<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"/>
 <uses-permission android:name="android.permission.REQUEST_INSTALL_PACKAGES" />
  <provider
   android:name="androidx.core.content.FileProvider"
   android:authorities="com.fengzhi.wuyemanagement.fileprovider"
   android:grantUriPermissions="true"
   android:exported="false">
   <meta-data
    android:name="android.support.FILE_PROVIDER_PATHS"
    android:resource="@xml/file_paths" />
  </provider>

<paths>
 <external-path path="." name="external_storage_root" />
</paths>

 implementation "com.lzy.net:okgo:3.0.4"//okgo 网络请求
 implementation 'com.google.code.gson:gson:2.8.2'//gson
 implementation "org.permissionsdispatcher:permissionsdispatcher:4.3.1"//权限
 annotationProcessor "org.permissionsdispatcher:permissionsdispatcher-processor:4.3.1"//权限

 private int version;
 /* 更新进度条 */
 private ProgressBar mProgress;
 private AlertDialog mDownloadDialog;
 
--------------------------------------------------------------------------------------------------------------------
 
 //点击按钮，检查权限，，，检查更新的方法
 @NeedsPermission({Manifest.permission.READ_EXTERNAL_STORAGE,
   Manifest.permission.WRITE_EXTERNAL_STORAGE,
   Manifest.permission.REQUEST_INSTALL_PACKAGES})
 protected void checkUpdate() {
  showLoadingDialog("检测更新中...");
  version = AppUpdateUtil.getAppVersionCode(this);//检查当前版本号
//  调用方法，，，接口的具体实现，接收传过来的参数，再调自己的方法，
  requestAppUpdate(version, new DataRequestListener<UpdateAppBean>() {
   @Override
   public void success(UpdateAppBean data) {
//    返回的json，getStatus为0时，去下载apk文件,这里是下载apk文件的方法
    updateApp(data.getData().getApk_url());
   }

   @Override
   public void fail(String msg) {
//    返回的json，getStatus为1时，提示："已是最新版本！"
    SToast(msg);
    dismissLoadingDialog();
   }
  });
 }

 //检查版本号，第一次请求(post)，，，UpdateAppBean根据服务器返回生成
 private void requestAppUpdate(int version, final DataRequestListener<UpdateAppBean> listener) {
  OkGo.<String>post(Const.HOST_URL + Const.UPDATEAPP).params("version", version).execute(new StringCallback() {
   @Override
   public void onSuccess(Response<String> response) {
    Gson gson = new Gson();
    UpdateAppBean updateAppBean = gson.fromJson(response.body(), UpdateAppBean.class);
    if (updateAppBean.getStatus() == 0) {
     listener.success(updateAppBean);
    } else {
     listener.fail(updateAppBean.getMsg());
    }
   }

   @Override
   public void onError(Response<String> response) {
    listener.fail("服务器连接失败");
    dismissLoadingDialog();
   }
  });
 }

 //如果有新版本，提示有新的版本，然后下载apk文件
 private void updateApp(String apk_url) {
  dismissLoadingDialog();
  DialogUtils.getInstance().showDialog(this, "发现新的版本，是否下载更新？",
    new DialogUtils.DialogListener() {
   @Override
   public void positiveButton() {
    downloadApp(apk_url);
   }
  });
 }

 //下载apk文件并跳转(第二次请求，get)
 private void downloadApp(String apk_url) {
  OkGo.<File>get(apk_url).tag(this).execute(new FileCallback() {
   @Override
   public void onSuccess(Response<File> response) {
    String filePath = response.body().getAbsolutePath();
    Intent intent = IntentUtil.getInstallAppIntent(mContext, filePath);
//    测试过这里必须用startactivity，不能用stratactivityforresult
    mContext.startActivity(intent);
    dismissLoadingDialog();
    mDownloadDialog.dismiss();
    mDownloadDialog=null;
   }

   @Override
   public void downloadProgress(Progress progress) {
//      showDownloadDialog();
//      mProgress.setProgress((int) (progress.fraction * 100));
    if (mDownloadDialog == null) {
     // 构造软件下载对话框
     AlertDialog.Builder builder = new AlertDialog.Builder(mContext);
     builder.setTitle("正在更新");
     // 给下载对话框增加进度条
     final LayoutInflater inflater = LayoutInflater.from(mContext);
     View v = inflater.inflate(R.layout.item_progress, null);
     mProgress = (ProgressBar) v.findViewById(R.id.update_progress);
     builder.setView(v);
     mDownloadDialog = builder.create();
     mDownloadDialog.setCancelable(false);
     mDownloadDialog.show();
    }
    mProgress.setProgress((int) (progress.fraction * 100));
   }
  });
 }

public interface DataRequestListener<T> {
 //请求成功
 void success(T data);
 //请求失败
 void fail(String msg);
}

 /**
  * 获取App版本码
  *
  * @param context 上下文
  * @return App版本码
  */
 public static int getAppVersionCode(Context context) {
  return getAppVersionCode(context, context.getPackageName());
 }

public class IntentUtil {

 /**
  * 获取安装App(支持7.0)的意图
  *
  * @param context
  * @param filePath
  * @return
  */
 public static Intent getInstallAppIntent(Context context, String filePath) {
  //apk文件的本地路径
  File apkfile = new File(filePath);
  if (!apkfile.exists()) {
   return null;
  }
  Intent intent = new Intent(Intent.ACTION_VIEW);
  Uri contentUri = FileUtil.getUriForFile(context, apkfile);
  intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
   intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
  }
  intent.setDataAndType(contentUri, "application/vnd.android.package-archive");
  return intent;
 }

 /**
  * 将文件转换成uri(支持7.0)
  *
  * @param mContext
  * @param file
  * @return
  */
 public static Uri getUriForFile(Context mContext, File file) {
  Uri fileUri = null;
  if (Build.VERSION.SDK_INT >= 24) {
   fileUri = FileProvider.getUriForFile(mContext, mContext.getPackageName() + ".fileprovider", file);
  } else {
   fileUri = Uri.fromFile(file);
  }
  return fileUri;
 }