Generate license html file from xml files of partitions

Treble-ization requires each partner to store their license information
into their own partition because each partition can be updated
individually.
So each partition will have its own NOTICE.xml.gz, and Settings should
be able to generate license html from xml files of partitions.

Test: building succeeded and tested on sailfish.
  make ROBOTEST_FILTER=LicenseHtmlGeneratorFromXmlTest RunSettingsRoboTests
  make ROBOTEST_FILTER=LicenseHtmlLoaderTest RunSettingsRoboTests
  make ROBOTEST_FILTER=SettingsLicenseActivityTest RunSettingsRoboTests
Bug: 37099941
Change-Id: If797759d300ee20dd43ad8efd7d17b4f7e0c4537

src/com/android/settings/SettingsLicenseActivity.java

@@ -17,32 +17,87 @@
 package com.android.settings;
 
 import android.app.Activity;
+import android.app.LoaderManager;
 import android.content.ActivityNotFoundException;
+import android.content.ContentResolver;
+import android.content.Context;
 import android.content.Intent;
+import android.content.Loader;
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.StrictMode;
 import android.os.SystemProperties;
+import android.support.annotation.VisibleForTesting;
+import android.support.v4.content.FileProvider;
 import android.text.TextUtils;
 import android.util.Log;
 import android.widget.Toast;
 
+import com.android.settings.users.RestrictedProfileSettings;
+
 import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * The "dialog" that shows from "License" in the Settings app.
  */
-public class SettingsLicenseActivity extends Activity {
+public class SettingsLicenseActivity extends Activity implements
+            LoaderManager.LoaderCallbacks<File> {
     private static final String TAG = "SettingsLicenseActivity";
 
     private static final String DEFAULT_LICENSE_PATH = "/system/etc/NOTICE.html.gz";
     private static final String PROPERTY_LICENSE_PATH = "ro.config.license_path";
 
+    private static final int LOADER_ID_LICENSE_HTML_LOADER = 0;
+
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 
-        final String path = SystemProperties.get(PROPERTY_LICENSE_PATH, DEFAULT_LICENSE_PATH);
+        final String licenseHtmlPath =
+                SystemProperties.get(PROPERTY_LICENSE_PATH, DEFAULT_LICENSE_PATH);
+        if (isFilePathValid(licenseHtmlPath)) {
+            showSelectedFile(licenseHtmlPath);
+        } else {
+            showHtmlFromDefaultXmlFiles();
+        }
+    }
+
+    @Override
+    public Loader<File> onCreateLoader(int id, Bundle args) {
+        return new LicenseHtmlLoader(this);
+    }
+
+    @Override
+    public void onLoadFinished(Loader<File> loader, File generatedHtmlFile) {
+        showGeneratedHtmlFile(generatedHtmlFile);
+    }
+
+    @Override
+    public void onLoaderReset(Loader<File> loader) {
+    }
+
+    private void showHtmlFromDefaultXmlFiles() {
+        getLoaderManager().initLoader(LOADER_ID_LICENSE_HTML_LOADER, Bundle.EMPTY, this);
+    }
+
+    @VisibleForTesting
+    Uri getUriFromGeneratedHtmlFile(File generatedHtmlFile) {
+        return FileProvider.getUriForFile(this, RestrictedProfileSettings.FILE_PROVIDER_AUTHORITY,
+                generatedHtmlFile);
+    }
+
+    private void showGeneratedHtmlFile(File generatedHtmlFile) {
+        if (generatedHtmlFile != null) {
+            showHtmlFromUri(getUriFromGeneratedHtmlFile(generatedHtmlFile));
+        } else {
+            Log.e(TAG, "Failed to generate.");
+            showErrorAndFinish();
+        }
+    }
+
+    private void showSelectedFile(final String path) {
         if (TextUtils.isEmpty(path)) {
             Log.e(TAG, "The system property for the license file is empty");
             showErrorAndFinish();
@@ -50,18 +105,24 @@ public class SettingsLicenseActivity extends Activity {
         }
 
         final File file = new File(path);
-        if (!file.exists() || file.length() == 0) {
+        if (!isFileValid(file)) {
             Log.e(TAG, "License file " + path + " does not exist");
             showErrorAndFinish();
             return;
         }
+        showHtmlFromUri(Uri.fromFile(file));
+     }
 
+     private void showHtmlFromUri(Uri uri) {
         // Kick off external viewer due to WebView security restrictions; we
         // carefully point it at HTMLViewer, since it offers to decompress
         // before viewing.
         final Intent intent = new Intent(Intent.ACTION_VIEW);
-        intent.setDataAndType(Uri.fromFile(file), "text/html");
+        intent.setDataAndType(uri, "text/html");
         intent.putExtra(Intent.EXTRA_TITLE, getString(R.string.settings_license_activity_title));
+        if (ContentResolver.SCHEME_CONTENT.equals(uri.getScheme())) {
+            intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
+        }
         intent.addCategory(Intent.CATEGORY_DEFAULT);
         intent.setPackage("com.android.htmlviewer");
 
@@ -79,4 +140,13 @@ public class SettingsLicenseActivity extends Activity {
                 .show();
         finish();
     }
+
+    private boolean isFilePathValid(final String path) {
+        return !TextUtils.isEmpty(path) && isFileValid(new File(path));
+    }
+
+    @VisibleForTesting
+    boolean isFileValid(final File file) {
+        return file.exists() && file.length() != 0;
+    }
 }