前面我們介紹了Serializable和Parcelable的基礎知識,以及Binder的相關內容。本篇,開始分析各種跨進程通信的方式,Intent中附加extra信息,共享文件,Binder。另外ContentProvider天生就是支持跨進程訪問的。此外,網絡通信也是跟進程無關,所以Socket也可以實現IPC。
ipc的BookSevice和MainActivity
Bundle
Android中四大組件中的三個組件(Activity、Service、Receiver)都是支持在Intent中傳遞數據的,Intent和Bunlde都實現了Parcelable接口,都支持跨進程通信,因為Intent.putExtra內部就是用Bundle實現的。
public Intent putExtra(String name, String value) {
if (mExtras == null) {
mExtras = new Bundle();
}
mExtras.putString(name, value);
return this;
}
這個跟平時一個進程中的寫法都一樣,可以說無感覺切換O(∩_∩)O
例子可見Bundle跨進程
文件共享
文章共享可參考前面關于serializable和Parcelable時的內容。可以實現進程間通信,因為畢竟是文件,跟進程無關,可是在處理并發時問題很嚴重,比如,一個進程寫了一半兒,另一個進程讀取了;或者一個進程寫,另一個也寫,那你說,同一個文件出來的是個啥?啥也不是!
Android中的SharedPreferences是個特例,雖然最終是在xml文件中,可是內部還有內存級的緩存,所以多進程模式下,數據極不可靠。不建議多進程使用。
Messenger
Messenger的底層其實也是AIDL。一次處理一個請求,所以不用考慮同步。
public Messenger(Handler target) {
mTarget = target.getIMessenger();
}
public Messenger(IBinder target) {
mTarget = IMessenger.Stub.asInterface(target);
}
簡單實用方式如下:
Service
public class MessengerService extends Service {
private final static String TAG = "MessengerService";
private Handler serverHanlder = new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case MyConstants.MSG_FROM_CLIENT:
Log.d(TAG, "handleMessage: receive msg "+msg.getData().getString("msg"));
Messenger clientMessenger = msg.replyTo;
Message obtain = Message.obtain(null, MyConstants.MSG_FROM_SERVER);
Bundle bundle = new Bundle();
bundle.putString("msg","Hi,This is from server.");
obtain.setData(bundle);
try {
clientMessenger.send(obtain);
} catch (RemoteException e) {
e.printStackTrace();
}
break;
}
}
};
private Messenger serverMessenger = new Messenger(serverHanlder);
@Nullable
@Override
public IBinder onBind(Intent intent) {
return serverMessenger.getBinder();
}
}
Activity
public class MessengerActivity extends AppCompatActivity {
private static final String TAG = "MessengerActivity";
private Handler clientHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case MyConstants.MSG_FROM_SERVER:
Log.d(TAG, "handleMessage: receive msg "+msg.getData().getString("msg"));
break;
}
}
};
private Messenger clientMessenger = new Messenger(clientHandler);
private ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
Messenger serviceMessenger = new Messenger(service);
Message message = Message.obtain(null, MyConstants.MSG_FROM_CLIENT);
Bundle bundle = new Bundle();
bundle.putString("msg", "Hello,This is client.");
message.setData(bundle);
message.replyTo = clientMessenger;
try {
serviceMessenger.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_messenger);
bindService(new Intent(this, MessengerService.class), mServiceConnection, Context.BIND_AUTO_CREATE);
}
@Override
protected void onDestroy() {
unbindService(mServiceConnection);
super.onDestroy();
}
}
Messenger使用message傳輸數據,Message的what、arg1、arg2、obj、Bundle以及replyTo都可以充當數據載體。有人就說了,你看你,有那么多簡單的不用,非用一個Bundle,別急,咱們來仔細看一下。
- what 就不說了,主要是區分不同消息
- arg1、arg2 如果是int類型時的簡寫形式
- obj 只能是Framework中的Parcelable類型的參數,自定義的不行
- replyTo 針對Messenger
- Bundle 所以你看,還能怎么辦,有用的就不錯了,走起來吧
借用下開發藝術探索的原理圖
AIDL
AIDL的簡單使用前面已經說過(Binder章節中),代碼也有,可以先大概熟悉下寫法。
接著以前的內容說
AIDL支持的數據類型
- 基本數據類型
- String、CharSequence
- Parcelable:所有實現了Parcelable的接口的對象
- List:只支持ArrayList,里面的每個元素需要支持AIDL
- Map:只支持HashMap,里面的每個元素都必須被AIDL支持,包括key和value
- AIDL:所有的AIDL接口本身也可以在AIDL中使用
- Parcelable對象和AIDL必須顯式的import進來。
- 使用都自定義的Parcelable對象時,必須新建一個同名的AIDL文件,并且聲明為Parcelable類型,如:
// Book.aidl
package com.breezehan.ipc;
parcelable Book;
- AIDL接口方法中,參數如果不是基礎類型,都需要標上方向:in、out、或者inout,in表示輸入型參數,out表示輸出型參數,inout表示輸入輸出型參數。你真的理解AIDL中的in,out,inout么?
我們改造下之前的AIDL寫法,BookSevice中有個List,改造如下
public class BookService extends Service{
CopyOnWriteArrayList<Book> mBookList = new CopyOnWriteArrayList<>();
private IBinder binder = new IBookManager.Stub() {
@Override
public List<Book> getBookList() throws RemoteException {
return mBookList;
}
@Override
public void addBook(Book book) throws RemoteException {
mBookList.add(book);
}
};
@Override
public void onCreate() {
super.onCreate();
mBookList.add(new Book(1, "三體"));
mBookList.add(new Book(2, "Android"));
}
@Nullable
@Override
public IBinder onBind(Intent intent) {
return binder;
}
}
可是前面不是說List只能是ArrayList嗎
AIDL是運行在Binder線程池中的,可以多個客戶端同時連接,會存在多個線程同時訪問的情況,而CopyOnWriteArrayList支持并發的讀寫
AIDL中支持抽象的List,雖然服務端返回的是CopyOnWriteArrayList,但是Binder中會按照List的規范訪問數據并最終形成一個ArrayList給客戶端。類似的還有ConcurrentHashMap。
代碼參考
改進型AIDL
有種情況,假如Service相當于圖書館,客戶端不想輪詢查詢有什么書,圖書館加入新書,直接通知我一下就好了,也可以取消提醒,這就是常說的觀察者模式。
首先,我們需要有個監聽接口,客戶端實現。這里只能是AIDL接口IOnNewBookArrivedListener.aidl
// IOnNewBookArrivedListener.aidl
package com.breezehan.ipc;
import com.breezehan.ipc.Book;
interface IOnNewBookArrivedListener {
void onNewBookArrived(in Book book);
}
IBookManager也需要改造
// IBookManager.aidl
package com.breezehan.ipc;
import com.breezehan.ipc.Book;
import com.breezehan.ipc.IOnNewBookArrivedListener;
interface IBookManager {
List<Book> getBookList();
void addBook(in Book book);
void registerListener(IOnNewBookArrivedListener listener);
void unRegisterListener(IOnNewBookArrivedListener listener);
}
Service和Activity見github代碼。
運行結果如下
com.breezehan.ipc進程中
com.breezehan.ipc:remote進程中
哈哈,你看,多進程的觀察者模式成功了。
不過,等會兒再高興,本來我們在Activity中的onDestroy中設置了
@Override
protected void onDestroy() {
if (iBookManager != null && iBookManager.asBinder().isBinderAlive()) {
Log.d(TAG, "onDestroy: unregister listener "+mOnNewBookArrivedListener);
try {
iBookManager.unRegisterListener(mOnNewBookArrivedListener);
} catch (RemoteException e) {
e.printStackTrace();
}
}
unbindService(mServiceConnection);
super.onDestroy();
}
真正推出Activity時,打印會出現
嘛意思,not found,can not unregister.
為什么呢?為什么會解注冊失敗呢。
我們要知道,Binder傳輸的的對象,整個是一個序列化、反序列化的過程,Binder會把客戶端傳過來的對象反序列化成一個新對象,不是一個對象,怎么能remote掉呢!
進階化改進型AIDL
這里我們要使用到RemoteCallbackList。使系統提供的專門用于刪除跨進程listener的接口,看它的定義,接收extend IInterface的參數,即所有的AIDL都可以支持。
public class RemoteCallbackList<E extends IInterface>
它的內部有個ArrayMap用戶保存AIDL的listener,Map中的key時IBInder類型,value是Callback類型
ArrayMap<IBinder, Callback> mCallbacks
= new ArrayMap<IBinder, Callback>();
看register(E callback)詳細代碼,我們知道,雖然每次客戶端傳輸過去的listener,最終都被binder生成一個個不同的對象(內部相同),但是底層的Binder對象只是一個。
public boolean register(E callback, Object cookie) {
synchronized (mCallbacks) {
if (mKilled) {
return false;
}
IBinder binder = callback.asBinder();
try {
Callback cb = new Callback(callback, cookie);
binder.linkToDeath(cb, 0);
mCallbacks.put(binder, cb);//使用binder作為key,同一個binder只有一個對象。
return true;
} catch (RemoteException e) {
return false;
}
}
}
使用RemoteCallbackList改進的Service如下:
@Override
public void registerListener(IOnNewBookArrivedListener listener) throws RemoteException {
mArrivedListeners.register(listener);
}
@Override
public void unRegisterListener(IOnNewBookArrivedListener listener) throws RemoteException {
mArrivedListeners.unregister(listener);
}
private void onNewBookArrived(Book newBook) throws RemoteException {
mBookList.add(newBook);
int N = mArrivedListeners.beginBroadcast();
for(int i=0;i<N;i++) {
IOnNewBookArrivedListener broadcastItem = mArrivedListeners.getBroadcastItem(i);
if (broadcastItem != null) {
broadcastItem.onNewBookArrived(newBook);
}
}
mArrivedListeners.finishBroadcast();
}
AIDL服務端 有時不想任何人都可以連接,必須加入驗證服務,驗證內容再次就不做探索了(我可不說是因為沒用過)。
使用ContentProvider
ContentProvider跟Messenger一樣,底層都是Binder實現。但是ContentProvider是Android中提供的專門用于不同應用間進行數據共享的方式,天生就適合進程間通信。封裝的很好,比AIDL簡單很多。
像通訊錄、日歷等,都實現了ContentProvider,我們只需要通過ContentResolver的query、update、insert、delete方法即可。
Provider,雖然沒有具體內容,但是不耽誤使用。對象代碼provider示例代碼
public class BookProvider extends ContentProvider {
private static final String TAG = "BookProvider";
@Override
public boolean onCreate() {
Log.d(TAG, "onCreate,current Thread: "+Thread.currentThread().getName());
return false;
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
Log.d(TAG, "onCreate,current Thread: "+Thread.currentThread().getName());
return null;
}
@Nullable
@Override
public String getType(@NonNull Uri uri) {
Log.d(TAG, "getType");
return null;
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
Log.d(TAG, "insert");
return null;
}
@Override
public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
Log.d(TAG, "delete");
return 0;
}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
Log.d(TAG, "update");
return 0;
}
}
ProviderActivity
public class ProviderActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_provider);
Uri uri = Uri.parse("content://com.breezehan.ipc.book.provider");
getContentResolver().query(uri, null, null, null, null);
getContentResolver().query(uri, null, null, null, null);
getContentResolver().query(uri, null, null, null, null);
}
清單文件配置,provider中android:authorities需要時唯一的,android:permission="com.breezehan.PROVIDER"表示權限,其他app想使用這個provider,必須聲明權限;process就不說了,不想弄兩個應用,開個進程。
<provider
android:name=".provider.BookProvider"
android:authorities="com.breezehan.ipc.book.provider"
android:permission="com.breezehan.PROVIDER"
android:process=":provider" />
<activity android:name=".provider.ProviderActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
運行結果如下
看到了吧,Binder線程池。onCreate是UI線程,三次query可能會在不同線程。
我們用Sqlite簡單實現邏輯內容,其實ContenProvider內部想怎么實現都行。
DbOpenHelper
public class DbOpenHelper extends SQLiteOpenHelper {
private static final String DB_NAME = "bookprovider.db";
private static final int DB_VERSION = 1;
public static final String BOOK_TABLE_NAME = "book";
public static final String USER_TABLE_NAME = "user";
public static final String CREATE_BOOK_TABLE = "CREATE TABLE IF NOT EXISTS " + BOOK_TABLE_NAME + "( _id INTEGER PRIMARY KEY, name TEXT)";
public static final String CREATE_USER_TABLE = "CREATE TABLE IF NOT EXISTS " + USER_TABLE_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);
db.execSQL(CREATE_USER_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
BookProvider改造
public class BookProvider extends ContentProvider {
private static final String TAG = "BookProvider";
public static final String AUTHRORITY = "com.breezehan.ipc.book.provider";
public static final Uri BOOK_CONTENT_URI = Uri.parse("content://" + AUTHRORITY + "/book");
public static final Uri USER_CONTENT_URI = Uri.parse("content://" + AUTHRORITY + "/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(AUTHRORITY, "book", BOOK_URI_CODE);//將uri和uricode關聯起來
sUriMatcher.addURI(AUTHRORITY,"user",USER_URI_CODE);
}
private Context mContext;
private SQLiteDatabase sqLiteDatabase;
@Override
public boolean onCreate() {
Log.d(TAG, "onCreate,current Thread: "+Thread.currentThread().getName());
mContext =getContext();
//初始化數據庫,真正使用不能這樣寫,MainThread
initProviderData();
return true;
}
private void initProviderData() {
sqLiteDatabase = new DbOpenHelper(mContext).getWritableDatabase();
sqLiteDatabase.execSQL("delete from "+DbOpenHelper.BOOK_TABLE_NAME);
sqLiteDatabase.execSQL("delete from "+DbOpenHelper.USER_TABLE_NAME);
sqLiteDatabase.execSQL("insert into book values(3,'Android');");
sqLiteDatabase.execSQL("insert into book values(4,'Ios');");
sqLiteDatabase.execSQL("insert into book values(5,'Html5');");
sqLiteDatabase.execSQL("insert into user values(1,'jake',1);");
sqLiteDatabase.execSQL("insert into user values(5,'Html5',0);");
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
Log.d(TAG, "query,current Thread: "+Thread.currentThread().getName());
String tableName = getTableName(uri);
if (tableName == null) {
throw new IllegalArgumentException("Unsupported URI:" + uri);
}
return sqLiteDatabase.query(tableName,projection,selection,selectionArgs,null,null,sortOrder,null);
}
@Nullable
@Override
public String getType(@NonNull Uri uri) {
Log.d(TAG, "getType");
return null;
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
Log.d(TAG, "insert");
String table = getTableName(uri);
if (table == null) {
throw new IllegalArgumentException("Unsupported URI:" + uri);
}
sqLiteDatabase.insert(table, null, values);
mContext.getContentResolver().notifyChange(uri,null);//通知外界,ContentProvider的數據已經改變
return uri;
}
@Override
public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
Log.d(TAG, "delete");
String table = getTableName(uri);
if (table == null) {
throw new IllegalArgumentException("Unsupported URI:" + uri);
}
int count = sqLiteDatabase.delete(table, selection, selectionArgs);
if (count > 0) {
mContext.getContentResolver().notifyChange(uri,null);
}
return count;
}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
Log.d(TAG, "update");
String table = getTableName(uri);
if (table == null) {
throw new IllegalArgumentException("Unsupported URI:" + uri);
}
int row = sqLiteDatabase.update(table, values, selection, selectionArgs);
if (row > 0) {
mContext.getContentResolver().notifyChange(uri,null);
}
return row;
}
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_TABLE_NAME;
break;
}
return tableName;
}
}
ProviderActivity中
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 bookUri = Uri.parse("content://com.breezehan.ipc.book.provider/book");//BOOK_CONTENT_URI
ContentValues values = new ContentValues();
values.put("_id", "6");
values.put("name","程序設計的藝術");
getContentResolver().insert(bookUri, values);
Cursor bookCursor = getContentResolver().query(bookUri, new String[]{"_id", "name"}, null, null, null);
while (bookCursor.moveToNext()) {
Book book = new Book(bookCursor.getInt(0),bookCursor.getString(1));
Log.d(TAG, "query book:"+book.toString());
}
bookCursor.close();
}
}
運行結果如下
上面只是簡單介紹ContentProvider的基本使用方法,深入使用還有很多知識。
使用Socket
內容略