我已經從一個網站的表中獲取了我在創建的android中的總統輪詢應用的值。我將四個列存儲在四個不同的列表中。當我嘗試使用arraylist.get()
獲取值並將它們存儲到數組中時,arraylist.get()
返回null
。我在ListView
上顯示了我的ArrayList
,並且所有值都顯示出來,所以我知道這些值是正確存儲的。 如果您查看我正在使用的網站,它具有投票開始時的所有投票數據。該數組將包含8個連續的民意調查,我將平均數,然後繪製在一張圖上。我將從八個民意測驗中的第一個民意測驗的開始日期和八個民意測驗中最後一個的結束日期開始,然後找到恰好在兩者之間的日期,並將該日期用作我的投票點的x座標。然後我會爲接下來的八次民意調查做同樣的事情。這就是爲什麼我首先檢查網站上的民意調查總數是否可以被八整除。如果網站上的民意調查數量不能被8整除,我會去其他地方,然後減去餘數。循環完成後,我將單獨計算剩餘的平均值。 這是我的代碼:Arraylist.get返回null
package com.pollapp.presidentialelectionpolls;
import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.os.StrictMode;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Context;
import android.view.Menu;
import android.widget.Toast;
@SuppressLint("NewApi")
public class MainActivity extends Activity {
Document doc;
Element table;
Elements rows;
Element row;
Elements cols;
Elements link;
int remainderNum = 0, i = 0;
String startingDate, endingDate;
Date start, end;
DateFormat df = new SimpleDateFormat("MM/dd");
String[][] average = new String[8][3];
ArrayList<String> nameOfSrc = new ArrayList<String>();
ArrayList<String> dateWidth = new ArrayList<String>();
ArrayList<String> Trump = new ArrayList<String>();
ArrayList<String> Clinton = new ArrayList<String>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);
try {
ConnectivityManager cm = (ConnectivityManager) this
.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo ni = cm.getActiveNetworkInfo();
Boolean isConnect = ni == null ? false : ni
.isConnectedOrConnecting();
if (isConnect) {
doc = Jsoup
.connect(
"http://www.realclearpolitics.com/epolls/2016/president/us/general_election_trump_vs_clinton-5491.html")
.get();
table = doc.select("table.data.large").get(1);
rows = table.select("tr");
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
for (int i = 2; i < rows.size(); i++) {
row = rows.get(i);
cols = row.select("td");
link = cols.get(0).select("a");
nameOfSrc.add(link.get(0).text());
dateWidth.add(cols.get(1).text());
Clinton.add(cols.get(4).text());
Trump.add(cols.get(5).text());
}
if ((dateWidth.size() % 8) == 0) {
for (i = (dateWidth.size()-1); i <= 7; i = i-8) {
average[i][0] = dateWidth.get(i);
average[i][1] = Clinton.get(i);
average[i][2] = Trump.get(i);
average[i-1][0] = dateWidth.get(i-1);
average[i-1][1] = Clinton.get(i-1);
average[i-1][2] = Trump.get(i-1);
average[i-2][0] = dateWidth.get(i-2);
average[i-2][1] = Clinton.get(i-2);
average[i-2][2] = Trump.get(i-2);
average[i-3][0] = dateWidth.get(i-3);
average[i-3][1] = Clinton.get(i-3);
average[i-3][2] = Trump.get(i-3);
average[i-4][0] = dateWidth.get(i-4);
average[i-4][1] = Clinton.get(i-4);
average[i-4][2] = Trump.get(i-4);
average[i-5][0] = dateWidth.get(i-5);
average[i-5][1] = Clinton.get(i-5);
average[i-5][2] = Trump.get(i-5);
average[i-6][0] = dateWidth.get(i-6);
average[i-6][1] = Clinton.get(i-6);
average[i-6][2] = Trump.get(i-6);
average[i-7][0] = dateWidth.get(i-7);
average[i-7][1] = Clinton.get(i-7);
average[i-7][2] = Trump.get(i-7);
startingDate = average[i][0].substring(0, average[i][0].indexOf(" "));
endingDate = average[i-7][0].substring(average[i-7][0].lastIndexOf(" ") + 1);
}
} else {
remainderNum = (dateWidth.size() % 8);
for (i = (dateWidth.size() - 1); i <= (remainderNum + 7); i = i-8) {
average[i][0] = dateWidth.get(i);
average[i][1] = Clinton.get(i);
average[i][2] = Trump.get(i);
average[i-1][0] = dateWidth.get(i-1);
average[i-1][1] = Clinton.get(i-1);
average[i-1][2] = Trump.get(i-1);
average[i-2][0] = dateWidth.get(i-2);
average[i-2][1] = Clinton.get(i-2);
average[i-2][2] = Trump.get(i-2);
average[i-3][0] = dateWidth.get(i-3);
average[i-3][1] = Clinton.get(i-3);
average[i-3][2] = Trump.get(i-3);
average[i-4][0] = dateWidth.get(i-4);
average[i-4][1] = Clinton.get(i-4);
average[i-4][2] = Trump.get(i-4);
average[i-5][0] = dateWidth.get(i-5);
average[i-5][1] = Clinton.get(i-5);
average[i-5][2] = Trump.get(i-5);
average[i-6][0] = dateWidth.get(i-6);
average[i-6][1] = Clinton.get(i-6);
average[i-6][2] = Trump.get(i-6);
average[i-7][0] = dateWidth.get(i-7);
average[i-7][1] = Clinton.get(i-7);
average[i-7][2] = Trump.get(i-7);
startingDate = average[i][0].substring(0, average[i][0].indexOf(" "));
endingDate = average[i-7][0].substring(average[i-7][0].lastIndexOf(" ") + 1);
}
}
Toast.makeText(getApplicationContext(), startingDate + ", " + endingDate, Toast.LENGTH_SHORT).show();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
只是旁註,'0%8'也是'0'。 – SomeJavaGuy
首先使用動態數組列表的要點是什麼,然後將東西放入不靈活的數組中?順便說一句:在命名上檢查java styleguides。變量名稱始終啓動lowerCase;甚至當他們表示具有諸如「黑暗王子」特朗普或希拉里「腐爛」克林頓這樣的巨大自我的人類時。 – GhostCat
@GhostCat如果你看看我正在使用的網站,它擁有投票開始時的所有輪詢數據。該數組將包含8個連續的民意調查,我將平均數,然後繪製在一張圖上。我將從八個民意測驗中的第一個民意測驗的開始日期和八個民意測驗中最後一個的結束日期開始,然後找到恰好在兩者之間的日期,並將該日期用作我的投票點的x座標。然後我會爲接下來的八次民意調查做同樣的事情。這就是爲什麼我首先檢查網站上的民意調查總數是否可以被八整除。 –