ListView和RecycleView使用

ListView

  1. 定义list中基本项的布局方式

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

    <ImageView
        android:id="@+id/fruit_item_iv_1"
        android:src="@mipmap/ic_launcher"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/fruit_item_tv_1"
        android:gravity="center"
        android:layout_marginLeft="80dp"
        android:text="111"
        android:layout_width="wrap_content"
        android:layout_height="match_parent" />
</LinearLayout>

  2. 定义list中基本项对应的类

    public class Fruit {
    private String name;

    public Fruit(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

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

  3. 在需要添加list的活动布局内添加ListView

    <?xml version="1.0" encoding="utf-8"?>

<LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
 xmlns:android="http://schemas.android.com/apk/res/android" >

    <ListView
        android:id="@+id/activity_fruit_lv_1"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

  4. 编写一个适配器类，该适配器类继承自ArrayAdapter类，适配器类内重写需要的构造方法，并且需要重写ArrayAdapter类的getView方法

    public class FruitAdapter extends ArrayAdapter<Fruit> {
    private int resourceId;

    public FruitAdapter(@NonNull Context context, int resource, @NonNull List<Fruit> objects) {
        super(context, resource, objects);
        resourceId = resource;
    }
    
     @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
     Fruit fruit = getItem(position);
        ViewHolder viewHolder;
        //减少实例化view次数
        if (convertView == null) { 
            view = LayoutInflater.from(getContext()).inflate(resourceId, null);
            //减少
            viewHolder = new ViewHolder();
            viewHolder.imageView = (ImageView) view.findViewById(R.id.fruit_item_iv_1);
            viewHolder.textView = (TextView) view.findViewById(R.id.fruit_item_tv_1);
            view.setTag(viewHolder)
        } else {
            view = convertView;
            viewHolder = (ViewHolder) view.getTag();
        }
        viewHolder.imageView.setImageResource(R.drawable.ic_launcher);
        viewHolder.textView.setText(fruit.getName());
        //TextView textView = (TextView) findViewById(R.id.fruit_item_tv_1);
        //textView.setText(fruit.getName());
        return view;
    }
    
    class ViewHolder {
        ImageView imageView;
        TextView textView;
    }
}

    实例化该适配器类时需要传入需要传入基本项布局资源id，将该布局资源id保存起来；重写getVIew方法内，首先获取了传入的 objects对应 position位置的基本项类；判断基本布局项之前是否已经加载过，如果没有，通过LayoutInflater找到基本项布局并将其实例化，如果有的化，直接获取该基本布局项即可；通过基本项布局找到textview控件，将控件中的内容设置为拿到实体类内对应的内容;最后将实例化的布局返回；

  5. 再活动内使用

    public class FruitActivity extends AppCompatActivity {
    private String[] data = {"Apple", "Banana", "Orange", "Pear", "Grape"};
    private List<Fruit> fruits = new ArrayList<>();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_fruit);
        init();
        FruitAdapter fruitAdapter = new FruitAdapter(this, R.layout.fruit_item, fruits);
        ListView listView = (ListView) findViewById(R.id.activity_fruit_lv_1);
        listView.setAdapter(fruitAdapter);
        //添加监听事件
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Fruit fruit = fruits.get(position);
                Toast.makeText(FruitActivity.this, "111111111111", Toast.LENGTH_SHORT).show();
            }
        });
    }
 
 //往fruits内填充数据
    public void init() {
        for (int i = 0; i< 4; i++) {
            for (int j=0; j< data.length; j++) {
                fruits.add(new Fruit(data[j]));
            }
        }
    }
}

RecycleView

  1. 添加recycleView依赖

    `implementation 'androidx.recyclerview:recyclerview:1.1.0'

  2. 定义list中基本项的布局方式，同上

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

    <ImageView
        android:id="@+id/fruit_item_iv_1"
        android:src="@mipmap/ic_launcher"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/fruit_item_tv_1"
        android:gravity="center"
        android:layout_marginLeft="80dp"
        android:text="111"
        android:layout_width="wrap_content"
        android:layout_height="match_parent" />
</LinearLayout>

  3. 在需要添加list的活动布局中添加recycleView

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

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/activity_recycle_view_rv_1"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />


</LinearLayout>

  4. 创建一个适配器类，该类继承自RecyclerView.Adapter，并重写其onCreateViewHolder， onBindViewHolder， getItemCount方法

    public class RvFruitAdapter extends RecyclerView.Adapter<RvFruitAdapter.ViewHolder> {
    private List<Fruit> mFruitList;

    static class ViewHolder extends RecyclerView.ViewHolder {
        ImageView imageView;
        TextView textView;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            imageView = (ImageView) itemView.findViewById(R.id.fruit_item_iv_1);
            textView = (TextView) itemView.findViewById(R.id.fruit_item_tv_1);
        }
    }

    public RvFruitAdapter(List<Fruit> fruits) {
        mFruitList = fruits;
    }

 //若需要添加监听事件，在该函数内添加即可（通过view拿到组件添加监听事件)
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position);
        holder.imageView.setImageResource(R.mipmap.ic_launcher);
        holder.textView.setText(fruit.getName());
    }

    @Override
    public int getItemCount() {
        return mFruitList.size();
    }


}

    getItemCount方法需要返回列表长度，该方法将影响界面最终返回的基本项数量

  5. 在活动内引用

    public class RecycleViewActivity extends AppCompatActivity {
    private String[] data = {"Apple", "Banana", "Orange", "Pear", "Grape"};
    private List<Fruit> fruits = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_recycle_view);
        init();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.activity_recycle_view_rv_1);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        //网格布局
        //GridLayoutManager gridLayoutManager = new GridLayoutManager(this, 3);
        //瀑布布局
        //StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL)
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setAdapter(new RvFruitAdapter(fruits));
    }

    public void init() {
        for (int i = 0; i< 4; i++) {
            for (int j=0; j< data.length; j++) {
                fruits.add(new Fruit(data[j]));
            }
        }
    }
}
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