IPC机制--利用ContentProvider

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本例Git地址：https://github.com/NoClay/MessagerTest.git

为什么使用ContentProvider？

ContentProvider是Android中提供的专门用于不同应用间进行数据共享的方式，从这点来看，它天生就是为了进程间通信的，和Messenger一样，ContentProvider的底层实现同样是Binder。

怎样使用ContentProvider？

自定义ContentProvider需要实现以下几个方法：

方法名含义 onCreate 创建ContentProvider，初始化工作 getType 返回一个Uri请求所对应的MIME类型，比如照片，视频等，可以直接在方法中返回null或者*/* query 查找 update 更新 insert 插入 delete 删除

对于ContentProvider数据存储的实现，我们可以选择使用文件，内存中的对象，也可以使用SQLite实现。

1. 实现SQLite

package com.example.no_clay.messagertest.Item255;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;/** * Created by no_clay on 2017/2/28. */public class DBOpenHelper extends SQLiteOpenHelper {    public static final String DB_NAME = "book_provider.db";    public static final String BOOK_TABLE_NAME = "book";    public static final String USER_TABLE_NAME = "user";    public static final int DB_VERSION = 1;    public static final String CREATE_BOOK_TABLE = "create table if not exists " +            BOOK_TABLE_NAME + " (id text primary key, name text)";    public static final String CREATE_USER_TABLE = "create table if not exists " +            USER_TABLE_NAME + " (id text primary key, name text)";    public DBOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);    }    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL(CREATE_BOOK_TABLE);        db.execSQL(CREATE_USER_TABLE);    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {    }}

2. 实现自定义的ContentProvider

package com.example.no_clay.messagertest.Item255;import android.content.ContentProvider;import android.content.ContentValues;import android.content.Context;import android.content.UriMatcher;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.net.Uri;import android.support.annotation.Nullable;import android.util.Log;import com.example.no_clay.messagertest.Util.MyConstants;/** * Created by no_clay on 2017/2/28. */public class BookProvider extends ContentProvider {    private static final String TAG = "BookProvider";    public static final String AUTHORITY = MyConstants.PACKAGE_NAME + ".BookProvider";    public static final Uri BOOK_CONTENT_URI = Uri.parse("content://" + AUTHORITY            + "/book");    public static final Uri USER_CONTENT_URI = Uri.parse("content://" + AUTHORITY            + "/user");    public static final int BOOK_URI_CODE = 0;    public static final int USER_URI_CODE = 1;    public static final UriMatcher URI_MATCHER = new UriMatcher(UriMatcher.NO_MATCH);    public Context mContext;    private SQLiteDatabase mDatabase;    static {        URI_MATCHER.addURI(AUTHORITY, "book", BOOK_URI_CODE);        URI_MATCHER.addURI(AUTHORITY, "user", USER_URI_CODE);    }    private String getTableName(Uri uri){        String tableName = null;        switch (URI_MATCHER.match(uri)){            case 0:tableName = DBOpenHelper.BOOK_TABLE_NAME;                break;            case 1:tableName = DBOpenHelper.USER_TABLE_NAME;                break;            default:break;        }        return tableName;    }    @Override    public boolean onCreate() {        Log.d(TAG, "onCreate: thread = " + Thread.currentThread().getName());        mContext = getContext();        mDatabase = new DBOpenHelper(mContext,                DBOpenHelper.DB_NAME,                null,                DBOpenHelper.DB_VERSION).getWritableDatabase();//        new Thread(new Runnable() {//            @Override//            public void run() {//                initData();//            }//        }).start();        return false;    }//    private void initData() {//        mDatabase.execSQL("insert into book values('num012', 'Android')");//        ContentValues value = new ContentValues();//        value.put("id", "num014");//        value.put("name", "Java编程思想");//        mDatabase.insert(DBOpenHelper.BOOK_TABLE_NAME, null, value);//        value.clear();//        value.put("id", "num016");//        value.put("name", "Android开发艺术探索");//        mDatabase.insert(DBOpenHelper.BOOK_TABLE_NAME, null, value);//        value.clear();//        value.put("id", "04141087");//        value.put("name", "高XX");//        mDatabase.insert(DBOpenHelper.USER_TABLE_NAME, null, value);//        value.clear();//        value.put("id", "04141085");//        value.put("name", "莫X");//        mDatabase.insert(DBOpenHelper.USER_TABLE_NAME, null, value);//        value.clear();//        value.put("id", "04141086");//        value.put("name", "张XX");//        mDatabase.insert(DBOpenHelper.USER_TABLE_NAME, null, value);////    }    @Nullable    @Override    public Cursor query(Uri uri, String[] projection, String selection,                        String[] selectionArgs, String sortOrder) {        Log.d(TAG, "query: thread = " + Thread.currentThread().getName());        String table = getTableName(uri);        if (table == null){            throw new IllegalArgumentException("不支持的URI");        }        return mDatabase.query(table, projection, selection, selectionArgs,                null, null, sortOrder, null);    }    @Nullable    @Override    public String getType(Uri uri) {        Log.d(TAG, "getType: thread = " + Thread.currentThread().getName());        return null;    }    @Nullable    @Override    public Uri insert(Uri uri, ContentValues values) {        Log.d(TAG, "insert: thread = " + Thread.currentThread().getName());        Log.d(TAG, "insert: uri = " + uri);        String table = getTableName(uri);        if (table == null){            throw new IllegalArgumentException("不支持的URI");        }        mDatabase.insert(table, null, values);        mContext.getContentResolver().notifyChange(uri, null);        return null;    }    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        Log.d(TAG, "delete: thread = " + Thread.currentThread().getName());        String table = getTableName(uri);        if (table == null){            throw new IllegalArgumentException("不支持的URI");        }        int count = mDatabase.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) {        Log.d(TAG, "update: thread = " + Thread.currentThread().getName());        String table = getTableName(uri);        if (table == null){            throw new IllegalArgumentException("不支持的URI");        }        int row = mDatabase.update(table, values, selection, selectionArgs);        if (row > 0){            getContext().getContentResolver().notifyChange(uri, null);        }        return 0;    }}

3. 注册ContentProvider组件

        <provider            android:name=".Item255.BookProvider"            android:authorities="com.example.no_clay.messagertest.BookProvider"            android:permission="com.example.no_clay.messagertest.PROVIDER"            android:process=":provider"/>

注意：
ContentProvider的onCreate方法由系统进行回调并运行在主线程方法中，而其他五个方法由外界回调并运行在Binder线程池中，这一点结果如下验证了：

03-01 15:45:41.168 12129-12129/com.example.no_clay.messagertest:provider D/BookProvider: onCreate: thread = main
03-01 15:45:41.176 12129-12146/com.example.no_clay.messagertest:provider D/BookProvider: query: thread = Binder_2
03-01 15:45:41.183 11082-11082/com.example.no_clay.messagertest D/BookProviderActivity: onCreate: book name = 程序设计的艺术
03-01 15:45:41.183 11082-11082/com.example.no_clay.messagertest D/BookProviderActivity: onCreate: book name = Android
03-01 15:45:41.183 11082-11082/com.example.no_clay.messagertest D/BookProviderActivity: onCreate: book name = Java编程思想
03-01 15:45:41.183 11082-11082/com.example.no_clay.messagertest D/BookProviderActivity: onCreate: book name = Android开发艺术探索
03-01 15:45:41.183 11082-11082/com.example.no_clay.messagertest D/BookProviderActivity: onCreate: book name = 程序设计的艺术
03-01 15:45:41.185 12129-12146/com.example.no_clay.messagertest:provider D/BookProvider: query: thread = Binder_2
03-01 15:45:41.187 11082-11082/com.example.no_clay.messagertest D/BookProviderActivity: query user:com.example.no_clay.messagertest.Data.User@42ca9ed8
03-01 15:45:41.187 11082-11082/com.example.no_clay.messagertest D/BookProviderActivity: query user:com.example.no_clay.messagertest.Data.User@42caa308
03-01 15:45:41.188 11082-11082/com.example.no_clay.messagertest D/BookProviderActivity: query user:com.example.no_clay.messagertest.Data.User@42caa658

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