详解 Android IPC 机制（七）使用 ContentProvider 实现进程间通信

ContentProvider 是 Andorid 中专门用于不同应用间进行数据共享的方式，底层实现也是 Binder 。

前面在 《第一行代码》读书笔记（五）– 应用组件之 ContentProvider 介绍过，这里就不再详细记录了。

首先继承 ContentProvider 类实现自己的 Provider ：

public class BookProvider extends ContentProvider {

    private static final String TAG = "BookProvider";
    public static final String AUTHORITY = "com.wshunli.ipc.demo.book.provider";

    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;
    private static final UriMatcher sUriMatcher = new UriMatcher(
            UriMatcher.NO_MATCH);

    static {
        sUriMatcher.addURI(AUTHORITY, "book", BOOK_URI_CODE);
        sUriMatcher.addURI(AUTHORITY, "user", USER_URI_CODE);
    }

    private Context context;
    private SQLiteDatabase db;

    public BookProvider() {
    }

    @Override
    public boolean onCreate() {
        context = getContext();
        initProviderData();
        return true;
    }

    private void initProviderData() {
        db = new DBHelper(context).getWritableDatabase();
        db.execSQL("delete from " + DBHelper.BOOK_TABLE_NAME);
        db.execSQL("delete from " + DBHelper.USER_TALBE_NAME);
        db.execSQL("insert into book values(3,'Android');");
        db.execSQL("insert into book values(4,'Ios');");
        db.execSQL("insert into book values(5,'Html5');");
        db.execSQL("insert into user values(1,'jake',1);");
        db.execSQL("insert into user values(2,'jasmine',0);");
    }

    @Override
    public String getType(Uri uri) {
        Log.d(TAG, "getType: ");
        return null;
    }

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

    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
                        String[] selectionArgs, String sortOrder) {
        String table = getTableName(uri);
        if (table == null) {
            throw new IllegalArgumentException("Unsupported URI: " + uri);
        }
        return db.query(table, projection, selection, selectionArgs, null, null, sortOrder, null);
    }

    @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 = db.update(table, values, selection, selectionArgs);
        if (row > 0) {
            context.getContentResolver().notifyChange(uri, null);
        }
        return row;
    }

    @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 = db.delete(table, selection, selectionArgs);
        if (count > 0) {
            context.getContentResolver().notifyChange(uri, null);
        }
        return count;
    }

    private String getTableName(Uri uri) {
        String tableName = null;
        switch (sUriMatcher.match(uri)) {
            case BOOK_URI_CODE:
                tableName = DBHelper.BOOK_TABLE_NAME;
                break;
            case USER_URI_CODE:
                tableName = DBHelper.USER_TALBE_NAME;
                break;
            default:
                break;
        }

        return tableName;
    }
}

记得在 AndroidManifest 中声明：

<provider
    android:name=".content.BookProvider"
    android:authorities="com.wshunli.ipc.demo.book.provider"
    android:enabled="true"
    android:exported="true"
    android:permission="com.wshunli.ipc.demo.PROVIDER"
    android:process=":remote" />

其中 DBHelper 为数据库帮助类，代码如下：

public class DBHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "book_provider.db";
    public static final String BOOK_TABLE_NAME = "book";
    public static final String USER_TALBE_NAME = "user";

    private static final int DB_VERSION = 3;

    private String CREATE_BOOK_TABLE = "CREATE TABLE IF NOT EXISTS "
            + BOOK_TABLE_NAME + "(_id INTEGER PRIMARY KEY," + "name TEXT)";

    private String CREATE_USER_TABLE = "CREATE TABLE IF NOT EXISTS "
            + USER_TALBE_NAME + "(_id INTEGER PRIMARY KEY," + "name TEXT,"
            + "sex INT)";


    public DBHelper(Context context) {
        super(context, DB_NAME, null, DB_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) {

    }
}

然后就是使用了，新建 Activity ：

public class ProviderActivity extends AppCompatActivity {

    private static final String TAG = "ProviderActivity";

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

//        Uri uri = Uri.parse("content://com.wshunli.ipc.demo.book.provider");
//        getContentResolver().query(uri, null, null, null, null);

        Uri bookUri = Uri.parse("content://com.wshunli.ipc.demo.book.provider/book");
        ContentValues values = new ContentValues();
        values.put("_id", 6);
        values.put("name", "程序设计的艺术");
        getContentResolver().insert(bookUri, values);
        Cursor bookCursor = getContentResolver().query(bookUri, new String[]{"_id", "name"}, null, null, null);
        while (bookCursor.moveToNext()) {
            Book book = new Book();
            book.bookId = bookCursor.getInt(0);
            book.bookName = bookCursor.getString(1);
            Log.d(TAG, "query book:" + book.toString());
        }
        bookCursor.close();

        Uri userUri = Uri.parse("content://com.wshunli.ipc.demo.book.provider/user");
        Cursor userCursor = getContentResolver().query(userUri, new String[]{"_id", "name", "sex"}, null, null, null);
        while (userCursor.moveToNext()) {
            User user = new User();
            user.userId = userCursor.getInt(0);
            user.userName = userCursor.getString(1);
            user.isMale = userCursor.getInt(2) == 1;
            Log.d(TAG, "query user:" + user.toString());
        }
        userCursor.close();
    }
}

日志结果如下：

参考资料
1、《Android开发艺术探索》 – 2.4.5 使用 ContentProvider