Java 为什么我的公共变量显示为';这';“不可用”;?
我试图用数据库中的数据填充listview,但它不允许我分配字符串变量 我读过其他一些关于这方面的文章,但我始终无法理解为什么在使用调试器时,我的变量显示为“'this'isnotavailable”Java 为什么我的公共变量显示为';这';“不可用”;?,java,android,Java,Android,我试图用数据库中的数据填充listview,但它不允许我分配字符串变量 我读过其他一些关于这方面的文章,但我始终无法理解为什么在使用调试器时,我的变量显示为“'this'isnotavailable” public class InventoryActivity extends AppCompatActivity { private RecyclerView varRecyclerView; private RecyclerView.Adapter varAdapter; private Rec
public class InventoryActivity extends AppCompatActivity
{
private RecyclerView varRecyclerView;
private RecyclerView.Adapter varAdapter;
private RecyclerView.LayoutManager varLayoutManager;
private static String URL_FindInventory = "MyPHPFile";
//IM TRYING TO SET THESE TWO VARIABLES
public String itemOneName, itemOneEffect;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_inventory);
String characterID = getIntent().getStringExtra("characterID");
ArrayList<LayoutItem> inventoryList = new ArrayList<>();
FindInventory(characterID);
inventoryList.add(new LayoutItem(R.drawable.ic_add_circle, itemOneName, itemOneEffect));
inventoryList.add(new LayoutItem(R.drawable.ic_add_circle, "Item Two Name", "Item Two's Effect"));
varRecyclerView = findViewById(R.id.recyclerView);
varRecyclerView.setHasFixedSize(true);
varLayoutManager = new LinearLayoutManager(this);
varAdapter = new LayoutAdapter(inventoryList);
varRecyclerView.setLayoutManager(varLayoutManager);
varRecyclerView.setAdapter(varAdapter);
}
private void FindInventory(final String characterID)
{
StringRequest stringRequest = new StringRequest(Request.Method.POST, URL_FindInventory,
new Response.Listener<String>()
{
@Override
public void onResponse(String response)
{
try
{
JSONObject jsonObject = new JSONObject(response);
String result = jsonObject.getString("result");
if (result != null)
{
JSONArray jsonArray = jsonObject.getJSONArray("result");
for(int i = 0; i < jsonArray.length(); i++)
{
JSONObject object = jsonArray.getJSONObject(i);
//IM TRYING TO USE THESE TWO VARIABLES TO SET THE PUBLIC ONES.
String itemName = object.getString("Name").trim(); // this has a value of "Cap of Thinking"
String itemEffect = object.getString("Effect").trim(); // this has a value of "Helps the user to think +2 Intelligence"
itemOneName = itemName; // THIS IS SHOWN AS "ItemOneName = 'this' is not available "
itemOneEffect = itemEffect; // THIS IS SHOWN AS "ItemOneEffect = 'this' is not available "
}
}
else if ((result.equals("error")))
{
Toast.makeText(InventoryActivity.this, "Cannot find Inventory", Toast.LENGTH_LONG).show();
}
} catch (JSONException e)
{
e.printStackTrace();
Toast.makeText(InventoryActivity.this, "Exception Error " + e.toString(), Toast.LENGTH_LONG).show();
}
}
},
new Response.ErrorListener()
{
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(InventoryActivity.this, "Error " + error.toString(), Toast.LENGTH_LONG).show();
}
}) {
@Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String, String> params = new HashMap<>();
params.put("characterid", characterID);
return params;
}
};
RequestQueue requestQueue = Volley.newRequestQueue(this);
requestQueue.add(stringRequest);
}
公共类InventoryActivity扩展了AppCompatActivity
{
私人RecyclerView varRecyclerView;
私有RecyclerView.Adapter变量适配器;
private RecyclerView.LayoutManager varLayoutManager;
私有静态字符串URL_FindInventory=“MyPHPFile”;
//我试图设置这两个变量
公共字符串itemOneName,itemOneEffect;
@凌驾
创建时受保护的void(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_inventory);
字符串characterID=getIntent().getStringExtra(“characterID”);
ArrayList inventoryList=新的ArrayList();
FindInventory(characterID);
inventoryList.add(新布局项(R.drawable.ic_add_circle,itemOneName,itemoneffect));
添加(新布局项目(R.drawable.ic_添加_圈,“项目二名称”,“项目二的影响”);
varRecyclerView=findviewbyd(R.id.recyclerView);
varRecyclerView.setHasFixedSize(true);
varLayoutManager=新的LinearLayoutManager(此);
varAdapter=新布局适配器(inventoryList);
setLayoutManager(varLayoutManager);
设置适配器(varAdapter);
}
私有void FindInventory(最终字符串字符)
{
StringRequest StringRequest=新的StringRequest(Request.Method.POST,URL\u FindInventory,
新的Response.Listener()
{
@凌驾
公共void onResponse(字符串响应)
{
尝试
{
JSONObject JSONObject=新JSONObject(响应);
字符串结果=jsonObject.getString(“结果”);
如果(结果!=null)
{
JSONArray JSONArray=jsonObject.getJSONArray(“结果”);
for(int i=0;i
当我试图将两个公共字符串的值设置为null时,我始终无法理解为什么它不允许我将从JSON对象读取的变量的值设置为null。它们为null,因为您的web请求是在将项目添加到列表后发生的 将
inventoryList
设置为一个字段,并删除您试图设置的两个字符串字段
移动两个
inventoryList。将
方法添加到onResponse中,然后需要通知RecyclerView适配器需要显示新数据它们为空的原因是当编译器在两行以下执行时(我们称之为第1行和第2行):
-在第1行,异步执行该方法(意味着它不会阻止第2行的执行,第2行将在第1行之后或之前执行)。这会导致变量itemOneName和itemOneEffect为null,因为第2行是在第1行之前执行的,请记住,第1行和第2行是并行执行或同时执行的
要解决此问题,请执行以下操作:
-您必须执行以下操作:
inventoryList.add(new LayoutItem(R.drawable.ic_add_circle, itemOneName, itemOneEffect));
inventoryList.add(new LayoutItem(R.drawable.ic_add_circle, "Item Two Name", "Item Two's Effect"));
...and other dependencies
在onResponse()中调用这些行之后:
现在看起来很明显,哈哈,感觉像是一个绝对的“坏词”…非常感谢你马上修复了它。我已经在这上面呆了一整天了,哈哈。添加过多的日志记录语句从来都没有坏处
inventoryList.add(new LayoutItem(R.drawable.ic_add_circle, itemOneName, itemOneEffect));
inventoryList.add(new LayoutItem(R.drawable.ic_add_circle, "Item Two Name", "Item Two's Effect"));
...and other dependencies
String itemName = object.getString("Name").trim(); // this has a value of "Cap of Thinking"
String itemEffect = object.getString("Effect").trim();