android - 如何同时比较两个列表中的选定项目..并对其进行操作？

Question

我是 android....我有两个 listviews 我想从每个列表中选择一个项目并从这两个 listviews 中选择一个项目...我尝试了 listview.setonselecteditemlistener 但每次我尝试加载时都会出错它....

here is program........



package com.a2zunitconverter.miniproject;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListView;

public class lenght extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.lenght);  
    double var1;
    double var2;
        final EditText query=(EditText)findViewById(R.id.lquery);
        final EditText result=(EditText)findViewById(R.id.lresult);
    var1=Double.parseDouble(query.getText().toString());
    final ListView listfrom=(ListView)findViewById(R.id.listfrom);
    final ListView listto=(ListView)findViewById(R.id.listto);
   String[] quantity={"Meter","Inches","Feet","Yard"};
    ArrayAdapter<String> adapter;
    adapter=new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,quantity);
    listfrom.setAdapter(adapter);
    listto.setAdapter(adapter);
    listfrom.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                long arg3) {
            // TODO Auto-generated method stub
            if (listfrom.getSelectedItem()=="Meter" && listto.getSelectedItem()=="Inches");{
                result.setText("" + query);
            }
        }
    });
}

}