我已经从一个网站的表中获取了我在创建的android中的总统轮询应用的值。我将四个列存储在四个不同的列表中。当我尝试使用arraylist.get()
获取值并将它们存储到数组中时,arraylist.get()
返回null
。我在ListView
上显示了我的ArrayList
,并且所有值都显示出来,所以我知道这些值是正确存储的。 如果您查看我正在使用的网站,它具有投票开始时的所有投票数据。该数组将包含8个连续的民意调查,我将平均数,然后绘制在一张图上。我将从八个民意测验中的第一个民意测验的开始日期和八个民意测验中最后一个的结束日期开始,然后找到恰好在两者之间的日期,并将该日期用作我的投票点的x坐标。然后我会为接下来的八次民意调查做同样的事情。这就是为什么我首先检查网站上的民意调查总数是否可以被八整除。如果网站上的民意调查数量不能被8整除,我会去其他地方,然后减去余数。循环完成后,我将单独计算剩余的平均值。 这是我的代码: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;
}
}
只是旁注,'0%8'也是'0'。 – SomeJavaGuy
首先使用动态数组列表的要点是什么,然后将东西放入不灵活的数组中?顺便说一句:在命名上检查java styleguides。变量名称始终启动lowerCase;甚至当他们表示具有诸如“黑暗王子”特朗普或希拉里“腐烂”克林顿这样的巨大自我的人类时。 – GhostCat
@GhostCat如果你看看我正在使用的网站,它拥有投票开始时的所有轮询数据。该数组将包含8个连续的民意调查,我将平均数,然后绘制在一张图上。我将从八个民意测验中的第一个民意测验的开始日期和八个民意测验中最后一个的结束日期开始,然后找到恰好在两者之间的日期,并将该日期用作我的投票点的x坐标。然后我会为接下来的八次民意调查做同样的事情。这就是为什么我首先检查网站上的民意调查总数是否可以被八整除。 –