管理栅栏回调

注册围栏后，应用必须添加一个回调，以便在围栏触发时做出响应。您可以使用 BroadcastReceiver 的子类来处理围栏中的 Intent 方法。

在向围栏添加回调之前，您必须先注册围栏。

创建 BroadcastReceiver 的子类

以下示例展示了扩展 BroadcastReceiver 的 FenceReceiver 类。该类实现了 BroadcastReceiver.onReceive() 回调方法，用于处理源自应用创建的围栏的所有 Intent 方法。收到 Intent 时，系统会使用 FenceState.extract() 方法获取围栏状态，并将其传递给回调。

public class FenceReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {

        FenceState fenceState = FenceState.extract(intent);

        if (TextUtils.equals(fenceState.getFenceKey(), FENCE_KEY)) {
            String fenceStateStr;
            switch (fenceState.getCurrentState()) {
                case FenceState.TRUE:
                    fenceStateStr = "true";
                    break;
                case FenceState.FALSE:
                    fenceStateStr = "false";
                    break;
                case FenceState.UNKNOWN:
                    fenceStateStr = "unknown";
                    break;
                default:
                    fenceStateStr = "unknown value";
            }
            mLogFragment.getLogView().println("Fence state: " + fenceStateStr);
        }
    }
}