Question

我正在通过静态指定的名称

来获取图像

{R.drawable.image1,R.drawable.image2,R.drawable.image3}

如果我有大约50张图像，我将无法给出数组中每个文件的名称，因此它必须是动态的，我该如何实现。并且还请告诉我将动态代码放在哪里

package com.example.nauman.swipeapp;

import android.annotation.SuppressLint;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v4.view.PagerAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RelativeLayout;

public class SwipeAdapter extends PagerAdapter {
    private int[]image =  {R.drawable.image1,R.drawable.image2,R.drawable.image3};

    private Context cx;

    SwipeAdapter(Context cx){

        this.cx=cx;
    }

    @Override
    public int getCount() {
        return image.length;
    }

    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
        return (view==(RelativeLayout)object);
    }

    @SuppressLint("SetTextI18n")
    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {

        LayoutInflater layoutInflater = (LayoutInflater) cx.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        assert layoutInflater != null;
        View view= layoutInflater.inflate(R.layout.page_fragment,container,false);
        ImageView imageView= view.findViewById(R.id.imageView);
        imageView.setImageResource(image[position]);
        container.addView(view);
        return view;
    }

    @Override
    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        container.removeView((RelativeLayout) object);
    }

}

Answer 1

此解决方案感到有点棘手，这不仅是因为它使用了反射，而且还因为它严重依赖于能够通过将它们的名称与特定模式进行匹配来识别您自己的可绘制资源（因此，您应该尝试使用真正唯一的名称作为图片）

话虽如此，您可以如下更改代码：

保留private int[] image;，但在适配器的构造函数中对其进行初始化：

SwipeAdapter(Context cx){
    this.cx=cx;
    buildImageArray();
}

使用新方法（注意：您必须导入java.lang.reflect.Field;）

private void buildImageArray() {

    // this will give you **all** drawables, including those from e.g. the support libraries!
    Field[] drawables = R.drawable.class.getDeclaredFields();
    SparseIntArray temp = new SparseIntArray();
    int index = 0;
    for (Field f : drawables) {
        try {
            System.out.println("R.drawable." + f.getName());
            // check the drawable is "yours" by comparing the name to your name pattern
            // this is the point where some unwanted drawable may slip in,
            // so you should spend some effort on the naming/ matching of your pictures
            if (f.getName().startsWith("image")) {
                System.out.println("R.drawable." + f.getName() + "==========================================");
                int id = cx.getResources().getIdentifier(f.getName(), "drawable", cx.getPackageName());
                temp.append(index, id);
                index++;
            }
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
    image = new int[index];
    for (int i = 0; i < index; i++) {
        image[i] = temp.valueAt(i);
    }
}

Answer 2

如果所有可绘制对象都具有以下名称：image1，image2，image3，...。
那么您可以像这样获取他们的资源ID：

int i = 1; // get the id of image1
int resId = context.getResources().getIdentifier("image" + i, "drawable", context.getPackageName());

并使用它：

imageView.setImageResource(resId);

为此，您必须提供有效的Context（在活动中可以使用this）。

Answer 3

如下所示更改适配器类的构造函数。只需添加图像列表作为参数

public class SwipeAdapter extends PagerAdapter {
private ArrayList<Integer> image;

private Context cx;

SwipeAdapter(Context cx, ArrayList<Integer> image){

    this.cx=cx
    this.image =image
}

@Override
public int getCount() {
    return image.size;
}

@Override
public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
   return (view==(RelativeLayout)object);
}

 @SuppressLint("SetTextI18n")
 @NonNull
 @Override
 public Object instantiateItem(@NonNull ViewGroup     container, int position) {

   LayoutInflater layoutInflater = (LayoutInflater)      cx.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
assert layoutInflater != null;
View view=   layoutInflater.inflate(R.layout.page_fragment,container,false);
ImageView imageView=  view.findViewById(R.id.imageView);
imageView.setImageResource(image[position]);
container.addView(view);
return view;
}

@Override
public void destroyItem(@NonNull ViewGroup container,     int position, @NonNull Object object) {
container.removeView((RelativeLayout) object);
}

实例化适配器，其图像列表如下。为了在可绘制资源中的图像之间循环，如果要在适配器中添加50张图像，则需要在其名称中按1到50的顺序添加索引

 ArrayList<Integer> images=new ArrayList<Integer>()
 for(int i =0;i<50; i++){
 int res = getResources().getIdentifier("<your pakecgename>:drawable/abc"+i, null, null);
 images.add(res);
}
SwipeAdapter adapter = new SwipeAdapter(activity, images)

如何从可绘制文件夹动态获取图像？

3 个答案: