PhotoView

PhotoView aims to help produce an easily usable implementation of a zooming Android ImageView.

Dependency

Add this in your root build.gradle file (not your module build.gradle file):

allprojects {
    repositories {
        maven { url "https://jitpack.io" }
    }
}

Then, add the library to your module build.gradle

dependencies {
    implementation 'com.github.chrisbanes:PhotoView:latest.release.here'
}

Features

• Out of the box zooming, using multi-touch and double-tap.
• Scrolling, with smooth scrolling fling.
• Works perfectly when used in a scrolling parent (such as ViewPager).
• Allows the application to be notified when the displayed Matrix has changed. Useful for when you need to update your UI based on the current zoom/scroll position.
• Allows the application to be notified when the user taps on the Photo.

Usage

There is a sample provided which shows how to use the library in a more advanced way, but for completeness, here is all that is required to get PhotoView working:

<com.github.chrisbanes.photoview.PhotoView
    android:id="@+id/photo_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

PhotoView photoView = (PhotoView) findViewById(R.id.photo_view);
photoView.setImageResource(R.drawable.image);

That's it!

Issues With ViewGroups

There are some ViewGroups (ones that utilize onInterceptTouchEvent) that throw exceptions when a PhotoView is placed within them, most notably ViewPager and DrawerLayout. This is a framework issue that has not been resolved. In order to prevent this exception (which typically occurs when you zoom out), take a look at HackyDrawerLayout and you can see the solution is to simply catch the exception. Any ViewGroup which uses onInterceptTouchEvent will also need to be extended and exceptions caught. Use the HackyDrawerLayout as a template of how to do so. The basic implementation is:

public class HackyProblematicViewGroup extends ProblematicViewGroup {

    public HackyProblematicViewGroup(Context context) {
        super(context);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        try {
            return super.onInterceptTouchEvent(ev);
        } catch (IllegalArgumentException e) {
                        //uncomment if you really want to see these errors
            //e.printStackTrace();
            return false;
        }
    }
}

Usage with Fresco

Due to the complex nature of Fresco, this library does not currently support Fresco. See this project as an alternative solution.

Subsampling Support

This library aims to keep the zooming implementation simple. If you are looking for an implementation that supports subsampling, check out this project

License

Copyright 2018 Chris Banes

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.