android arraylist应用白屏

Question

我正在开发一个Android应用程序，该应用程序从网站下载信息并将其加载到可以与之交互的数组列表中。

我的问题是，由于某种原因我无法发现，用于构建ArrayList的某些变量无法正确初始化或为null。

这是我的活动和课程：

Tenda.java（MainActivity）

public class Tenda extends Activity implements OnItemClickListener, LocationListener {

ProgressDialog lDialog;
String json_string;
ArticleAdapter adapter_article;
int user_id;
private LocationManager locationManager;
public String provider;
private String  lattitude , longitude; 

/*************************************************/

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_tenda);
    locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
    Criteria criteria = new Criteria();
    provider = locationManager.getBestProvider(criteria, false);
    init_conf();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.tenda, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle item selection
    switch (item.getItemId()) {
        case R.id.menu_update:
            updateList();
            return true;
        case R.id.menu_search:
            alert_search();
            return true;   
        case R.id.menu_cancel:
            finish();
            return true;

        default:
            return super.onOptionsItemSelected(item);
    }
}

@Override
public void onItemClick(AdapterView<?> arg0, View view, int position, long arg3) {

    TextView stock = (TextView) view.findViewById(R.id.list_product_stock);
    int num_stock = Integer.parseInt(stock.getText().toString()) ; 

    if(num_stock!=0){
        ArrayList<Article> productes=adapter_article.getItems_producte();
        Article current_product= productes.get(position);

        alert_comprar(num_stock,current_product);
    }
    else
    {
        Toast.makeText(this, "OUT OF STOCK", Toast.LENGTH_LONG).show();
    }

}

private void init_conf(){

    Bundle extras = getIntent().getExtras();
    user_id = extras.getInt("user_id");

    Toast.makeText(this, "user id"+Integer.toString(user_id), Toast.LENGTH_LONG).show();
    ListView lsv_super = (ListView)findViewById(R.id.list_productes);
    adapter_article = new ArticleAdapter(Tenda.this, null);
    Log.i ("adapter-super", "" + adapter_article);
    lsv_super.setAdapter(adapter_article);
    lsv_super.setOnItemClickListener(this);

    updateList();

}

private void updateList(){
    loading();
    String url = "http://www.v2msoft.com/clientes/lasalle/curs-android/products.php?user_id="+user_id;

    boolean is_con=is_connected();

    if(is_con){
        AsyncTask(url);
        Toast.makeText(this, "You're connected to Internet", Toast.LENGTH_LONG).show();
    }
    else{
        json_string=storeRead();
        refreshListByJson(json_string);
        Toast.makeText(this, "You're not connected to Internet", Toast.LENGTH_LONG).show();
    }

}

private void search(String text){
    loading();
    String url="http://www.v2msoft.com/clientes/lasalle/curs-android/search.php?user_id="+user_id+"&q="+text;

    boolean is_con=is_connected();
    if(is_con){
        Toast.makeText(this, url, Toast.LENGTH_LONG).show();
        searchAsyncTask(url);
    }
    else{
        Toast.makeText(this, "NO CONNECTION", Toast.LENGTH_LONG).show();
    }


}

private void comprar(Article article, int value){

    int product_id=  article.getId();

    String url="http://www.v2msoft.com/clientes/lasalle/curs-android/buy.php?user_id="+user_id+
                "&product_id="+product_id+
                "&items="+value+
                "&lat="+1+
                "&long="+1;

    Toast.makeText(this, url, Toast.LENGTH_LONG).show();

}

private void AsyncTask(String url){
    LongAsyncTask task = new LongAsyncTask();
    task.execute(url);
}

private void searchAsyncTask(String url){
    SearchAsyncTask task = new SearchAsyncTask();
    task.execute(url);
}

public void alert_search(){
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Searcher");

    final EditText input = new EditText(this);
    input.setInputType(InputType.TYPE_CLASS_TEXT);
    builder.setView(input);

    builder.setPositiveButton("OK", new DialogInterface.OnClickListener() { 
        @Override
        public void onClick(DialogInterface dialog, int which) {
            String m_Text = input.getText().toString();
            Toast.makeText(getApplicationContext(), m_Text, Toast.LENGTH_LONG).show();
            search(m_Text);
        }
    });

    builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
        }
    });

    builder.show();

}

public void alert_comprar(int max_value,final Article article){

    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Comprar");

    final NumberPicker number= new NumberPicker(this);
    number.setMaxValue(max_value);
    number.setMinValue(0);
    builder.setView(number);

    builder.setPositiveButton("OK", new DialogInterface.OnClickListener() { 
        @Override
        public void onClick(DialogInterface dialog, int which) {
            int value= number.getValue();
            Toast.makeText(getApplicationContext(), value+"", Toast.LENGTH_LONG).show();
            comprar(article,value);
        }
    });

    builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
        }
    });

    builder.show();

}

/*************************ASYNC TASK************************/

public class LongAsyncTask extends AsyncTask<String,String,String>{

    @Override
    protected String doInBackground(String... url) {
        String url_result= conect(url[0]);
        Log.i("DO IN BACKGROUND", url_result);
        return url_result;

    }
   protected void onPostExecute(String url_result) {
       Log.i("On Post EXECUTE", url_result);
       json_string= url_result;
       storeWrite(json_string);
       refreshListByJson(json_string);//line 257
   }

}

    public class SearchAsyncTask extends AsyncTask<String,String,String>{

    @Override
    protected String doInBackground(String... url) {
        String url_result= conect(url[0]);
        Log.i("Search result", url_result);
        return url_result;

    }

   protected void onPostExecute(String url_result) {
       Log.i("On Post EXECUTE SEARCH", url_result);
       json_string= url_result;
       Toast.makeText(getApplicationContext(), json_string, Toast.LENGTH_LONG).show();
       refreshListByJson(json_string);
   }

}

public class BuyAsyncTask extends AsyncTask<String,String,String>{

    @Override
    protected String doInBackground(String... url) {
        String url_result= conect(url[0]);
        Log.i("buy result", url_result);
        return url_result;

    }
   protected void onPostExecute(String url_result) {
       Log.i("On Post EXECUTE BUY", url_result);
       json_string= url_result;
       Toast.makeText(getApplicationContext(), json_string, Toast.LENGTH_LONG).show();
   }

}

/*************************************************/

private void refreshListByJson(String json){//line 300
    lDialog.dismiss();
   Store store=Store.newStore(json);
   Log.i ("store", "" + store);
   Log.i("store-nom", "" + store.getStore());//line 305
   Log.i("store-producte", "" + store.getProductes().toString()); //line 306

   //if (store.getProductes() != null && store.getProductes().size()>0)
   //{

       adapter_article.setItems_producte(store.getProductes());    
   //}

ListView lsv_producte = (ListView)findViewById(R.id.list_productes);
adapter_article = new ArticleAdapter(Tenda.this, store.getProductes());
lsv_producte.setAdapter(adapter_article);
Log.i ("adapter-article", "" + lsv_producte);
lsv_producte.setOnItemClickListener(this);



}

private void storeWrite(String data){
    String FILENAME = "json_store";

    FileOutputStream fos;
    try {
        fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
        fos.write(data.getBytes());
        fos.close();
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    Log.i("Write STORAGE", data);

}

private String storeRead(){
    String FILENAME = "json_store";

    FileInputStream  fis;
    StringBuilder fileContent = new StringBuilder();
    Log.i ("file-content", "" + fileContent);
    try {
        fis= openFileInput (FILENAME);
        BufferedReader br= new BufferedReader(new InputStreamReader(fis));
        String line="";


        while((line = br.readLine())!= null)
        {
            fileContent.append(line);
        }
        br.close();
        fis.close();
        Log.i("READ STORAGE", fileContent.toString());

    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return fileContent.toString();
}

public String conect(String url_string){

    HttpURLConnection con = null;
    BufferedReader reader= null;

    try{
        URL url = new URL(url_string);
        con = (HttpURLConnection)url.openConnection();

        reader= new BufferedReader(new InputStreamReader(con.getInputStream()));

        String line ="";
        StringBuffer responseBuffer = new StringBuffer();

        while((line=reader.readLine())!=null)
        {
            responseBuffer.append(line);
        }

        return responseBuffer.toString(); 
    }
    catch(Exception ex){
        Log.e(getClass().getName(), ex.getMessage(),ex);
        return  null;
    }

}

public boolean is_connected(){
    ConnectivityManager conMgr = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo i = conMgr.getActiveNetworkInfo();
      if (i == null)
        return false;
      if (!i.isConnected())
        return false;
      if (!i.isAvailable())
        return false;
      return true;
}

private void loading(){
     lDialog = new ProgressDialog(this);
     lDialog.setMessage("Loading...");
     lDialog.setCancelable(false);
     lDialog.show();
}


/*** Location ***/

@Override
public void onLocationChanged(Location arg0) {
// TODO Auto-generated method stub
int lat = (int) (arg0.getLatitude());
int lng = (int) (arg0.getLongitude());
lattitude = "Lattitude: "+ lat ;
longitude = "Longitude: "+ lng; 
}

@Override
public void onProviderDisabled(String arg0) {
// TODO Auto-generated method stub

}

@Override
public void onProviderEnabled(String arg0) {
// TODO Auto-generated method stub

}

@Override
public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
////TODO Auto-generated method stub

}               

}

类Article.java

公共类文章{

private int id;
private String fabricante;
private String nombre;
private float precio;
private int stock;

public int getId() {
return id;
    }

public void setId(int id) {
this.id = id;
}
public String getFabricante() {
return fabricante;
}
public void setFabricante(String fabricante) {
this.fabricante = fabricante;
}
public String getNombre() {
    return nombre;
}
public void setNombre(String nombre) {
    this.nombre = nombre;
}
public float getPrecio() {
    return precio;
}
public void setPrecio(float precio) {
    this.precio = precio;
}
public int getStock() {
return stock;
}
public void setStock(int stock) {
this.stock = stock;
}

}

类ArticleAdapter.java

public class ArticleAdapter extends BaseAdapter {

    public ArrayList<Article> getItems_producte() {
        return items_producte;
    }

    private Activity activity;
    private ArrayList<Article> items_producte;

    public ArticleAdapter(Activity activity, ArrayList<Article> items_producte){
        this.activity = activity;
        this.items_producte= items_producte;
    }

        @Override
    public int getCount() {
        if(items_producte==null){
            return 0;
        }
        else{
            return items_producte.size();
        }   }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return items_producte.get(position);
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public View getView(int position, View contentView, ViewGroup Parent) {
        // TODO Auto-generated method stub
        View view = contentView;

        if(view==null){
            LayoutInflater inflate =(LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = inflate.inflate(R.layout.info_product, null,false);
        }

        Article item_producte = items_producte.get(position);

        TextView id = (TextView)view.findViewById(R.id.list_product_id);
        TextView fabricant = (TextView)view.findViewById(R.id.list_product_fabricant);
        TextView nom = (TextView)view.findViewById(R.id.list_product_nom);
        TextView preu = (TextView)view.findViewById(R.id.list_product_preu);
        TextView stock = (TextView)view.findViewById(R.id.list_product_stock);

        id.setText(Integer.toString(item_producte.getId()));
        fabricant.setText(item_producte.getFabricante());
        nom.setText(item_producte.getNom());
        preu.setText(Float.toString(item_producte.getPreu()));
        stock.setText(Integer.toString(item_producte.getStock()));

        fabricant.setTextColor(activity.getResources().getColor(R.color.fabricant));
        nom.setTextColor(activity.getResources().getColor(R.color.fabricant));
        preu.setTextColor(activity.getResources().getColor(R.color.fabricant));
        stock.setTextColor(activity.getResources().getColor(R.color.fabricant));

        if(position%2==0){
            view.setBackgroundColor(activity.getResources().getColor(R.color.files_parelles));

        }
        else{
            view.setBackgroundColor(activity.getResources().getColor(R.color.files_imparelles));
        }

        /*STOCK COLOR*/
        if(item_producte.getStock()<=0){
            view.setBackgroundColor(activity.getResources().getColor(R.color.stock_null_bg));

            fabricant.setTextColor(activity.getResources().getColor(R.color.stock_null_tx));
            nom.setTextColor(activity.getResources().getColor(R.color.stock_null_tx));
            preu.setTextColor(activity.getResources().getColor(R.color.stock_null_tx));
            stock.setTextColor(activity.getResources().getColor(R.color.stock_null_tx));

        }

        return view;
    }


    public void setItems_producte(ArrayList<Article> items_producte) {
        this.items_producte = items_producte;
        this.notifyDataSetChanged();
    }

}

类LongAsyncTask.java

public class LongAsyncTask extends AsyncTask<String,String,String>{

    @Override
    protected String doInBackground(String... arg0) {

        return null;
    }


   protected void onPostExecute(String result) {

   }

}

类Store.java

导入java.util.ArrayList;

导入com.google.gson.Gson；

公共类商店{

private String supermercado;
private ArrayList<Article> productes;

public String getSupermercado() {
    return supermercado;
}
public void setSupermercado(String supermercado) {
    this.supermercado = supermercado;
}
public ArrayList<Article> getProductes() {
return productes;
}
public void setProductes(ArrayList<Article> productes) {
this.productes = productes;
}

static Store newStore(String json_string){
Gson gson= new Gson();
Store store = gson.fromJson(json_string,Store.class);
return store;
}

}

Logcat输出

04-29 08:54:14.254: I/DO IN BACKGROUND(1124): {"succeed":true,"user_id":362}
04-29 08:54:14.265: I/MESSAGE(1124): {"succeed":true,"user_id":362}
04-29 08:54:14.324: I/put Extra user id(1124): 362
04-29 08:54:19.495: I/adapter-super(1124): com.example.shop.ArticleAdapter@416f9d00
04-29 08:54:24.904: I/DO IN BACKGROUND(1124): { "supermercado": "La Salle - Curs Android II",   "productos" : [     
{"id" : 1, "fabricante" : "Nestlé", "nombre" : "NESQUIK", "precio" : 12.85,         "stock" : 10        },      {           "id" : 2,           "fabricante" : "Coca-cola",         "nombre" : "Coca-cola",         "precio" : 3.21,            "stock" : 150       },      {           "id" : 3,           "fabricante" : "Borges",            "nombre" : "Aceite girasol 1L",         "precio" : 1.88,            "stock" : 0     },      {           "id" : 4,           "fabricante" : "Serpis",            "nombre" : "Aceitunas rellenas de anchoa 160g",         "precio" : 1.39,            "stock" : 1523      },      {           "id" : 5,           "fabricante" : "Carretilla",            "nombre" : "Pimientos piquillo ajillo 290g",            "precio" : 2.25,            "stock" : 14        },      {           "id" : 6,           "fabricante" : "Orlando",           "nombre" : "Tomate frito con aceite de oliva virgen brik 390g",         "precio" : 0.95,            "stock" : 0     },      {           "id" : 7,           "fabricante" : "Kellogg's",         "nombre" : "Cereales Special K chocolate 300g",         "precio" : 2.39,            "stock" : 152       },      {           "id" : 8,           "fabricante" : "Lu",            "nombre" : "Galletas rellenas mini Principe 160g",          "precio" : 1.59,            "stock" : 29        },      {           "id" : 9,           "fabricante" : "Pascual",           "nombre" : "Leche sin lactosa desnatada brik 1l",           "precio" : 1.49,            "stock" : 1596      },      {           "id" : 10,          "fabricante" : "Danone",            "nombre" : "Danet vainilla 4x125g",         "precio" : 1.90,            "stock" : 856       },      {           "id" : 11,          "fabricante" : "Hornimans",         "nombre" : "Infusueños 20 sobres",          "precio" : 2.35,            "stock" : 598       }   ]}
04-29 08:54:26.394: I/On Post EXECUTE(1124): {  "supermercado": "La Salle - Curs Android II",   "productos" : [     {           "id" : 1,           "fabricante" : "Nestlé",            "nombre" : "NESQUIK",           "precio" : 12.85,           "stock" : 10        },      {           "id" : 2,           "fabricante" : "Coca-cola",         "nombre" : "Coca-cola",         "precio" : 3.21,            "stock" : 150       },      {           "id" : 3,           "fabricante" : "Borges",            "nombre" : "Aceite girasol 1L",         "precio" : 1.88,            "stock" : 0     },      {           "id" : 4,           "fabricante" : "Serpis",            "nombre" : "Aceitunas rellenas de anchoa 160g",         "precio" : 1.39,            "stock" : 1523      },      {           "id" : 5,           "fabricante" : "Carretilla",            "nombre" : "Pimientos piquillo ajillo 290g",            "precio" : 2.25,            "stock" : 14        },      {           "id" : 6,           "fabricante" : "Orlando",           "nombre" : "Tomate frito con aceite de oliva virgen brik 390g",         "precio" : 0.95,            "stock" : 0     },      {           "id" : 7,           "fabricante" : "Kellogg's",         "nombre" : "Cereales Special K chocolate 300g",         "precio" : 2.39,            "stock" : 152       },      {           "id" : 8,           "fabricante" : "Lu",            "nombre" : "Galletas rellenas mini Principe 160g",          "precio" : 1.59,            "stock" : 29        },      {           "id" : 9,           "fabricante" : "Pascual",           "nombre" : "Leche sin lactosa desnatada brik 1l",           "precio" : 1.49,            "stock" : 1596      },      {           "id" : 10,          "fabricante" : "Danone",            "nombre" : "Danet vainilla 4x125g",         "precio" : 1.90,            "stock" : 856       },      {           "id" : 11,          "fabricante" : "Hornimans",         "nombre" : "Infusueños 20 sobres",          "precio" : 2.35,            "stock" : 598       }   ]}
04-29 08:54:26.534: I/Write STORAGE(1124): {    "supermercado": "La Salle - Curs Android II",   "productos" : [     {           "id" : 1,           "fabricante" : "Nestlé",            "nombre" : "NESQUIK",           "precio" : 12.85,           "stock" : 10        },      {           "id" : 2,           "fabricante" : "Coca-cola",         "nombre" : "Coca-cola",         "precio" : 3.21,            "stock" : 150       },      {           "id" : 3,           "fabricante" : "Borges",            "nombre" : "Aceite girasol 1L",         "precio" : 1.88,            "stock" : 0     },      {           "id" : 4,           "fabricante" : "Serpis",            "nombre" : "Aceitunas rellenas de anchoa 160g",         "precio" : 1.39,            "stock" : 1523      },      {           "id" : 5,           "fabricante" : "Carretilla",            "nombre" : "Pimientos piquillo ajillo 290g",            "precio" : 2.25,            "stock" : 14        },      {           "id" : 6,           "fabricante" : "Orlando",           "nombre" : "Tomate frito con aceite de oliva virgen brik 390g",         "precio" : 0.95,            "stock" : 0     },      {           "id" : 7,           "fabricante" : "Kellogg's",         "nombre" : "Cereales Special K chocolate 300g",         "precio" : 2.39,            "stock" : 152       },      {           "id" : 8,           "fabricante" : "Lu",            "nombre" : "Galletas rellenas mini Principe 160g",          "precio" : 1.59,            "stock" : 29        },      {           "id" : 9,           "fabricante" : "Pascual",           "nombre" : "Leche sin lactosa desnatada brik 1l",           "precio" : 1.49,            "stock" : 1596      },      {           "id" : 10,          "fabricante" : "Danone",            "nombre" : "Danet vainilla 4x125g",         "precio" : 1.90,            "stock" : 856       },      {           "id" : 11,          "fabricante" : "Hornimans",         "nombre" : "Infusueños 20 sobres",          "precio" : 2.35,            "stock" : 598       }   ]}
04-29 08:54:28.634: I/store(1124): com.example.shop.Store@41860630
04-29 08:54:28.634: I/store-nom(1124): null
04-29 08:54:28.667: I/get-productes(1124): null
04-29 08:54:28.667: I/get-productes(1124): null
04-29 08:54:28.694: I/adapter-article(1124): android.widget.ListView{416e41e8 V.ED.VC. ......ID 0,0-480,0 #7f090004 app:id/list_productes}

问题的核心位于Tenda.java中的“ refreshListbyJson”函数中：在此使用的大多数变量为空或为null。

在其中一个类中是否存在导致这些变量未正确初始化的问题？ Logcat显示该应用程序确实下载了Internet信息并将其存储在存储器中。

非常感谢您的帮助。

Answer 1

json键与object字段不匹配。 例如：json返回productos，但在Store.java中，数组列表名称为productes。如果将此名称更改为productos（“ o”而不是“ e”），它将起作用。 同样，Article类中也存在名称不匹配的情况，在类字段中也存在“ nom”，而json对象具有“ nombre”。 希望这可以帮助。

Store.java

import java.util.ArrayList;

import com.google.gson.Gson;

public class Store {

    private String supermercado;
    private ArrayList<Article> productes;

    public String getSupermercado() {
        return supermercado;
    }
    public void setSupermercado(String supermercado) {
        this.supermercado = supermercado;
    }
    public ArrayList<Article> getProductes() {
    return productes;
    }
    public void setProductes(ArrayList<Article> productes) {
    this.productes = productes;
    }

    static Store newStore(String json_string){
    Gson gson= new Gson();
    Store store = gson.fromJson(json_string,Store.class);
    return store;
    }
}

Article.java

public class Article {

    private int id;
    private String fabricant;
    private String nombre;
    private float precio;
    private int stock;

    public int getId() {
    return id;
        }

    public void setId(int id) {
    this.id = id;
    }
    public String getFabricant() {
    return fabricant;
    }
    public void setFabricant(String fabricant) {
    this.fabricant = fabricant;
    }
    public String getNombre() {
        return nombre;
    }
    public void setNombre(String nombre) {
        this.nombre = nombre;
    }
    public float getPrecio() {
        return precio;
    }
    public void setPrecio(float precio) {
        this.precio = precio;
    }
    public int getStock() {
    return stock;
    }
    public void setStock(int stock) {
    this.stock = stock;
    }
}