Android N安装apk报错：android.os.FileUriExposedException

StackOverflow: http://stackoverflow.com/questions/38200282/android-os-fileuriexposedexception-file-storage-emulated-0-test-txt-exposed

1.在AndroidMainifest.xml文件中添加:

<provider

            android:name="android.support.v4.content.FileProvider"

            android:authorities="${applicationId}.provider"

            android:exported="false"

            android:grantUriPermissions="true">

            <meta-data

                android:name="android.support.FILE_PROVIDER_PATHS"

                android:resource="@xml/provider_paths"/>

</provider>

###:

authorities：app的包名.fileProvider 
grantUriPermissions：true，表示授予 URI 临时访问权限 
exported：false 
resource：下一步添加的文件

2.在res下新建一个名为xml的文件家，再新建文件provider_paths:

<?xml version="1.0" encoding="utf-8"?>

<paths>

    <external-path

        name="files_root"

        path="Android/data/com.example.downloadapk/"/>

    <external-path

        name="external_storage_root"

        path="."/>

</paths>

###：

path：需要临时授权访问的路径（.代表所有路径） 
name：给访问路径命名

3.安装apk文件:

   /**

     * 安装apk文件

     *

     * @param apkFile 安装包所在目录

     */

    private void installApk(File apkFile) {

        Intent intent = new Intent(Intent.ACTION_VIEW);

        try {

            String[] command = {"chmod", "777", apkFile.toString()};

            ProcessBuilder builder = new ProcessBuilder(command);

            builder.start();

        } catch (IOException ignored) {

        }

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {

            intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);

            Uri contentUri = FileProvider.getUriForFile(getApplicationContext(),

                    BuildConfig.APPLICATION_ID + ".fileProvider", apkFile);

            intent.setDataAndType(contentUri, "application/vnd.android.package-archive");

        } else {

            intent.setDataAndType(Uri.fromFile(apkFile), "application/vnd.android.package-archive");

            intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

        }

        startActivity(intent);

    }