Android 5.0+(RecycleView、CardView、Palette)
Android L 开发者预览支持库提供两个新的Widgets,RecyclerView和CardView。使用这两个Widgets可以显示复杂的Listview和卡片布局,这两个Widgets默认使用Material design。
RecyclerView
RecyclerView是一个更高级柔性版本的Listview,RecyclerView是一个能包含很多视图的容器,它能完美的处理循环和滚动。在item动态变化的Listview使用RecyclerView。
RecyclerView使用很简单,因为它提供了:
1、定位item的布局管理器
2、常见的item操作默认动画
你能够灵活的为RecyclerView自定义布局管理器和动画。
使用RecyclerView,必须使用指定一个adapter、定义一个布局管理器。创建adapter必须继承自RecyclerView.Adapter。实施的细节需要看数据类型和需要的视图。
RecyclerView widget
RecyclerView 提供了 LayoutManager,RecylerView 不负责子 View 的布局
目前提供了
LinearLayoutManager(显示垂直或水平滚动列表中的条目。)
GridLayoutManager(在一个网格显示项)
StaggeredGridLayoutManager(在交错网格显示项。)
以上如果不满足要求,那么你可以继承RecyclerView.LayoutManager
Animations
动画添加和删除项目在RecyclerView默认启用。自定义动画只需要继承RecyclerView.ItemAnimator类并使用RecyclerView.setItemAnimator()方法。
使用:
studio build.gradle 添加
dependencies { compile 'com.android.support:recyclerview-v7:22.2.0’ }
RecyclerView Demo:
1、布局文件
<!-- A RecyclerView with some commonly used attributes --> <android.support.v7.widget.RecyclerView android:id="@+id/my_recycler_view" android:scrollbars="vertical" android:layout_width="match_parent" android:layout_height="match_parent"/>
2、Activity文件
public class MyActivity extends Activity { private RecyclerView mRecyclerView; private RecyclerView.Adapter mAdapter; private RecyclerView.LayoutManager mLayoutManager; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.my_activity); mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view); // improve performance if you know that changes in content // do not change the size of the RecyclerView mRecyclerView.setHasFixedSize(true); // use a linear layout manager mLayoutManager = new LinearLayoutManager(this); mRecyclerView.setLayoutManager(mLayoutManager); // specify an adapter (see also next example) mAdapter = new MyAdapter(myDataset); mRecyclerView.setAdapter(mAdapter); } ... } To create a simple adapter: public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> { private String[] mDataset; // Provide a reference to the type of views that you are using // (custom viewholder) public static class ViewHolder extends RecyclerView.ViewHolder { public TextView mTextView; public ViewHolder(TextView v) { super(v); mTextView = v; } } // Provide a suitable constructor (depends on the kind of dataset) public MyAdapter(String[] myDataset) { mDataset = myDataset; } // Create new views (invoked by the layout manager) @Override public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { // create a new view View v = LayoutInflater.from(parent.getContext()) .inflate(R.layout.my_text_view, null); // set the view's size, margins, paddings and layout parameters ... ViewHolder vh = new ViewHolder(v); return vh; } // Replace the contents of a view (invoked by the layout manager) @Override public void onBindViewHolder(ViewHolder holder, int position) { // - get element from your dataset at this position // - replace the contents of the view with that element holder.mTextView.setText(mDataset[position]); } // Return the size of your dataset (invoked by the layout manager) @Override public int getItemCount() { return mDataset.length; } }
3、Recycler adapter
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> { private String[] mDataset; // Provide a reference to the type of views that you are using // (custom viewholder) public static class ViewHolder extends RecyclerView.ViewHolder { public TextView mTextView; public ViewHolder(TextView v) { super(v); mTextView = v; } } // Provide a suitable constructor (depends on the kind of dataset) public MyAdapter(String[] myDataset) { mDataset = myDataset; } // Create new views (invoked by the layout manager) @Override public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { // create a new view View v = LayoutInflater.from(parent.getContext()) .inflate(R.layout.my_text_view, null); // set the view's size, margins, paddings and layout parameters ... ViewHolder vh = new ViewHolder(v); return vh; } // Replace the contents of a view (invoked by the layout manager) @Override public void onBindViewHolder(ViewHolder holder, int position) { // - get element from your dataset at this position // - replace the contents of the view with that element holder.mTextView.setText(mDataset[position]); } // Return the size of your dataset (invoked by the layout manager) @Override public int getItemCount() { return mDataset.length; } }
RecyclerView 的标准化了 ViewHolder, 编写 Adapter 面向的是 ViewHoder 而不在是View 了, 复用的逻辑被封装了, 写起来更加简单。
CardView
CardView继承自FrameLayout类,可以在一个卡片布局中一致性的显示内容,卡片可以包含圆角和阴影。
可以使用android:elevation属性,创建一个阴影的卡片。
怎样指定CardView的属性:
1、使用android:cardCornerRadius属性指定圆角半径
2、使用CardView.setRadius 设置圆角半径。
3、使用 android:cardBackgroundColor属性设置卡片颜色
studio build.gradle 添加
dependencies { compile 'com.android.support:cardview-v7:22.2.0’ }
在创建布局文件中创建CardView:
<!-- A CardView that contains a TextView --> <android.support.v7.widget.CardView xmlns:card_view="http://schemas.android.com/apk/res-auto" android:id="@+id/card_view" android:layout_gravity="center" android:layout_width="200dp" android:layout_height="200dp" card_view:cardCornerRadius="4dp"> <TextView android:id="@+id/info_text" android:layout_width="match_parent" android:layout_height="match_parent" /> </android.support.v7.widget.CardView>
官方文档可参看:https://developer.android.com/intl/zh-CN/training/material/lists-cards.html
Palette
根据图片来决定标题的颜色和标题栏的背景色,这样视觉上更具有冲击力和新鲜感,而不像统一色调那样呆板。
大家想知道这个效果如何实现的吗?
学习Palette轻轻松松搞定此效果哦~!
Palette是什么?
它能让你从图像中提取突出的颜色。这个类能提取以下突出的颜色:
Vibrant(充满活力的)
Vibrant dark(充满活力的黑)
Vibrant light(充满活力的亮)
Muted(柔和的)
Muted dark(柔和的黑)
Muted lighr(柔和的亮)
如何使用?
Android Studio 要在你的项目中使用Palette类,增加下面的Gradle依赖到你的程序的模块(module)中:
dependencies { compile 'com.android.support:palette-v7:22.2.0' }
相关代码
//获取一张位图 Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.img_test); //获取一个Builder Palette.Builder from = Palette.from(bitmap); //生成颜色 Builder.generate().getter方法 这里简单演示 int color =from.generate().getDarkVibrantColor(getResources().getColor(android.R.color.transparent)); mHead.setBackgroundColor(color);
如果是Eclipse首先我们找到sdk/extras/android/support/v7/palette/libs/android-support-v7-palette.jar导入我们的工程。