README.md

Readme

This is an annotation processor for making Fragment construction type safe, and making saving state easier.

There are two annotations provided, @Argument for fragment arguments and @Frozen for saving and restoring state in onSaveInstanceState.

@Argument

Construction of Fragments can be painful if you need to pass arguments to construct them. The problem is that you need to construct a Bundle, put values in it by key and set it on the Fragment instance. This is not only cumbersome to do, but also not very type safe.

The @Argument annotation helps by generating a builder class for your Fragment. For example:

:::java
public class TestFragment extends Fragment {
    @Argument
    boolean mCheese;
    @Argument(required=false)
    int mTotal;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);        
        // Use the generated builder class to "inject" the arguments on creation
        // you can use a static import to shorten this line to injectArguments(this)
        TestFragmentBuilder.injectArguments(this);
    }
}

To construct this fragment you'd do something like this:

:::java
TestFragment fragment = new Test2FragmentBuilder(false).build();
TestFragment fragment2 = new Test2FragmentBuilder(false).total(10).build();

Required arguments must be passed into the builder constructor, while non-required arguments have a builder method.

@Frozen

The @Frozen annotation aids with saving Activity or Fragment state in onSaveInstanceState and restoring it in onCreate or other places. A class State is generated for this purpose. Here's an example:

:::java
package test;

import static test.MyActivityState.restoreInstanceState;
import static test.MyActivityState.saveInstanceState;
import android.app.Activity;
import android.os.Bundle;

import com.neenbedankt.bundles.annotation.Frozen;

public class MyActivity extends Activity {
    @Frozen
    String mName;
    @Frozen
    boolean mCheeseActive;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        restoreInstanceState(this, savedInstanceState);
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        saveInstanceState(this, outState);
    }
}

Using

Either build from source using Gradle, or download the jar