Android读取“_File”里面的文件

Android读取“_File”里面的文件，例如图片，哪位大侠请给一份例程，我是新手
这是我写的，哪位大侠指点一下
package com.qqhr.leadcloud;

import androidx.appcompat.app.AppCompatActivity;

import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.os.Environment;
import android.provider.ContactsContract;
import android.util.Log;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.HashMap;
import java.util.List;

import cn.leancloud.AVFile;
import cn.leancloud.AVObject;
import cn.leancloud.AVQuery;
import io.reactivex.Observer;
import io.reactivex.disposables.Disposable;

public class MainActivity extends AppCompatActivity {

private AVFile file;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    file = new AVFile(
            "ic_launcher_shi.png",
            "http://lc-x5xUS9c8.cn-n1.lcfile.com/sWahVRAXIB505GL3wlJQAff2JV0zGIQ0/ic_launcher_shi.png",
            new HashMap<String, Object>()
    );

    AVObject todo = new AVObject("Todo");
    todo.put("title", "数据库");
    todo.add("fuJia", file);
    todo.save();

    //程序到这就停止了
    AVQuery<AVObject> query = new AVQuery<>("Todo");
    query.whereEqualTo("title", "数据库");
    query.whereExists("fuJia");
    query.include("fuJia");
    query.findInBackground().subscribe(new Observer<List<AVObject>>() {
        @Override
        public void onSubscribe(Disposable d) {
        }

        @Override
        public void onNext(List<AVObject> avObjects) {
            for (AVObject avObject : avObjects)
            {
                AVFile avFile = avObject.getAVFile("fuJia");

                avFile.getDataStreamInBackground().subscribe(new Observer<InputStream>() {
                    @Override
                    public void onSubscribe(Disposable d) {
                    }

                    @Override
                    public void onNext(InputStream inputStream) {
                        try {
                            byte[] buffer = new byte[102400];
                            int read = inputStream.read(buffer);
                            Log.i("tongzhi", "file data length:" + read);
                            inputStream.close();
                            Log.i("tongzhi", "成功");
                        } catch (IOException e) {
                            e.printStackTrace();
                            Log.i("tongzhi", "失败");
                        }
                    }
                    @Override
                    public void onError(Throwable e) {
                        Log.i("tongzhi", "没有获取数据：" + e.getMessage());
                    }
                    @Override
                    public void onComplete() {
                    }
                });
            }
        }

        @Override
        public void onError(Throwable e) {
            Log.i("tongzhi", "查询失败");
        }

        @Override
        public void onComplete() {

        }
    });
}

}