) {
    Cursor c = getContentResolver().query(Provider.PersonColumns.CONTENT_URI, new String[] { Provider.PersonColumns.NAME, Provider.PersonColumns.AGE }, Provider.PersonColumns._ID + "=?", new String[] { id + "" }, null);
    if (c != null && c.moveToFirst()) {
    Person p = new Person();
    p.name = c.getString(c.getColumnIndexOrThrow(Provider.PersonColumns.NAME));
    p.age = c.getInt(c.getColumnIndexOrThrow(Provider.PersonColumns.AGE));
    Log.i(TAG, "person.name="+p.name+"---person.age="+p.age);
    } else {
    Log.i(TAG, "query failure!");
    }
    }
}

Manifest.xml文件中注册配置：

<?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>

        <!-- 注意这个地方的位置，是在application标签里面；android:authorities对应Provider.AUTHORITY -->
        <provider android:name=".provider.PersonProvider"
            android:authorities="com.jacp.provider.demo.person" />

    </application>

</manifest>

如果对ContentProvider不熟悉，把SDK中的NotePad项目copy改几遍，在改的时候就会明白每个地方起的作用，copy改了几次就会慢慢熟悉了。

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！
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