RecyclerView简单使用

       RecyclerView相比于ListView, 在回收重用时更具有灵活性, 也就是低耦合, 并且提供了扩展. 加载多个视图时, 应该多用RecyclerView代替ListView.

那么我们来看看这东西应该怎么用? 比如生成一个瀑布流的视图.

瀑布流

首先我们从一个HelloWorld写起, 看看如何构建一个RecyclerView.

1. 依赖库

Gradle配置, 添加Recycler库
compile 'com.android.support:recyclerview-v7:+'

2. 资源文件

资源文件

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

3. 代码

LayoutManager: 管理RecyclerView的结构.
Adapter: 处理每个Item的显示.
ItemDecoration: 添加每个Item的装饰.
ItemAnimator: 负责添加\移除\重排序时的动画效果.

LayoutManager\Adapter是必须, ItemDecoration\ItemAnimator是可选.

    /**     * 初始化RecyclerView     *     * @param recyclerView 主控件     */    private void initRecyclerView(RecyclerView recyclerView) {        recyclerView.setHasFixedSize(true); // 设置固定大小        initRecyclerLayoutManager(recyclerView); // 初始化布局        initRecyclerAdapter(recyclerView); // 初始化适配器        initItemDecoration(recyclerView); // 初始化装饰        initItemAnimator(recyclerView); // 初始化动画效果    }

4. LayoutManager

管理RecyclerView的布局结构.

    private void initRecyclerLayoutManager(RecyclerView recyclerView) {        // 错列网格布局        recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,                StaggeredGridLayoutManager.VERTICAL));    }

提供了多种LayoutManager, 瀑布流使用错列网格布局.

5. Adapter

适配器, 处理RecyclerView的Item事务.

    private void initRecyclerAdapter(RecyclerView recyclerView) {        mAdapter = new MyAdapter(getData());        recyclerView.setAdapter(mAdapter);    }

对于Adapter, 我们需要展开来说, 先看看类.

public class MyAdapter extends RecyclerView.Adapter<MyViewHolder> {    private List<DataModel> mDataModels;    private List<Integer> mHeights;    MyAdapter(List<DataModel> dataModels) {        if (dataModels == null) {            throw new IllegalArgumentException("DataModel must not be null");        }        mDataModels = dataModels;        mHeights = new ArrayList<>();    }    @Override    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {        View itemView = LayoutInflater.from(parent.getContext())                .inflate(R.layout.item_recycler_view, parent, false);        return new MyViewHolder(itemView);    }    @Override    public void onBindViewHolder(MyViewHolder holder, int position) {        DataModel dataModel = mDataModels.get(position);        // 随机高度, 模拟瀑布效果.        if (mHeights.size() <= position) {            mHeights.add((int) (100 + Math.random() * 300));        }        ViewGroup.LayoutParams lp = holder.getTvLabel().getLayoutParams();        lp.height = mHeights.get(position);        holder.getTvLabel().setLayoutParams(lp);        holder.getTvLabel().setText(dataModel.getLabel());        holder.getTvDateTime().setText(new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH)                .format(dataModel.getDateTime()));    }    @Override    public int getItemCount() {        return mDataModels.size();    }    public void addData(int position) {        DataModel model = new DataModel();        model.setDateTime(getBeforeDay(new Date(), position));        model.setLabel("No. " + (int) (new Random().nextDouble() * 20.0f));        mDataModels.add(position, model);        notifyItemInserted(position);    }    public void removeData(int position) {        mDataModels.remove(position);        notifyItemRemoved(position);    }    /**     * 获取日期的前一天     *     * @param date 日期     * @param i    偏离     * @return 新的日期     */    private static Date getBeforeDay(Date date, int i) {        Calendar calendar = Calendar.getInstance();        calendar.setTime(date);        calendar.add(Calendar.DAY_OF_YEAR, i * (-1));        return calendar.getTime();    }}

onCreateViewHolder创建ViewHolder.
onBindViewHolder绑定每一项数据.
getItemCount返回列表长度.

RecyclerView强制使用ViewHolder.

public class MyViewHolder extends RecyclerView.ViewHolder {    private TextView mTvLabel; // 标签    private TextView mTvDateTime; // 日期    public MyViewHolder(View itemView) {        super(itemView);        mTvLabel = (TextView) itemView.findViewById(R.id.item_text);        mTvDateTime = (TextView) itemView.findViewById(R.id.item_date);    }    public TextView getTvLabel() {        return mTvLabel;    }    public TextView getTvDateTime() {        return mTvDateTime;    }}

在onCreateViewHolder方法, 创建类; 在onBindViewHolder方法, 绑定数据.

DataModel

public class DataModel {    private String mLabel;    private Date mDateTime;    public String getLabel() {        return mLabel;    }    public void setLabel(String label) {        mLabel = label;    }    public Date getDateTime() {        return mDateTime;    }    public void setDateTime(Date dateTime) {        mDateTime = dateTime;    }}

6. ItemDecoration

项的装饰, 比如ListView中的分割线, 在本例中, 左右两条粉线.

    private void initItemDecoration(RecyclerView recyclerView) {        recyclerView.addItemDecoration(new MyItemDecoration(this));    }

ItemDecoration, 注意parent和child的使用方式.

public class MyItemDecoration extends RecyclerView.ItemDecoration {    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};    private Drawable mDivider;    public MyItemDecoration(Context context) {        final TypedArray array = context.obtainStyledAttributes(ATTRS);        mDivider = array.getDrawable(0);        array.recycle();    }    @Override    public void onDraw(Canvas c, RecyclerView parent, State state) {        drawHorizontal(c, parent);        drawVertical(c, parent);    }    // 水平线    public void drawHorizontal(Canvas c, RecyclerView parent) {        final int childCount = parent.getChildCount();        // 在每一个子控件的底部画线        for (int i = 0; i < childCount; i++) {            final View child = parent.getChildAt(i);            final int left = child.getLeft() + child.getPaddingLeft();            final int right = child.getWidth() + child.getLeft() - child.getPaddingRight();            final int top = child.getBottom() - mDivider.getIntrinsicHeight() - child.getPaddingBottom();            final int bottom = top + mDivider.getIntrinsicHeight();            mDivider.setBounds(left, top, right, bottom);            mDivider.draw(c);        }    }    // 竖直线    public void drawVertical(Canvas c, RecyclerView parent) {        final int childCount = parent.getChildCount();        // 在每一个子控件的右侧画线        for (int i = 0; i < childCount; i++) {            final View child = parent.getChildAt(i);            int right = child.getRight() - child.getPaddingRight();            int left = right - mDivider.getIntrinsicWidth();            final int top = child.getTop() + child.getPaddingTop();            final int bottom = child.getTop() + child.getHeight() - child.getPaddingBottom();            mDivider.setBounds(left, top, right, bottom);            mDivider.draw(c);        }    }    // Item之间的留白    @Override    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, State state) {        outRect.set(0, 0, mDivider.getIntrinsicWidth(), mDivider.getIntrinsicHeight());    }}

本例重写了listDivider

    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">        ...        <item name="android:listDivider">@drawable/divider_bg</item>    </style>

<?xml version="1.0" encoding="utf-8"?><shape xmlns:android="http://schemas.android.com/apk/res/android"       android:shape="rectangle">    <solid android:color="#ff00ff"/>    <size android:height="4dp"/>    <size android:width="4dp"/></shape>

7. ItemAnimator

动画效果比较复杂, 使用默认动画. 如要定制的话, 继承DefaultItemAnimator; 如设置null, 则不显示任何动画.

    private void initItemAnimator(RecyclerView recyclerView) {        recyclerView.setItemAnimator(new DefaultItemAnimator()); // 默认动画    }

8. 最终Activity

public class MainActivity extends AppCompatActivity {    private MyAdapter mAdapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);        fab.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)                        .setAction("Action", null).show();            }        });        // 初始化RecyclerView        initRecyclerView((RecyclerView) findViewById(R.id.test_recycler_view));    }    /**     * 初始化RecyclerView     *     * @param recyclerView 主控件     */    private void initRecyclerView(RecyclerView recyclerView) {        recyclerView.setHasFixedSize(true); // 设置固定大小        initRecyclerLayoutManager(recyclerView); // 初始化LayoutManager        initRecyclerAdapter(recyclerView); // 初始化Adapter        initItemDecoration(recyclerView); // 初始化边界装饰        initItemAnimator(recyclerView); // 初始化动画效果    }    /**     * 初始化RecyclerView的LayoutManager     *     * @param recyclerView 主控件     */    private void initRecyclerLayoutManager(RecyclerView recyclerView) {        // 错列网格布局        recyclerView.setLayoutManager(new StaggeredGridLayoutManager(4,                StaggeredGridLayoutManager.VERTICAL));    }    /**     * 初始化RecyclerView的Adapter     *     * @param recyclerView 主控件     */    private void initRecyclerAdapter(RecyclerView recyclerView) {        mAdapter = new MyAdapter(getData());        recyclerView.setAdapter(mAdapter);    }    /**     * 初始化RecyclerView的(ItemDecoration)项目装饰     *     * @param recyclerView 主控件     */    private void initItemDecoration(RecyclerView recyclerView) {        recyclerView.addItemDecoration(new MyItemDecoration(this));    }    /**     * 初始化RecyclerView的(ItemAnimator)项目动画     *     * @param recyclerView 主控件     */    private void initItemAnimator(RecyclerView recyclerView) {        recyclerView.setItemAnimator(new DefaultItemAnimator()); // 默认动画    }    /**     * 模拟的数据     *     * @return 数据     */    private ArrayList<DataModel> getData() {        int count = 57;        ArrayList<DataModel> data = new ArrayList<>();        for (int i = 0; i < count; i++) {            DataModel model = new DataModel();            model.setDateTime(getBeforeDay(new Date(), i));            model.setLabel("No. " + i);            data.add(model);        }        return data;    }    /**     * 获取日期的前一天     *     * @param date 日期     * @param i    偏离     * @return 新的日期     */    private static Date getBeforeDay(Date date, int i) {        Calendar calendar = Calendar.getInstance();        calendar.setTime(date);        calendar.add(Calendar.DAY_OF_YEAR, i * (-1));        return calendar.getTime();    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.menu_main, menu);        return true;    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        // Handle action bar item clicks here. The action bar will        // automatically handle clicks on the Home/Up button, so long        // as you specify a parent activity in AndroidManifest.xml.        int id = item.getItemId();        switch (item.getItemId()) {            case R.id.id_action_add:                mAdapter.addData(1);                break;            case R.id.id_action_delete:                mAdapter.removeData(1);                break;        }        //noinspection SimplifiableIfStatement        if (id == R.id.action_settings) {            return true;        }        return super.onOptionsItemSelected(item);    }}

为了测试动画, Menu额外添加两个按钮.

OK, 基本要点就是这些了.