需求：
壁纸是url链接，get就能请求到，所以就用get请求到图片，把图片转化为bitmap，然后设置壁纸。
代码：
这里我封装了工具类
package xxxxx.utils;import android.app.Activity;
import android.app.WallpaperManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;/*** 设置壁纸* 1、下载网络图片，使用HttpURLConnection* 2、设置壁纸* Created by zst on 2018/10/15.*/public class HttpURLConnectionUtil {/*** 设置系统壁纸* 1、把网络图片设置系统壁纸* 2、因为谷歌不维护其他框架了，所以使用HttpURLConnection来下载和配置** @param activity* @param imgUrl*/public static void setWallpaper(final Activity activity, final String imgUrl) {//Log.e("壁纸", "链接：" + imgUrl);new Thread(new Runnable() {@Overridepublic void run() {try {URL httpUrl = new URL(imgUrl);//获取传入进来的url地址 并捕获解析过程产生的异常//使用是Http访问 所以用HttpURLConnection 同理如果使用的是https 则用HttpsURLConnectiontry {HttpURLConnection conn = (HttpURLConnection) httpUrl.openConnection();//通过httpUrl开启一个HttpURLConnection对象conn.setReadTimeout(5000);//设置显示超市时间为5秒conn.setRequestMethod("GET");//设置访问方式conn.setDoInput(true);//设置可以获取输入流InputStream in = conn.getInputStream();//获取输入流//创建一个写入ID卡的文件对象FileOutputStream out = null;File download = null;String filename = String.valueOf(System.currentTimeMillis());//获取系统时间//判断文件是否存在 Environment.MEDIA_MOUNTEDID卡是否挂载 如果是则创建文件对象if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {File parent = Environment.getExternalStorageDirectory();//获取ID卡目录download = new File(parent, filename);//在父类的目录下创建一个以当前下载的系统时间为文件名的文件out = new FileOutputStream(download);}byte[] b = new byte[2 * 1024];int len;if (out != null) {//id卡如果存在 则写入while ((len = in.read(b)) != -1) {out.write(b, 0, len);}}//读取该文件中的内容final Bitmap bitmap = BitmapFactory.decodeFile(download.getAbsolutePath());activity.runOnUiThread(new Runnable() {@Overridepublic void run() {//设置图片为壁纸//Bitmap bitmap = BitmapFactory.decodeResource(this.getResources(),R.drawable.bg_user_top);//设置项目res中的图片WallpaperManager manager = WallpaperManager.getInstance(activity);try {manager.setBitmap(bitmap);UiUtil.showToastLong(activity, "壁纸设置成功，请在桌面上查看");} catch (IOException e) {UiUtil.showToast(activity, "壁纸设置成失败");e.printStackTrace();}}});} catch (IOException e) {e.printStackTrace();}} catch (MalformedURLException e) {e.printStackTrace();}}}).start();}}
