Android Studio錯誤：無法找到變量itemclicklistener，儘管已經導入了OnItemClickListener API

Question

爲什麼Android Studio不能識別我已經導入了onClickListener API？

以下行錯誤： listView.setOnItemClickListener（itemClickListener）;

Code for my main activity is below: 
import android.content.Intent; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.view.View; 
import android.widget.AdapterView; 
import android.widget.ListView; 
import android.widget.AdapterView.OnItemClickListener; 
import android.widget.AdapterView.OnItemClickListener; 


public class MainActivity extends AppCompatActivity { 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 


     new AdapterView.OnItemClickListener() { 
      public void onItemClick(AdapterView<?> listView, 
            View v, 
            int position, 
            long id) { 
       if (position == 0) { 
        //main activity launches food categories when the food option is clicked 
        Intent intent = new Intent(MainActivity.this, 
          FoodCategories.class); 
        startActivity(intent); 
       } 
      } 
     }; 

     //Add the listener to my listview 
     ListView listView = (ListView) findViewById(R.id.list_options); 
     listView.setOnItemClickListener(itemClickListener); 

     } 
} 

Answer 1

AdapterView.OnItemClickListener itemClickListener = new AdapterView.OnItemClickListener() { 
      public void onItemClick(AdapterView<?> listView, 
            View v, 
            int position, 
            long id) { 
       if (position == 0) { 
        //main activity launches food categories when the food option is clicked 
        Intent intent = new Intent(MainActivity.this, 
          FoodCategories.class); 
        startActivity(intent); 
       } 
      } 
     }; 

您在使用之前創建一個變量，它

Answer 2

你還沒有指定`itemClickListener：

AdapterView.OnItemClickListener itemClickListener = {rest of your code} 

Answer 3

只是做..

AdapterView.OnItemClickListener itemClickListener = new AdapterView.OnItemClickListener(){/*your code here*/ } 

Answer 4

有一個初始化問題，T他是一個正確的方式..請檢查它。 我可以幫你嗎？

public class MainActivity extends AppCompatActivity { 
ListView listView; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     //Add the listener to my listview 
     listView = (ListView) findViewById(R.id.list_options); 
     listView.setOnItemClickListener(itemClickListener); 

     } 


     AdapterView.OnItemClickListener itemClickListener = new AdapterView.OnItemClickListener() { 
      public void onItemClick(AdapterView<?> listView, 
            View v, 
            int position, 
            long id) { 
       if (position == 0) { 
        //main activity launches food categories when the food option is clicked 
        Intent intent = new Intent(MainActivity.this, 
          FoodCategories.class); 
        startActivity(intent); 
       } 
      } 
     }; 
} 

Answer 5

這樣做。

public class MainActivity extends AppCompatActivity { 

     @Override 
     protected void onCreate(Bundle savedInstanceState) { 
      super.onCreate(savedInstanceState); 

      AdapterView.OnItemClickListener itemClickListener = new AdapterView.OnItemClickListener() { 
       public void onItemClick(AdapterView<?> listView, 
             View v, 
             int position, 
             long id) { 
        if (position == 0) { 
         //main activity launches food categories when the food option is clicked 
         Intent intent = new Intent(MainActivity.this, 
           FoodCategories.class); 
         startActivity(intent); 
        } 
       } 
      }; 


      ListView listView = (ListView) findViewById(R.id.list_options); 
      listView.setOnItemClickListener(itemClickListener);     
      } 
    }