android根据物理按键上下选中listview的item，回车进入点击相应事件

最近做扫码枪程序，因应用于冷库，用户需求在列表选择上可以用上下键代替滑动，所以做了一个小demo,记录一下

话不多说，直接上代码

1.布局文件很简单 主界面：

一个输入框一个列表，因为是手持采集枪，输入框经常用到，所以在做demo的时候也加上了，不需要的可以忽略

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:orientation="vertical"
        android:layout_height="match_parent"
        tools:context="jg.wanghf.com.listviewdemo.MainActivity">
    <EditText
            android:id="@+id/edit"
            android:layout_width="match_parent"
              android:layout_height="wrap_content"/>
<ListView
        android:id="@+id/listview"
        android:layout_width="match_parent"
          android:layout_height="match_parent">

</ListView>

</LinearLayout>

自布局文件+适配器：

简单的一个显示文本

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <TextView
            android:id="@+id/textview"
            android:layout_width="match_parent"
              android:layout_height="80dp"/>
</LinearLayout>

package jg.wanghf.com.listviewdemo;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

import java.util.List;

public class VxAdapter extends BaseAdapter {

    private List<String> stringList ;
    private Context context ;
    private LayoutInflater inflater;
    public VxAdapter(List<String> stringList,Context context) {
        this.context = context;
        this.stringList = stringList;
        this.inflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return stringList.size();
    }

    @Override
    public Object getItem(int position) {
        return stringList.get(position);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder viewHolder;
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.item_string, null);
            viewHolder = new ViewHolder();
            viewHolder.textView =  convertView.findViewById(R.id.textview);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        viewHolder.textView.setText(stringList.get(position));
        return convertView;
    }

    class ViewHolder {
        //                          商品编码                   商品名称                 预期单位                    预期数量
        private TextView textView;

    }
}

 这样基本的列表就完成了；

item获取焦点的方法setSelection(pisition);

根据上下键进行item获取焦点方法很简单；只需要监听按键，然后调用此方法就好了：

    @Override
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        final int action = event.getAction();
        switch (keyCode) {
            case KeyEvent.KEYCODE_DPAD_DOWN:
                // 移到下一项
                if (select_item<stringList.size()-1&&action==0){
                    listView.setSelection(select_item + 1);
                }
                break;
            case KeyEvent.KEYCODE_DPAD_UP:
                // 移到上一项
                if (select_item>0&&action==0){
                    listView.setSelection(select_item - 1);

                }
                break;
            case KeyEvent.KEYCODE_ENTER:

                switch (v.getId()){
                    case R.id.edit:
                        System.out.println("edit======"+1111111);
                        break;
                    default:
                        System.out.println(v.getId());
                        break;
                }
                break;
        }
        return false;
    }

此时要注意，推荐使用OnKeyListener来获取，这样可以根据不同的列表做处理，如果是单独的列表可以直接使用dispatchKeyEvent方法，此时，应该注意到我这边使用的是select_item变量值来得到当前获取到焦点的item的pisition并不是直接select_item++，select_item怎么获取呢

listView.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                System.out.println("onItemSelected========"+stringList.get(position)+"======"+position);
                select_item = position;
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {
                select_item = -1;
                listView.setSelection(select_item);
                System.out.println("onNothingSelected========");
            }
        });

listview 有一个监听方法可以获取当前被选中的item，setOnItemSelectedListener，在这获取被选中的item可以避免混乱

至此，功能基本完成了，但是要注意，如果用户滑动后再按上下键，此时默认选中的还是从第一个开始，所以要对listview滑动进行监听，当用户滑动完成后更新select_item的值

 listView.setOnScrollListener(new AbsListView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                System.out.println("onScrollStateChanged========="+scrollState);
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                select_item = firstVisibleItem-1;
                System.out.println("onScroll==========="+firstVisibleItem+"======="+visibleItemCount+"======"+totalItemCount);
            }
        });

 参数对应含义：

firstVisibleItem: 表示在屏幕中第一条显示的数据在adapter中的位置
  visibleItemCount：则表示屏幕中最后一条数据在adapter中的数据，
  totalItemCount则是在adapter中的总条数

我这边默认select_item为显示界面的上一条，这样当向下按键时会选中屏幕显示的第一条

若点击事件触发后返回此界面不刷新list,注意在点击时也更新select_item，

listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                select_item = position;
                System.out.println("onItemClick111111========"+stringList.get(position)+"======"+position);
            }
        });

activity完整代码

package jg.wanghf.com.listviewdemo;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.view.View;
import android.widget.*;

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

public class MainActivity extends AppCompatActivity implements View.OnKeyListener {

    private List<String> stringList;
    private VxAdapter vxAdapter;
    private ListView listView;
    private int select_item;
    private EditText editText;

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

    private void initView() {
        listView = findViewById(R.id.listview);
        editText = findViewById(R.id.edit);
        listView.setOnKeyListener(this);
        editText.setOnKeyListener(this);
        stringList = new ArrayList<>();
        select_item = -1;
    }

    private void initData() {
        for (int i=0;i<30;i++){
            stringList.add("test==="+i);
        }
        vxAdapter = new VxAdapter(stringList,this);
        listView.setAdapter(vxAdapter);
//        listView.setSelection(select_item);
        listView.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                System.out.println("onItemSelected========"+stringList.get(position)+"======"+position);
                select_item = position;
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {
                select_item = -1;
                listView.setSelection(select_item);
                System.out.println("onNothingSelected========");
            }
        });
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                select_item = position;
                System.out.println("onItemClick111111========"+stringList.get(position)+"======"+position);
            }
        });
        listView.setOnScrollListener(new AbsListView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                System.out.println("onScrollStateChanged========="+scrollState);
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                select_item = firstVisibleItem-1;
                System.out.println("onScroll==========="+firstVisibleItem+"======="+visibleItemCount+"======"+totalItemCount);
            }
        });
    }




    @Override
    public boolean onKey(View v, int keyCode, KeyEvent event) {
        final int action = event.getAction();
        switch (keyCode) {
            case KeyEvent.KEYCODE_DPAD_DOWN:
                // 移到下一项
                if (select_item<stringList.size()-1&&action==0){
                    listView.setSelection(select_item + 1);
                }
                break;
            case KeyEvent.KEYCODE_DPAD_UP:
                // 移到上一项
                if (select_item>0&&action==0){
                    listView.setSelection(select_item - 1);

                }
                break;
            case KeyEvent.KEYCODE_ENTER:

                switch (v.getId()){
                    case R.id.edit:
                        System.out.println("edit======"+1111111);
                        break;
                    default:
                        System.out.println(v.getId());
                        break;
                }
                break;
        }
        return false;
    }
}

 至此，功能算完成了