我正在研究从json到sqlite存储数据的android应用程序，直到现在我已将数据从json存储到sqlite并在listview中显示（当应用程序有Internet时），现在当我运行我的应用程序时没有互联网，我什么都没得到，我没有得到我做错的事。
MainActivity
public class MainActivity extends Activity {
private String[] navMenuTitles;
private TypedArray navMenuIcons;
private EditText editTextName;
SharedPreferences sp;
private String jsonResult;
private ListView listView;
private Button b;
EditText etname, et;
TextView tv;
String myJSON;
private static final String TAG = "MainActivity.java";
private static final String TAG_NAME = "notice";
private CategoryHelper databaseHelper;
Button get, store, select;
JSONArray peoples = null;
ArrayList<HashMap<String, String>> personList;
ListView list;
public static final String USER_NAME = "USERNAME";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.noticelist);
//select = (Button) findViewById(R.id.button3);
databaseHelper=new CategoryHelper(MainActivity.this);
databaseHelper.getTimeRecordList();
//SharedPreferences myprefs= getSharedPreferences("user", MODE_WORLD_READABLE);
// String session_id= myprefs.getString("session_id", null);
//TextView textView = (TextView) findViewById(R.id.fname);
//textView.setText("Welcome "+session_id);
/*select.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
select_seqlite();
}
});*/
// load icons from
// strings.xml
list = (ListView) findViewById(R.id.listView);
personList = new ArrayList<HashMap<String,String>>();
if (isOnline()) { getData(); }
else { showList(); }
}
public boolean isOnline() {
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
return netInfo != null && netInfo.isConnectedOrConnecting();
}
protected void showList(){
try {
JSONArray peoples = new JSONArray(myJSON);
for(int i=0;i<peoples.length();i++){
JSONObject c = peoples.getJSONObject(i);
String name=null, date=null;
if(c.has("notice"))
name = c.getString("notice");
databaseHelper.saveCategoryRecord(name);
Cursor c1 = databaseHelper.getTimeRecordList();
if( c1 != null && c1.moveToFirst())
do {
date = c1.getString(0);
}while(c1.moveToNext());
HashMap<String,String> persons = new HashMap<String,String>();
persons.put(TAG_NAME,date);
Log.i("tagconvertstr", "[" + date + "]");
personList.add(persons);
}
ListAdapter adapter = new SimpleAdapter(
MainActivity.this, personList, R.layout.list_item1,
new String[]{TAG_NAME},
new int[]{R.id.name}
);
list.setAdapter(adapter);
/* list.setAdapter(adapter);*/
} catch (JSONException e) {
Log.i("tagconvertstr", "["+myJSON+"]");
}
}
private void DisplayContact(Cursor c) {
// TODO Auto-generated method stub
Toast.makeText(getBaseContext(),"name " + c.getString(0), Toast.LENGTH_LONG).show();
}
public void getData(){
class GetDataJSON extends AsyncTask<String, Void, String>{
@Override
protected String doInBackground(String... params) {
SharedPreferences myprefs= getSharedPreferences("user", MODE_WORLD_READABLE);
String session_id= myprefs.getString("session_id", null);
InputStream inputStream = null;
String result = null;
try {
String postReceiverUrl = "http://10.0.2.2/progress_card/teacher/teacher_notice.php";
// HttpClient
HttpClient httpClient = new DefaultHttpClient();
// post header
HttpPost httpPost = new HttpPost(postReceiverUrl);
// add your data
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(2);
nameValuePairs.add(new BasicNameValuePair("username", "suyash1"));
httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpClient.execute(httpPost);
HttpEntity resEntity = response.getEntity();
inputStream = resEntity.getContent();
// json is UTF-8 by default
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
{
sb.append(line + "\n");
}
result = sb.toString();
} catch (Exception e) {
Log.i("tagconvertstr", "["+result+"]");
System.out.println(e);
}
finally {
try{if(inputStream != null)inputStream.close();}catch(Exception squish){}
}
return result;
}
@Override
protected void onPostExecute(String result){
myJSON = result;
showList();
}
}
GetDataJSON g = new GetDataJSON();
g.execute();
}
//get json data stop
}
CategoryHelper.java
public class CategoryHelper {
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_NAME = "category.db";
private static final String TABLE_NAME = "tbcategory";
public static final String CATEGORY_COLUMN_NAME = "name";
Category openHelper;
private SQLiteDatabase database;
public CategoryHelper(Context context){
openHelper = new Category(context);
database = openHelper.getWritableDatabase();
}
public void saveCategoryRecord(String name) {
ContentValues contentValues = new ContentValues();
contentValues.put(CATEGORY_COLUMN_NAME, name);
database.insert(TABLE_NAME, null, contentValues);
}
public Cursor getTimeRecordList() {
return database.rawQuery("select * from " + TABLE_NAME, null);
}
private class Category extends SQLiteOpenHelper {
public Category(Context context) {
// TODO Auto-generated constructor stub
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE " + TABLE_NAME + "( "
+ CATEGORY_COLUMN_NAME + " TEXT )" );
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS"+ TABLE_NAME);
onCreate(db);
}
}
}
答案 0 :(得分：0)
添加
SearchView而不是getData（）：
public boolean isOnline() {
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
return netInfo != null && netInfo.isConnectedOrConnecting();
}
您需要保存myList，因此下次打开应用程序时，它会在本地保存：
myJSON = loadResults();
if (isOnline()) { getData(); }
else if (myJSON != null) { showList(); }
else { Toast.makeText(getContext(), "no data available to show", Toast.LENGTH_SHORT).show(); }
答案 1 :(得分：0)
在单独的函数中输入以下代码，例如loadData（）
public void loadData() {
Cursor c1 = databaseHelper.getTimeRecordList();
//Code to iterate c1 cursor.
//Create Adapter with data from c1 cursor
//Add adapter to list.
}
public boolean isOnline() {
ConnectivityManager cm =
(ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo netInfo = cm.getActiveNetworkInfo();
return netInfo != null && netInfo.isConnectedOrConnecting();
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.noticelist);
//select = (Button) findViewById(R.id.button3);
databaseHelper=new CategoryHelper(MainActivity.this);
databaseHelper.getTimeRecordList(); //remove this line as your not catching cursor in any variable.
...
list = (ListView) findViewById(R.id.listView);
personList = new ArrayList<HashMap<String,String>>();
if (isOnline()) { getData(); }
else { loadData(); }
}