Question

创建活动后，我收到此警告：

永远不会使用变量'station'

我不确定该警告意味着什么，也不确定如何解决。我猜测'station'变量尚未声明，但我不知道正确的声明方式。所有的帮助将不胜感激。

FragmentWCLine.java

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class FragmentWCLine extends android.support.v4.app.Fragment {

    public final static String EXTRA_MESSAGE = "Station_key";

    private class WC {
        private CharSequence station;
        private CharSequence zone;
        private Class<? extends Activity> activityClass;
        private Class<? extends android.support.v4.app.Fragment> fragmentClass;

        public WC(int stationResId, int zoneResId, Class<? extends Activity> activityClass, Class<? extends android.support.v4.app.Fragment> fragmentClass) {
            this.fragmentClass = fragmentClass;
            this.activityClass = activityClass;
            this.station = getResources().getString(stationResId);
            this.zone = getResources().getString(zoneResId);
        }

        @Override
        public String toString() { return station.toString(); }
        public String getzone(){ return zone.toString(); }
    }

    private static WC[] mWC;

    private boolean mTwoPane;

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
        View v = inflater.inflate(R.layout.fragment_wc_line, container, false);

        // Instantiate the list of stations.
        mWC = new WC[]{
                new WC(R.string.bank, R.string.zone_1, WCBankActivity.class, FragmentWCBank.class),
                new WC(R.string.wat, R.string.zone_1, WCWATActivity.class, FragmentWCWAT.class)
        };

        final ListView listView = (ListView)v.findViewById(R.id.list_wc);
        listView.setAdapter(new MyAdapter(getActivity(), mWC));
        listView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);

        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                if(mTwoPane){

                    setItemNormal();
                    View rowView = view;
                    setItemSelected(rowView);
                }
                else{
                    Intent intent = new Intent(getActivity(), mWC[position].activityClass);
                    String station = mWC[position].station.toString();
                    intent.putExtra(EXTRA_MESSAGE, station);

                    startActivity(intent);
                }
            }

            public void setItemSelected(View view){
                View rowView = view;
                view.setBackgroundColor(Color.parseColor("#66CCCC"));

                TextView tv0 = (TextView)rowView.findViewById(R.id.list_item_station);
                tv0.setTextColor(Color.parseColor("#000099"));

                TextView tv1 = (TextView)rowView.findViewById(R.id.list_item_zone);
                tv1.setTextColor(Color.parseColor("#000099"));
            }

            public void setItemNormal()
            {
                for (int i=0; i< listView.getChildCount(); i++) {
                    View v = listView.getChildAt(i);
                    v.setBackgroundColor(Color.TRANSPARENT);

                    TextView tv0 = ((TextView) v.findViewById(R.id.list_item_station));
                    tv0.setTextColor(Color.WHITE);

                    TextView tv1 = ((TextView) v.findViewById(R.id.list_item_zone));
                    tv1.setTextColor(Color.parseColor("#B5B5B5"));
                }
            }
        });

        return v;
    }

    static class MyAdapter extends BaseAdapter {

        static class ViewHolder {
            TextView station;
            TextView zone;
        }

        LayoutInflater inflater;
        WC[] mWC;

        public MyAdapter(Context contexts, WC[] samples) {
            this.mWC = samples;
            inflater = LayoutInflater.from(contexts);
        }

        @Override
        public int getCount() {
            return mWC.length;
        }

        @Override
        public Object getItem(int position) {
            return mWC[position];
        }

        @Override
        public long getItemId(int position) {
            return 0;
        }

        /**set selected position**/
        private int selectPosition = -1;
        public void setSelectPosition(int position){
            if(position!=selectPosition){
                selectPosition = position;
            }
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder viewHolder;
            if (convertView == null) {
                convertView = inflater.inflate(R.layout.list_item_dualline, null);
                viewHolder = new ViewHolder();

                viewHolder.station = (TextView) convertView.findViewById(R.id.list_item_station);
                viewHolder.zone = (TextView) convertView.findViewById(R.id.list_item_zone);
                convertView.setTag(viewHolder);
            } else {
                viewHolder = (ViewHolder) convertView.getTag();
            }
            viewHolder.station.setText(mWC[position].station);
            viewHolder.zone.setText(mWC[position].getzone());

            //change item color
            if(position==selectPosition){
                convertView.setBackgroundColor(Color.parseColor("#000099"));
                viewHolder.station.setTextColor(Color.parseColor("#000099"));
            }else {

            }

            return convertView;
        }
    }
}

WCBankActivity.java

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.ActionBarActivity;


public class WCBankActivity extends ActionBarActivity {

    public final static String EXTRA_MESSAGE = "Station_key";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_wc_bank);

        if (savedInstanceState == null) {
            // Get the message from the intent
            Intent intent = getIntent();
            // Notice to specify the sender Activity for the message
            String station = intent.getStringExtra(WCBankActivity.EXTRA_MESSAGE);

            FragmentWCBank newFragment = new FragmentWCBank();
            FragmentTransaction transaction = this.getSupportFragmentManager().beginTransaction();
            transaction.replace(R.id.detail_container, newFragment);
            transaction.commit();
        }
    }
}

FragmentWCBank.java

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class FragmentWCBank extends android.support.v4.app.Fragment {

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment_wc_bank, container, false);

        return v;
    }
}

Answer 1

您看到的是警告而不是错误。差异是警告不会阻止您的程序运行，但会出现错误。

您看到的警告是由于您声明变量station但从未使用过它。你的IDE很聪明，可以注意到这一点，并试图警告你，提醒你不要使用你创建的变量。

在这种情况下，这一行：

String station = intent.getStringExtra(WCBankActivity.EXTRA_MESSAGE);

你声明一个变量station并给它一个值但是你永远不会读取它或用它做任何其他事情。因此，理论上您可以删除变量而不会对您的应用产生任何影响。

Android变量从未使用过

1 个答案: