Android Volley网络访问的参数传递方法

网络上的错误方法

网络上有很多关于Volley使用的例子，由于大家都在偷懒，相互搬运代码，结果大多数例子都是在做错误的向导，来看Volley的两个参数Request， StringRequest与JsonObjectRequest，网上的传参例子如下：

    StringRequest stringRequest = new StringRequest(Method.POST, url,  listener, errorListener) {  
    @Override  
    protected Map<String, String> getParams() throws AuthFailureError {  
        Map<String, String> map = new HashMap<String, String>();  
        map.put("params1", "value1");  
        map.put("params2", "value2");  
        return map;  
    }  
};  

这对于StringRequest来说是没错的，但是对于JsonObjectRequest，如果用类似的方法：

JsonRequest<JSONObject> jsonRequest = new JsonObjectRequest(Method.POST,httpurl, null,
    new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            Log.d(TAG, "response -> " + response.toString());
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Log.e(TAG, error.getMessage(), error);
    }
    })
             
    @Override
    public Map<String, String> getHeaders() {
        HashMap<String, String> headers = new HashMap<String, String>();
        headers.put("Accept", "application/json");
        headers.put("Content-Type", "application/json; charset=UTF-8");
                 
        return headers;
    }
};

你会发现，传入的参数更不不起作用。

部分源码

来看JsonObjectRequest的代码：

public class JsonObjectRequest extends JsonRequest<JSONObject> {
    public JsonObjectRequest(int method, String url, JSONObject jsonRequest, Listener<JSONObject> listener, ErrorListener errorListener) {
        super(method, url, jsonRequest == null?null:jsonRequest.toString(), listener, errorListener);
    }

    public JsonObjectRequest(String url, JSONObject jsonRequest, Listener<JSONObject> listener, ErrorListener errorListener) {
        this(jsonRequest == null?0:1, url, jsonRequest, listener, errorListener);
    }

然后再看JsonRequest的代码：

public abstract class JsonRequest<T> extends Request<T> {
    private static final String PROTOCOL_CHARSET = "utf-8";
    private static final String PROTOCOL_CONTENT_TYPE = String.format("application/json; charset=%s", new Object[]{"utf-8"});
    private final Listener<T> mListener;
    private final String mRequestBody;

    /** @deprecated */
    public JsonRequest(String url, String requestBody, Listener<T> listener, ErrorListener errorListener) {
        this(-1, url, requestBody, listener, errorListener);
    }

    public JsonRequest(int method, String url, String requestBody, Listener<T> listener, ErrorListener errorListener) {
        super(method, url, errorListener);
        this.mListener = listener;
        this.mRequestBody = requestBody;
    }

    protected void deliverResponse(T response) {
        this.mListener.onResponse(response);
    }

    protected abstract Response<T> parseNetworkResponse(NetworkResponse var1);

    /** @deprecated */
    public String getPostBodyContentType() {
        return this.getBodyContentType();
    }

    /** @deprecated */
    public byte[] getPostBody() {
        return this.getBody();
    }

    public String getBodyContentType() {
        return PROTOCOL_CONTENT_TYPE;
    }

    public byte[] getBody() {
        try {
            return this.mRequestBody == null?null:this.mRequestBody.getBytes("utf-8");
        } catch (UnsupportedEncodingException var2) {
            VolleyLog.wtf("Unsupported Encoding while trying to get the bytes of %s using %s", new Object[]{this.mRequestBody, "utf-8"});
            return null;
        }
    }
}

我们可以发现getBody与getPostBody已被重载，而参数只能从mRequestBody 中读取。在看Request相关代码部分：

public abstract class Request<T> implements Comparable<Request<T>> {
 public byte[] getPostBody() throws AuthFailureError {
        Map<String, String> postParams = this.getPostParams();
        return postParams != null && postParams.size() > 0?this.encodeParameters(postParams, this.getPostParamsEncoding()):null;
    }

    protected Map<String, String> getParams() throws AuthFailureError {
        return null;
    }

从这可以看出之所以可以通过重载getParams()来设置参数，是因为getBody与getPostBody调用了它的关系，而在JsonRequest重载后，没有再调用getParams()，所以通过getParams()就无效了

正确方法

其实通过上面的源代码我们也知道对于JsonObjectRequest只能在构造函数中传入相关网络参数，例如：

 Map<String, String> params = new HashMap<String, String>();
        params.put("mobileNo", name);
        params.put("pwd", password);
        params.put("smsCode", code);
        JSONObject jsonRequest = new JSONObject(params);
        JsonObjectRequest request = new JsonObjectRequest(Request.Method.POST, Config.REGISTER, jsonRequest, new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                Log.d(LOGTAG, response.toString());
                try {
                    int status = response.getInt("status");
                    if(status == 200) {
                        saveLoginToken(response.getString("loginToken"));
                        gotoMainActivity();
                    }
                } catch(JSONException jse) {

                }
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                Log.d(LOGTAG, "Error: " + error.getMessage());
                Toast.makeText(RegisterActivity.this, "Register Fail:" + error.getMessage(), Toast.LENGTH_SHORT).show();
            }