Question

我使用Android Studio创建了一个活动，该活动由一个表单组成，该表单允许用户向用户希望的表中的数据库添加项目。就设计而言，到目前为止一切都很好。我正在使用微调器，以便从表中检索特定列并在微调器中显示数据，但是，每当我在Emulator / smartphone上运行应用程序时，它都不会显示从数据库中检索到的数据（与数据库的连接）确实成功，并且数据以json格式在网络浏览器中输出）。有什么建议吗？非常感谢。

在另一台笔记本电脑上，创建了一个新的android studio项目，并将我在此处显示的代码用于测试目的。显然，当我尝试此操作时，微调器起作用了，我不知道为什么，但是我怀疑使用了不同的Gradle或Android Studio版本？

public class add_activity extends AppCompatActivity {

private int PICK_IMAGE_REQUEST = 1;
private static final String typearray = "type_name";
private static final String type  = "type_name";
private static final String JSON_ARRAY ="result";
private JSONArray result;
private Button btn_choose ;
Spinner spinner;
private ArrayList<String> arrayList;
TextView food_type;
String type_name;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_add);

    btn_choose = findViewById(R.id.btn_choosedesign);

    this.spinner = (Spinner) findViewById(R.id.spinnertype);
    food_type = (TextView) findViewById(R.id.hiddentype);
  //  findViewById(R.id.hiddentype).setVisibility(View.GONE);

    arrayList = new ArrayList<String>();
    getdata();

    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            //Setting the values to textviews for a selected item
            food_type.setText(getlocation(position));
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {
            food_type.setText("");
        }
    });

    btn_choose.setOnClickListener(new View.OnClickListener() {
       ...
        }
    });
}

private void showFileChooser() {
    ...
}

private void getdata() {
    StringRequest stringRequest = new StringRequest("http://.../.../gettype.php",
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    JSONObject j = null;
                    try {
                        j = new JSONObject(response);
                        result = j.getJSONArray(JSON_ARRAY);
                        details(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 details(JSONArray j) {
    for (int i = 0; i < j.length(); i++) {
        try {
            JSONObject json = j.getJSONObject(i);
            arrayList.add(json.getString(typearray));
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }
    this.spinner.setAdapter(new ArrayAdapter<>(add_activity.this, android.R.layout.simple_spinner_dropdown_item, arrayList));
}

//Method to get location name which user selects
private String getlocation(int position) { // method is used to post name of marker to database accordingly
    String loc = "";
    try {
        //Getting object of given index
        JSONObject json = result.getJSONObject(position);
        //Fetching location from that object
        loc = json.getString(type);
    } catch (JSONException e) {
        e.printStackTrace();
    }
    //Return location
    return loc;
}
}

Android Studio：微调框未显示数据库中的信息

0 个答案: