当我按下后退按钮时，我的列表再次加载

Question

当我在方向为 changed.As 时按下列表项时，我也得到 ArrayListIndexOutofBound 就我所知 android 我已经编写了 Parcelable 代码 correctly.But 我认为我的问题在于回收者观点 setup.I 与我 adapter.Help 我

的两个声明混淆

MainActivity.class

 package com.reader.ashishyadav271.hackernewsmaterial;


import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteStatement;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Parcelable;
import android.os.PersistableBundle;
import android.support.v4.util.LruCache;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;
import android.widget.Toast;

import com.wang.avi.AVLoadingIndicatorView;

import org.json.JSONArray;
import org.json.JSONObject;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends AppCompatActivity implements MyCustomAdapter.ClickListener {

    private static final String STATE_LIST = "state_list";
    Map<Integer, String> articleURLs = new HashMap<>();
    Map<Integer, String> articleTitles = new HashMap<>();
    Map<Integer, String> articleDates =new HashMap<>();
    Map<Integer, String> articleAuthors =new HashMap<>();
    ArrayList<Integer> articleIds=new ArrayList<>();

    SQLiteDatabase articlesDB;

    ArrayList<Information> data=new ArrayList<>();

    ArrayList<String> titles=new ArrayList<>();
    ArrayList<String> urls=new ArrayList<>();
    ArrayList<String> authors=new ArrayList<>();
    ArrayList<String> dateAndTimes=new ArrayList<>();
    MyCustomAdapter adapter;
    RecyclerView recyclerView;
    AVLoadingIndicatorView av;
    List<DownloadTask> tasks;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        av= (AVLoadingIndicatorView) findViewById(R.id.avloadingIndicatorView);
        av.setVisibility(View.INVISIBLE);
        tasks = new ArrayList<>();

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        recyclerView= (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));

        recyclerView.addItemDecoration(new SimpleDividerItemDecoration(
                getApplicationContext()
        ));



        articlesDB = this.openOrCreateDatabase("Articles", MODE_PRIVATE, null);

        articlesDB.execSQL("CREATE TABLE IF NOT EXISTS article (id INTEGER PRIMARY KEY," +
                " articleId INTEGER," +
                " url VARCHAR," +
                " title VARCHAR," +
                " author VARCHAR," +
                " date VARCHAR)");

        if(savedInstanceState != null) {

            data=savedInstanceState.getParcelableArrayList(STATE_LIST);
            adapter=new MyCustomAdapter(getApplicationContext(),data);
            adapter.setClickListener(this);
            recyclerView.setAdapter(adapter);


        }else{
            if (isOnline()) {

                requestData("https://hacker-news.firebaseio.com/v0/topstories.json?print=pretty");
            } else {
                updateDisplay();
                Toast.makeText(this, "Network isn't available", Toast.LENGTH_LONG).show();
            }

        }

        //adapter=new MyCustomAdapter(getApplicationContext(),getData());
        //adapter.setClickListener(this);
        //recyclerView.setAdapter(adapter);
    }


    protected boolean isOnline() {
        ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo netInfo = cm.getActiveNetworkInfo();
        if (netInfo != null && netInfo.isConnectedOrConnecting()) {
            return true;
        } else {
            return false;
        }
    }

    private void requestData(String uri) {
        DownloadTask task = new DownloadTask();
        task.execute(uri);
    }

    @Override
    public void itemClicked(View view, int position) {
        Intent i = new Intent(getApplicationContext(), Main2Activity.class);
        i.putExtra("articleUrl", urls.get(position));
        startActivity(i);

    }

    protected void updateDisplay() {
        adapter=new MyCustomAdapter(getApplicationContext(),getData());
        adapter.setClickListener(this);
        recyclerView.setAdapter(adapter);;
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);

        outState.putParcelableArrayList(STATE_LIST, data);

    }

    public class DownloadTask extends AsyncTask<String, Void, String> {
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            if (tasks.size() == 0) {
                av.setVisibility(View.VISIBLE);
            }
            tasks.add(this);
        }

        @Override
        protected String doInBackground(String... urls) {

            String result = "";
            URL url;
            HttpURLConnection urlConnection;

            try {

                url = new URL(urls[0]);

                urlConnection = (HttpURLConnection) url.openConnection();

                InputStream in = urlConnection.getInputStream();

                InputStreamReader reader = new InputStreamReader(in);

                int data = reader.read();

                while (data != -1) {

                    char current = (char) data;

                    result += current;

                    data = reader.read();

                }

                JSONArray jsonArray = new JSONArray(result);

                articlesDB.execSQL("DELETE FROM article");

                for (int i = 0; i < 15; i++) {

                    String articleId = jsonArray.getString(i);

                    url = new URL("https://hacker-news.firebaseio.com/v0/item/" + articleId + ".json?print=pretty");

                    urlConnection = (HttpURLConnection) url.openConnection();

                    in = urlConnection.getInputStream();

                    reader = new InputStreamReader(in);

                    data = reader.read();

                    String articleInfo = "";

                    while (data != -1 ) {

                        char current = (char) data;

                        articleInfo += current;

                        data = reader.read();

                    }

                    JSONObject jsonObject = new JSONObject(articleInfo);

                    String articleTitle = jsonObject.getString("title");

                    String articleURL = jsonObject.getString("url");

                    String articleDate=jsonObject.getString("time");

                    String articleAuthor=jsonObject.getString("by");


                    long unixSeconds = Long.valueOf(articleDate);
                    Date date = new Date(unixSeconds*1000L); // *1000 is to convert seconds to milliseconds
                    SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss"); // the format of your date
                    String formattedarticleDate = sdf.format(date);

                    articleIds.add(Integer.valueOf(articleId));
                    articleTitles.put(Integer.valueOf(articleId), articleTitle);
                    articleURLs.put(Integer.valueOf(articleId), articleURL);
                    articleDates.put(Integer.valueOf(articleId), formattedarticleDate);
                    articleAuthors.put(Integer.valueOf(articleId), articleAuthor);

                    String sql = "INSERT INTO article (articleId, url, title, author, date) VALUES (? , ? , ? , ?, ?)";


                    SQLiteStatement statement = articlesDB.compileStatement(sql);

                    statement.bindString(1, articleId);
                    statement.bindString(2, articleURL);
                    statement.bindString(3, articleTitle);
                    statement.bindString(4, articleAuthor);
                    statement.bindString(5, formattedarticleDate);

                    statement.execute();



                }


            }catch (Exception e) {

                e.printStackTrace();

            }


            return result;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            tasks.remove(this);
            if (tasks.size() == 0) {
                av.setVisibility(View.INVISIBLE);
            }
            updateDisplay();
        }
    }

    private List<Information> getData() {
        /*List<Information> data=new ArrayList<>();
        for(int i=0;i<20;i++){
            titles.add(i,"Wikileaks Asssange wins UN ruling on arbitrary detention");
            url.add(i,"https://www.google.co.in/search?q=best+custom+list+row");
            date.add(i,"3 hrs");
            author.add(i,"aburan28");
        }
        for(int i=0;i<20;i++){
            Information current=new Information();
            current.title=titles.get(i);
            current.url=url.get(i);
            current.author=author.get(i);
            current.date=date.get(i);
            data.add(current);
        }
        return data;*/

        Cursor c = articlesDB.rawQuery("SELECT * FROM article", null);

        try {
            int urlIndex = c.getColumnIndex("url");
            int titleIndex = c.getColumnIndex("title");
            int authorIndex = c.getColumnIndex("author");
            int dateIndex = c.getColumnIndex("date");

            c.moveToFirst();

            titles.clear();
            //urls.clear();
            authors.clear();
            dateAndTimes.clear();


            int i=0;
            while (c != null) {
                titles.add(c.getString(titleIndex));
                urls.add(c.getString(urlIndex));
                authors.add(c.getString(authorIndex));
                dateAndTimes.add(c.getString(dateIndex));
                Information current=new Information();
                current.title=titles.get(i);
                current.url=urls.get(i);
                current.author=authors.get(i);
                current.date = dateAndTimes.get(i);
                data.add(current);
                i++;
                c.moveToNext();

            }


        }catch (Exception e) {

            e.printStackTrace();

        }finally {
            c.close();
        }
        return data;
    }

    @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) {
            startActivity(new Intent(getApplicationContext(),SettingsActivity.class));
            return true;
        }
        if (id == R.id.action_about) {
            startActivity(new Intent(getApplicationContext(),About.class));
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

Information.class

package com.reader.ashishyadav271.hackernewsmaterial;

import android.os.Parcel;
import android.os.Parcelable;

public class Information implements Parcelable {
    public String title;
    public String author;
    public String date;
    public String url;

    public Information(){

    }

    protected Information(Parcel in) {
        title = in.readString();
        author = in.readString();
        date = in.readString();
        url = in.readString();
    }

    public static final Creator<Information> CREATOR = new Creator<Information>() {
        @Override
        public Information createFromParcel(Parcel in) {
            return new Information(in);
        }

        @Override
        public Information[] newArray(int size) {
            return new Information[size];
        }
    };

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(title);
        dest.writeString(author);
        dest.writeString(date);
        dest.writeString(url);
    }
}

记录猫错误

02-06 14:52:58.106 8369-8369/com.reader.ashishyadav271.hackernewsmaterial E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.reader.ashishyadav271.hackernewsmaterial, PID: 8369
java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
    at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
    at java.util.ArrayList.get(ArrayList.java:308)
    at com.reader.ashishyadav271.hackernewsmaterial.MainActivity.itemClicked(MainActivity.java:137)
    at com.reader.ashishyadav271.hackernewsmaterial.MyCustomAdapter$MyViewHolder.onClick(MyCustomAdapter.java:77)
    at android.view.View.performClick(View.java:4471)
    at android.view.View$PerformClick.run(View.java:18778)
    at android.os.Handler.handleCallback(Handler.java:808)
    at android.os.Handler.dispatchMessage(Handler.java:103)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:5345)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:515)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:828)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:644)
    at dalvik.system.NativeStart.main(Native Method)

Answer 1

现在我得到它后 years.I 本来可以简单使用的。 FLAG_ACTIVITY_CLEAR_TOP - 如果已设置，并且正在启动的 activity 已经在当前任务中运行，则不会启动该 activity 的新实例，而是启动所有其他活动在它之上将被关闭，并且这个 Intent 将作为新 Intent 传递给（现在在顶部）旧 activity。

当我按下后退按钮时，我的列表再次加载

My list is loading again when I am Pressing Back Button

android

android-json

android-recyclerview