应用程序不会运行第一次但是当菜单中的项目被点击时它运行s

Question

我从 json 文件读取数据到适配器，并在 oncreate 下的 main.java 中读取数据，当我尝试运行它时，它没有显示任何内容。

我在菜单 onclick 下尝试了相同的代码并且它有效，我希望它在应用程序首次运行时出现。

public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {

    String url = "myjsonurl.php";
    JSONArray jArray;
    ProgressDialog dialog;
    ListView mycustomlist = null;
    WebView mywebview =null;
    CustomAdapter myadapter = null;

    ArrayList<news> mydatalist = new ArrayList<news>();
    ArrayList<news> maşetData = new ArrayList<news>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myadapter = new CustomAdapter(this, mydatalist);
        mycustomlist = (ListView)findViewById(R.id.listview);
        mycustomlist.setAdapter(myadapter);
        dialog = new ProgressDialog(this);
        dialog.setMessage("Loading....");
        dialog.show();

        StringRequest request = new StringRequest(url, new Response.Listener<String>() {
            @Override
            public void onResponse(String string) {
                parseJsonData(string);
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError volleyError) {
                Toast.makeText(getApplicationContext(), "Some error occurred!!", Toast.LENGTH_SHORT).show();
                dialog.dismiss();
                dialog.cancel();
            }
        });

        RequestQueue rQueue = Volley.newRequestQueue(MainActivity.this);
        rQueue.add(request);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


       /* FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });
*/



        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }

    public void parseJsonData(final String jsonString) {

        try {
            jArray = new JSONArray(jsonString);

            for(int i=0; i < jArray.length(); i++) {

                JSONObject jObject = jArray.getJSONObject(i);
                news news1 = new news();

                news1.setTitle(jObject.getString("title"));
                news1.setContent(Html.fromHtml(jObject.getString("content")));
                news1.setDate(jObject.getString("date"));
                news1.setImage("http://www.bolgegundem.com/d/news/" + jObject.getString("image").concat(".jpg"));
                news1.setId(jObject.getString("id"));
                news1.setCategory(jObject.getString("category"));
                news1.set__comment_count(jObject.getString("__comment_count"));
                news1.setHeadline(jObject.getString("headline"));

                mydatalist.add(news1);




                //  http://www.bolgegundem.com/d/gallery/81_2.jpg
               /* images.add("http://www.bolgegundem.com/d/gallery/" + id +  "_" + imgUrl.replace(",", ".jpg") );*/
                // al.add(title);
                //imagelinks[i] = "http://www.bolgegundem.com/d/gallery/" + id + "_" + i + ".jpg";

            }


            // ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_activated_1, al);

            //listview.setAdapter(adapter);

            // listview.setBackgroundColor(rgb(0, 255, 255));
              /*  listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                    if(i < links.length){
                        Uri uri = Uri.parse(links[i]);
                        Intent intent = new Intent(Intent.ACTION_VIEW, uri);
                        startActivity(intent);
                    }
                }
            });*/
            if (dialog.isShowing()){
                dialog.dismiss();
            }
        } catch (JSONException e) {
            e.printStackTrace();
            dialog.dismiss();
        }
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @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 boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.manşet) {
            // Handle the camera action
        } else if (id == R.id.Anasayfa) {

            myadapter = new CustomAdapter(this, mydatalist);
            mycustomlist = (ListView)findViewById(R.id.listview);
            mycustomlist.setAdapter(myadapter);


        } else if (id == R.id.ajansTv) {

        } else if (id == R.id.foto) {

        } else if (id == R.id.gundem) {

        } else if (id == R.id.siyaset) {

        }else if (id ==R.id.Ekonomi ){


        }else if (id ==R.id.spor ){


        }else if (id ==R.id.saglik ){

        }else if (id ==R.id.nav_share ){


        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

我的适配器class在这里

public class CustomAdapter extends BaseAdapter {

    Context mycontext = null;
    ArrayList<news> mydatalist;

    public CustomAdapter(Context mycontext, ArrayList<news> mydatalist)
    {

        this.mycontext = mycontext;
        this.mydatalist = mydatalist;

    }

    @Override
    public int getCount() {
        return this.mydatalist.size();
    }

    @Override
    public Object getItem(int position) {
        return this.mydatalist.get(position);
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @SuppressLint("InflateParams")
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater myinflater = (LayoutInflater)mycontext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        ViewHolder myholder = null;
        if(convertView == null)
        {
            convertView = myinflater.inflate(R.layout.customlayout, null);

            myholder = new ViewHolder();
            myholder.mytextview1 = (TextView)convertView.findViewById(R.id.mytextview1);
            myholder.mytextview2 = (TextView)convertView.findViewById(R.id.mytextview2);
            myholder.mytextview3 = (TextView)convertView.findViewById(R.id.mytextview3);
            myholder.myimageview1 = (ImageView)convertView.findViewById(R.id.imageView);

            convertView.setTag(myholder);
        }
        else
        {
            myholder = (ViewHolder)convertView.getTag();
        }


        myholder.mytextview1.setText(mydatalist.get(position).getTitle());
        myholder.mytextview2.setText(mydatalist.get(position).getContent());
        myholder.mytextview3.setText(mydatalist.get(position).getDate());
        myholder.myimageview1.setImageResource(R.drawable.bolgegundem);
        new DownloadImageTask(myholder.myimageview1).execute(mydatalist.get(position).getImage());

        return convertView;
    }

    static class ViewHolder
    {
           public TextView mytextview1;
           public TextView mytextview2;
           public TextView mytextview3;
           public ImageView myimageview1;
    }

    private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
        ImageView bmImage;

        public DownloadImageTask(ImageView bmImage) {
            this.bmImage = bmImage;
        }
        protected Bitmap doInBackground(String... urls) {
            String urldisplay = urls[0];
            Bitmap mIcon = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon;
        }

        protected void onPostExecute(Bitmap result) {
            bmImage.setImageBitmap(result);
        }
    }
}

我该如何解决这个问题？

Answer 1

放三行

    myadapter = new CustomAdapter(this, mydatalist);
        mycustomlist = (ListView)findViewById(R.id.listview);
        mycustomlist.setAdapter(myadapter);

在这个方法中：

 @Override
 public void onResponse(String string) {
    parseJsonData(string);
    // put them here
 }

这会起作用，因为它会在 数据解析后填充列表 然后将其添加到适配器。如果在 OnCreate 中将列表添加到适配器，onResponse 方法将在运行之后（返回数据时）并且列表将为空。

Answer 2

您需要为您在导航中声明的每个项目创建片段并进行解析以及其中的所有内容，并且该片段是从 onNavigationItemSelected 调用的，如果您想要它总是首先显示，那么您也必须在其中调用它来自 onCreate() 方法。

应用程序不会运行第一次但是当菜单中的项目被点击时它运行s

App will not run the first time but when item in menu is clicked it runs

java

android

listview

navigation-drawer

baseadapter

应用程序不会 运行 第一次但是当菜单中的项目被点击时它 运行s

App will not run the first time but when item in menu is clicked it runs

java

android

listview

navigation-drawer

baseadapter

应用程序不会运行第一次但是当菜单中的项目被点击时它运行s