Android设置Volley从caching中使用
我正在尝试创build和使用服务器JSON响应caching。
例如：
将JSON对象caching到内部存储器中，当我们没有互联网连接时使用它。
在下面的示例代码中， 找不到有关如何使用Volleycaching的任何文档，并在再次更新服务器头时不会再过期。
像这样：将过期设置为标题并使用caching，并在到期后再次尝试加载。
我试图为此方法设置caching机制：
private void makeJsonArryReq() { JsonArrayRequest req = new JsonArrayRequest(Const.URL_JSON_ARRAY, new Response.Listener<JSONArray>() { @Override public void onResponse(JSONArray response) { msgResponse.setText(response.toString()); } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { } }); AppController.getInstance().addToRequestQueue(req,tag_json_arry); }
caching方法：
public static Cache.Entry parseIgnoreCacheHeaders(NetworkResponse response) { long now = System.currentTimeMillis(); Map<String, String> headers = response.headers; long serverDate = 0; String serverEtag = null; String headerValue; headerValue = headers.get("Date"); if (headerValue != null) { serverDate = HttpHeaderParser.parseDateAsEpoch(headerValue); } serverEtag = headers.get("ETag"); final long cacheHitButRefreshed = 3 * 60 * 1000; // in 3 minutes cache will be hit, but also refreshed on background final long cacheExpired = 24 * 60 * 60 * 1000; // in 24 hours this cache entry expires completely final long softExpire = now + cacheHitButRefreshed; final long ttl = now + cacheExpired; Cache.Entry entry = new Cache.Entry(); entry.data = response.data; entry.etag = serverEtag; entry.softTtl = softExpire; entry.ttl = ttl; entry.serverDate = serverDate; entry.responseHeaders = headers; return entry; }
请注意，如果Web服务支持caching输出，则不必使用下面的CacheRequest ，因为Volley会自动caching。
对于你的问题，我使用parseCacheHeaders （并参考@ oleksandr_yefremov的代码）内的一些代码。 下面的代码我已经testing过了。 当然，也可以使用JsonArrayRequest 。 希望这个帮助！
JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(0, mUrl, new Response.Listener<JSONObject>() { @Override public void onResponse(JSONObject response) { try { mTextView.setText(response.toString(5)); } catch (JSONException e) { mTextView.setText(e.toString()); } } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { } }) { @Override protected Response<JSONObject> parseNetworkResponse(NetworkResponse response) { try { Cache.Entry cacheEntry = HttpHeaderParser.parseCacheHeaders(response); if (cacheEntry == null) { cacheEntry = new Cache.Entry(); } final long cacheHitButRefreshed = 3 * 60 * 1000; // in 3 minutes cache will be hit, but also refreshed on background final long cacheExpired = 24 * 60 * 60 * 1000; // in 24 hours this cache entry expires completely long now = System.currentTimeMillis(); final long softExpire = now + cacheHitButRefreshed; final long ttl = now + cacheExpired; cacheEntry.data = response.data; cacheEntry.softTtl = softExpire; cacheEntry.ttl = ttl; String headerValue; headerValue = response.headers.get("Date"); if (headerValue != null) { cacheEntry.serverDate = HttpHeaderParser.parseDateAsEpoch(headerValue); } headerValue = response.headers.get("Last-Modified"); if (headerValue != null) { cacheEntry.lastModified = HttpHeaderParser.parseDateAsEpoch(headerValue); } cacheEntry.responseHeaders = response.headers; final String jsonString = new String(response.data, HttpHeaderParser.parseCharset(response.headers)); return Response.success(new JSONObject(jsonString), cacheEntry); } catch (UnsupportedEncodingException e) { return Response.error(new ParseError(e)); } catch (JSONException e) { return Response.error(new ParseError(e)); } } @Override protected void deliverResponse(JSONObject response) { super.deliverResponse(response); } @Override public void deliverError(VolleyError error) { super.deliverError(error); } @Override protected VolleyError parseNetworkError(VolleyError volleyError) { return super.parseNetworkError(volleyError); } }; MySingleton.getInstance(this).addToRequestQueue(jsonObjectRequest);
更新 ：
如果你想要一个基类，请参考以下代码：
public class CacheRequest extends Request<NetworkResponse> { private final Response.Listener<NetworkResponse> mListener; private final Response.ErrorListener mErrorListener; public CacheRequest(int method, String url, Response.Listener<NetworkResponse> listener, Response.ErrorListener errorListener) { super(method, url, errorListener); this.mListener = listener; this.mErrorListener = errorListener; } @Override protected Response<NetworkResponse> parseNetworkResponse(NetworkResponse response) { Cache.Entry cacheEntry = HttpHeaderParser.parseCacheHeaders(response); if (cacheEntry == null) { cacheEntry = new Cache.Entry(); } final long cacheHitButRefreshed = 3 * 60 * 1000; // in 3 minutes cache will be hit, but also refreshed on background final long cacheExpired = 24 * 60 * 60 * 1000; // in 24 hours this cache entry expires completely long now = System.currentTimeMillis(); final long softExpire = now + cacheHitButRefreshed; final long ttl = now + cacheExpired; cacheEntry.data = response.data; cacheEntry.softTtl = softExpire; cacheEntry.ttl = ttl; String headerValue; headerValue = response.headers.get("Date"); if (headerValue != null) { cacheEntry.serverDate = HttpHeaderParser.parseDateAsEpoch(headerValue); } headerValue = response.headers.get("Last-Modified"); if (headerValue != null) { cacheEntry.lastModified = HttpHeaderParser.parseDateAsEpoch(headerValue); } cacheEntry.responseHeaders = response.headers; return Response.success(response, cacheEntry); } @Override protected void deliverResponse(NetworkResponse response) { mListener.onResponse(response); } @Override protected VolleyError parseNetworkError(VolleyError volleyError) { return super.parseNetworkError(volleyError); } @Override public void deliverError(VolleyError error) { mErrorListener.onErrorResponse(error); } }
然后在MainActivity中，你可以这样调用
CacheRequest cacheRequest = new CacheRequest(0, mUrl, new Response.Listener<NetworkResponse>() { @Override public void onResponse(NetworkResponse response) { try { final String jsonString = new String(response.data, HttpHeaderParser.parseCharset(response.headers)); JSONObject jsonObject = new JSONObject(jsonString); mTextView.setText(jsonObject.toString(5)); } catch (UnsupportedEncodingException | JSONException e) { e.printStackTrace(); } } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { mTextView.setText(error.toString()); } }); MySingleton.getInstance(this).addToRequestQueue(cacheRequest);
更新与完整的源代码：
MainActivity.java：
package com.example.cachevolley; import android.content.Context; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.view.Menu; import android.view.MenuItem; import android.widget.TextView; import android.widget.Toast; import com.android.volley.Cache; import com.android.volley.NetworkResponse; import com.android.volley.Request; import com.android.volley.RequestQueue; import com.android.volley.Response; import com.android.volley.VolleyError; import com.android.volley.toolbox.HttpHeaderParser; import com.android.volley.toolbox.Volley; import org.json.JSONException; import org.json.JSONObject; import java.io.UnsupportedEncodingException; public class MainActivity extends AppCompatActivity { private final Context mContext = this; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); final TextView textView = (TextView) findViewById(R.id.textView); RequestQueue queue = Volley.newRequestQueue(this); String url = "http://192.168.0.100/apitest"; CacheRequest cacheRequest = new CacheRequest(0, url, new Response.Listener<NetworkResponse>() { @Override public void onResponse(NetworkResponse response) { try { final String jsonString = new String(response.data, HttpHeaderParser.parseCharset(response.headers)); JSONObject jsonObject = new JSONObject(jsonString); textView.setText(jsonObject.toString(5)); Toast.makeText(mContext, "onResponse:\n\n" + jsonObject.toString(), Toast.LENGTH_SHORT).show(); } catch (UnsupportedEncodingException | JSONException e) { e.printStackTrace(); } } }, new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { Toast.makeText(mContext, "onErrorResponse:\n\n" + error.toString(), Toast.LENGTH_SHORT).show(); } }); // Add the request to the RequestQueue. queue.add(cacheRequest); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.menu_main, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); //noinspection SimplifiableIfStatement if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } private class CacheRequest extends Request<NetworkResponse> { private final Response.Listener<NetworkResponse> mListener; private final Response.ErrorListener mErrorListener; public CacheRequest(int method, String url, Response.Listener<NetworkResponse> listener, Response.ErrorListener errorListener) { super(method, url, errorListener); this.mListener = listener; this.mErrorListener = errorListener; } @Override protected Response<NetworkResponse> parseNetworkResponse(NetworkResponse response) { Cache.Entry cacheEntry = HttpHeaderParser.parseCacheHeaders(response); if (cacheEntry == null) { cacheEntry = new Cache.Entry(); } final long cacheHitButRefreshed = 3 * 60 * 1000; // in 3 minutes cache will be hit, but also refreshed on background final long cacheExpired = 24 * 60 * 60 * 1000; // in 24 hours this cache entry expires completely long now = System.currentTimeMillis(); final long softExpire = now + cacheHitButRefreshed; final long ttl = now + cacheExpired; cacheEntry.data = response.data; cacheEntry.softTtl = softExpire; cacheEntry.ttl = ttl; String headerValue; headerValue = response.headers.get("Date"); if (headerValue != null) { cacheEntry.serverDate = HttpHeaderParser.parseDateAsEpoch(headerValue); } headerValue = response.headers.get("Last-Modified"); if (headerValue != null) { cacheEntry.lastModified = HttpHeaderParser.parseDateAsEpoch(headerValue); } cacheEntry.responseHeaders = response.headers; return Response.success(response, cacheEntry); } @Override protected void deliverResponse(NetworkResponse response) { mListener.onResponse(response); } @Override protected VolleyError parseNetworkError(VolleyError volleyError) { return super.parseNetworkError(volleyError); } @Override public void deliverError(VolleyError error) { mErrorListener.onErrorResponse(error); } } }
清单文件：
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.cachevolley" > <uses-permission android:name="android.permission.INTERNET" /> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name=".MainActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
布局文件：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".MainActivity"> <TextView android:id="@+id/textView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/hello_world" /> </RelativeLayout>
如果响应是从服务器使用string请求，然后只是更换线路
return Response.success(new JSONObject(jsonString), cacheEntry);
有了这个
return Response.success(new String(jsonString), cacheEntry);
它适用于我的情况。 尝试在你自己的代码。
