Question

我使用volley库实现了SyncAdapter。它正在工作，但后来我意识到Iam从onPerformSync方法调用异步（排球请求）代码。

Q1：coudl onPerformSync并行执行多次？（对于一个用户/一个权限）。我需要编写内码安全吗？用锁？同步？ SyncAdapter本身不是同步的，所以任何内部同步都没用吗？
Q2：是onPerformSync线程安全，哪个线程？在我看来，所有onPerformSync调用都是由相同的线程引用完成的。这是否意味着SyncAdapter实际上被系统多次重用？
问题3：在同步代码完成之前结束onPerformSync是否安全？（凌空调用可能比创建抽射请求，运行并完成更长时间）

    @Override
    public void onPerformSync(Account account, Bundle extras, String authority, ContentProviderClient contentProviderClient, SyncResult syncResult) {
        JsonObjectRequest jsObjRequest = new JsonObjectRequest
                (Request.Method.GET, url, null, new Response.Listener() {
                    @Override
                    public void onResponse(JSONObject response) {
                        // time consuming code
                    }
                }, new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        // TODO Auto-generated method stub
                    }
                });
        // Access the RequestQueue through your singleton class.
        MySingleton.getInstance(this).addToRequestQueue(jsObjRequest);
        // onPerformSync end reached before volley request processing ends
    }

Answer 1

您可以使用CountDownLatch ，但我读过，这不是在同步适配器中实现它对我有用的好方法

    
    private CountDownLatch doneSignal = new CountDownLatch(1);
    
    @Override
    public void onPerformSync(Account account, Bundle extras, String authority, ContentProviderClient contentProviderClient, SyncResult syncResult) {
        JsonObjectRequest jsObjRequest = new JsonObjectRequest
                (Request.Method.GET, url, null, new Response.Listener() {
                    @Override
                    public void onResponse(JSONObject response) {
                        // time consuming code
                        //put this line as the last line when everything is done
                        doneSignal.countDown();
                    }
                }, new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        // TODO Auto-generated method stub
                    }
                });
        // Access the RequestQueue through your singleton class.
        MySingleton.getInstance(this).addToRequestQueue(jsObjRequest);
        try {
            doneSignal.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // onPerformSync end reached before volley request processing ends
    }

android SyncAdapter中的异步齐射调用

1 个答案: