Fix error 1101 on Android versions before Nougat (#1526)

Installing a package via the QR code scanner fails on Android versions
before SDK 24. The issue is that we switched to using content: URIs,
which is required on SDK 24+, but this fails to resolve the package
installer activity on SDK < 24. This commit adds a helper method for
constructing the correct URI based on the device's SDK version.

Change-Id: Ieaec37b79d6189f75535b5a9be4d0f38b756e63a

appinventor/components/src/com/google/appinventor/components/runtime/util/ErrorMessages.java

 // -*- mode: java; c-basic-offset: 2; -*-
 // Copyright 2009-2011 Google, All Rights reserved
-// Copyright 2011-2018 MIT, All rights reserved
+// Copyright 2011-2019 MIT, All rights reserved
 // Released under the Apache License, Version 2.0
 // http://www.apache.org/licenses/LICENSE-2.0
 
@@ -245,7 +245,10 @@ public final class ErrorMessages {
   // Phone Call Errors
   public static final int ERROR_NO_CALL_PERMISSION = 3501;
 
-  // Start the next group of errors at 3600
+  // REPL Errors
+  public static final int ERROR_UNABLE_TO_INSTALL_PACKAGE = 3601;
+
+  // Start the next group of errors at 3700
 
   // Mapping of error numbers to error message format strings.
   private static final Map<Integer, String> errorMessages;
@@ -614,6 +617,10 @@ public final class ErrorMessages {
     // Phone Call errors
     errorMessages.put(ERROR_NO_CALL_PERMISSION,
         "You do not have permission to make phone calls.");
+
+    // REPL errors
+    errorMessages.put(ERROR_UNABLE_TO_INSTALL_PACKAGE,
+        "Unable to launch the package installer for %1$s.");
   }
 
   private ErrorMessages() {

appinventor/components/src/com/google/appinventor/components/runtime/util/NougatUtil.java

+// -*- mode: java; c-basic-offset: 2; -*-
+// Copyright 2019 MIT, All rights reserved
+// Released under the Apache License, Version 2.0
+// http://www.apache.org/licenses/LICENSE-2.0
+
+package com.google.appinventor.components.runtime.util;
+
+import android.net.Uri;
+import android.os.Build;
+import android.support.v4.content.FileProvider;
+import android.util.Log;
+import com.google.appinventor.components.runtime.Form;
+
+import java.io.File;
+
+public final class NougatUtil {
+
+  private static final String LOG_TAG = NougatUtil.class.getSimpleName();
+
+  private NougatUtil() {
+  }
+
+  public static Uri getPackageUri(Form form, File apk) {
+    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
+      // Use file: URI on versions of Android older the Nougat
+      return Uri.fromFile(apk);
+    } else {
+      // File provider used for SDK 24+ to get a content: URI
+      String packageName = form.$context().getPackageName();
+      Log.d(LOG_TAG, "packageName = " + packageName);
+      return FileProvider.getUriForFile(form.$context(), packageName + ".provider", apk);
+    }
+  }
+}

appinventor/components/src/com/google/appinventor/components/runtime/util/PackageInstaller.java

 // -*- mode: java; c-basic-offset: 2; -*-
-// Copyright 2011-2018 MIT, All rights reserved
+// Copyright 2011-2019 MIT, All rights reserved
 // Released under the Apache License, Version 2.0
 // http://www.apache.org/licenses/LICENSE-2.0
 // This work is licensed under a Creative Commons Attribution 3.0 Unported License.
 
 package com.google.appinventor.components.runtime.util;
 
+import android.content.ActivityNotFoundException;
 import android.content.Intent;
 
 import android.net.Uri;
 
+import android.os.Build;
 import android.os.Environment;
 
 import android.support.v4.content.FileProvider;
@@ -41,6 +43,7 @@ public class PackageInstaller {
     AsynchUtil.runAsynchronously(new Runnable() {
         @Override
         public void run() {
+          Uri packageuri = null;
           try {
             URL url = new URL(inurl);
             URLConnection conn = url.openConnection();
@@ -48,7 +51,7 @@ public class PackageInstaller {
             InputStream instream = new BufferedInputStream(conn.getInputStream());
             File apkfile = new File(rootDir + "/package.apk");
             FileOutputStream apkOut = new FileOutputStream(apkfile);
-            byte [] buffer = new byte[32768];
+            byte[] buffer = new byte[32768];
             int len;
             while ((len = instream.read(buffer, 0, 32768)) > 0) {
               apkOut.write(buffer, 0, len);
@@ -58,12 +61,14 @@ public class PackageInstaller {
             // Call Package Manager Here
             Log.d(LOG_TAG, "About to Install package from " + inurl);
             Intent intent = new Intent(Intent.ACTION_VIEW);
-            String packageName = form.$context().getPackageName();
-            Log.d(LOG_TAG, "packageName = " + packageName);
-            Uri packageuri = FileProvider.getUriForFile(form.$context(), packageName + ".provider", new File(rootDir + "/package.apk"));
+            packageuri = NougatUtil.getPackageUri(form, apkfile);
             intent.setDataAndType(packageuri, "application/vnd.android.package-archive");
             intent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
             form.startActivity(intent);
+          } catch (ActivityNotFoundException e) {
+            Log.e(LOG_TAG, "Unable to install package", e);
+            form.dispatchErrorOccurredEvent(form, "PackageInstaller",
+              ErrorMessages.ERROR_UNABLE_TO_INSTALL_PACKAGE, packageuri);
           } catch (Exception e) {
             Log.e(LOG_TAG, "ERROR_UNABLE_TO_GET", e);
             form.dispatchErrorOccurredEvent(form, "PackageInstaller",