5月4日，创建 BeatBox 应用，Android 开发，每日20行，第56天。

BeatBoxActivity.java

package com.example.aster.beatbox;

import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class BeatBoxActivity extends SingleFragmentActivity {
    @Override
    protected Fragment createFragment() {
        return BeatBoxFragment.newInstance();
    }
}

BeatBoxFragment.java

package com.example.aster.beatbox;

import android.databinding.DataBindingUtil;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.aster.beatbox.databinding.FragmentBeatBoxBinding;
import com.example.aster.beatbox.databinding.ListItemSoundBinding;

public class BeatBoxFragment extends Fragment {
    public static BeatBoxFragment newInstance() {
        return new BeatBoxFragment();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        FragmentBeatBoxBinding binding = DataBindingUtil
                .inflate(inflater, R.layout.fragment_beat_box, container, false);

        binding.recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 3));
        binding.recyclerView.setAdapter(new SoundAdapter());

        return binding.getRoot();
    }

    private class SoundHolder extends RecyclerView.ViewHolder {
        private ListItemSoundBinding mBinding;

        private SoundHolder(ListItemSoundBinding binding) {
            super(binding.getRoot());
            mBinding = binding;
        }
    }

    private class SoundAdapter extends RecyclerView.Adapter<SoundHolder> {
        @Override
        public SoundHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            LayoutInflater inflater = LayoutInflater.from(getActivity());
            ListItemSoundBinding binding = DataBindingUtil
                    .inflate(inflater, R.layout.list_item_sound, parent, false);
            return new SoundHolder(binding);
        }

        @Override
        public void onBindViewHolder(SoundHolder holder, int position) {

        }

        @Override
        public int getItemCount() {
            return 0;
        }
    }
}

SingleFragmentActivity.java

package com.example.aster.beatbox;


import android.os.Bundle;
import android.support.annotation.LayoutRes;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v7.app.AppCompatActivity;

public abstract class SingleFragmentActivity extends AppCompatActivity {

    protected abstract Fragment createFragment();

    @LayoutRes
    protected int getLayoutResId() {
        return R.layout.activity_fragment;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(getLayoutResId());

        FragmentManager fm = getSupportFragmentManager();
        Fragment fragment = fm.findFragmentById(R.id.fragment_container);

        if (fragment == null) {
            fragment = createFragment();
            fm.beginTransaction().add(R.id.fragment_container, fragment).commit();
        }
    }
}

avtivity_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

fragment_beat_box.xml

<?xml version="1.0" encoding="utf-8"?>
<layout
    xmlns:android="http://schemas.android.com/apk/res/android">
    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</layout>

list_item_sound.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
         xmlns:tools="http://schemas.android.com/tools">
    <Button
        android:layout_width="match_parent"
        android:layout_height="120dp"
        tools:text="Sound name"/>
</layout>