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我的ListView沒有顯示任何東西。ListView沒有顯示任何東西
我從下載黑客新聞的頭條新聞API並且把它們放在我的應用程序。我想把這些故事的標題放在我的列表視圖中（它們超過100）。
我下載它們，並將它們存儲在永久存儲數據庫，然後將它們添加到我的列表視圖，但沒有什麼是顯示在我的應用程序了。任何人都可以向我解釋爲什麼？
更新：我得到一個CursorIndexOutOfBoundException問題。 （指數350出的350）
public class MainActivity extends AppCompatActivity {
ListView listView;
private SQLiteDatabase myDatabase;
private Cursor cursor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listView);
DownloadIDs ids = new DownloadIDs();
String URL = "https://hacker-news.firebaseio.com/v0/topstories.json?print=pretty";
ids.execute(URL);
try {
ArrayList<String> titles = new ArrayList<String>();
ArrayAdapter arrayAdapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, titles);
listView.setAdapter(arrayAdapter);
myDatabase = this.openOrCreateDatabase("HackerNews", MODE_PRIVATE, null);
Cursor cursor1 = myDatabase.rawQuery("SELECT * FROM ids", null);
int index = cursor1.getColumnIndex("urlID");
cursor1.moveToFirst();
while (cursor1 != null) {
String newUrl = "https://hacker-news.firebaseio.com/v0/item/" + cursor1.getString(index) + ".json?print=pretty";
new DownloadContent().execute(newUrl);
cursor1.moveToNext();
}
Cursor cursor2 = myDatabase.rawQuery("SELECT * FROM content", null);
int titleIndex = cursor2.getColumnIndex("title");
cursor2.moveToFirst();
titles.add("Hello");
while(cursor2 != null){
titles.add(cursor2.getString(titleIndex));
arrayAdapter.notifyDataSetChanged();
cursor2.moveToNext();
}
}catch (Exception e){
e.printStackTrace();
}
}
public class DownloadIDs extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
String result = "";
URL url;
HttpURLConnection urlConnection = null;
try {
url = new URL(params[0]);
urlConnection = (HttpURLConnection) url.openConnection();
InputStream inputStream = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(inputStream);
int data = reader.read();
while (data >= 0) {
char current = (char) data;
result += current;
data = reader.read();
}
return result;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
try {
myDatabase.execSQL("CREATE TABLE IF NOT EXISTS ids (id INTEGER PRIMARY KEY, urlID VARCHAR)");
cursor = myDatabase.rawQuery("SELECT COUNT(*) FROM ids", null);
cursor.moveToFirst();
int count = cursor.getInt(0);
if (!(count > 0)) {
JSONArray ids = new JSONArray(s);
for (int i = 0; i < ids.length(); i++) {
myDatabase.execSQL("INSERT INTO ids (urlID) VALUES ('" + ids.getString(i) + "')");
}
}
}catch (Exception e){
e.printStackTrace();
}
}
}
public class DownloadContent extends AsyncTask<String, Void, String> {
@Override
protected String doInBackground(String... params) {
String result = "";
URL url;
HttpURLConnection urlConnection = null;
try {
url = new URL(params[0]);
urlConnection = (HttpURLConnection) url.openConnection();
InputStream inputStream = urlConnection.getInputStream();
InputStreamReader reader = new InputStreamReader(inputStream);
int data = reader.read();
while (data >= 0) {
char current = (char) data;
result += current;
data = reader.read();
}
return result;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
try {
myDatabase.execSQL("CREATE TABLE IF NOT EXISTS content(id INTEGER PRIMARY KEY, title VARCHAR, url VARCHAR)");
cursor = myDatabase.rawQuery("SELECT COUNT(*) FROM content", null);
cursor.moveToFirst();
int count = cursor.getInt(0);
if (!(count > 0)) {
JSONObject jsonObject = new JSONObject(s);
String title = jsonObject.getString("title");
Log.i("title", title);
String url = jsonObject.getString("url");
Log.i("url", url);
myDatabase.execSQL("INSERT INTO content (title, url) VALUES('" + title + "','" + url + "')");
}
}catch(Exception e){
e.printStackTrace();
}
}
}
}
在哪一行，你得到的異常？ –
對不起。我在onCreate方法的兩個while循環上都得到它。 –