Android5.0(lollipop)新特性引见（一）

今年6月的Google I/O大会上，Android L的初次见面我相信让会让很多android粉丝有些小激动和小期待，当然作为开发者的我来说，激动不言而喻，毕竟这是自08年以来改变最大的一个版本。新的设计语言(Material Design),5000多个新增api。废话不多说，今天要说的基本都是在Android5.0中很常见，也算是对自己学习的一种记录。

1.CardView

顾名思义，CardView 卡片视图，继承自framelayout，可以通过设置圆角以及阴影来展示带有像卡片一样的效果

用法：在布局声明CardView（注意：需要引入android-support-v7-cardview.jar）

<span style="font-size:14px;"><android.support.v7.widget.CardView            android:id="@+id/cardview"            android:layout_width="fill_parent"            android:layout_height="wrap_content"            android:elevation="100dp"            card_view:cardBackgroundColor="@color/cardview_initial_background"            card_view:cardCornerRadius="8dp"            android:layout_marginLeft="@dimen/margin_large"            android:layout_marginRight="@dimen/margin_large">            <TextView                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_margin="@dimen/margin_medium"                android:text="@string/cardview_contents"/></android.support.v7.widget.CardView></span>

2.RecyclerView

RecyclerView的出现可以替代ListView和GridView，它标准化了ViewHolder，之前我们在写ListView的Adapter时需要自定义ViewHolder来提升ListView速度。使用RecyclerView的时候必须要设置LayoutManager，它会通知系统以什么样的布局来展示RecyclerView，目前系统提供了2种LayoutManager，LinearLayoutManager和GridLayoutManager对应着线性和格子，当然了也可以自定义LayoutManager来满足各种需求

用法：布局文件中声明RecyclerView(注意：需要引入android-support-v7-recyclerview.jar)

<span style="font-size:14px;"><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <RadioGroup        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:gravity="center_horizontal"        android:orientation="horizontal"        android:checkedButton="@+id/linear_layout_rb">        <RadioButton android:id="@+id/linear_layout_rb"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="@string/linear_layout_manager"/>        <RadioButton android:id="@+id/grid_layout_rb"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="@string/grid_layout_manager"/>    </RadioGroup>    <android.support.v7.widget.RecyclerView        android:id="@+id/recyclerView"        android:layout_width="match_parent"        android:layout_height="match_parent"/></LinearLayout></span>

在Activity中调用如下代码

<span style="font-size:14px;">mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerView);//类似listviewmRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));//类似grdiviewmRecyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 3));mAdapter = new CustomAdapter(mDataset);// Set CustomAdapter as the adapter for RecyclerView.mRecyclerView.setAdapter(mAdapter);</span>

CustomAdapter代码如下

<span style="font-size:14px;">public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {    private static final String TAG = "CustomAdapter";    private String[] mDataSet;    /**     * Provide a reference to the type of views that you are using (custom ViewHolder)     */    public static class ViewHolder extends RecyclerView.ViewHolder {        private final TextView textView;        public ViewHolder(View v) {            super(v);            // Define click listener for the ViewHolder's View.            v.setOnClickListener(new View.OnClickListener() {                @Override                public void onClick(View v) {                }            });            textView = (TextView) v.findViewById(R.id.textView);        }        public TextView getTextView() {            return textView;        }    }    /**     * Initialize the dataset of the Adapter.     *     * @param dataSet String[] containing the data to populate views to be used by RecyclerView.     */    public CustomAdapter(String[] dataSet) {        mDataSet = dataSet;    }    // Create new views (invoked by the layout manager)    @Override    public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {        // Create a new view.        View v = LayoutInflater.from(viewGroup.getContext())                .inflate(R.layout.text_row_item, viewGroup, false);        return new ViewHolder(v);    }    // Replace the contents of a view (invoked by the layout manager)    @Override    public void onBindViewHolder(ViewHolder viewHolder, final int position) {        // Get element from your dataset at this position and replace the contents of the view        // with that element        viewHolder.getTextView().setText(mDataSet[position]);        viewHolder.getTextView().setPadding(0, position, 0, 0);    }    // Return the size of your dataset (invoked by the layout manager)    @Override    public int getItemCount() {        return mDataSet.length;    }}</span>

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