android開發(fā) 之 Bolts-Android

目錄

多線程編程對比: iOS與Android

android的多線程編程有

  • Thread

  • Handler

  • AsyncTask

  • IntentService

android多線程詳細(xì)可以參考android學(xué)習(xí) 之 Service

iOS的多線程編程有

  • NSthread

  • GCD

  • NSOperationQueue

iOS多線程詳細(xì)可以參考Objective-C學(xué)習(xí) 之 GCD / iOS最佳實踐 之 優(yōu)先使用NSOperationQueue而不是GCD / iOS開發(fā) 之 Queue和Thread

對比兩個平臺的多線程編程, android還是稍遜一些

  • Handler和IntentService的多線程編程, 開銷有些大, 而GCD配合Block, 簡潔好用并且功能也很強(qiáng)大

  • AsyncTask處理消息隊列和多線程同步, 是比較費勁的, 而NSOperationQueue, 仍然是簡單好用五顆星

那有沒有一種方案可以讓android變得和iOS一樣簡單好用呢?

答案就是今天的主角BoltsFramework/Bolts-Android

Bolts-Android

Bolts-Android由Parse"榮譽(yù)"出品, 為什么說是"榮譽(yù)"呢?

因為作為Baas的鼻祖, Parse已經(jīng)成功地死在了沙灘上, 但是被Facebook關(guān)門之后, 它仍然發(fā)揮了余熱, Parse的很多項目都在Github Parse上開源了

廢話不多說, 直接看例子吧

Tasks

想要在當(dāng)前線程執(zhí)行Task, 就是這么簡單

Task.call(new Callable<Boolean>() {
    @Override
    public Boolean call() throws Exception {
        XLog.d(Thread.currentThread().getName() + " " + "call in current thread");
        return true;
    }
});

如果想在后臺線程執(zhí)行Task

Task.callInBackground(new Callable<Boolean>() {
    @Override
    public Boolean call() throws Exception {
        XLog.d(Thread.currentThread().getName() + " " + "call in background thread");
        return true;
    }
});

如果想在UI主線程執(zhí)行Task

Task.call(new Callable<Boolean>() {
    @Override
    public Boolean call() throws Exception {
        XLog.d(Thread.currentThread().getName() + " " + "call in main thread");
        return true;
    }
}, Task.UI_THREAD_EXECUTOR);

如果想要延時執(zhí)行Task

Task.delay(2000).continueWith(new Continuation<Void, Void>() {
    @Override
    public Void then(Task<Void> task) throws Exception {
        XLog.d(Thread.currentThread().getName() + " " + "call in main thread (after delay 2 seconds)");
        return null;
    }
});

是不是簡單到讓人無法相信? 其實這里的Task和iOS中的GCD編程是類似的(詳細(xì)可以參考Objective-C學(xué)習(xí) 之 GCD)

Chaining Tasks

熱完身, 我們來看下Bolts-Android的函數(shù)式編程(關(guān)于函數(shù)式編程詳細(xì)可以參考談?wù)労瘮?shù)式響應(yīng)式編程(Functional Reactive Programming))

Task.call(new Callable<Boolean>() {
    @Override
    public Boolean call() throws Exception {
        XLog.d(Thread.currentThread().getName() + " calling");
        return true;
    }
}, Task.UI_THREAD_EXECUTOR).continueWith(new Continuation<Boolean, String>() {
    @Override
    public String then(Task<Boolean> task) throws Exception {
        Thread.sleep(2000);
        XLog.d(Thread.currentThread().getName() + " onSuccess " + task.getResult());

        return "hello bolts";
    }
}, Task.BACKGROUND_EXECUTOR).continueWith(new Continuation<String, Void>() {
    @Override
    public Void then(Task<String> task) throws Exception {
        XLog.d(Thread.currentThread().getName() + " continueWith " + task.getResult());
        return null;
    }
}, Task.UI_THREAD_EXECUTOR);

打印結(jié)果如下

main calling
pool-2-thread-1 onSuccess true
main continueWith hello bolts

通過函數(shù)式的鏈?zhǔn)骄幊? 輕松地實現(xiàn)了Task的同步和多線程的切換(怎么忽然就想到了RxJava了呢? 看來下期可以來個Bolts-Android大戰(zhàn)RxJava的專題)

Group Tasks

Group Task是我取得名字哈, 所謂Group Tasks, 就是指多個Task組成的一組Tasks

Task.call(new Callable<Boolean>() {
    @Override
    public Boolean call() throws Exception {
        XLog.d(Thread.currentThread().getName() + " calling");
        return true;
    }
}, Task.UI_THREAD_EXECUTOR).continueWith(new Continuation<Boolean, List<Task<Void>>>() {
    @Override
    public List<Task<Void>> then(Task<Boolean> task) throws Exception {
        XLog.d(Thread.currentThread().getName() + " tasks start");
        List<Task<Void>> tasks = new ArrayList<Task<Void>>();
        tasks.add(asyncOperation1());
        tasks.add(asyncOperation2());
        Task.whenAll(tasks).waitForCompletion();
        XLog.d(Thread.currentThread().getName() + " tasks end");
        return tasks;
    }
}, Task.BACKGROUND_EXECUTOR).continueWith(new Continuation<List<Task<Void>>, Void>() {
    @Override
    public Void then(Task<List<Task<Void>>> task) throws Exception {
        XLog.d(Thread.currentThread().getName() + " done");
        return null;
    }
}, Task.UI_THREAD_EXECUTOR);

其中asyncOperation1和asyncOperation2的定義如下

private Task<Void> asyncOperation1() {
    return Task.callInBackground(new Callable<Void>() {
        @Override
        public Void call() throws Exception {
            XLog.i("asyncOperation1 start");

            try {
                Thread.sleep(1000);
            } catch (Exception e) {
                XLog.e(e.getMessage());
            }

            XLog.i("asyncOperation1 end");
            return null;
        }
    });
}

private Task<Void> asyncOperation2() {
    return Task.callInBackground(new Callable<Void>() {
        @Override
        public Void call() throws Exception {
            XLog.i("asyncOperation2 start");

            try {
                Thread.sleep(3000);
            } catch (Exception e) {
                XLog.e(e.getMessage());
            }

            XLog.i("asyncOperation2 end");
            return null;
        }
    });
}

后面的continueWith會等asyncOperation1和asyncOperation2都執(zhí)行完成后再執(zhí)行

打印結(jié)果如下

main calling
pool-2-thread-1 tasks start
asyncOperation1 start
asyncOperation2 start
asyncOperation1 end
asyncOperation2 end
pool-2-thread-1 tasks end
main done

有沒有小試牛刀的感覺? 我們接著來看下面的用法

Tasks in Parallel

final Executor PARALLEL_EXECUTOR = Executors.newCachedThreadPool();

Task.call(new Callable<Void>() {
    @Override
    public Void call() throws Exception {
        for (int i = 0; i < 100; i++) {
            if (i % 2 == 0) {
                XLog.i(Thread.currentThread().getName() + " i = " + i);
            }
        }
        return null;
    }
}, PARALLEL_EXECUTOR);

Task.call(new Callable<Void>() {
    @Override
    public Void call() throws Exception {
        for (int i = 0; i < 100; i++) {
            if (i % 2 == 1) {
                XLog.i(Thread.currentThread().getName() + " i = " + i);
            }
        }
        return null;
    }
}, PARALLEL_EXECUTOR);

打印結(jié)果如下

pool-2-thread-1 i = 0
pool-2-thread-2 i = 50
pool-2-thread-1 i = 1
pool-2-thread-2 i = 51
pool-2-thread-1 i = 2
pool-2-thread-2 i = 52
pool-2-thread-1 i = 3
pool-2-thread-2 i = 53
pool-2-thread-1 i = 4
pool-2-thread-2 i = 54
pool-2-thread-1 i = 5
pool-2-thread-1 i = 6
pool-2-thread-2 i = 55
pool-2-thread-2 i = 56
pool-2-thread-1 i = 7
pool-2-thread-1 i = 8
pool-2-thread-2 i = 57
pool-2-thread-2 i = 58
pool-2-thread-1 i = 9
pool-2-thread-2 i = 59
pool-2-thread-1 i = 10
pool-2-thread-2 i = 60
pool-2-thread-1 i = 11
pool-2-thread-2 i = 61
pool-2-thread-1 i = 12
pool-2-thread-2 i = 62
pool-2-thread-1 i = 13
pool-2-thread-2 i = 63
pool-2-thread-1 i = 14
pool-2-thread-2 i = 64
pool-2-thread-1 i = 15
pool-2-thread-2 i = 65
pool-2-thread-1 i = 16
pool-2-thread-2 i = 66
pool-2-thread-1 i = 17
pool-2-thread-2 i = 67
pool-2-thread-1 i = 18
pool-2-thread-1 i = 19
pool-2-thread-2 i = 68
pool-2-thread-1 i = 20
pool-2-thread-2 i = 69
pool-2-thread-1 i = 21
pool-2-thread-2 i = 70
pool-2-thread-1 i = 22
pool-2-thread-2 i = 71
pool-2-thread-1 i = 23
pool-2-thread-2 i = 72
pool-2-thread-1 i = 24
pool-2-thread-2 i = 73
pool-2-thread-2 i = 74
pool-2-thread-1 i = 25
pool-2-thread-2 i = 75
pool-2-thread-1 i = 26
pool-2-thread-2 i = 76
pool-2-thread-1 i = 27
pool-2-thread-2 i = 77
pool-2-thread-1 i = 28
pool-2-thread-2 i = 78
pool-2-thread-1 i = 29
pool-2-thread-2 i = 79
pool-2-thread-1 i = 30
pool-2-thread-1 i = 31
pool-2-thread-2 i = 80
pool-2-thread-1 i = 32
pool-2-thread-2 i = 81
pool-2-thread-1 i = 33
pool-2-thread-2 i = 82
pool-2-thread-1 i = 34
pool-2-thread-2 i = 83
pool-2-thread-2 i = 84
pool-2-thread-1 i = 35
pool-2-thread-2 i = 85
pool-2-thread-1 i = 36
pool-2-thread-2 i = 86
pool-2-thread-1 i = 37
pool-2-thread-2 i = 87
pool-2-thread-1 i = 38
pool-2-thread-1 i = 39
pool-2-thread-2 i = 88
pool-2-thread-1 i = 40
pool-2-thread-2 i = 89
pool-2-thread-1 i = 41
pool-2-thread-2 i = 90
pool-2-thread-1 i = 42
pool-2-thread-2 i = 91
pool-2-thread-1 i = 43
pool-2-thread-2 i = 92
pool-2-thread-1 i = 44
pool-2-thread-2 i = 93
pool-2-thread-1 i = 45
pool-2-thread-2 i = 94
pool-2-thread-1 i = 46
pool-2-thread-2 i = 95
pool-2-thread-1 i = 47
pool-2-thread-2 i = 96
pool-2-thread-1 i = 48
pool-2-thread-2 i = 97
pool-2-thread-1 i = 49
pool-2-thread-2 i = 98
pool-2-thread-2 i = 99

打印結(jié)果有兩個發(fā)現(xiàn)

  • 線程池有兩個線程: pool-2-thread-1和pool-2-thread-2

  • 線程池里的線程是并行執(zhí)行的: 數(shù)字都是

Tasks in Serial

那有沒有方法可以讓線程池中只有一個線程, 所有Tasks按照queue的方式FIFO依次執(zhí)行呢? 辦法如下

final Executor SERIAL_EXECUTOR = Executors.newSingleThreadExecutor();

Task.call(new Callable<Void>() {
    @Override
    public Void call() throws Exception {
        for (int i = 0; i < 50; i++) {
            XLog.i(Thread.currentThread().getName() + " i = " + i);
        }
        return null;
    }
}, SERIAL_EXECUTOR);

call(new Callable<Void>() {
    @Override
    public Void call() throws Exception {
        for (int i = 50; i < 100; i++) {
            XLog.i(Thread.currentThread().getName() + " i = " + i);
        }
        return null;
    }
}, SERIAL_EXECUTOR);

打印結(jié)果如下

pool-2-thread-1 i = 0
pool-2-thread-1 i = 1
pool-2-thread-1 i = 2
pool-2-thread-1 i = 3
pool-2-thread-1 i = 4
pool-2-thread-1 i = 5
pool-2-thread-1 i = 6
pool-2-thread-1 i = 7
pool-2-thread-1 i = 8
pool-2-thread-1 i = 9
pool-2-thread-1 i = 10
pool-2-thread-1 i = 11
pool-2-thread-1 i = 12
pool-2-thread-1 i = 13
pool-2-thread-1 i = 14
pool-2-thread-1 i = 15
pool-2-thread-1 i = 16
pool-2-thread-1 i = 17
pool-2-thread-1 i = 18
pool-2-thread-1 i = 19
pool-2-thread-1 i = 20
pool-2-thread-1 i = 21
pool-2-thread-1 i = 22
pool-2-thread-1 i = 23
pool-2-thread-1 i = 24
pool-2-thread-1 i = 25
pool-2-thread-1 i = 26
pool-2-thread-1 i = 27
pool-2-thread-1 i = 28
pool-2-thread-1 i = 29
pool-2-thread-1 i = 30
pool-2-thread-1 i = 31
pool-2-thread-1 i = 32
pool-2-thread-1 i = 33
pool-2-thread-1 i = 34
pool-2-thread-1 i = 35
pool-2-thread-1 i = 36
pool-2-thread-1 i = 37
pool-2-thread-1 i = 38
pool-2-thread-1 i = 39
pool-2-thread-1 i = 40
pool-2-thread-1 i = 41
pool-2-thread-1 i = 42
pool-2-thread-1 i = 43
pool-2-thread-1 i = 44
pool-2-thread-1 i = 45
pool-2-thread-1 i = 46
pool-2-thread-1 i = 47
pool-2-thread-1 i = 48
pool-2-thread-1 i = 49
pool-2-thread-1 i = 50
pool-2-thread-1 i = 51
pool-2-thread-1 i = 52
pool-2-thread-1 i = 53
pool-2-thread-1 i = 54
pool-2-thread-1 i = 55
pool-2-thread-1 i = 56
pool-2-thread-1 i = 57
pool-2-thread-1 i = 58
pool-2-thread-1 i = 59
pool-2-thread-1 i = 60
pool-2-thread-1 i = 61
pool-2-thread-1 i = 62
pool-2-thread-1 i = 63
pool-2-thread-1 i = 64
pool-2-thread-1 i = 65
pool-2-thread-1 i = 66
pool-2-thread-1 i = 67
pool-2-thread-1 i = 68
pool-2-thread-1 i = 69
pool-2-thread-1 i = 70
pool-2-thread-1 i = 71
pool-2-thread-1 i = 72
pool-2-thread-1 i = 73
pool-2-thread-1 i = 74
pool-2-thread-1 i = 75
pool-2-thread-1 i = 76
pool-2-thread-1 i = 77
pool-2-thread-1 i = 78
pool-2-thread-1 i = 79
pool-2-thread-1 i = 80
pool-2-thread-1 i = 81
pool-2-thread-1 i = 82
pool-2-thread-1 i = 83
pool-2-thread-1 i = 84
pool-2-thread-1 i = 85
pool-2-thread-1 i = 86
pool-2-thread-1 i = 87
pool-2-thread-1 i = 88
pool-2-thread-1 i = 89
pool-2-thread-1 i = 90
pool-2-thread-1 i = 91
pool-2-thread-1 i = 92
pool-2-thread-1 i = 93
pool-2-thread-1 i = 94
pool-2-thread-1 i = 95
pool-2-thread-1 i = 96
pool-2-thread-1 i = 97
pool-2-thread-1 i = 98
pool-2-thread-1 i = 99

Error Handling

看完上面的內(nèi)容, 想必各位從此都是android多線程的"磚家"了吧, 不過請稍等片刻, 還有一個重要的問題沒有解釋

Task.call(new Callable<String>() {
    @Override
    public String call() throws Exception {
        Thread.sleep(2000);

        if (1 < 10) {
            XLog.d(Thread.currentThread().getName() + " RuntimeException");
            throw new RuntimeException("There was an error.");
        }
        return "hello bolts";
    }
}, Task.BACKGROUND_EXECUTOR).onSuccess(new Continuation<String, Void>() {
    @Override
    public Void then(Task<String> task) throws Exception {
        XLog.d(Thread.currentThread().getName() + " onSuccess");
        return null;
    }
}, Task.UI_THREAD_EXECUTOR).continueWith(new Continuation<Void, Void>() {
    @Override
    public Void then(Task<Void> task) throws Exception {
        if (task.isFaulted()) {
            XLog.e(Thread.currentThread().getName() + " error");
            return null;
        }
        XLog.d(Thread.currentThread().getName() + " done");
        return null;
    }
}, Task.UI_THREAD_EXECUTOR);

請問這里的打印結(jié)果是如何呢?

  • A: onSuccess

  • B: error

  • C: done

  • D: onSuccess & done

正確答案是B

小結(jié)

android多線程的方案還有諸如: yigit/android-priority-jobqueue, 不過經(jīng)過實測, 和Bolts-Android比較起來, android-priority-jobqueue還是"略重量級"了一些, 如果你有更好的方案和實現(xiàn), 歡迎留言和分享

參考

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