无法解析符号"OnItemSelectedListener“

Question

package com.example.android.mycalculator;

import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends ActionBarActivity implements ***OnItemSelectedListener***{

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

        // Spinner element
        Spinner spinner = (Spinner) findViewById(R.id.spinner);

        spinner.setOnItemSelectedListener(this);



        // Spinner Drop down elements
        List<String> categories = new ArrayList<String>();
        categories.add("Multiply");
        categories.add("Divide");
        categories.add("Subtract");
        categories.add("Add");
        // Creating adapter for spinner
        ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, categories);

        // Drop down layout style - list view with radio button
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        // attaching data adapter to spinner
        spinner.setAdapter(dataAdapter);
    }

    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        // On selecting a spinner item
        String item = parent.getItemAtPosition(position).toString();

        // Showing selected spinner item
        Toast.makeText(parent.getContext(), "Selected: " + item, Toast.LENGTH_LONG).show();
    }
}

我无法在android中的主java文件上导入我的OnItemSelectedListener类。我已经选择了自动导入settings..It为我的上述代码显示错误；当我为我的类使用接口时不能解析‘OnItemSelectedListener’。

Answer 1

用下面的代码替换您的代码，它现在可以工作了。

import android.app.Activity;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;



public class MainActivity extends Activity implements AdapterView.OnItemSelectedListener {

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

        // Spinner element
        Spinner spinner = (Spinner) findViewById(R.id.spinner);

        spinner.setOnItemSelectedListener(this);



        // Spinner Drop down elements
        List<String> categories = new ArrayList<String>();
        categories.add("Multiply");
        categories.add("Divide");
        categories.add("Subtract");
        categories.add("Add");
        // Creating adapter for spinner
        ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, categories);

        // Drop down layout style - list view with radio button
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        // attaching data adapter to spinner
        spinner.setAdapter(dataAdapter);
        }

public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        // On selecting a spinner item
        String item = parent.getItemAtPosition(position).toString();

        // Showing selected spinner item
        Toast.makeText(parent.getContext(), "Selected: " + item, Toast.LENGTH_LONG).show();
        }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {

    }
}

Answer 2

只需将其与其他包导入一起粘贴：

import android.widget.AdapterView.OnItemSelectedListener;