Question

我正在尝试将元素（名称）从JSONArray复制到ArrayList，然后从ArrayList复制到Spinner。我没有收到任何错误消息但是在执行时Spinner没有显示任何元素。 Spinner如何显示元素？

package com.example.klarity;

import java.util.ArrayList;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

 import android.os.Bundle;
 import android.support.v7.app.ActionBarActivity;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.widget.ArrayAdapter;
 import android.widget.Spinner;

 import com.example.klarity1.R;

  public class MainActivity extends ActionBarActivity {

  Spinner practiceSpin;
  Spinner projectSpin;
  JSONObject projDet;
  JSONArray projArr;
  ArrayList<String> arrData=new ArrayList<String>();
  int[] project;



  public final static String JSON_DATA =
          "{" 
                   + "  \"project\": [" 
                   + "    {"                  
                   + "      \"name\": \"xxxx\""                   
                   + "    }," 
                   + "    {" 
                   + "      \"name\": \"yyyy\"" 
                   + "    },"                                                   //JSONArray created
                   + "    {" 
                   + "      \"name\": \"zzzz\""
                   + "    },"
                   + "    {" 
                   + "      \"name\": \"hhhh\""
                   + "    }"
                   + "  ]" 
                   + "}"; 


   @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);



    try {
           projDet=new JSONObject(JSON_DATA);
           projArr=projDet.getJSONArray("project");

           ArrayList<String> arrData=new ArrayList<String>();
           for(int n = 0; n < projArr.length(); n++)
           {
               //JSONObject projDet = projArr.getJSONObject(n);
                arrData.add(projArr.getJSONObject(n).getString("name"));
           }


        } catch (JSONException e) {
            e.printStackTrace();
            System.out.println(e.getMessage());
            System.out.println("exception occured");
        }


    try {
        practiceSpin=(Spinner) findViewById(R.id.spinnerPractice);
        ArrayAdapter<CharSequence> ar=   ArrayAdapter.createFromResource(this,R.array.practices ,android.R.layout.simple_list_item_1);
        ar.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);
        practiceSpin.setAdapter(ar);

        /*projectSpin=(Spinner) findViewById(R.id.spinnerProject);
        ArrayAdapter<CharSequence> ar1= ArrayAdapter.createFromResource(this,R.array.projects  ,android.R.layout.simple_list_item_1);
        ar1.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);
        projectSpin.setAdapter(ar1);*/

        ArrayAdapter<String> adapter_proj = new ArrayAdapter<String>(this,R.array.projects, android.R.layout.simple_spinner_item,arrData);     //"The constructor ArrayAdapter<String>(MainActivity, int, int, JSONArray) 
         adapter_proj.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        projectSpin.setAdapter(adapter_proj); 
    } catch (Exception e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
        System.out.println(e1.getMessage());
        System.out.println("exception occured in 2nd catch");
    }
    finally{

    }






}

 @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();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
   }
}

Answer 1

问题在于您的本地varibable名为arrData：替换

ArrayList<String> arrData=new ArrayList<String>();

用这个

this.arrData=new ArrayList<String>();（删除ArrayList）。

arrData仅存在于第一个try-cacth块中，而在第二个try-catch块中，arrData恰好是您班级的字段。我强烈建议您尽可能使用“this”以避免类似的问题。

微调器不显示元素

1 个答案: