Android文件列表 RecyclerView

Android文件列表 RecyclerView

1. app gradle

dependencies {

implementation 'androidx.recyclerview:recyclerview:1.1.0'

2. AndroidManifest配置权限

权限

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

3. activity布局

MainActivity

<?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="wrap_content"
    android:orientation="vertical">

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

    </androidx.recyclerview.widget.RecyclerView>

</LinearLayout>

my_text_view

<?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="wrap_content">

    <TextView
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="TextView" />
</LinearLayout>

4. Activity代码

MainActivity

package com.example.myfile;

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

import android.os.Bundle;
import android.os.Environment;

import java.io.File;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    private RecyclerView recyclerView;
    private RecyclerView.Adapter adapter;
    private RecyclerView.LayoutManager layoutManager;
    private List<MyFile> myFileList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        recyclerView = findViewById(R.id.recyclerview);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        recyclerView.setHasFixedSize(true);

        // use a linear layout manager
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        // specify an adapter (see also next example)
        adapter = new MyAdapter(myFileList);
        recyclerView.setAdapter(adapter);

        initMyFile(Environment.getExternalStorageDirectory());
    }

    private void initMyFile(File externalStorageDirectory) {
        myFileList.clear();
        List<File> files = new ArrayList<>();
        Collections.addAll(files, externalStorageDirectory.listFiles());
        for (File file : files) {
            String fileName = file.getName();
            MyFile myFile = new MyFile(fileName);
            myFileList.add(myFile);
        }
        adapter.notifyDataSetChanged();
    }
}

MyAdapter

package com.example.myfile;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
    private List<MyFile> mFileList;
    public static class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView textView;
        public MyViewHolder(View v) {
            super(v);
            textView = v.findViewById(R.id.textView);
        }
    }
    public MyAdapter(List<MyFile> list) {
        mFileList = list;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.my_view, parent, false);
        MyViewHolder myViewHolder = new MyViewHolder(v);
        return myViewHolder;
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        MyFile myFile = mFileList.get(position);
        holder.textView.setText(myFile.getFileName());
    }

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

MyFile

package com.example.myfile;

public class MyFile {
    private String fileName;

    public MyFile(String fileName) {
        super();
        this.fileName = fileName;
    }

    public String getFileName() {
        return fileName;
    }
}

5. 关键代码

//在布局中添加了 RecyclerView 微件之后，获取对象句柄，将其连接到布局管理器，并为要显示的数据附加适配器

// use this setting to improve performance if you know that changes
// in content do not change the layout size of the RecyclerView
recyclerView.setHasFixedSize(true);

// use a linear layout manager
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);

// specify an adapter (see also next example)
adapter = new MyAdapter(myFileList);
recyclerView.setAdapter(adapter);

//要将所有数据输入列表中，您必须扩展 RecyclerView.Adapter 类。此对象会创建项的视图，并在原始项不再可见时用新数据项替换部分视图的内容。

//MyViewHolder参数需要是View,否则报错(TextView与String[]类型不匹配)

public MyViewHolder(View v) {
      super(v);
      textView = v.findViewById(R.id.textView);
}

@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.my_text_view, parent, false);
    MyViewHolder vh = new MyViewHolder(v);
    return vh;
}

//初始化文件列表，将指定文件夹内的所有文件信息，添加到List中；
//通过List中保存的每一个信息，生成RecyclerView Adapter需要的数据，并添加进去。

private void initMyFile(File externalStorageDirectory) {
        myFileList.clear();
        List<File> files = new ArrayList<>();
        Collections.addAll(files, externalStorageDirectory.listFiles());
        //生成RecyclerView Adapter需要的数据
        for (File file : files) {
            String fileName = file.getName();
            MyFile myFile = new MyFile(fileName);
            myFileList.add(myFile);
        }
        adapter.notifyDataSetChanged();
}

参考链接：
https://developer.android.google.cn/guide/topics/ui/layout/recyclerview?hl=zh_cn#java

MyViewHolder参数需要是View,否则报错(TextView与String[]类型不匹配)
https://www.jianshu.com/p/4fc6164e4709

RecyclerView 的item显示的间距过大(item占满父布局)
https://www.jianshu.com/p/3047c050b556

文件列表
https://blog.csdn.net/qq_40019723/article/details/79369529
https://blog.csdn.net/u013372185/article/details/52415234