需求：点击更新应用进行安装的过程中弹出“未知来源”设置提示，需要跳过该步骤直接安装。

方案1 

分析：

1.首先9.0 app安装是通过packages/apps/PackageInstaller里面的应用进行安装的。

2.其次定位到安装界面是/src/com/android/packageinstaller/PackageInstallerActivity.java

3.查看handleUnknownSources里面进行了代码控制，至此问题已解决（或者直接通过appOpMode和包名进行判断调用initiateInstall（）函数也行，不建议），但是我们还得深入看下弹框做了什么动作。。。

 private void handleUnknownSources() {
        if (mOriginatingPackage == null) {
            Log.i(TAG, "No source found for package " + mPkgInfo.packageName);
            showDialogInner(DLG_ANONYMOUS_SOURCE);
            return;
        }

        Log.e(TAG, "wgd==No source found for package " + mPkgInfo.packageName);
        // Shouldn't use static constant directly, see b/65534401.
        //提前设置允许该应用获取未知来源权限
        if("com.ctg.itrdc.clouddesk".equals(mPkgInfo.packageName)){
            mAppOpsManager.setMode(AppOpsManager.OP_REQUEST_INSTALL_PACKAGES, mOriginatingUid,
            mPkgInfo.packageName, AppOpsManager.MODE_ALLOWED);
        }

        final int appOpCode =
                AppOpsManager.permissionToOpCode(Manifest.permission.REQUEST_INSTALL_PACKAGES);
        final int appOpMode = mAppOpsManager.noteOpNoThrow(appOpCode,
                mOriginatingUid, mOriginatingPackage);
       //根据appOpMode判断是否已获得未知来源安装权限   MODE_ERRORED没获取  MODE_ALLOWED已获取  
        switch (appOpMode) {
            case AppOpsManager.MODE_DEFAULT:
                mAppOpsManager.setMode(appOpCode, mOriginatingUid,
                        mOriginatingPackage, AppOpsManager.MODE_ERRORED);
                // fall through
            case AppOpsManager.MODE_ERRORED:
                showDialogInner(DLG_EXTERNAL_SOURCE_BLOCKED);
                break;
            case AppOpsManager.MODE_ALLOWED:
                initiateInstall();
                break;
            default:
                Log.e(TAG, "Invalid app op mode " + appOpMode
                        + " for OP_REQUEST_INSTALL_PACKAGES found for uid " + mOriginatingUid);
                finish();
                break;
        }
    }

4.showDialogInner(DLG_EXTERNAL_SOURCE_BLOCKED)弹框做了什么工作呢？ 接下来调用了创建窗口函数createDialog（）

 /**
     * Replace any dialog shown by the dialog with the one for the given {@link #createDialog id}.
     *
     * @param id The dialog type to add
     */
    private void showDialogInner(int id) {
        DialogFragment currentDialog =
                (DialogFragment) getFragmentManager().findFragmentByTag("dialog");
        if (currentDialog != null) {
            currentDialog.dismissAllowingStateLoss();
        }

        DialogFragment newDialog = createDialog(id);
        if (newDialog != null) {
            newDialog.showAllowingStateLoss(getFragmentManager(), "dialog");
        }
    }

 /**
     * Create a new dialog.
     *
     * @param id The id of the dialog (determines dialog type)
     *
     * @return The dialog
     */
    private DialogFragment createDialog(int id) {
        switch (id) {
            case DLG_PACKAGE_ERROR:
                return SimpleErrorDialog.newInstance(R.string.Parse_error_dlg_text);
            case DLG_OUT_OF_SPACE:
                return OutOfSpaceDialog.newInstance(
                        mPm.getApplicationLabel(mPkgInfo.applicationInfo));
            case DLG_INSTALL_ERROR:
                return InstallErrorDialog.newInstance(
                        mPm.getApplicationLabel(mPkgInfo.applicationInfo));
            case DLG_NOT_SUPPORTED_ON_WEAR:
                return NotSupportedOnWearDialog.newInstance();
            case DLG_INSTALL_APPS_RESTRICTED_FOR_USER:
                return SimpleErrorDialog.newInstance(
                        R.string.install_apps_user_restriction_dlg_text);
            case DLG_UNKNOWN_SOURCES_RESTRICTED_FOR_USER:
                return SimpleErrorDialog.newInstance(
                        R.string.unknown_apps_user_restriction_dlg_text);
            case DLG_EXTERNAL_SOURCE_BLOCKED:
                //未知来源
                return ExternalSourcesBlockedDialog.newInstance(mOriginatingPackage);
            case DLG_ANONYMOUS_SOURCE:
                return AnonymousSourceDialog.newInstance();
        }
        return null;
    }

 /**
     * An error dialog shown when external sources are not allowed
     */
    public static class ExternalSourcesBlockedDialog extends AppErrorDialog {
        static AppErrorDialog newInstance(@NonNull String originationPkg) {
            ExternalSourcesBlockedDialog dialog = new ExternalSourcesBlockedDialog();
            dialog.setArgument(originationPkg);
            return dialog;
        }

        @Override
        protected Dialog createDialog(@NonNull CharSequence argument) {
            try {
                PackageManager pm = getActivity().getPackageManager();

                ApplicationInfo sourceInfo = pm.getApplicationInfo(argument.toString(), 0);

                return new AlertDialog.Builder(getActivity())
                        .setTitle(pm.getApplicationLabel(sourceInfo))
                        .setIcon(pm.getApplicationIcon(sourceInfo))
                        .setMessage(R.string.untrusted_external_source_warning)
                        .setPositiveButton(R.string.external_sources_settings,
                                (dialog, which) -> {
                                    Intent settingsIntent = new Intent();
                                    settingsIntent.setAction(
                                            Settings.ACTION_MANAGE_UNKNOWN_APP_SOURCES);
                                    final Uri packageUri = Uri.parse("package:" + argument);
                                    settingsIntent.setData(packageUri);
                                    try {
                                        getActivity().startActivityForResult(settingsIntent,
                                                REQUEST_TRUST_EXTERNAL_SOURCE);
                                    } catch (ActivityNotFoundException exc) {
                                        Log.e(TAG, "Settings activity not found for action: "
                                                + Settings.ACTION_MANAGE_UNKNOWN_APP_SOURCES);
                                    }
                                })
                        .setNegativeButton(R.string.cancel,
                                (dialog, which) -> getActivity().finish())
                        .create();
            } catch (NameNotFoundException e) {
                Log.e(TAG, "Did not find app info for " + argument);
                getActivity().finish();
                return null;
            }
        }
    }

 Intent settingsIntent = new Intent();

 settingsIntent.setAction(Settings.ACTION_MANAGE_UNKNOWN_APP_SOURCES);

 接下来主要看看是跳转到哪了，这其实调用到设置apk里面了。通过界面文字搜索最终定位到

/src/com/android/settings/applications/appinfo/ExternalSourcesDetails.java类

 最终发现设置打开应用“未知来源”权限执行了以下代码，至此得出第3步修改方案。

我们也可以按照下面进行初始化实现 

    private void openAppInstallUnknownSource(Context context){
        try {
            String packageName = SystemProperties.get("persist.sys.app_install_unknown_source");
            if(!android.text.TextUtils.isEmpty(packageName)){
                AppOpsManager mAppOpsManager = (AppOpsManager) context.getSystemService(Context.APP_OPS_SERVICE);
                PackageManager mPm = context.getPackageManager();
                PackageInfo mPackageInfo = mPm.getPackageInfo(packageName,
                    PackageManager.MATCH_DISABLED_COMPONENTS |
                    PackageManager.MATCH_ANY_USER |
                    PackageManager.GET_SIGNATURES |
                    PackageManager.GET_PERMISSIONS);
                mAppOpsManager.setMode(AppOpsManager.OP_REQUEST_INSTALL_PACKAGES,
                mPackageInfo.applicationInfo.uid, packageName,AppOpsManager.MODE_ALLOWED);
            }
        }catch (Exception e) {
            Log.e(TAG, "Exception" + e);
        }
    }

修改方案2：

frameworks/base/services/core/java/com/android/server/pm/permission/DefaultPermissionGrantPolicy.java

在private void grantDefaultSystemHandlerPermissions(int userId) 函数中添加如下代码：

 PackageParser.Package feedBackPackage = getPackage("net.sunniwell.dss");
            if (feedBackPackage != null
                && doesPackageSupportRuntimePermissions(feedBackPackage)) {
                    grantRuntimePermissions(feedBackPackage, STORAGE_PERMISSIONS, userId);
        } 

2.判断是否已获取未知来源权限

//getPackageManager()表示当前应用是否获得未知来源权限，一般用于自升级判断
boolean canRequestPackageInstalls = getPackageManager().canRequestPackageInstalls();
log.d("upgradech:canRequestPackageInstalls = " + canRequestPackageInstalls);