Question

大家好我正在做一个应用程序，我想更新我的列表视图，但一切都工作正常只有列表视图没有更新我不明白我做错了帮助我

代码

    public class MainActivity extends AppCompatActivity implements Spinner.OnItemSelectedListener{
    private Spinner spinner;
    private ArrayList<String> students;
    private JSONArray result;
    CallbackManager callbackManager;
    ShareDialog shareDialog;

    //  listveiw data
    private static final String TAG = MainActivity.class.getSimpleName();
    String url = "http://www.example.com/json/json.php";
    private ProgressDialog pDialog;
    private List<Model> movieList = new ArrayList<Model>();
    private ListView listView;
    private CustomListAdapter adapter;
    final Model model = new Model();
    final Json_Data j_data = new Json_Data();



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        FacebookSdk.sdkInitialize(getApplicationContext());
        setContentView(R.layout.activity_main);
        callbackManager = CallbackManager.Factory.create();
        students = new ArrayList<String>();
        spinner = (Spinner) findViewById(R.id.txtSpinner);
        listView = (ListView) findViewById(R.id.list);
        spinner.setOnItemSelectedListener(this);
        getData();
        listdata();
        adapter = new CustomListAdapter(this, movieList);
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                final TextView tv_id = (TextView) view.findViewById(R.id.title);
                String txt = tv_id.getText().toString();
                model.setItemText(txt);
                Log.e(TAG, "====>" + txt);
                _Dialog_Custom();
            }
        });
        pDialog = new ProgressDialog(this);
        pDialog.setMessage("Loading...");
        pDialog.show();
    }
    public void listdata(){
        JsonArrayRequest movieReq = new JsonArrayRequest(url,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        hidePDialog();
                        Log.e(TAG, response.toString());
                        for (int i = 0; i < response.length(); i++) {
                            try {
                                JSONObject obj = response.getJSONObject(i);
                                Model model = new Model();
                                String status = obj.getString("txt");
                                String cate = obj.getString("category");
                                model.setList_category(cate);
                                model.setTitle(status);
                                movieList.add(model);
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }
                        adapter.notifyDataSetChanged();
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                hidePDialog();
            }
        });
        AppController.getInstance().addToRequestQueue(movieReq);
    }
    private void getData() {
        StringRequest stringRequest = new StringRequest(Config.DATA_URL,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        JSONObject j_obj = null;
                        try {
                            j_obj = new JSONObject(response);
                            result = j_obj.getJSONArray(Config.JSON_ARRAY);
                            //Calling method getStudents to get the students from the JSON Array
                            getStudents(result);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                    }
                });
        RequestQueue requestQueue = Volley.newRequestQueue(this);
        requestQueue.add(stringRequest);
    }
    private void getStudents(JSONArray j) {
        for (int i = 0; i < j.length(); i++) {
            try {
                JSONObject json = j.getJSONObject(i);
                students.add(json.getString(Config.TAG_USERNAME));
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
        //Setting adapter to show the items in the spinner
        spinner.setAdapter(new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_dropdown_item, students));
    }
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        String text_spinner = spinner.getSelectedItem().toString();
        //Log.e("Selected value in","==>"+text_spinner);
        j_data.setSpintext(text_spinner);
        makeJsonArrayRequest();
        Toast.makeText(MainActivity.this, "Get Value from spinner"    +text_spinner, Toast.LENGTH_SHORT).show();
    }
    @Override
    public void onNothingSelected(AdapterView<?> parent) {
    }

    private void _Dialog_Custom() {
        final Dialog dialog = new Dialog(this);
        final String txt1 = model.getItemText().toString();
        Log.e("Hello Dialog", ":=>" + txt1);
        dialog.setContentView(R.layout.dialogbox);
        dialog.setTitle("Share via");
        dialog.setCanceledOnTouchOutside(true);
        ImageButton _Fb_Sharebtn = (ImageButton) dialog.findViewById(R.id.share_facebook);
        _Fb_Sharebtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ShareDialog.canShow(ShareLinkContent.class)) {
                    // https://developers.facebook.com/docs/sharing/android
                    ShareLinkContent linkContent = new ShareLinkContent.Builder()
                            .setContentTitle("Hello Facebook")
                            .setContentDescription(
                                    "The 'Hello Facebook' sample  showcases simple Facebook integration")
                            .setContentUrl(Uri.parse("http://developers.facebook.com/android"))
                            .build();
                      shareDialog.show(linkContent);
                }
            }
        });

        ImageButton _Sharebtn_google = (ImageButton) dialog.findViewById(R.id.share_btn_google);
        _Sharebtn_google.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent shareIntent = new PlusShare.Builder(MainActivity.this)
                        .setType("text/plain")
                        .setText(txt1)
                        .getIntent();
                try {
                    startActivity(shareIntent);
                } catch (ActivityNotFoundException ex) {
                    startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id=com.google.android.apps.plus&hl=en")));
                }
            }
        });

        ImageButton whtsapp_sahre = (ImageButton) dialog.findViewById(R.id.whatsapp_btn);
        whtsapp_sahre.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent whatsappIntent = new Intent(Intent.ACTION_SEND);
                whatsappIntent.setType("text/plain");
                whatsappIntent.setPackage("com.whatsapp");
                String result = txt1;
                whatsappIntent.putExtra(Intent.EXTRA_TEXT, result);
                try {
                    startActivity(whatsappIntent);
                } catch (ActivityNotFoundException ex) {
                    startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id=com.whatsapp")));
                }
            }
        });
        ImageButton _Twwiterbtn = (ImageButton) dialog.findViewById(R.id.twwiter_btn);
        _Twwiterbtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Intent.ACTION_SEND);
                String result = txt1;
                intent.setType("text/plain")
                        .setPackage("com.twitter.android");
                intent.putExtra(Intent.EXTRA_TEXT, result);

                try {
                    startActivity(intent);
                } catch (ActivityNotFoundException ex) {
                    startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("https://play.google.com/store/apps/details?id=com.twitter.android&hl=en")));
                }
            }
        });
        dialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
            @Override
            public void onCancel(DialogInterface dialog) {

            }
        });
        dialog.setOnDismissListener(new DialogInterface.OnDismissListener() {
            @Override
            public void onDismiss(DialogInterface dialog) {

            }
        });
        dialog.show();
    }

    protected void onActivityResult(final int requestCode, final int resultCode, final Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        callbackManager.onActivityResult(requestCode, resultCode, data);
    }


    @Override
    public void onBackPressed() {
        super.onBackPressed();
        Intent backintent = new Intent(getApplicationContext(), Main_Selected_Activity.class);
        startActivity(backintent);
        finish();
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        hidePDialog();
    }

    private void hidePDialog() {
        if (pDialog != null) {
            pDialog.dismiss();
            pDialog = null;
        }
    }


    private void makeJsonArrayRequest() {
        String spinner_data =j_data.getSpintext().toString().trim();
        Log.e(TAG, spinner_data.toString());
        String arrayurl = "http://www.example.com/jsoncategory.php?category="+spinner_data;
        Log.e("Link is here","==>"+arrayurl);
        ArrayList<String> newdata = new ArrayList<String>();
        movieList = new ArrayList<Model>();
        JsonArrayRequest movieReq = new JsonArrayRequest(arrayurl,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Log.e(TAG, "link response=>" + response);
                        for (int i = 0; i < response.length(); i++) {
                            try {
                                JSONObject obj = response.getJSONObject(i);
                                String name = obj.getString("txt");
                                model.setList_category(name);
                                movieList.add(model);
                            }catch (JSONException e) {
                                e.printStackTrace();
                                Log.e("Hello error","==>"+e);
                            }
                        }
                        adapter.notifyDataSetChanged();
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                hidePDialog();
            }
        });
        AppController.getInstance().addToRequestQueue(movieReq);

    }
  }

请帮帮我

Answer 1

遵循以下方法

在适配器类中创建公共方法：

private List<Model> adapterInitialMovieList = null;

 public void setDataOnSpinnerSelected(List<Model> movieList){
 adapterInitialMovieList  = movieList;
notifyDataSetChanged();
}

在您的活动类内部Spinner onClick方法：

if(adapter  != null){
adapter.setDataOnSpinnerSelected(yourChangedArrayListOfModelClass);
}

Answer 2

从makeJsonArrayRequest()

中删除此行

movieList = new ArrayList<Model>();

您正在为movieList分配一个新对象（ArrayList），并在新对象中添加值，而不是您传递给列表适配器的值。因此，列表适配器正在使用的对象的引用将丢失，并且当您调用adapter.notifyDataSetChanged();时，没有更新，因为列表适配器使用的对象未更改。

Answer 3

使用 movieList.clear();

而不是

movieList = new ArrayList<Model>();

问题在于创建一个新的arraylist。因此，ArrayAdapter不知道＆＃39;你想要创建一个新的ArrayList（具有不同的地址）。排队 adapter = new CustomListAdapter(this, movieList); 你推了一些arraylist的地址。在以后的新行中，您将使用不同的arraylist生成一个新的arraylist并使用它。但适配器适用于旧的变体＆＃39; arraylist。

在微调器选择后，Listview没有在android中更新

3 个答案: