Android列表(ListView)

 

效果图

 

1.activity_main.xml页面

        <ListView
            android:layout_width="match_parent"
            android:layout_height="460dp"
            android:id="@+id/list_item">

        </ListView>

2.同级layout目录下创建一个item_list.xml页面，编辑布局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#fff"
    android:orientation="vertical"
    android:padding="10dp"
   >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center_vertical"
            >


            <LinearLayout
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="6"
                android:orientation="vertical"
                >

                <TextView
                    android:id="@+id/title"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textColor="#000"
                    android:textSize="18sp" />

                <LinearLayout
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_marginTop="10dp"
                    android:layout_marginBottom="10dp">

                    <ImageView
                        android:id="@+id/icon"
                        android:layout_width="20dp"
                        android:layout_height="20dp"/>

                    <TextView
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:id="@+id/warning"
                        android:textColor="#cccc33"
                        android:textSize="16sp" />
                </LinearLayout>


                <TextView
                    android:id="@+id/time"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:textColor="#666"
                    android:textSize="14sp" />

            </LinearLayout>

            <Button
                android:layout_width="0dp"
                android:layout_height="48dp"
                android:layout_weight="1"
                android:background="@drawable/radius"
                android:text="确认" />

        </LinearLayout>


</RelativeLayout>

3.MainActivity.java

public class MovingActivity extends AppCompatActivity {
    private ListView listItem;
17     private ImageView icon;
    private TextView title,warning,time;
//    1.定义适配器中的数组内容
    private  int[] icons = {R.drawable.jinggao1,R.drawable.jinggao2,R.drawable.jinggao3};
    private  String[] titles ={"除湿机通讯失败","温湿度温度高报警","门开"};
    private  String[] warnings ={"一般报警","次要报警","主要报警"};
    private  String[] times ={"2021-08-05 09:58:21","2021-08-05 09:58:21","2021-08-05 09:58:21"};


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_moving);
        listItem = findViewById(R.id.list_item);
        MyAdapter md = new MyAdapter();
        listItem.setAdapter(md);
    }
    private class MyAdapter extends BaseAdapter {

        @Override
        public int getCount() { // 获取item的数量
            return titles.length;
        }

        @Override
        public Object getItem(int i) { //记录当前item的序号，从0开始，getItem获取某个item对象
            return titles[i];
        }

        @Override
        public long getItemId(int i) { //获取到选中的item项的编号
            return i;
        }

        @Override //用于适配listview要加载的内容，包括视图和数据
        public View getView(int i, View convertView, ViewGroup viewGroup) {
            // 将item布局文件解析成一个view对象
//            View view =View.inflate(MovingActivity.this,R.layout.item_list,null);
//            title= view.findViewById(R.id.title);
//            warning= view.findViewById(R.id.warning);
//            time= view.findViewById(R.id.time);
//            icon= view.findViewById(R.id.icon);
//
//            title.setText(titles[i]);
//            warning.setText(warnings[i]);
//            time.setText(times[i]);
//            icon.setBackgroundResource(icons[i]);

//            return view;



            //优化
            Object holder =null;
            // convertView 用于缓存item的对象
            if(convertView==null){
                convertView=View.inflate(MovingActivity.this,R.layout.item_list,null);
                holder = new ViewHolder();
                 ((ViewHolder) holder).title = convertView.findViewById(R.id.title);
                 ((ViewHolder) holder).warning = convertView.findViewById(R.id.warning);
                ((ViewHolder) holder).time = convertView.findViewById(R.id.time);
                 ((ViewHolder) holder).icon = convertView.findViewById(R.id.icon);
                convertView.setTag(holder);

            }else {
                holder = convertView.getTag();
            }
            ((ViewHolder) holder).icon.setBackgroundResource(icons[i]);
            ((ViewHolder) holder).title.setText(titles[i]);
            ((ViewHolder) holder).warning.setText(warnings[i]);
            ((ViewHolder) holder).time.setText(times[i]);
            return convertView;
        }


    }
    static  class ViewHolder{
        TextView title;
        TextView time;
        TextView warning;
        ImageView icon;
    }
}