《Android 基础（四）》 RecyclerView

public class MainActivity extends AppCompatActivity {
    @Bind(R.id.rv_content)
    RecyclerView rvContent;
    @Bind(R.id.fab_add)
    FloatingActionButton fabAdd;
    @Bind(R.id.fab_del)
    FloatingActionButton fabDel;
    @Bind(R.id.root_layout)
    LinearLayout rootLayout;

    private LayoutManager mLayoutManager; //LayoutManager
    private RVAdapter recyclerAdapter;    //RecyclerView对应的Adapter
    private ArrayList<String> mContentList; //内容list这里只是使用了字符串，当然也可以替换成其他的JavaBean类
    private Random mRandom = new Random(); //用于产生随机字符串
    private int mSum = 50; //初始化子项数目

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);  //ButterKnife注入，减少代码负担

        mContentList = new ArrayList<String>();
        for (int i = 0; i < mSum; i++) {
            mContentList.add(getRandomString());
        } //随机生成数据
        recyclerAdapter = new RVAdapter(mContentList);
        mLayoutManager = new StaggeredGridLayoutManager(3, LinearLayoutManager.VERTICAL); //3列纵向
        rvContent.setAdapter(recyclerAdapter);
        rvContent.setLayoutManager(mLayoutManager);
        rvContent.setItemAnimator(new DefaultItemAnimator()); //设置动画效果，可以看下上面的效果图，动画效果还是比较明显的
    }

    @OnClick({R.id.fab_add, R.id.fab_del})
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.fab_add:
                recyclerAdapter.addData(1); //加一个
                makeSnackBar(rootLayout, "添加一个 :)", null, null);//显示一个Snackbar
                break;
            case R.id.fab_del:
                recyclerAdapter.removeData(1); //去掉一个
                makeSnakeBar(rootLayout, "删除一个 :(", null, null); //显示一个Snackbar
                break;
            default:
                break;
        }
    }
    //用于产生随机字符串的方法
    public String getRandomString() {
        String src = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
        StringBuilder dst = new StringBuilder(4);
        for (int i = 0; i < 4; i++) {
            dst.append(src.charAt(mRandom.nextInt(62)));
        }
        return dst.toString();
    }

    //构建一个Snackbar并显示出来
    private void makeSnackBar(View view, String message, String buttonText, View.OnClickListener onClickListener) {
        Snackbar.make(view, message, Snackbar.LENGTH_SHORT)
                .setAction(buttonText, onClickListener)
                .show();
    }
}

public class RVAdapter extends RecyclerView.Adapter<RVAdapter.MyViewHolder>{
    ArrayList<String> mContentList;
    Random mRandom = new Random();
    //ViewHolder继承自RecyclerView.ViewHolder  子View拿到方便后面访问
    public class MyViewHolder  extends RecyclerView.ViewHolder {
        TextView textView;
        CardView cardView;
        public MyViewHolder(View itemView) {
            super(itemView);
            textView = (TextView) itemView.findViewById(R.id.tv_name);
            cardView = (CardView) itemView.findViewById(R.id.cv_bg);
        }
    }
    public RVAdapter(ArrayList<String> mContentList) {
        this.mContentList = mContentList;
    }
    //创建ViewHolder，由于RecyclerView.ViewHolder是一个抽象类无法实例化，所以必须实现一个子类才能使用，这里自己尝试的过程中走了一些弯路，注意inflate最后一个参数设置成false不然可能会出现crash
    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recycler_item, parent, false);
        return new MyViewHolder(view);
    }

    //onBindView  用于设置需要显示的View中的内容和一些属性值
    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        holder.cardView.setCardBackgroundColor(getRandomColor());
        holder.textView.setText(mContentList.get(position));
        holder.itemView.getLayoutParams().height = getRandomHeight(200,400);//产生随机高度，看上去像瀑布
    }

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

    //产生随机颜色
    private int getRandomColor() {
        return (0xff000000|mRandom.nextInt(0x00ffffff));
    }
    //产生随机高度
    private int getRandomHeight(int min , int max) {
        return (mRandom.nextInt(max - min) + min );
    }
    //添加一个子项
    public void addData(int position) {
        mContentList.add(position, "Insert One");
        notifyItemInserted(position);//不调用这个没有动画效果
    }
    //删除一个子项
    public void removeData(int position) {
        mContentList.remove(position);
        notifyItemRemoved(position);//不调用这个没有动画效果
    }
}

mLayoutManager = new LinearLayoutManager(this);
rvContent.addItemDecoration(new DividerItemDecoration(this, StaggeredGridLayoutManager.VERTICAL));

mLayoutManager = new GridLayoutManager(this, 3);//3列
rvContent.addItemDecoration(new DividerItemDecoration(this, StaggeredGridLayoutManager.VERTICAL));

mLayoutManager = new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.HORIZONTAL);

RVAdapter.java中onBindViewHolder
holder.itemView.getLayoutParams().width = getRandomHeight(200,400);

public class DividerItemDecoration extends RecyclerView.ItemDecoration {

    private static final int[] ATTRS = new int[]{
            android.R.attr.listDivider
    };
    public static final int HORIZONTAL_LIST = LinearLayoutManager.HORIZONTAL;
    public static final int VERTICAL_LIST = LinearLayoutManager.VERTICAL;
    private Drawable mDivider;
    private int mOrientation;

    public DividerItemDecoration(Context context, int orientation) {
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        a.recycle();
        setOrientation(orientation);
    }


    public void setOrientation(int orientation) {
        if (orientation != HORIZONTAL_LIST && orientation != VERTICAL_LIST) {
            throw new IllegalArgumentException("invalid orientation");
        }
        mOrientation = orientation;
    }


    @Override
    public void onDraw(Canvas c, RecyclerView parent) {
        if (mOrientation == VERTICAL_LIST) {
            drawVertical(c, parent);
        } else {
            drawHorizontal(c, parent);
        }

    }

    public void drawVertical(Canvas c, RecyclerView parent) {
        final int left = parent.getPaddingLeft();
        final int right = parent.getWidth() - parent.getPaddingRight();

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int top = child.getBottom() + params.bottomMargin +
                    Math.round(ViewCompat.getTranslationY(child));
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }


    public void drawHorizontal(Canvas c, RecyclerView parent) {
        final int top = parent.getPaddingTop();
        final int bottom = parent.getHeight() - parent.getPaddingBottom();

        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                    .getLayoutParams();
            final int left = child.getRight() + params.rightMargin +
                    Math.round(ViewCompat.getTranslationX(child));
            final int right = left + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, int itemPosition, RecyclerView parent) {
        if (mOrientation == VERTICAL_LIST) {
            outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
        } else {
            outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
        }
    }
}