管理圍欄回呼

註冊圍欄後，應用程式必須新增回呼，以便在圍欄觸發時做出回應。您可以透過 BroadcastReceiver 的子類別處理來自柵欄的 Intent 方法，達到這個目的。

如要將回呼新增至柵欄，請先註冊柵欄。

建立 BroadcastReceiver 的子類別

下列範例顯示 FenceReceiver 類別，該類別會擴充 BroadcastReceiver。這個類別會實作 BroadcastReceiver.onReceive() 回呼方法，處理源自應用程式建立的圍欄的所有 Intent 方法。收到 Intent 時，系統會使用 FenceState.extract() 方法取得圍欄狀態，並傳遞至回呼。

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);
        }
    }
}