我想让我的应用程序脱机。当我将数据从 url 插入数据库时，它在互联网可用时工作正常，但是当没有互联网可用时，我的应用程序在 gridview 中没有显示任何东西我的应用程序有什么问题请帮助我为什么 gridview 不加载数据从数据库帮助我
public class MainActivity extends Activity {
CategoryListAdapter3 cla;
static ArrayList<String> Category_ID = new ArrayList<String>();
static ArrayList<String> Category_name = new ArrayList<String>();
static ArrayList<String> Category_image = new ArrayList<String>();
String URL, URL2;
String SelectMenuAPI;
String _response;
String status;
GridView gridview;
private DbHelper mHelper;
private SQLiteDatabase dataBase;
private boolean isUpdate;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mHelper=new DbHelper(this);
dataBase=mHelper.getWritableDatabase();
gridview = (GridView) findViewById(R.id.gridview);
cla = new CategoryListAdapter3(MainActivity.this);
new TheTask().execute();
gridview.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> arg0, View arg1,
int position, long arg3) {
// TODO Auto-generated method stub
Intent iMenuList = new Intent(MainActivity.this,
Subcategory.class);
iMenuList.putExtra("Category_ID", Category_ID.get(position));
iMenuList.putExtra("Category_name", Category_name.get(position));
startActivity(iMenuList);
}
});
}
void clearData() {
Category_ID.clear();
Category_name.clear();
Category_image.clear();
}
public class TheTask extends AsyncTask<Void, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected String doInBackground(Void... arg0) {
SelectMenuAPI = "http://www.fff/mobile_api.php?response=getmaincategories";
clearData();
URL = SelectMenuAPI;
URL2 = URL.replace(" ", "%20");
try {
Log.i("url", "" + URL2);
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet(URL2);
HttpResponse response = client.execute(request);
HttpEntity resEntity = response.getEntity();
_response = EntityUtils.toString(resEntity);
} catch (Exception e) {
e.printStackTrace();
}
return _response;
}
@Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
try {
JSONObject json2 = new JSONObject(result);
status = json2.getString("Status");
if (status.equals("1")) {
JSONArray school2 = json2.getJSONArray("data");
//
for (int i = 0; i < school2.length(); i++) {
JSONObject object = school2.getJSONObject(i);
String id = object.getString("category_id");
String name =object.getString("name");
String image_path = object.getString("image_path");
dataBase=mHelper.getWritableDatabase();
ContentValues values=new ContentValues();
values.put(DbHelper.KEY_MYID,id);
values.put(DbHelper.KEY_FNAME,name);
values.put(DbHelper.KEY_LNAME,image_path );
System.out.println("");
if(isUpdate)
{
//update database with new data
dataBase.update(DbHelper.TABLE_NAME, values, DbHelper.KEY_ID+"="+id, null);
}
else
{
//insert data into database
dataBase.insert(DbHelper.TABLE_NAME, null, values);
}
//close database
dataBase.close();
}
}
else {
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
displayData();
}
}
private void displayData() {
dataBase = mHelper.getWritableDatabase();
Cursor mCursor = dataBase.rawQuery("SELECT * FROM "
+ DbHelper.TABLE_NAME, null);
//
// Category_ID.clear();
// Category_name.clear();
// Category_image.clear();
if (mCursor.moveToFirst()) {
do {
Category_ID.add(mCursor.getString(mCursor.getColumnIndex(DbHelper.KEY_ID)));
Category_name.add(mCursor.getString(mCursor.getColumnIndex(DbHelper.KEY_FNAME)));
Category_image.add(mCursor.getString(mCursor.getColumnIndex(DbHelper.KEY_LNAME)));
} while (mCursor.moveToNext());
}
gridview.setAdapter(cla);
mCursor.close();
}
public class DbHelper extends SQLiteOpenHelper {
static String DATABASE_NAME="userdata";
public static final String TABLE_NAME="user";
public static final String KEY_FNAME="fname";
public static final String KEY_LNAME="lname";
public static final String KEY_ID="id";
public static final String KEY_MYID="myid";
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_TABLE="CREATE TABLE "+TABLE_NAME+" ("+KEY_ID+" INTEGER PRIMARY
KEY,"+KEY_MYID+" TEXT, "+KEY_FNAME+" TEXT, "+KEY_LNAME+" BLOB)";
db.execSQL(CREATE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
onCreate(db);
}
}
public class CategoryListAdapter3 extends BaseAdapter {
private Activity activity;
private AQuery androidAQuery;
public CategoryListAdapter3(Activity act) {
this.activity = act;
// imageLoader = new ImageLoader(act);
}
public int getCount() {
// TODO Auto-generated method stub
return MainActivity.Category_ID.size();
}
public Object getItem(int position) {
// TODO Auto-generated method stub
return position;
}
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
ViewHolder holder;
androidAQuery = new AQuery(getcontext());
if(convertView == null){
LayoutInflater inflater = (LayoutInflater) activity
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.viewitem2, null);
holder = new ViewHolder();
convertView.setTag(holder);
}else{
holder = (ViewHolder) convertView.getTag();
}
holder.txtText = (TextView) convertView.findViewById(R.id.title2);
holder.imgThumb = (ImageView) convertView.findViewById(R.id.image2);
holder.txtText.setText(MainActivity.Category_name.get(position));
a
ndroidAQuery.id(holder.imgThumb).image(MainActivity.Category_image.get(position), true,
true);
return convertView;
}
private Activity getcontext() {
// TODO Auto-generated method stub
return null;
}
static class ViewHolder {
TextView txtText;
ImageView imgThumb;
}
}