fix #272 #267 #262, over.

Author: 郑梓斌

example/src/main/assets/img_0

@@ -37,6 +37,7 @@
 
 public class MainActivity extends AppCompatActivity {
   private static final String TAG = "Luban";
+  private static final int range = 3;
 
   private List<ImageBean> mImageList = new ArrayList<>();
   private ImageAdapter mAdapter = new ImageAdapter(mImageList);
@@ -93,7 +94,7 @@ public boolean onOptionsItemSelected(MenuItem item) {
   private List<File> assetsToFiles() {
     final List<File> files = new ArrayList<>();
 
-    for (int i = 0; i < 3; i++) {
+    for (int i = 0; i < range; i++) {
       try {
         InputStream is = getResources().getAssets().open("img_" + i);
         File file = new File(getExternalFilesDir(null), "test_" + i);
@@ -122,7 +123,7 @@ private List<Uri> assetsToUri() {
     final List<Uri> uris = new ArrayList<>();
     final List<File> files = assetsToFiles();
 
-    for (int i = 0; i < 2; i++) {
+    for (int i = 0; i < range; i++) {
       Uri uri = Uri.fromFile(files.get(i));
       uris.add(uri);
     }

example/src/main/assets/img_1

@@ -157,19 +157,10 @@ && pack(jpeg, offset + 6, 2, false) == 0) {
 
   String extSuffix(InputStreamProvider input) {
     try {
-      Bitmap bitmap = BitmapFactory.decodeStream(input.open(), null, new BitmapFactory.Options());
-      String suffix = TextUtils.isEmpty(input.getPath()) ? "" :
-          input.getPath().substring(input.getPath().lastIndexOf("."), input.getPath().length());
-
-      if (bitmap.hasAlpha()) {
-        return PNG;
-      } else if (TextUtils.isEmpty(suffix)) {
-        return JPG;
-      } else if (!format.contains(suffix)) {
-        return JPG;
-      }
-
-      return suffix;
+      BitmapFactory.Options options = new BitmapFactory.Options();
+      options.inJustDecodeBounds = true;
+      BitmapFactory.decodeStream(input.open(), null, options);
+      return options.outMimeType.replace("image/", ".");
     } catch (Exception e) {
       return JPG;
     }