安装APK，启动系统Activity

    private void installApk(File file) {
        Intent intent = new Intent("android.intent.action.VIEW");
        intent.addCategory("android.intent.category.DEFAULT");
//        intent.setData(Uri.fromFile(file));
//        intent.setType("application/vnd.android.package-archive");
        intent.setDataAndType(Uri.fromFile(file), "application/vnd.android.package-archive");
        startActivity(intent);
    }