5月7日，绑定数据，Android 开发，每日20行，第59天。

BeatBox.java

package com.example.aster.beatbox;

import android.content.Context;
import android.content.res.AssetManager;
import android.util.Log;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class BeatBox {
    private static final String TAG = "BeatBox";

    private static final String SOUNDS_FOLDER = "sample_sounds";

    private AssetManager mAssets;
    private List<Sound> mSounds = new ArrayList<>();

    public BeatBox(Context context) {
        mAssets = context.getAssets();
        loadSounds();
    }

    private void loadSounds() {
        String[] soundNames;
        try {
            soundNames = mAssets.list(SOUNDS_FOLDER);
            Log.i(TAG, "Found " + soundNames.length + " sounds");
        } catch (IOException ioe) {
            Log.e(TAG, "Could not list assets", ioe);
            return;
        }

        for (String filename : soundNames) {
            String assetPath = SOUNDS_FOLDER + "/" + filename;
            Sound sound = new Sound(assetPath);
            mSounds.add(sound);
        }
    }

    public List<Sound> getSounds() {
        return mSounds;
    }
}

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;

import java.util.List;

public class BeatBoxFragment extends Fragment {

    private BeatBox mBeatBox;

    public static BeatBoxFragment newInstance() {
        return new BeatBoxFragment();
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mBeatBox = new BeatBox(getActivity());
    }

    @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(mBeatBox.getSounds()));

        return binding.getRoot();
    }

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

        private SoundHolder(ListItemSoundBinding binding) {
            super(binding.getRoot());
            mBinding = binding;
            mBinding.setViewModel(new SoundViewModel(mBeatBox));
        }

        public void bind(Sound sound) {
            mBinding.getViewModel().setSound(sound);
            mBinding.executePendingBindings();
        }
    }

    private class SoundAdapter extends RecyclerView.Adapter<SoundHolder> {
        private List<Sound> mSounds;

        public SoundAdapter(List<Sound> sounds) {
            mSounds = sounds;
        }

        @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) {
            Sound sound = mSounds.get(position);
            holder.bind(sound);
        }

        @Override
        public int getItemCount() {
            return mSounds.size();
        }
    }
}

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();
        }
    }
}

Sound.java

package com.example.aster.beatbox;

public class Sound {
    private String mAssetPath;
    private String mName;

    public Sound(String assetPath) {
        mAssetPath = assetPath;
        String[] components = assetPath.split("/");
        String filename = components[components.length - 1];
        mName = filename.replace(".wav", "");
    }

    public String getAssetPath() {
        return mAssetPath;
    }

    public String getName() {
        return mName;
    }
}

SoundViewModel.java

package com.example.aster.beatbox;

import android.databinding.BaseObservable;
import android.databinding.Bindable;

public class SoundViewModel extends BaseObservable {
    private Sound mSound;
    private BeatBox mBeatBox;

    public SoundViewModel(BeatBox beatBox) {
        mBeatBox = beatBox;
    }

    @Bindable
    public String getTitle() {
        return mSound.getName();
    }

    public Sound getSound() {
        return mSound;
    }

    public void setSound(Sound sound) {
        mSound = sound;
        notifyChange();
    }
}

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">
    <data>
        <variable
            name="viewModel"
            type="com.example.aster.beatbox.SoundViewModel"/>
    </data>
    <Button
        android:layout_width="match_parent"
        android:layout_height="120dp"
        android:text="@{viewModel.title}"
        tools:text="Sound name"/>
</layout>