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);
}