BaseAdapter实现的投票案例

1.知识补充

android:descendantFocusability="blocksDescendants"，关键是让谁先去获取焦点

beforeDescendants：viewgroup会优先其子类控件而获取到焦点
afterDescendants：viewgroup只有当其子类控件不需要获取焦点时才获取焦点
blocksDescendants：viewgroup会覆盖子类控件而直接获得焦点

2.案例：投票案例

2.2目录结构

2.2参考代码

1）toupaio_item.xml子列表项代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:descendantFocusability="blocksDescendants">
<!--
    android:descendantFocusability="blocksDescendants"
    beforeDescendants：viewgroup会优先其子类控件而获取到焦点
    afterDescendants：viewgroup只有当其子类控件不需要获取焦点时才获取焦点
    blocksDescendants：viewgroup会覆盖子类控件而直接获得焦点

-->

    <LinearLayout
        android:id="@+id/toupiao"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <TextView
            android:id="@+id/vusername"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="张三"
            />
        <ProgressBar
            android:id="@+id/vpro"
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:max="100"
            style="@style/Widget.AppCompat.ProgressBar.Horizontal"
            />
        <Button
            android:id="@+id/vbutton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="投票"
            />
    </LinearLayout>



</LinearLayout>

2）activity_vote_list_view.xml主布局文件代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    tools:context=".VoteListViewActivity">
    <ListView
        android:id="@+id/toupiao_listView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />

</LinearLayout>

3）VoteListViewActivity代码

包含Student类
包含StudentAdapter（继承BaseAdapter）

//投票的案例
public class VoteListViewActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_vote_list_view);
        //1.获取ListView
        ListView listView=findViewById(R.id.toupiao_listView);
        //2.创建数据集合(线性的和ArrayList都是可以的)
        LinkedList<Student> list=new LinkedList<>();
        list.add(new Student("张三",0));
        list.add(new Student("李四",0));
        list.add(new Student("王五",0));
        //3.创建StudnetAdapter(需要传入数据集合和Context上下文对象)
        StudnetAdapter adapter=new StudnetAdapter(list,this);
        //4.绑定适配器
        listView.setAdapter(adapter);
    // 5.创建事件监听
    listView.setOnItemClickListener(
        new AdapterView.OnItemClickListener() {
          @Override
          public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
              ProgressBar progressBar=view.findViewById(R.id.vpro);
              TextView text=view.findViewById(R.id.vusername);
              int tcount=progressBar.getProgress();//获取进度就是获取当前的票数
              String tname=text.getText().toString();
              String str=tname+"票数为"+tcount;
              //结合页面跳转显示信息
              /* 省略，采用的是Toast显示当前投票人的信息*/
              Toast.makeText(VoteListViewActivity.this, ""+str, Toast.LENGTH_SHORT).show();

          }
        });
    }


//    创建BaseApdapter
    private class StudnetAdapter extends BaseAdapter {

        private Context context;
        private LinkedList<Student> listStudent;

    public StudnetAdapter(LinkedList<Student> listStudent, Context context) {
        this.context=context;
        this.listStudent=listStudent;
    }

    /*
    * 显示列表的项数
    * */
    @Override
    public int getCount() {
        return listStudent.size();
    }

    /*
    *返回的是第几个列表项的内容
    * */
    @Override
    public Object getItem(int position) {
        return listStudent.get(position);
    }

    /*
    * 返回第几个的id，其实就是position的值
    * */
    @Override
    public long getItemId(int id) {
        return id;
    }

    /*
    * 核心方法，控制每一项显示的内容
    * 结果：生成一个View对象的ContentView，这个View就是ListView
    *关键是给view赋成当前的列表项
    *
    * */
    @Override
    public View getView(int position, View view, ViewGroup viewGroup) {
        view=LayoutInflater.from(context).inflate(R.layout.toupaio_item,null,false);
        ProgressBar progressBar=view.findViewById(R.id.vpro);
        TextView text=view.findViewById(R.id.vusername);
        Button button=view.findViewById(R.id.vbutton);
        text.setText(listStudent.get(position).getName());
        progressBar.setProgress(listStudent.get(position).getCount());
        //设置投票的事件监听器
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                listStudent.get(position).setCount(listStudent.get(position).getCount()+1);
                progressBar.setProgress(listStudent.get(position).getCount()+1);

            }
        });



        return view;
    }
}
    //  学生类
    protected class Student{
        private String name;
        private int count;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public int getCount() {
            return count;
        }

        public void setCount(int count) {
            this.count = count;
        }

        public Student(String name, int count) {
            this.name = name;
            this.count = count;
        }

    }
}