Question

如何访问主类以外的值？我想打印elementarytxtview的值在参数的主类中但是在参数中打印null值我想将参数中的elementarytextview值传递给其他活动

     public class HomeMenu extends Activity {
ImageButton imgNews, imgContact, imgSetting;
ListView listMainMenu;
ListView Middleschoollist, HighSchoollist, Atipicalschoollist;
String status;
firstscreenadapter mma;
String SelectMenuAPI;
String SelectMenuAPI2;
String url1;
String elementry;

// String High;
String message;
TextView Elementarytxt, Middletxt, Hightxt, Atypicaltxt;
static ArrayList<Long> Category_ID = new ArrayList<Long>();
static ArrayList<String> Category_name = new ArrayList<String>();
String elementarytxtview;

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

    ExpandableHeightListView listMainMenu = (ExpandableHeightListView) 
   findViewById(R.id.listMainMenu11);
    ExpandableHeightListView Middleschoollist = (ExpandableHeightListView) 
    findViewById(R.id.listMainMenu22);
    ExpandableHeightListView HighSchoollist = (ExpandableHeightListView) 
   findViewById(R.id.listMainMenu33);
    ExpandableHeightListView Atipicalschoollist = (ExpandableHeightListView) 
         findViewById(R.id.listMainMenu44);

    Elementarytxt = (TextView) findViewById(R.id.Elementaryschool);
    Middletxt = (TextView) findViewById(R.id.MiddleSchool);
    Hightxt = (TextView) findViewById(R.id.HighSchool);
    Atypicaltxt = (TextView) findViewById(R.id.AtipicalSchool);

    mma = new firstscreenadapter(this);

    if (!Utils.isNetworkAvailable(HomeMenu.this)) {
        Toast.makeText(HomeMenu.this, "NO NETWORK Available",
                Toast.LENGTH_SHORT).show();
    }

    if (!Utils.isUserOnline(this)) {
        Toast.makeText(this, "No NETWORK", Toast.LENGTH_LONG).show();
    }

    url1 = "http://198.57.208.46/~school/ajax.php?action=get_school";


    listMainMenu.setAdapter(mma);
    Middleschoollist.setAdapter(mma);
    HighSchoollist.setAdapter(mma);
    Atipicalschoollist.setAdapter(mma);


    listMainMenu.setExpanded(true);
    Middleschoollist.setExpanded(true);
    HighSchoollist.setExpanded(true);
    Atipicalschoollist.setExpanded(true);
    Toast.makeText(this, elementarytxtview, Toast.LENGTH_SHORT).show();
    listMainMenu.setOnItemClickListener(new OnItemClickListener() {

        public void onItemClick(AdapterView<?> arg0, View arg1,
                int position, long arg3) {
            // TODO Auto-generated method stub
            Intent iMenuList = new Intent(HomeMenu.this, 
          SecondStep.class);
iMenuList.putExtra("category_name",xxx.xxx.xxxx/~school/index.php
  /api/index/getschools?mg="+ Category_name.get(position)+  "&sl="+elementarytxtview);

            startActivity(iMenuList);

        }
    });

    parseJSONData();
}

void clearData() {
    Category_ID.clear();
    Category_name.clear();

}

public void parseJSONData() {

    SelectMenuAPI = Utils.Homemenu2;
    SelectMenuAPI2 = Utils.Homemenu;

    clearData();

    try {

        HttpClient client = new DefaultHttpClient();
        HttpConnectionParams
                .setConnectionTimeout(client.getParams(), 15000);
        HttpConnectionParams.setSoTimeout(client.getParams(), 15000);
        HttpUriRequest request = new HttpGet(SelectMenuAPI);
        HttpResponse response = client.execute(request);
        InputStream atomInputStream = response.getEntity().getContent();
        BufferedReader in = new BufferedReader(new InputStreamReader(
                atomInputStream));

        String line;
        String str = "";
        while ((line = in.readLine()) != null) {
            str += line;
        }

        HttpClient client2 = new DefaultHttpClient();
        HttpConnectionParams.setConnectionTimeout(client2.getParams(),
                15000);
        HttpConnectionParams.setSoTimeout(client2.getParams(), 15000);
        HttpUriRequest request2 = new HttpGet(SelectMenuAPI2);
        HttpResponse response2 = client2.execute(request2);
        InputStream atomInputStream2 = response2.getEntity().getContent();
        BufferedReader in2 = new BufferedReader(new InputStreamReader(
                atomInputStream2));

        String line2;
        String str2 = "";
        while ((line2 = in2.readLine()) != null) {
            str2 += line2;
        }

        JSONObject json3 = new JSONObject(str2);
        // message = json2.getString("message");
        status = json3.getString("status");
        if (status.equals("1")) {

            JSONArray school2 = json3.getJSONArray("data");

            String[] mVal = new String[school2.length()];

            for (int i = 0; i < school2.length(); i++) {
                mVal[i] = 
          school2.getJSONObject(i).getString("title");

                Elementarytxt.setText(mVal[0]);

                Middletxt.setText(mVal[1]);
                Hightxt.setText(mVal[2]);
                Atypicaltxt.setText(mVal[3]);

            }

            elementarytxtview = mVal[0];
        }

        JSONObject json2 = new JSONObject(str);
        // message = json2.getString("message");
        status = json2.getString("status");
        if (status.equals("1")) {

            // JSONObject data = json.getJSONObject("data");

            JSONArray school = json2.getJSONArray("data");

            for (int i = 0; i < school.length(); i++) {
                JSONObject object = school.getJSONObject(i);

                // 
         Category_ID.add(Long.parseLong(object.getString("id")));
                Category_ID.add((long) i);
                Category_name.add(object.getString("title"));

            }

        } else {

            Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
        }

    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        // IOConnect = 1;
        e.printStackTrace();
    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

      }

Answer 1

在您尝试通过elementarytxtview展示之前，未初始化

Toast。首先，你需要在其中加入一些价值。

Answer 2

我不是100％肯定你的意思。

但是如果你想在类之间轻松访问变量，你应该String elementarytxtview; public static

因此：public static String elementarytxtview;

这意味着基本上variable是共享的，可以在所有类之间使用。只需在您的案例中写下HomeMenu.elementarytxtview;即可。

Answer 3

您在onCreate方法之前运行的parseJSONData()方法中显示Toast。您尚未初始化String elementarytxtview因此它将显示null，因为您只声明了该变量。

如何从main方法中的main方法中打印出值

3 个答案: