Question

下面是我的源代码我的问题是如何从服务器第一次更新数据库应用程序在数据库中插入值formserver现在服务器更新数据库后如何知道服务器更改数据库现在需要更新数据库？

     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>();


     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();


      isInternetPresent = cd.isConnectingToInternet();

      // check for Internet status
      if (isInternetPresent) {
          // Internet Connection is Present
          // make HTTP requests
          new TheTask().execute();

      } else {
          // Internet connection is not present
          // Ask user to connect to Internet
          displayData();

      }



         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.xyz/_webservices/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();
    //         IOConnect = 1;

        }
        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_MYID)));

      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 UNIQUE NOT NULL, "+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);

}

      }

Answer 1

有不同的方法可以解决这个问题，但您可以在某些时间间隔内刷新应用程序。您可以每隔X分钟调用Web服务并询问是否有任何更改，或者您可以使用Google Cloud Messaging从服务器接收通知，然后刷新数据希望它有所帮助：）

如何从服务器更新数据库以及我如何知道服务器更改数据库

1 个答案: