Android动态批量加载Drawable中的图片

public static List<Drawable> getImageResourable(Context context, String imgName) {
    List<Drawable> imgList = new ArrayList<>();
    Resources resources = context.getResources();
    String packagename= context.getPackageName();
    Field[] fields = R.drawable.class.getDeclaredFields();
    for (int i = 0; i < fields.length; i++) {
        fields[i].setAccessible(true);
        String name = fields[i].getName();
        if (name.contains(imgName)) {
            int resId = resources.getIdentifier(name, "drawable", packagename);
            Drawable drawable = resources.getDrawable(resId);
            imgList.add(drawable);
        }
    }
    return imgList;
}

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

    //加载drawable中的img开头的图片资源
    mImageables=imgdeal.getImageResourable(this, "img");
    currentimgid=0;

    //在imageview中显示第一张资源图片
    imgv=findViewById(R.id.imgsrc);
    ShowImg(currentimgid);

    //第一张图片
    btnfirst=findViewById(R.id.btnfirst);
    btnfirst.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            currentimgid=0;
            ShowImg(currentimgid);
        }
    });

    //上一张按钮
    btnprev=findViewById(R.id.btnprev);
    btnprev.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (currentimgid > 0) {
                currentimgid--;
            }
            ShowImg(currentimgid);
        }
    });

    //下一张按钮
    btnnext=findViewById(R.id.btnnext);
    btnnext.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (currentimgid < mImageables.size() - 1) {
                currentimgid++;
            }
            ShowImg(currentimgid);
        }
    });


    //最后一张
    btnend=findViewById(R.id.btnend);
    btnend.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            currentimgid=mImageables.size() - 1;
            ShowImg(currentimgid);
        }
    });

}