Defrag

Defrag is a simple to use library that allows for Fragment-free Android applications. Why avoid fragments? I couldn't explain it any better than square's article: https://corner.squareup.com/2014/10/advocating-against-android-fragments.html

Download

Defrag is available in the jCenter repository:

dependencies {
  compile 'com.solera.defrag:defrag:0.9.0'
}

Usage

Add ViewStack to your layout and push/pop your views to it. View state are saved and restored as the stack changes, and smooth traversal animations happen automatically. In your Activity's onCreate:

final ViewStack viewStack = (ViewStack) findViewById(R.id.viewstack);
if (savedInstanceState == null) {
  //no previous state, so push the first view
  viewStack.push(R.layout.first_layout);
}

To push a new view to the foreground:

viewStack.push(R.layout.second_layout);

Or to go back:

viewStack.pop();

Or to replace the top:

viewStack.replace(R.layout.third_layout);

is easy!

Custom transition animations

It's easy to create custom transition animations, all you have to do is implement HasTraversalAnimation:

public class ViewWithTraversalAnimation extends FrameLayout implements HasTraversalAnimation {
...
    /**
   * @param fromView the view that we are traversing from.
   * @return an animation that will be run for the traversal, or null if the default should be run.
   */
  @Override @Nullable Animator createAnimation(@NonNull View fromView) {
    final AnimatorSet set = new AnimatorSet();
    
    final AnimatorSet exitAnim = new AnimatorSet();
    exitAnim.setInterpolator(new AccelerateInterpolator());
    exitAnim.play(ObjectAnimator.ofFloat(fromView, View.ALPHA, 0.0f))
        .with(ObjectAnimator.ofFloat(fromView, View.TRANSLATION_X, 0f, -200));

    setAlpha(0f);
    final AnimatorSet enterAnim = new AnimatorSet();
    enterAnim.setInterpolator(new DecelerateInterpolator());
    enterAnim.setStartDelay(300);
    enterAnim.play(ObjectAnimator.ofFloat(this, View.ALPHA, 0.0f, 1.0f))
        .with(ObjectAnimator.ofFloat(this, View.TRANSLATION_X, 100f, 0));

    set.play(exitAnim).with(enterAnim);
    
    return set;
  }
}

Start parameters and results

You can push a view with start parameters, these parameters will be saved if the activity is re-created:

  viewStack.pushWithParameter(R.layout.layout_hello,"World!");

Any Class that implements Serializable can be used, if you need something more complex, use a Bundle:

  final Bundle parameters = ...
  viewStack.pushWithParameters(R.layout.layout_hello,parameters);

then, when the view is inflated & created:

  final String parameters = viewStack.getParameter(this);
  //or a bundle:
  final Bundle parameterBundle  = viewStack.getParameters(this);
  textView.setText("Hullo "+parameters);
  //save the parameters to something different, this is a way to save state when recreating the stack:
  viewStack.setParameter(this,"Android!");

Likewise, you can return information to another view by calling setResult, this is equivalent to the startActivityForResult & onActivityResult methods:

  //finished with this view, pop back a particular view, with a result:
  viewStack.popWithResult(R.layout.first_layout,"Result");

Retrieving the result is similar to getting Parameters (and is persisted when the Activity is recreated):

  final String result = viewStack.getResult();

Take a look at the sample app for an example implementation.

Thanks to

The inspiration of this library was from Square's article on Fragments, and from their library Flow (https://github.com/square/flow).

License:

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.