andorid jar/库源码解析之Bolts

目录：andorid jar/库源码解析 

Bolts：

　　作用：

　　　　用于链式执行跨线程代码，且传递数据

　　栗子：

Task.call(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return true;
            }
        }, Task.UI_THREAD_EXECUTOR);

        Task.callInBackground(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return false;
            }
        });

        Task.callInBackground(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return true;
            }
        }).onSuccess(new Continuation<Boolean, Object>() {
            @Override
            public Object then(Task<Boolean> task) throws Exception {
                if (task.getResult()) {
                    return null;
                } else {
                    return new Object();
                }
            }
        }, Task.BACKGROUND_EXECUTOR).continueWith(new Continuation<Object, Object>() {
            @Override
            public Object then(Task<Object> task) throws Exception {
                if (task.getResult() == null) {
                    Toast.makeText(getBaseContext(), "null", Toast.LENGTH_SHORT).show();
                } else {
                    Toast.makeText(getBaseContext(), "not null", Toast.LENGTH_SHORT).show();
                }

                return null;
            }
        }, Task.UI_THREAD_EXECUTOR);

　　源码解读：

　　在内部通过维护多中 ExecutorService 对象，并且通过串联的方式进行调用。

　　并且通过维护内部变量在，在指定流程处，就是特定的，值，值通过Task的对象getResult拿到。

　　UIThread

/**
   * An {@link java.util.concurrent.Executor} that runs tasks on the UI thread.
   */
  private static class UIThreadExecutor implements Executor {
    @Override
    public void execute(Runnable command) {
      new Handler(Looper.getMainLooper()).post(command);
    }
  }

　　BackgroundThread

private BoltsExecutors() {
    background = !isAndroidRuntime()
        ? java.util.concurrent.Executors.newCachedThreadPool()
        : AndroidExecutors.newCachedThreadPool();
    scheduled = Executors.newSingleThreadScheduledExecutor();
    immediate = new ImmediateExecutor();
  }

　　源码：https://github.com/BoltsFramework/Bolts-Android

　　引入：

implementation 'com.parse.bolts:bolts-android:1.2.0'