Simplify permission check (#39)

* Simplify permission check

* Check preferences before write

* Destroy on pause

Author: mathiascode

app/src/main/java/org/cuberite/android/MainActivity.java

@@ -108,34 +108,31 @@ public static void showSnackBar(Activity activity, String message) {
     }
 
     private void showPermissionPopup() {
-        AlertDialog.Builder permissionPopupBuilder = new AlertDialog.Builder(this);
-        permissionPopupBuilder.setTitle(getString(R.string.status_permissions_needed));
-        permissionPopupBuilder.setMessage(R.string.message_externalstorage_permission);
-        permissionPopupBuilder.setCancelable(false);
-        permissionPopupBuilder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
-            public void onClick(DialogInterface dialog, int id) {
-                Log.d(LOG, "Requesting permissions for external storage");
-                ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_WRITE_EXTERNAL_STORAGE_PERMISSION);
-            }
-        });
+        permissionPopup = new AlertDialog.Builder(this)
+            .setTitle(getString(R.string.status_permissions_needed))
+            .setMessage(R.string.message_externalstorage_permission)
+            .setCancelable(false)
+            .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
+                public void onClick(DialogInterface dialog, int id) {
+                    Log.d(LOG, "Requesting permissions for external storage");
+                    permissionPopup = null;
+                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_WRITE_EXTERNAL_STORAGE_PERMISSION);
+                }
+            })
+            .create();
 
-        permissionPopup = permissionPopupBuilder.create();
         permissionPopup.show();
     }
 
     private void checkPermissions() {
-        if (preferences.getString("cuberiteLocation", null) == null) {
-            if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
-                // Always use public dir in Lollipop and earlier, since permissions are granted when the app is installed
-                preferences.edit().putString("cuberiteLocation", PUBLIC_DIR + "/cuberite-server").apply();
-            } else {
+        if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
+            // User is running Android 6 or above, show permission popup on first run
+            // or if user granted permission and later denied it
+
+            if (!preferences.getString("cuberiteLocation", "").startsWith(PRIVATE_DIR)) {
                 showPermissionPopup();
             }
-        } else if (preferences.getString("cuberiteLocation", "").startsWith(PUBLIC_DIR) &&
-                ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
-            showPermissionPopup();
-        } else if (preferences.getString("cuberiteLocation", "").startsWith(PRIVATE_DIR) &&
-                ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
+        } else if (!preferences.getString("cuberiteLocation", "").startsWith(PUBLIC_DIR)) {
             preferences.edit().putString("cuberiteLocation", PUBLIC_DIR + "/cuberite-server").apply();
         }
     }
@@ -144,7 +141,8 @@ private void checkPermissions() {
     public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
         if (requestCode == REQUEST_WRITE_EXTERNAL_STORAGE_PERMISSION) {
             // If request is cancelled, the result arrays are empty.
-            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
+            if (grantResults.length > 0
+                    && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                 Log.i(LOG, "Got permissions, using public directory");
                 preferences.edit().putString("cuberiteLocation", PUBLIC_DIR + "/cuberite-server").apply();
             } else {
@@ -168,4 +166,4 @@ public void onResume() {
         super.onResume();
         checkPermissions();
     }
-}
+}