第二章 IPC机制详解(3)

本文为Android开发艺术探索的笔记，仅供学习

本节主要讲解AIDL和ContentProvider的使用

4.4 AIDL的使用

前面Messenger进程通信中，如果客户端有大量的消息需要发送到服务端，那么服务端也只能一个个处理，所以在处理大数据的时候使用Messenger并不是好方法。我们可以使用AIDL来实现跨进程，所以Messenger的底层是AIDL换句话说Messenger就是AIDL，只不过系统做了封装方便我们使用。有了Binder的基础我们可以更好的理解AIDL。

服务端要创建一个Service去监听客户端发来的消息，然后建立一个AIDL的文件夹，将暴露给客户端的接口在AIDL文件夹里声明，最后在Service去实现这个AIDL即可。

客户端，需要绑带Service，绑带成功后把服务端返回的Binder转化为AIDL所属的类型，接着调用AIDL里的方法即可。

我们来举个例子，大致的业务逻辑就是主要有三个功能，1.客户端可以向服务端添加Book 2.客户端可以向服务端获取Book信息 3.向服务端添加Book监听，监听每次添加新Book的信息

下面上代码
AIDL
// Book.aidl
package com.example.gyh.myapplication;
// Declare any non-default types here with import statements
parcelable Book;
该类主要就是用来声明Book这个Bean

// IOnNewBookArrivedListener.aidl
package com.example.gyh.myapplication;
// Declare any non-default types here with import statements
import com.example.gyh.myapplication.Book;
interface IOnNewBookArrivedListener {
/**
* Demonstrates some basic types that you can use as parameters
* and return values in AIDL.
*/
void onNewBookArrived(in Book newBook);
}

// IBookManager.aidl
package com.example.gyh.myapplication;
// Declare any non-default types here with import statements
import com.example.gyh.myapplication.Book;
import com.example.gyh.myapplication.IOnNewBookArrivedListener;
interface IBookManager {
/**
* Demonstrates some basic types that you can use as parameters
* and return values in AIDL.
*/
void addBook(in Book book);
List<Book> getBookList();
void registerListener(IOnNewBookArrivedListener listener);
void unregisterListener(IOnNewBookArrivedListener listener);

接下来附上服务端的代码,正如前面Binder机制一样，创建AIDL业务的接口IBookManager.Stub这是运行在客户端的，然后就会自动生成方法。

public class ServiceBook extends Service {
private CopyOnWriteArrayList<Book> mBookList = new CopyOnWriteArrayList<Book>();//CopyOnWriteArrayList支持并发的读写
//    private CopyOnWriteArrayList<IOnNewBookArrivedListener> mlListeners = new CopyOnWriteArrayList<IOnNewBookArrivedListener>();不支持多进程对Listener的增删
private RemoteCallbackList<IOnNewBookArrivedListener> mListenerList = new RemoteCallbackList<IOnNewBookArrivedListener>();//为什么要用这方式的List？因为RemoteCallbackList支持多进程对Listener的增删
String TAG = "Service";
boolean isadd = true;

private Binder binder = new IBookManager.Stub() {//里面的方法和AIDL接口一一对应
@Override
public void addBook(Book book) throws RemoteException {
mBookList.add(book);
}

@Override
public List<Book> getBookList() throws RemoteException {
return mBookList;
}

@Override
public void registerListener(IOnNewBookArrivedListener listener) throws RemoteException {
//            if (!mlListeners.contains(listener)) {
//                mlListeners.add(listener);
//            } else {
//                Log.i(TAG, "have the same");
//            }
mListenerList.register(listener);
Log.i(TAG, "register size" + mListenerList.beginBroadcast());
mListenerList.finishBroadcast();//每一次执行完都要finish一下

}

@Override
public void unregisterListener(IOnNewBookArrivedListener listener) throws RemoteException {
//            if (mlListeners.contains(listener)) {
//                mlListeners.remove(listener);
//            } else {
//                Log.i(TAG, "no find");
//            }
mListenerList.unregister(listener);
Log.i(TAG, "unregister size " + mListenerList.beginBroadcast());
mListenerList.finishBroadcast();

}
};

@Override
public void onCreate() {
super.onCreate();
mBookList.add(new Book(1, "ios"));
mBookList.add(new Book(2, "android"));
new Thread(new ServiceWorker()).start();//定义一个线程，每隔两秒去增加一个Book，目的是为了验证监听是否成功
}

@Override
public void onDestroy() {
isadd = false;

super.onDestroy();

}

void addNewbook(Book book) throws RemoteException {
mBookList.add(book);
final int N = mListenerList.beginBroadcast();
for (int i = 0; i < N; i++) {
IOnNewBookArrivedListener l = mListenerList.getBroadcastItem(i);
if (l != null) {
try {
l.onNewBookArrived(book);//给这个回掉赋值，以并于客户端在使用时有返回值
} catch (RemoteException e) {
e.printStackTrace();
}
}
}
mListenerList.finishBroadcast();
}

@Override
public IBinder onBind(Intent intent) {
// TODO: Return the communication channel to the service.
return binder;
}

private class ServiceWorker implements Runnable {
@Override
public void run() {
while (isadd) {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
int id = mBookList.size() + 1;
String name = mBookList.size() + 1 + "";
try {
addNewbook(new Book(id, name));
} catch (RemoteException e) {
e.printStackTrace();
}
}
}
}
}

下面是客户端的代码

通过服务端返回的Binder对于也就是 IBookManager.Stub()对象，里面的asInterface方法可以返回对于的AIDL接口，没印象的可以看看IPC机制详解(1),从而去调用相应的方法

public class Main2Activity extends AppCompatActivity {
String TAG = "Main2";
IBookManager manager;

ServiceConnection connection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
IBookManager iBookManager = IBookManager.Stub.asInterface(service);/通过这个Binder去使用服务端的方法
manager = iBookManager;
List<Book> list = new ArrayList<>();
try {
list = iBookManager.getBookList();//服务端的方法
Log.i(TAG, list.size() + " " + list.get(0).getName());
iBookManager.addBook(new Book(3, "nihao"));//服务端的方法
Log.i(TAG, list.size() + " " + list.get(list.size() - 1).getName());
iBookManager.registerListener(listener);//服务端的方法
} catch (RemoteException e) {
e.printStackTrace();
}
}

@Override
public void onServiceDisconnected(ComponentName name) {

}
};
IOnNewBookArrivedListener listener = new IOnNewBookArrivedListener.Stub() {
@Override
public void onNewBookArrived(Book newBook) throws RemoteException {
if (newBook != null) {
Log.i(TAG, "Add new Book" + newBook.getId() + "  " + newBook.getName());//因为在服务端的Addnewbook的方法里添加了回掉的数据，所以newBook是有值得
}
}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
Intent intent = new Intent(Main2Activity.this, ServiceBook.class);
bindService(intent, connection, BIND_AUTO_CREATE);
}

@Override
protected void onDestroy() {
Log.i(TAG, "Destory");
if (manager != null && manager.asBinder().isBinderAlive()) {
try {
Log.i(TAG, "unregister activity" + manager);
manager.unregisterListener(listener);
} catch (RemoteException e) {
e.printStackTrace();
}
}//当Activity销毁的时候，去接触注册
unbindService(connection);
super.onDestroy();
}
}

4.5 ContentProvider的使用

ContentProvider在Android中专门用于不同App之间的数据共享的，由此可见ContentProvider天生就可以用来实现跨进程通信。ContentProvider的底层也是用到了Binder，可见Binder在Android系统中是多么的重要。虽然ContentProvider的底层是Binder，但是系统已经为我们封装好了，使用起来也比AIDL要简单的多。

那么我们就来自定义个ContentProvider，首先去建一个类叫BookProvider 继承ContentProvider，

public class BookProvider extends ContentProvider {
@Override
//可以进行一些初始化 该方法运行在主线程里，其他五个方法运行在Binder线程池里
public boolean onCreate() {
return false;
}

@Nullable
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
return null;
}

@Nullable
@Override
//用于返回Uri请求对于的MIME类型（媒体类型）
public String getType(Uri uri) {
return null;
}

@Nullable
@Override
public Uri insert(Uri uri, ContentValues values) {
return null;
}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
return 0;
}

@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
return 0;
}
}

接着我们要去注册ContentProvider

<provider
android:name=".ContentProvider_text.BookProvider"
android:authorities="com.example.gyh.myapplication.ContentProvider_text.BookProvider"//是ContentProvider的唯一标识
android:permission="com.example.gyh.Provider"//访问权限
android:process=":provider"//ContentProvider运行在单独的进程中
android:readPermission="com.example.gyh.Provider.read"//读取权限
android:writePermission="com.example.gyh.Provider.write" //写权限   />

建一个Activity

Uri uri = Uri.parse("content://com.example.gyh.myapplication.ContentProvider_text.BookProvider");这就是xml里生命的唯一标识符
getContentResolver().query(uri, null, null, null, null);
getContentResolver().query(uri, null, null, null, null);
getContentResolver().query(uri, null, null, null, null);

我们可以看一下输出

12-08 14:05:57.775 22494-22506/com.example.gyh.myapplication:provider I/Provider: query Binder_2

12-08 14:05:57.775 22494-22505/com.example.gyh.myapplication:provider I/Provider: query Binder_1

12-08 14:05:57.775 22494-22506/com.example.gyh.myapplication:provider I/Provider: query Binder_2

每次线程都不一样，因为这些方法是运作在Binder线程池里的 除了onCreate是运行在主线程里，所以在onCreate是不能进行耗时操作的。

这样简单的ContentProvider就使用成功了，但是为了更好是使用我们需要

结合SqliteOpenHelper去创建数据库去存储数据,所以我们又建立了类去继承SqliteOpenHelper去创建数据库

public class DbOpenHelper extends SQLiteOpenHelper {

private static final String DB_NAME = "book_provider.db";//数据库名
public static final String BOOK_TABLE_NAME = "book";//数据表名
public static final String USER_TALBE_NAME = "user";

private static final int DB_VERSION = 3;//版本号

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 DbOpenHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK_TABLE);//建表
db.execSQL(CREATE_USER_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
//用于版本更换的时候调用
}

然后我们在对ContentProvider进行修改

public class BookProvider extends ContentProvider {
String TAG = "Provider";
static String AUTHORITY = "com.example.gyh.myapplication.ContentProvider_text.BookProvider";
private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
public static final int BOOK_URI_CODE = 0;
public static final int USER_URI_CODE = 1;

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

}

Context mContext;
SQLiteDatabase mDb;

@Override
//可以进行一些初始化 该方法运行在主线程里，其他五个方法运行在Binder线程池里
public boolean onCreate() {
mContext = getContext();
initProviderData();
return true;
}

private void initProviderData() {
mDb = new DbOpenHelper(mContext).getWritableDatabase();
mDb.execSQL("delete from " + DbOpenHelper.BOOK_TABLE_NAME);
mDb.execSQL("delete from " + DbOpenHelper.USER_TALBE_NAME);
mDb.execSQL("insert into book values(3,'Android');");
mDb.execSQL("insert into book values(4,'Ios');");
mDb.execSQL("insert into book values(5,'Html5');");
}

@Nullable
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
Log.i(TAG, "query " + Thread.currentThread().getName());
String table = getTableName(uri);
if (table == null) {
throw new IllegalArgumentException("Unsupported URI: " + uri);
}
return mDb.query(table, projection, selection, selectionArgs, null, null, sortOrder, null);
}

@Nullable
@Override
//用于返回Uri请求对于的MIME类型（媒体类型）
public String getType(Uri uri) {
Log.i(TAG, "getType " + Thread.currentThread().getName());
return null;
}

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

return tableName;
}

@Nullable
@Override
public Uri insert(Uri uri, ContentValues values) {
Log.i(TAG, "insert " + Thread.currentThread().getName());
String tablename = getTableName(uri);
if (tablename == null) {
throw new IllegalArgumentException("Unsupported URI: " + uri);
}
Log.i(TAG, "insert table name " + tablename);

mDb.insert(tablename, null, values);
mContext.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) {
Log.i(TAG, "update " + Thread.currentThread().getName());
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;
}
}

对Activity进行修改

Uri bookUri = Uri.parse("content://com.example.gyh.myapplication.ContentProvider_text.BookProvider/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()) {//这里的0指的是筛选的第一个条件就是_id
Log.d(TAG, "query book:" + bookCursor.getInt(0) + "  " + bookCursor.getString(1));
}
bookCursor.close();

意思代码完成了ContentProvider的基本使用

对上述代码中可能大家会对Uri和UriMatcher的使用不是很了解 那么我来举个例子

第一部初始化

UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);

第二部将Uri和UriMatcher配对

matcher.addURI("com.yfz.Lesson", "people", PEOPLE);  这里的“people”就是Path

matcher.addURI("com.yfz.Lesson", "person/#", PEOPLE_ID);  PEOPLE_ID是code int

第三步我们就可以通过请求的Uri进行操作

Uri uri = Uri.parse("content://" + "com.yfz.Lesson" + "/people");

int match = matcher.match(uri);

switch (match)

{

case PEOPLE:

return "vnd.android.cursor.dir/people";

case PEOPLE_ID:

return "vnd.android.cursor.item/people";

default:

return null;

}

返回的结果就是”vnd.android.cursor.dir/person”.

我们可以看到UriMatcher作用是可以组合Uri 这里将com.yfz.Lesson和people结合content://com.yfz.Lesson/people 所以我们后面输入的Uri不再是content://com.yfz.Lesson而是content://com.yfz.Lesson/people，我们可以通过输入的Uri判断出他们的Code，进行一些判断和操作。