尝试调用虚拟方法的android.content.Context android.content.Context.getApplicationContext()‘
尝试调用虚拟方法的android.content.Context android.content.Context.getApplicationContext()‘
提问于 2018-06-21 00:50:05
我的代码遇到了一些问题，出现了这个错误：
java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.content.Context.getApplicationContext()' on a null object reference
at android.content.ContextWrapper.getApplicationContext(ContextWrapper.java:106)
at com.uuaba.uuaba.utils.QueryUtils.<init>(QueryUtils.java:23)
at com.uuaba.uuaba.helper.RVAdapter$1.onClick(RVAdapter.java:132)
at android.view.View.performClick(View.java:5637)
at android.view.View$PerformClick.run(View.java:22429)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)在我的RecyclerView适配器中，我想用下面的代码调用另一个类(QueryUtils.java)的方法：
QueryUtils queryUtils = new QueryUtils();
queryUtils.upgPollAnswer("String1", "String2");这是我的QueryUtils.java：
public class QueryUtils extends Application{
private String tag_string_req = "req_poll_answer_upg";
// SqLite data management
SQLiteHandler db = new SQLiteHandler(getApplicationContext());
HashMap<String, String> user = db.getUserDetails();
private final String userid = user.get("uid");
public void upgPollAnswer(final String idPoll, final String idAnswer){
StringRequest strReq = new StringRequest(Request.Method.POST, AppConfig.POLL_ANSWER_UPG, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
try {
JSONObject jObj = new JSONObject(response);
boolean error = jObj.getBoolean("error");
if (!error) {
PollActivity pollActivity = new PollActivity();
pollActivity.reloadActivity();
} else {
}
} catch (JSONException e) {
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
}
}) {
@Override
protected Map<String, String> getParams() {
// Posting parameters to loading url
Map<String, String> params = new HashMap<String, String>();
params.put("userid", userid);
params.put("id_poll", idPoll);
params.put("id_answer", idAnswer);
return params;
}
};
// Adding request to request queue
AppVolleyController.getInstance().addToRequestQueue(strReq, tag_string_req);
}
}错误(QueryUtils.java:23)对应于下面这行代码：
SQLiteHandler db = new SQLiteHandler(getApplicationContext());也许我只是还不明白上下文的含义，但我尝试了不同的解决方案，但都不起作用！
请帮帮我
回答 1
Stack Overflow用户
回答已采纳
发布于 2018-06-21 00:59:55
试试这个：
SQLiteHandler db;
@Override
public void onCreate() {
super.onCreate()
SQLiteHandler db = new SQLiteHandler(getApplicationContext());
....rest of db calls..
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/50953332
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