我有一个每天发布新闻的网站。
现在，我发送 JsonArrayRequest 来检索和解析网站上发布的每条新闻的标题和摘要。然后使用已解析的项目填充RecyclerView。
我遇到的问题是排球实现缓存的方式。
让我们来看看这个场景：安装，启动应用程序并填充RecyclerView。用户阅读新闻并忘记应用
稍后，用户启动应用程序并获取项目并填充RecyclerView。
在第一次和第二次发布之间，网站上发布了新消息。但在第二次发布时，这些新项目不会显示。但是，如果用户手动转到应用设置并清除应用的缓存，然后重新启动，则会显示新项目。
你明白我的观点？
虽然我不想禁用Volley缓存，但如何让它始终获取新项？
修改
MainActivity
public class MainActivity extends AppCompatActivity {
private final String TAG = "MainActivity";
//Creating a list of newss
private List<NewsItems> mNewsItemsList;
//Creating Views
private RecyclerView recyclerView;
private RecyclerView.Adapter adapter;
private RecyclerView.LayoutManager layoutManager;
private ProgressDialog mProgressDialog;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.d(TAG, "onCreate called");
//Initializing Views
recyclerView = (RecyclerView) findViewById(R.id.news_recycler);
LinearLayoutManager layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
//Initializing the newslist
mNewsItemsList = new ArrayList<>();
adapter = new NewsAdapter(mNewsItemsList, this);
recyclerView.setAdapter(adapter);
if (NetworkCheck.isAvailableAndConnected(this)) {
//Calling method to get data
getData();
} else {
//Codes for building Alert Dialog
alertDialogBuilder.setPositiveButton(R.string.alert_retry, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
if (!NetworkCheck.isAvailableAndConnected(mContext)) {
alertDialogBuilder.show();
} else {
getData();
}
}
});
alertDialogBuilder.setNegativeButton(R.string.alert_cancel, new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
alertDialogBuilder.show();
}
}
//This method will get data from the web api
private void getData(){
Log.d(TAG, "getData called");
//Codes for Showing progress dialog
//Creating a json request
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(ConfigNews.GET_URL + getNumber(),
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
Log.d(TAG, "onResponse called");
//Dismissing the progress dialog
if (mProgressDialog != null) {
mProgressDialog.hide();
}
//calling method to parse json array
parseData(response);
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
});
//Creating request queue
RequestQueue requestQueue = Volley.newRequestQueue(this);
//Adding request to the queue
requestQueue.add(jsonArrayRequest);
}
//This method will parse json data
private void parseData(JSONArray array){
Log.d(TAG, "Parsing array");
for(int i = 0; i<array.length(); i++) {
NewsItems newsItem = new NewsItems();
JSONObject jsonObject = null;
try {
jsonObject = array.getJSONObject(i);
newsItem.setNews_title(jsonObject.getString(ConfigNews.TAG_VIDEO_TITLE));
newsItem.setNews_body(jsonObject.getString(ConfigNews.TAG_VIDEO_BODY));
} catch (JSONException w) {
w.printStackTrace();
}
mNewsItemsList.add(newsItem);
}
adapter.notifyItemRangeChanged(0, adapter.getItemCount());
}
@Override
public void onDestroy() {
super.onDestroy();
Log.d(TAG, "onDestroy called");
if (mProgressDialog != null){
mProgressDialog.dismiss();
Log.d(TAG, "mProgress dialog dismissed");
}
}
}
答案 0 :(得分：1)
选项1）删除缓存
在拨打电话之前，您可以按myDiskBasedCache.clear()删除整个缓存，或按myDiskBasedCache.remove(entryUrl)
选项2）自定义CacheParser （在请求中）
@Override
protected Response<Bitmap> parseNetworkResponse(NetworkResponse response) {
Response<Bitmap> resp = super.parseNetworkResponse(response);
if(!resp.isSuccess()) {
return resp;
}
long now = System.currentTimeMillis();
Cache.Entry entry = resp.cacheEntry;
if(entry == null) {
entry = new Cache.Entry();
entry.data = response.data;
entry.responseHeaders = response.headers;
entry.ttl = now + 60 * 60 * 1000; //keeps cache for 1 hr
}
entry.softTtl = 0; // will always refresh
return Response.success(resp.result, entry);
}
选项3）发送不缓存的请求
myRequest.setShouldCache(false);
选项4）使用自定义缓存实施
<强>更新
代码示例：
//Creating a json request
JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(ConfigNews.GET_URL + getNumber(),
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
Log.d(TAG, "onResponse called");
//Dismissing the progress dialog
if (mProgressDialog != null) {
mProgressDialog.hide();
}
//calling method to parse json array
parseData(response);
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
}) {
@Override
protected Response<JSONArray> parseNetworkResponse(NetworkResponse response) {
Response<JSONArray> resp = super.parseNetworkResponse(response);
if(!resp.isSuccess()) {
return resp;
}
long now = System.currentTimeMillis();
Cache.Entry entry = resp.cacheEntry;
if(entry == null) {
entry = new Cache.Entry();
entry.data = response.data;
entry.responseHeaders = response.headers;
entry.ttl = now + 60 * 60 * 1000; //keeps cache for 1 hr
}
entry.softTtl = 0; // will always refresh
return Response.success(resp.result, entry);
}
};
更新2
Http协议缓存支持许多方法来定义客户端如何缓存响应以及何时更新响应。 Volley将这些规则简化为：
和
entry.softTtl （以ms为单位的软时间:)如果大于当前时间 缓存绝对有效，不需要向服务器发出请求，否则仍然会发出新请求（即使ttl正常），如果有更改，则会传递新的响应。
请注意，如果ttl有效且softTtl不是，则可以接收2次onResponse电话