Activity 类型为“固定标签+滑动”。我需要从我的 Listvew 中的 DB sqlite 读取数据，它位于 fragment xml 文件中(不在主 xml 中)。我使用一些程序中的旧代码，有一种创建 ListView 的方法:
public void createList(){
db = new DB(this);
db.open();
String[] from = new String[] {DB.COLUMN_NAME, DB.COLUMN_TIME };
int[] to = new int[] { R.id.tvTextName, R.id.tvText_time};
scAdapter = new SimpleCursorAdapter(this, R.layout.item, null, from, to, 0);
lvData = (ListView) findViewById(R.id.lvData);
lvData.setAdapter(scAdapter);
getSupportLoaderManager().initLoader(0, null, this);
}
在简单的 Activity 代码中工作正常，但我不知道如何在 fragment Activity 中使用该代码。我尝试在主类中调用该方法，但该代码:
lvData = (ListView) findViewById(R.id.lvData);
lvData.setAdapter(scAdapter);
我放入 fragment 类。程序工作，但 ListView 是空的。数据库不为空。主要部分代码:
public class MainActivity extends FragmentActivity implements
ActionBar.TabListener, LoaderCallbacks<Cursor> {
//*****ОСНОВНЫЕ ПЕРЕМЕННЫЕ*****
private static String TAG = "MainActivity";
private static final int CM_DELETE_ID = 1;
private static final int RESET_STOPWATCH = 2;
static ListView lvData;
static DB db;
static SimpleCursorAdapter scAdapter;
static Context ctx;
static String[] from = new String[] {DB.COLUMN_NAME, DB.COLUMN_TIME };
static int[] to = new int[] { R.id.tvTextName, R.id.tvText_time};
SectionsPagerAdapter mSectionsPagerAdapter;
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Set up the action bar.
final ActionBar actionBar = getActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
mViewPager
.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
actionBar.addTab(actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
ctx = this;
createList();
}
public void createList(){
db = new DB(this);
db.open();
scAdapter = new SimpleCursorAdapter(this, R.layout.item, null, from, to, 0);Log.d(TAG, "1");
getSupportLoaderManager().initLoader(0, null, this);
}
@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;
}
@Override
public void onTabSelected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
if(position == 0){
Fragment fragment = new DummySectionFragment();
Bundle args = new Bundle();
args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, position + 1);
fragment.setArguments(args);
//getSupportLoaderManager().initLoader(0, null, this);
return fragment;
}
if (position == 1)
{
Fragment fragment2 = new DummySectionFragment2();
Bundle args = new Bundle();
args.putInt(DummySectionFragment2.ARG_SECTION_NUMBER, position + 2);
fragment2.setArguments(args);
return fragment2;
}
return null;
}
@Override
public int getCount() {
// Show 3 total pages.
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
}
return null;
}
}
public static class DummySectionFragment extends Fragment{
public static final String ARG_SECTION_NUMBER = "section_number";
public DummySectionFragment() {
}
static View v;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activity_tracker,
container, false);
v = inflater.inflate(R.layout.activity_tracker, container, false);
lvData = (ListView) v.findViewById(R.id.lvData);Log.d(TAG, "2");
lvData.setAdapter(scAdapter);Log.d(TAG, "3");
return rootView;
}
}
public static class DummySectionFragment2 extends Fragment {
//code page 2
}
}
//Класс по управлению БД
static class MyCursorLoader extends CursorLoader {
DB db;
public MyCursorLoader(Context context, DB db) {
super(context);
this.db = db;
}
@Override
public Cursor loadInBackground() {
Cursor cursor = db.getAllData();
return cursor;
}
}
}
}
最佳答案
我已经设置了一个类似的应用程序，将数据库详细信息读取到包含 ListView 的 fragment 中。我已通过 JSON 解析完成此操作。
请看以下内容:
public static class EventFragment extends ListFragment {
ArrayList<HashMap<String, String>> eventsList;
private String url_all_events = "//url of the location of your database";
//used a Progressbar to prompt the user that the data is downloading until it downloads.
private ProgressDialog pDialog;
JSONParser jParser = new JSONParser();
// JSON Node names
private static final String CONNECTION_STATUS = "success";
private static final String TABLE_EVENT = "Event";
private static final String pid = "pid";
private static final String COL_GROUP = "Group";
private static final String COL_NAME = "Event_Name";
private static final String COL_DESC = "Event_Desc";
private static final String COL_DATE = "Event_Date";
private static final String COL_TIME = "Event_Time";
JSONArray Events = null;
public static final String ARG_SECTION_NUMBER = "section_number";
public EventFragment() {
}
public void onStart() {
super.onStart();
eventsList = new ArrayList<HashMap<String, String>>();
new LoadAllEvents().execute();
// selecting single ListView item
ListView lv = getListView();
// Lauching the Event details screen on selecting a single event
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String ID = ((TextView) view.findViewById(R.id.pid))
.getText().toString();
Intent intent = new Intent(view.getContext(),
EventDetails.class);
intent.putExtra(pid, ID);
view.getContext().startActivity(intent);
}
});
}
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_events,
container, false);
return rootView;
}
class LoadAllEvents extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Just a moment...");
pDialog.setIndeterminate(true);
pDialog.setCancelable(true);
pDialog.show();
}
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_events,
"GET", params);
try {
// Checking for SUCCESS TAG
int success = json.getInt(CONNECTION_STATUS);
if (success == 1) {
// products found
// Getting Array of Products
Events = json.getJSONArray(TABLE_EVENT);
// looping through All Contacts
for (int i = 0; i < Events.length(); i++) {
JSONObject evt = Events.getJSONObject(i);
// Storing each json item in variable
id = evt.getString(pid);
group = evt.getString(COL_GROUP);
name = evt.getString(COL_NAME);
desc = evt.getString(COL_DESC);
date = evt.getString(COL_DATE);
time = evt.getString(COL_TIME);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(pid, id);
map.put(COL_GROUP, group);
map.put(COL_NAME, name);
map.put(COL_DESC, desc);
map.put(COL_DATE, date);
map.put(COL_TIME, time);
// adding HashList to ArrayList
eventsList.add(map);
}
} else {
// Options are not available or server is down.
// Dismiss the loading dialog and display an alert
// onPostExecute
pDialog.dismiss();
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
// updating UI from Background Thread
getActivity().runOnUiThread(new Runnable() {
public void run() {
ListAdapter adapter = new SimpleAdapter(getActivity(),
eventsList, R.layout.list_item, new String[] {
pid, COL_GROUP, COL_NAME, COL_DATE, COL_TIME },
new int[] { R.id.pid, R.id.group, R.id.name, R.id.header,
R.id.title2 });
setListAdapter(adapter);
}
});
}
}
}
对于 JSON 解析器，我使用了以下类:
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// constructor
public JSONParser() {
}
// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
List<NameValuePair> params) {
// Making HTTP request
try {
// check for request method
if (method == "POST") {
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} else if (method == "GET") {
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
最后，这是 fragment 布局的 xml 文件。
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<!-- Main ListView
Always give id value as list(@android:id/list)
-->
<ListView
android:id="@android:id/list"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
</LinearLayout>
这里我使用了自定义 ListView ，所以请注意我实现它的方式可能有点复杂。
希望这有帮助:)
关于java - 无法在listview android中读取sqlite数据库，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/22838323/