Android5.0(lollipop)新特性介绍（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>

在Activity中通过调用mCardView.setRadius(progress)与mCardView.setElevation(progress)方法来分别设置CardView的圆角和阴影。

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listview
mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
//类似grdiview
mRecyclerView.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>