Android IPC机制之ContentProvider

ContentProvider：即内容提供者，用来管理数据，并对外暴露一个uri，外部可以通过uri和数据建立联系并获取或操作数据；

服务端：
1、首先创建一个数据库类，并创建一个表；
2、创建一个ContentProvider,用来操作这个数据库和表，实现增删改查和获取所有表里的数据信息；然后注册uri（对外暴露），其他客户端可以通过ContentResolver和对外暴露的uri使用ContentProvider来操作数据库并获取数据

客户端：
1、创建一个工具类，通过ContentResolver和服务端暴露的uri来和服务端建立联系，并通过服务端的ContentProvider来操作服务端的数据库并获取数据

 示例代码

服务端：

首先创建一个数据库

package com.jiao.myaidl;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by jiaocg on 2016/3/12.
 * 数据库类
 */
public class EmployeeDBHelper extends SQLiteOpenHelper {

    private final static String DB_NAME = "myDatabase.db";//数据库名字
    private final static int DB_VERSION = 1;
    public final static String EMPLOYEE_TABLE_NAME = "employee";
    private String CREATE_BOOK_TABLE = "CREATE TABLE IF NOT EXISTS "
            + EMPLOYEE_TABLE_NAME + " (id INTEGER PRIMARY KEY,"
            + "workNum TEXT," + "name TEXT," + "department TEXT)";

    public EmployeeDBHelper(Context context) {
        super(context, DB_NAME, null, DB_VERSION);

    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL(CREATE_BOOK_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

创建一个ContentProvider操作数据库

package com.jiao.myaidl;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.support.annotation.Nullable;

/**
 * Created by jiaocg on 2016/3/12.
 */
public class EmployeeProvider extends ContentProvider {

    private SQLiteDatabase mDb;
    private final static String AUTOORITY = "com.jiao.myaidl.employee.EmployeeProvider";
    private final static int EMPLOYEE_URI_CODE = 0;
    private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);


    //注册uri
    static {
        sUriMatcher.addURI(AUTOORITY, "employee", EMPLOYEE_URI_CODE);
    }


    @Override
    public boolean onCreate() {

        insertDataToDb();
        return true;
    }


    @Nullable
    void insertDataToDb() {

        mDb = new EmployeeDBHelper(getContext()).getWritableDatabase();
        mDb.execSQL("delete from " + EmployeeDBHelper.EMPLOYEE_TABLE_NAME);
        mDb.execSQL("insert into employee values(1,'1001','张三','销售部');");
        mDb.execSQL("insert into employee values(2,'1002','李四','人事部');");
        mDb.execSQL("insert into employee values(3,'1003','王五','研发部');");
        mDb.execSQL("insert into employee values(4,'1004','小明','研发部');");
        mDb.execSQL("insert into employee values(5,'1005','小强','销售部');");
    }


    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {

        String tableName = getTableName(uri);

        if (tableName == null) {
            throw new IllegalArgumentException("Unsupported URI: " + uri);
        }
        Cursor cursor = mDb.query(tableName, projection, selection, selectionArgs, null, null, sortOrder, null);
        return cursor;
    }

    @Nullable
    @Override
    public String getType(Uri uri) {
        return null;
    }

    @Nullable
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        String table = getTableName(uri);
        if (table == null) {
            throw new IllegalArgumentException("Unsupported URI: " + uri);
        }
        mDb.insert(table, null, values);
        getContext().getContentResolver().notifyChange(uri, null);
        return uri;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        String table = getTableName(uri);
        if (table == null) {
            throw new IllegalArgumentException("Unsupported URI: " + uri);
        }
        int count = mDb.delete(table, selection, selectionArgs);
        if (count > 0) {
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        String table = getTableName(uri);
        if (table == null) {
            throw new IllegalArgumentException("Unsupported URI: " + uri);
        }
        int row = mDb.update(table, values, selection, selectionArgs);
        if (row > 0) {
            getContext().getContentResolver().notifyChange(uri, null);
        }
        return row;
    }


    private String getTableName(Uri uri) {
        String tableName = null;
        if (sUriMatcher.match(uri) == EMPLOYEE_URI_CODE) {
            tableName = EmployeeDBHelper.EMPLOYEE_TABLE_NAME;
        }
        return tableName;
    }
}

清单文件中注册ContentProvider

　

 <provider
            android:name="com.jiao.myaidl.EmployeeProvider"
            android:authorities="com.jiao.myaidl.employee.EmployeeProvider"
            android:exported="true" />

客户端：

创建一个工具类，通过服务端暴露的uri和服务端的数据库建立联系

package com.jiao.myaidl;

import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.net.Uri;
import android.util.Log;
import com.jiao.myaidl.entity.Employee;
import java.util.ArrayList;
import java.util.List;

/**
 * Created by jiaocg on 2016/3/12.
 */
public class HandleProvider {

    private static Context mContext;
    private static HandleProvider mInstance;
    private static Uri mEmployeeUri;
    private static final String EMPLOYEE_CONTENT_URI = "content://com.jiao.myaidl.employee.EmployeeProvider/employee";

    private HandleProvider(Context context) {
        this.mContext = context;
        mEmployeeUri = Uri.parse(EMPLOYEE_CONTENT_URI);
    }


    //单例
    public static HandleProvider getmInstance(Context context) {
        if (mInstance == null) {
            synchronized (HandleProvider.class) {
                if (mInstance == null) {
                    mInstance = new HandleProvider(context);
                }
            }
        }

        return mInstance;
    }


    public void delete() {
        ContentResolver contentResolver = mContext.getContentResolver();
        String where = "id=?";
        String[] where_args = {"7"};//满足条件的 值集合
        contentResolver.delete(mEmployeeUri, where, where_args);
    }


    public void update() {
        ContentResolver contentResolver = mContext.getContentResolver();
        ContentValues values = new ContentValues();
        values.put("name", "梁山伯");
        String where = "id=?";
        String[] where_args = {"1"};
        contentResolver.update(mEmployeeUri, values, where, where_args);
    }

    public void create() {
        ContentValues values = new ContentValues();
        values.put("id", 7);
        values.put("workNum", "1006");
        values.put("name", "张三丰");
        values.put("department", "研发部");
        mContext.getContentResolver().insert(mEmployeeUri, values);
    }


    public List<String> query() {
        List<String> list = new ArrayList<>();
        Cursor cursor = mContext.getContentResolver().query(mEmployeeUri, new String[]{"id", "workNum", "name", "department"}, null, null, null);

        while (cursor.moveToNext()) {
            Employee employee = new Employee();
            employee.setId(cursor.getInt(0));
            employee.setWorkNum(cursor.getString(1));
            employee.setName(cursor.getString(2));
            employee.setDepartment(cursor.getString(3));
            String str = employee.toString();
            list.add(str);
            Log.d("mainActivity", "query employee:" + str);
        }
        cursor.close();
        return list;
    }
}

主代码，获取和使用服务端的数据

package com.jiao.myaidl;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;

import com.jiao.myaidl.client.R;

import java.util.List;

public class EmployeeActivity extends AppCompatActivity implements View.OnClickListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_employee);

        initView();
    }

    private void initView() {

        Button insert_button = (Button) findViewById(R.id.insert_button);
        Button delete_button = (Button) findViewById(R.id.delete_button);
        Button update_button = (Button) findViewById(R.id.update_button);
        Button query_button = (Button) findViewById(R.id.query_button);
        Button clear_button = (Button) findViewById(R.id.clear_button);
        insert_button.setOnClickListener(this);
        delete_button.setOnClickListener(this);
        update_button.setOnClickListener(this);
        query_button.setOnClickListener(this);
        clear_button.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.insert_button://插入

                HandleProvider.getmInstance(this).create();

                break;

            case R.id.delete_button:
                HandleProvider.getmInstance(this).delete();
                break;

            case R.id.update_button:
                HandleProvider.getmInstance(this).update();
                break;
            case R.id.query_button:
                List<String> list = HandleProvider.getmInstance(this).query();
                for (int i = 0; i < list.size(); i++) {
                    System.out.println(list.get(i));

                }
                break;
            case R.id.clear_button:

                break;
        }

    }
}

布局代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.ljd.client.MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/insert_button"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="插入" />

        <Button
            android:id="@+id/delete_button"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="删除" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <Button
            android:id="@+id/update_button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="更新" />

        <Button
            android:id="@+id/query_button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="查询" />
    </LinearLayout>

</LinearLayout>