Android加载网络图片并保存到系统相册

加载网络图片并点击保存图片到系统相册
1.首先在清单文件上加入相关权限

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

2.定义一个ImageUtils工具类

	import android.content.Context;
	import android.content.Intent;
	import android.graphics.Bitmap;
	import android.graphics.BitmapFactory;
	import android.net.Uri;
	import android.os.Environment;
	import android.provider.MediaStore;
	import android.util.Log;

	import java.io.File;
	import java.io.FileNotFoundException;
	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.io.InputStream;
	import java.net.HttpURLConnection;
	import java.net.MalformedURLException;
	import java.net.URL;

	public class ImageUtils {

    private static File mPhotoFile = null;
    public static void setPhotoFile(File photoFile){
        mPhotoFile = photoFile;
    }

    public static File getPhotoFile(){

        return mPhotoFile;
    }


    /**
     * 保存图片到图库
     * @param bmp
     */
    public static void saveImageToGallery(Bitmap bmp, String bitName ) {
        // 首先保存图片
        File appDir = new File(Environment.getExternalStorageDirectory(),
                "picture");
        if (!appDir.exists()) {
            appDir.mkdir();
        }

        String fileName = bitName + ".png";
        File file = new File(appDir, fileName);
        Log.v("Photo",fileName);
        try {
            FileOutputStream fos = new FileOutputStream(file);
            bmp.compress(Bitmap.CompressFormat.PNG, 100, fos);
            fos.flush();
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        setPhotoFile(file);

    }

    /**
     * @param bmp 获取的bitmap数据
     * @param picName 自定义的图片名
     */
    public static void saveBmp2Gallery(Context context, Bitmap bmp, String picName) {
        saveImageToGallery(bmp,picName);
        String fileName = null;
        //系统相册目录
        String galleryPath = Environment.getExternalStorageDirectory()
                + File.separator + Environment.DIRECTORY_DCIM
                + File.separator + "Camera" + File.separator;


        // 声明文件对象
        File file = null;
        // 声明输出流
        FileOutputStream outStream = null;
        try {
            // 如果有目标文件，直接获得文件对象，否则创建一个以filename为名称的文件
            file = new File(galleryPath, picName + ".png");
            // 获得文件相对路径
            fileName = file.toString();
            // 获得输出流，如果文件中有内容，追加内容
            outStream = new FileOutputStream(fileName);
            if (outStream!=null) {
                bmp.compress(Bitmap.CompressFormat.PNG, 90, outStream);
            }
        }catch (Exception e) {
            e.getStackTrace();
        } finally {
            try {
                if (outStream != null) {
                	//关闭输出流
                    outStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
		//添加图片到系统相册并更新通知
        MediaStore.Images.Media.insertImage(context.getContentResolver(),bmp,fileName,null);
        Intent intent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
        Uri uri = Uri.fromFile(file);
        intent.setData(uri);
        context.sendBroadcast(intent);


    }
    /**
     * 将URL转化成bitmap形式
     * @param url
     * @return bitmap type
     */
    public final static Bitmap returnBitMap(String url) {
        URL myFileUrl;
        Bitmap bitmap = null;
        try {
            myFileUrl = new URL(url);
            HttpURLConnection conn;
            conn = (HttpURLConnection) myFileUrl.openConnection();
            conn.setDoInput(true);
            conn.connect();
            InputStream is = conn.getInputStream();
            bitmap = BitmapFactory.decodeStream(is);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return bitmap;
    }

	}
	

Notes:这里Bitmap.compress(Bitmap.CompressFormat.PNG, 90, outStream);解压缩是PNG格式的图片
推荐阅读：BitmapFactory.decodeResource为null的处理方法之一

• 3.使用Glide加载图片

  • 3.1添加依赖

  	//glide加载图片
  	implementation 'com.github.bumptech.glide:glide:4.6.1'
  	annotationProcessor 'com.github.bumptech.glide:compiler:4.6.1'
  

• 3.2加载图片

   	String imgUrl;//设置全局变量
   	imgURl=mData.get(0).url;//通过下标获得第一张图片
       GlideApp.with(BaseApplication.getContext()).load(imgURl).apply(options).into(mImage);

4.开启子线程获取网络图片，更新UI

	//保存图片必须在子线程中操作，是耗时操作
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        Bitmap bp = ImageUtils.returnBitMap(imgURl);
                        if (EmptyUtils.isNotEmpty(bp))
                        ImageUtils.saveBmp2Gallery(BaseApplication.getContext(), bp, "picName");
                    }
                }).start();

Notes:保存图片之前先一层判断，判断Bitmap对象是否为空，否则程序容易出现空指针异常错误。一旦出现空指针异常的错误，一定要去找哪一个引用没有指向实际存在的对象，导致为null

Attempt to invoke virtual method 'boolean android.graphics.Bitmap.compress(android.graphics.Bitmap$CompressFormat, int, java.io.OutputStream)' on a null object reference

5.用到的EmptyUtils工具类

	import android.os.Build;
	import android.util.SparseArray;
	import android.util.SparseBooleanArray;
	import android.util.SparseIntArray;
	import android.util.SparseLongArray;

	import java.lang.reflect.Array;
	import java.util.Collection;
	import java.util.Map;

	public final class EmptyUtils {

    private EmptyUtils() {
        throw new UnsupportedOperationException("u can't instantiate me...");
    }

    /**
     * 判断对象是否为空
     *
     * @param obj 对象
     * @return {@code true}: 为空
{@code false}: 不为空
     */
    public static boolean isEmpty(Object obj) {
        if (obj == null) {
            return true;
        }
        if (obj instanceof String && obj.toString().length() == 0) {
            return true;
        }
        if (obj.getClass().isArray() && Array.getLength(obj) == 0) {
            return true;
        }
        if (obj instanceof Collection && ((Collection) obj).isEmpty()) {
            return true;
        }
        if (obj instanceof Map && ((Map) obj).isEmpty()) {
            return true;
        }
        if (obj instanceof SparseArray && ((SparseArray) obj).size() == 0) {
            return true;
        }
        if (obj instanceof SparseBooleanArray && ((SparseBooleanArray) obj).size() == 0) {
            return true;
        }
        if (obj instanceof SparseIntArray && ((SparseIntArray) obj).size() == 0) {
            return true;
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
            if (obj instanceof SparseLongArray && ((SparseLongArray) obj).size() == 0) {
                return true;
            }
        }
        return false;
    }

    /**
     * 判断对象是否非空
     *
     * @param obj 对象
     * @return {@code true}: 非空
{@code false}: 空
     */
    public static boolean isNotEmpty(Object obj) {
        return !isEmpty(obj);
    }
}

感谢查看！