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>