1.准备工作，首先需要在AndroidManifest.xml中的application中加入以下内容

        <providerandroid:name="android.support.v4.content.FileProvider"android:authorities="需要更新app的包名.fileprovider"android:grantUriPermissions="true"android:exported="false"><meta-dataandroid:name="android.support.FILE_PROVIDER_PATHS"android:resource="@xml/filepaths"/></provider>

2.在res的xml中创建filepaths.xml的文件

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android"><external-files-path path="Android/data/当前运行app的包名/files" name="files_root" /><external-files-path path="." name="external_storage_root" />
</paths>

详情可见此参考，此链接阐述了filepaths.xml中path和代码中的关系。

Environment.getExternalStorageDirectory()过时的替代方法

 /*** 下载最新版本的apk** @param path apk下载地址*/private void downFile(final String path) {pBar = new ProgressDialog(this);pBar.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);pBar.setCancelable(false);pBar.setTitle("正在下载...");pBar.setMessage("请稍候...");pBar.setProgress(0);pBar.show();new Thread() {public void run() {try {URL url = new URL(path);HttpURLConnection con = (HttpURLConnection) url.openConnection();con.setReadTimeout(5000);con.setConnectTimeout(5000);con.setRequestProperty("Charset", "UTF-8");con.setRequestMethod("GET");if (con.getResponseCode() == 200) {int length = con.getContentLength();// 获取文件大小InputStream is = con.getInputStream();pBar.setMax(length); // 设置进度条的总长度FileOutputStream fileOutputStream = null;if (is != null) {//对apk进行保存Log.d("路径",getExternalFilesDir(null).toString());File file = new File(getExternalFilesDir(null),"levee.apk");apkfile = file;fileOutputStream = new FileOutputStream(file);byte[] buf = new byte[1024];int ch;int process = 0;while ((ch = is.read(buf)) != -1) {fileOutputStream.write(buf, 0, ch);process += ch;pBar.setProgress(process); // 实时更新进度了}}if (fileOutputStream != null) {fileOutputStream.flush();fileOutputStream.close();}//apk下载完成，使用Handler()通知安装apkhandler.sendEmptyMessage(0);}} catch (Exception e) {e.printStackTrace();}}}.start();}

    //JSON数据不可再子线程中转换输出，要在主线程中转换输出。Handler handler = new Handler() {@SuppressLint({"HandlerLeak", "LongLogTag"})public void handleMessage(Message msg) {super.handleMessage(msg);switch (msg.what){case 0://将下载进度对话框取消pBar.cancel();//安装apk，也可以进行静默安装File apkfile = new File(getExternalFilesDir(null), "levee.apk");Intent intent = new Intent(Intent.ACTION_VIEW);if (!apkfile.exists()) {return;}
//判断是否是AndroidN以及更高的版本if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);try {String ss = "com.sina.lovepea.Androidhongdou" + ".fileprovider";Uri contentUri = FileProvider.getUriForFile(MainActivity.this.getApplicationContext(), ss, apkfile);intent.setAction(Intent.ACTION_VIEW);intent.setDataAndType(contentUri, "application/vnd.android.package-archive");} catch (Exception e) {e.printStackTrace();}} else {intent.setDataAndType(Uri.fromFile(apkfile), "application/vnd.android.package-archive");intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);}try {MainActivity.this.startActivity(intent);} catch (Exception e) {e.printStackTrace();}break;}}};

重要内容

defaultConfig {applicationId "com.sina.lovepea.AndroidHongDou" //不能与android:authorities="需要更新app的包名.fileprovider" 重名minSdkVersion build_versions.min_sdktargetSdkVersion build_versions.target_sdkversionCode 1         //需要大于上一个版本versionName "0.1.3"   //需要大于上一个版本testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}