RecyclerView的简单使用【一】

RecyclerView的简单使用【一】

本文参考bilibili博主天哥在奔跑教程：
地址：[https://www.bilibili.com/video/BV1Rt411e76H?p=14]

在原代码的基础上稍作改动，功能：纵向滑动的列表、可以自己控制显示输出列表item

activity_linear_recycler_view.xml

LinearRecyclerViewActivity.java

package android.example.myapplication.recyclerview;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.example.myapplication.R;
import android.graphics.Rect;
import android.os.Bundle;
import android.view.View;

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

public class LinearRecyclerViewActivity extends AppCompatActivity {
    private RecyclerView mRvMain;
    private LinearAdapter mAdapter;
    private List textInfos;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_linear_recycler_view);//在Activity中显示布局视图
        mRvMain = findViewById(R.id.rv_main);
        //Item的布局
        mRvMain.setLayoutManager(new LinearLayoutManager(LinearRecyclerViewActivity.this));
        //添加分隔线
        mRvMain.addItemDecoration(new MyDecoration());
        //为item提供数据
        textInfos = TextInit();             //初始化字符串list

        upDateAdapter();
    }

    private List TextInit() {
        List text = new ArrayList<>();      //模拟数据
        text.add(0,"北京");
        text.add(1,"上海");
        text.add(2,"广州");
        text.add(3,"深圳");
        text.add(4,"武汉");
        return text;
    }

    private void upDateAdapter() {              //新建调用Adapter
        mAdapter = new LinearAdapter(this, textInfos);
        mRvMain.setAdapter(mAdapter);
    }

    class MyDecoration extends RecyclerView.ItemDecoration{
        public void getItemOffsets(Rect outRect, View view,RecyclerView parent,RecyclerView.State state) {
            super.getItemOffsets(outRect,view,parent,state);
            outRect.set(0,0,0,getResources().getDimensionPixelOffset(R.dimen.dividerHeight));
        }
    }
}

layout_linear_item.xml

LinearAdapter.java

package android.example.myapplication.recyclerview;

import android.content.Context;
import android.example.myapplication.R;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;

import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class LinearAdapter extends RecyclerView.Adapter {
    private Context mContext;
    private List mText;

    public LinearAdapter(Context context,List textInfo) {
        this.mContext = context;
        this.mText = textInfo;
    }

    @Override
    public LinearAdapter.LinearViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new LinearViewHolder(LayoutInflater.from(mContext).inflate(R.layout.layout_linear_item, parent,false));
    }

    @Override
    public void onBindViewHolder(LinearAdapter.LinearViewHolder holder, final int position) {
        String texts = mText.get(position);
        holder.bindText(texts);

        holder.textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(mContext,"click..."+position,Toast.LENGTH_SHORT).show();
            }
        });
    }

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

    class LinearViewHolder extends RecyclerView.ViewHolder {
        private TextView textView;

        public LinearViewHolder(View itemView) {
            super(itemView);
            textView = itemView.findViewById(R.id.tv_title);
        }
        public void bindText(String text){
            textView.setText(text);
        }
    }
}

运行效果截图：

总结

三、总结
现在recyclerview可以替代传统的listview，recyclerview包含四个重要的组成部分：Layout Manager：Item的布局；Adapter：为Item提供数据；Item Decoration：Item之间的分割线；Item Animator：添加、删除Item动画。

1. 我在使用ItemDecoration添加item之间的分割线时，出现设置了但运行还是看不见的问题，后来才得知它默认是白色的，textview需要设置背景色才能看见。
2. 另一个问题是在新建调用Adapter 时，由于已经创建了一个继承RecyclerView.Adapter的类LinearAdapter，所以声明时要使用LinearAdapter而不再是Adapter。