无法将 rss 提要保存到数据库并在列表视图中显示答案

【问题标题】：can't save rss feed to database and display it on a listview无法将 rss 提要保存到数据库并在列表视图中显示
【发布时间】：2017-05-17 13:09:03
【问题描述】：

我想将 rss 提要（json 请求）保存到新的 sqllite 数据库，然后在列表视图中显示它。将非常感谢任何帮助。有日志

05-17 15:30:19.971 16775-16775/com.example.buh.rssfeed E/AndroidRuntime：致命异常：主进程：com.example.buh.rssfeed，PID：16775 java.lang.RuntimeException：无法启动活动 ComponentInfo{com.example.buh.rssfeed/com.example.buh.rssfeed.MainActivity}：java.lang.IllegalStateException：无法从 CursorWindow 读取第 0 行第 5 列。确保在从光标访问数据之前正确初始化光标。在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2436) 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2498) 在 android.app.ActivityThread.access$900(ActivityThread.java:179) 在 android.app .ActivityThread$H.handleMessage(ActivityThread.java:1324) 在 android.os.Handler.dispatchMessage(Handler.java:102) 在 android.os.Looper.loop(Looper.java:146) 在 android.app.ActivityThread。 java.lang 的 main(ActivityThread.java:5641)。 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1288) 的 java.lang.reflect.Method.invoke(Method.java:515) 的 reflect.Method.invokeNative(Native Method)。 dalvik.system.NativeStart.main(Native Method) 的 android.internal.os.ZygoteInit.main(ZygoteInit.java:1104) 原因：java.lang.IllegalStateException：无法从 CursorWindow 读取第 0 行第 5 列。确保在从光标访问数据之前正确初始化光标。在 android.database.CursorWindow.nativeGetString(Native Method) 在 android.database.CursorWindow.getString(CursorWindow.java:439) 在 android.database.AbstractWindowedCursor.getString(AbstractWindowedCursor.java:51) 在 com.example.buh.rssfeed .FeedDBHelper.cursorToItem(FeedDBHelper.java:62) 在 com.example.buh.rssfeed.FeedDBHelper.getArticleList(FeedDBHelper.java:47) 在 com.example.buh.rssfeed.MainActivity.onCreate(MainActivity.java:54) 在android.app.Activity.performCreate(Activity.java:5484)在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093) 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2400) 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2498) 在 android.app。 ActivityThread.access$900(ActivityThread.java:179) 位于 android.os.Looper 的 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1324) 的 android.os.Handler.dispatchMessage(Handler.java:102)。循环（Looper.java:146）在 android.app.ActivityThread.main(ActivityThread.java:5641) 在 java.lang.reflect.Method.invokeNative(Native Method) 在 java.lang.reflect.Method.invoke(Method.java:515) 在 com.android .internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1288) 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1104) 在 dalvik.system.NativeStart.main(Native Method)

我的代码

public class FeedContract {
private FeedContract() {
}

public static final String CONTENT_AUTHORITY = "com.example.buh.rssfeed";

public static final Uri BASE_CONTENT_URI = Uri.parse("content://" + CONTENT_AUTHORITY);

private static final String PATH_ENTRIES = "articles";

public static class Entry implements BaseColumns {

    public static final String CONTENT_TYPE =
            ContentResolver.CURSOR_DIR_BASE_TYPE + "/vnd.rssfeed.articles";

    public static final String CONTENT_ITEM_TYPE =
            ContentResolver.CURSOR_ITEM_BASE_TYPE + "/vnd.rssfeed.article";

    public static final Uri CONTENT_URI =
            BASE_CONTENT_URI.buildUpon().appendPath(PATH_ENTRIES).build();

    public static final String TABLE_NAME = "article";



    public static final String COLUMN_NAME_TITLE = "title";

    public static final String COLUMN_NAME_DESCRIPTION = "description";

    public static final String COLUMN_NAME_AUTHOR = "author";

    public static final String COLUMN_NAME_DATETIME = "datetime";

    public static final String COLUMN_NAME_URL = "url";


}

}

public class FeedDBHelper {
FeedDatabase openHelper;
NewsItem item;
private SQLiteDatabase db;
private String [] columnItemName = {FeedContract.Entry.COLUMN_NAME_TITLE,
    FeedContract.Entry.COLUMN_NAME_DESCRIPTION,         FeedContract.Entry.COLUMN_NAME_AUTHOR,
    FeedContract.Entry.COLUMN_NAME_DATETIME,  FeedContract.Entry.COLUMN_NAME_URL};
public FeedDBHelper(Context context) {
    openHelper = new FeedDatabase(context);
    db = openHelper.getWritableDatabase();
}
public void saveArticleItem(String title, String description, String author, String datetime, String url){
    ContentValues cv = new ContentValues();
   // cv.put(FeedContract.Entry.COLUMN_NAME_IMAGE, image);
    cv.put(FeedContract.Entry.COLUMN_NAME_TITLE, title);
    cv.put(FeedContract.Entry.COLUMN_NAME_DESCRIPTION, description);
    cv.put(FeedContract.Entry.COLUMN_NAME_AUTHOR, author);
    cv.put(FeedContract.Entry.COLUMN_NAME_DATETIME, datetime);
    cv.put(FeedContract.Entry.COLUMN_NAME_URL, url);
    db.insert(FeedContract.Entry.TABLE_NAME, null, cv);
}
public void close() {
    db.close();
}
public ArrayList<NewsItem> getArticleList() {
        ArrayList<NewsItem> items = new ArrayList<NewsItem>();
        Cursor cursor = db.query(FeedContract.Entry.TABLE_NAME,
                columnItemName, null, null, null, null, null);
        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            NewsItem item = cursorToItem(cursor);
            items.add(item);
            cursor.moveToNext();
        }
        // make sure to close the cursor
        cursor.close();
        return items;
    }
    private NewsItem cursorToItem(Cursor cursor) {
        NewsItem item = new NewsItem();
        item.setNewsHeading(cursor.getString(1));
        item.setNewsDescSmall(cursor.getString(2));
        item.setAuthor(cursor.getString(3));
        item.setDateTime(cursor.getString(4));
        item.setUrl(cursor.getString(5));
        return item;
    }
static class FeedDatabase extends SQLiteOpenHelper {
    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "feed.db";
    private static final String TYPE_TEXT = " TEXT";
    private static final String TYPE_INTEGER = " INTEGER";
    private static final String TYPE_BLOB = " BLOB NOT NULL";
    private static final String COMMA_SEP = ",";
    private static final String SQL_CREATE_ARTICLES =
            "CREATE TABLE " + FeedContract.Entry.TABLE_NAME + " (" +
                    FeedContract.Entry._ID + " INTEGER PRIMARY KEY," +
                    FeedContract.Entry.COLUMN_NAME_TITLE    + TYPE_TEXT + COMMA_SEP +
                    FeedContract.Entry.COLUMN_NAME_DESCRIPTION + TYPE_TEXT + COMMA_SEP +
                    FeedContract.Entry.COLUMN_NAME_AUTHOR + TYPE_TEXT + COMMA_SEP +
                    FeedContract.Entry.COLUMN_NAME_DATETIME + TYPE_TEXT + COMMA_SEP +
                    FeedContract.Entry.COLUMN_NAME_URL + TYPE_TEXT + ")";
    private static final String SQL_DELETE_ARTICLES =
            "DROP TABLE IF EXISTS " + FeedContract.Entry.TABLE_NAME;
    public FeedDatabase(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_ARTICLES);
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL(SQL_DELETE_ARTICLES);
        onCreate(db);
    }
}

}

public class NewsItem {

private String newsHeading;
private String newsDesc;
private String author;
private String dateTime;
private String url;
public void setNewsHeading(String newsHeading) {
    this.newsHeading = newsHeading;
}
public void setNewsDesc(String newsDesc) {
    this.newsDesc = newsDesc;
}
public void setAuthor(String author) {
    this.author = author;
}
public void setDateTime(String dateTime) {
    this.dateTime = dateTime;
}
public void setNewsDescSmall(String newsDescSmall) {
    this.newsDescSmall = newsDescSmall;
}
public void setUrl(String url) {
    this.url = url;
}
private String newsDescSmall;
public NewsItem() {
}
public NewsItem(String newsHeading, String newsDesc, String author, String dateTime, String url) {
    this.newsHeading = newsHeading;
    this.newsDesc = newsDesc;
    this.author = author;
    this.dateTime = dateTime;
    this.url = url;
    this.newsDescSmall = this.newsDesc.substring(0, 19) + "...";
}
public String getNewsDesc() {
    return newsDesc;
}
public String getAuthor() {
    return author;
}
public String getNewsHeading() {
    return newsHeading;
}
public String getDateTime() {
    return dateTime;
}
public String getUrl() {
    return url;
}
public String getNewsDescSmall() {
    return newsDescSmall;
}

}

public class MainActivity extends AppCompatActivity  {

private static final String TAG_TITLE = "title";
private static final String TAG_DESCRIPTION = "description";
private static final String TAG_AUTHOR = "author";
private static final String TAG_PUBLISHEDAT = "publishedAt";
private static final String TAG_URL = "url";
CustomAdapter adapter;
Context ctx;
private List<NewsItem> newsFeed = new ArrayList<>();
FeedDBHelper feedDBHelper;
ListView lv;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    feedDBHelper = new FeedDBHelper(this);
    lv = (ListView) findViewById(R.id.list);
    jsonParser();
newsFeed = feedDBHelper.getArticleList();
    addClickListener();
    adapter = new CustomAdapter();
    lv.setAdapter(adapter);
}
public void jsonParser() {
    RequestQueue queue = Volley.newRequestQueue(this);
    final JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, "https://newsapi.org/v1/articles?source=the-next-web&sortBy=latest&apiKey=264e1f7afdff497aaaa6458de9bab1de",
            null, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            try {
                JSONArray articlesItem = response.getJSONArray("articles");
                for (int i = 0; i < articlesItem.length(); i++) {
                    JSONObject item = articlesItem.getJSONObject(i);
                    String title = item.getString(TAG_TITLE);
                    String description = item.getString(TAG_DESCRIPTION);
                    String author = item.getString(TAG_AUTHOR);
                    String dateTime = item.getString(TAG_PUBLISHEDAT);
                    String url = item.getString(TAG_URL);
                    Log.e("my", title+ " " + description + " " + author + " " + dateTime+ " "+url);
                    feedDBHelper.saveArticleItem(title, description, author, dateTime, url);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Log.e("mylog", error.toString());
        }
    });
    request.setRetryPolicy(new DefaultRetryPolicy(
            5000, DefaultRetryPolicy.DEFAULT_MAX_RETRIES, DefaultRetryPolicy.DEFAULT_BACKOFF_MULT
    ));
    queue.add(request);
}
private void addClickListener() {
    lv = (ListView) findViewById(R.id.list);
    lv.setOnItemClickListener(new AdapterView.OnItemClickListener()
                              {
                                  @Override
                                  public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                                      NewsItem currentItem = newsFeed.get(i);
                                      Intent intent = new Intent(Intent.ACTION_VIEW);
                                      intent.setData(Uri.parse(currentItem.getUrl()));
                                      startActivity(intent);
                                  }
                              }
    );
}
public class CustomAdapter extends ArrayAdapter<NewsItem> {
    private CustomAdapter() {
        super(MainActivity.this, R.layout.item_list, newsFeed);
    }
    @Override
    @NonNull
    @SuppressWarnings("NullableProblems")
    public View getView(int position, View convertView, ViewGroup parent)  {
        MyViewHolder mViewHolder;
        if (convertView == null) {
            convertView = getLayoutInflater().inflate(R.layout.item_list, parent, false);
            mViewHolder = new MyViewHolder(convertView);
            convertView.setTag(mViewHolder);
        } else {
            mViewHolder = (MyViewHolder) convertView.getTag();
        }
        NewsItem currentItem = newsFeed.get(position);
        mViewHolder.heading.setText(currentItem.getNewsHeading());
        mViewHolder.desc.setText(currentItem.getNewsDescSmall());
        mViewHolder.author.setText(currentItem.getAuthor());
        mViewHolder.date.setText(currentItem.getDateTime());
        mViewHolder.url.setText(currentItem.getUrl());
        return convertView;
    }
    private class MyViewHolder {
        TextView heading, desc, author, date, url ;
        private MyViewHolder(View item) {
            heading = (TextView) item.findViewById(R.id.heading);
            desc = (TextView) item.findViewById(R.id.desc);
            author = (TextView) item.findViewById(R.id.author);
            date = (TextView) item.findViewById(R.id.datetime);
            url = (TextView) item.findViewById(R.id.url);
        }
    }
}
@Override
protected void onPause() {
feedDBHelper.close();
    super.onPause();
}
@Override
protected void onResume() {
    super.onResume();
    feedDBHelper = new FeedDBHelper(this);
    addClickListener();
}

}

【问题讨论】：

标签： android

【解决方案1】：

如果能正确理解，请在检查是否有可用数据之前尝试获取数据。

所以请你尝试替换这个

while (!cursor.isAfterLast()) {
            NewsItem item = cursorToItem(cursor);
            items.add(item);
            cursor.moveToNext();
        }

以下

   while (cursor.moveToNext()) {
     NewsItem item = cursorToItem(cursor);
     items.add(item);
   }

【讨论】：