android recyclerview+GalleryLayoutManager 实现广告画廊效果

相信大家平常在项目中遇到过画廊的效果，网上也有多种方式，类似viewPager、recyclerview等等方式实现，今天推荐一个三方库GalleryLayoutManager，便于快速实现，以解燃眉之急。

依赖

gradle依赖

compile 'github.hellocsl:GalleryLayoutManager:1.0.6'

实现

布局文件

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

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

recyclerView设置的adapter

private class Adapter extends RecyclerView.Adapter<RecyclerHolder> {

    private Context context;

    private Adapter(Context context) {
        this.context = context;
    }

    @Override
    public RecyclerHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.item_view, null);
        //自定义view的宽度，控制一屏显示个数
        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
        int width = context.getResources().getDisplayMetrics().widthPixels;
        params.width = width / 3;
        view.setLayoutParams(params);
        return new RecyclerHolder(view);
    }

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

    @Override
    public int getItemCount() {
        return 10;
    }
}

private class RecyclerHolder extends RecyclerView.ViewHolder {
    private View view;

    public RecyclerHolder(View itemView) {
        super(itemView);
        view = itemView;
    }

    public View getView() {
        return view;
    }
}

每个item简单的放置一个布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:orientation="vertical">

    <ImageView
        android:layout_width="100dp"
        android:layout_height="wrap_content"
        android:src="@mipmap/dota" />

</LinearLayout>

采用第三方的GalleryLayoutManager 与 recyclerView绑定，设置为横向滑动布局

GalleryLayoutManager manager = new GalleryLayoutManager(GalleryLayoutManager.HORIZONTAL);
manager.attach(recycler);
//设置滑动缩放效果
manager.setItemTransformer(new Transformer());
recycler.setAdapter(new Adapter(this));

缩放效果处理

//滑动过程中的缩放
public class Transformer implements GalleryLayoutManager.ItemTransformer {
    @Override
    public void transformItem(GalleryLayoutManager layoutManager, View item, float fraction) {
        //以圆心进行缩放
        item.setPivotX(item.getWidth() / 2.0f);
        item.setPivotY(item.getHeight() / 2.0f);
        float scale = 1 - 0.3f * Math.abs(fraction);
        item.setScaleX(scale);
        item.setScaleY(scale);
    }
}

可以自定义RecyclerView里每项view的宽度，控制一屏显示效果，adapter的onCreateViewHolder里操作

@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(context).inflate(R.layout.item_view, null);
    //自定义view的宽度，控制一屏显示个数
    LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
    int width = context.getResources().getDisplayMetrics().widthPixels;
    params.width = width / 3;
    view.setLayoutParams(params);
    return new RecyclerHolder(view);
}

滑动监听

滑动监听最终停止的位置

manager.setOnItemSelectedListener(new GalleryLayoutManager.OnItemSelectedListener() {
    @Override
    public void onItemSelected(RecyclerView recyclerView, View item, int position) {
        //滑动到某一项的position
    }
});

同时支持点击每一项滑动切换，adapter的onBindViewHolder方法里

@Override
public void onBindViewHolder(RecyclerHolder holder, final int position) {
    holder.getView().setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            recycler.smoothScrollToPosition(position);
        }
    });
}

至此，一个简单的画廊效果实现，如果你项目正好需要这个，而我正好有。
当然这里只是简单介绍了画廊效果的实现，这个库还提供支持上下滑动的效果，贴上github地址 https://github.com/BCsl/GalleryLayoutManager， 便于大家进一步研究
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