Android弹出选项框及指示箭头动画选择



Android弹出选项框及指示箭头动画选择

Android原生的Spinner提供了下拉列表选项框，但在一些流行的APP中，原生的Spinner似乎不太受待见，而通常会有下图所示的下拉列表选项框：
初始化状态：

点击弹出下拉选择选项框：

选中后：

注意那个指示箭头，如果把这个控件写的比较精细的话，在下拉-选择-复位过程中箭头是应该有动画旋转效果的。
这种样式的选择框实现方案很多，并且常见、常用，我自己写了一个，我写的这个例子的代码运行结果就是上图所示。
首先是MainActivity.java：

package zhangphil.app;

import android.content.Context;
import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.ListPopupWindow;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.PopupWindow;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private ListPopupWindow listPopupWindow = null;

    private ImageView arrowImageView;
    private TextView chooseText;
    private LinearLayout linearLayout;
    private SortAadapter adapter = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        linearLayout= (LinearLayout) findViewById(R.id.linearLayout);

        arrowImageView = (ImageView)findViewById(R.id.arrow);
        chooseText= (TextView) findViewById(R.id.chooseText);

        linearLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showListPopupWindow(linearLayout);
            }
        });
    }

    private class SortAadapter extends ArrayAdapter {

        private String[] strs = {"最新", "推荐", "全部", "最热"};
        private LayoutInflater inflater;
        private int res;

        public SortAadapter(Context context, int resource) {
            super(context, resource);
            inflater = LayoutInflater.from(context);
            res = resource;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null)
                convertView = inflater.inflate(res, null);

            TextView text = (TextView) convertView.findViewById(android.R.id.text1);
            text.setText(getItem(position));
            text.setTextColor(Color.WHITE);
            text.setTextSize(10);

            convertView.setBackgroundColor(Color.RED);

            return convertView;
        }

        @Override
        public String getItem(int position) {
            return strs[position];
        }

        @Override
        public int getCount() {
            return strs.length;
        }
    }

    public void showListPopupWindow(View view) {
        if (listPopupWindow == null)
            listPopupWindow = new ListPopupWindow(this);

        if (adapter == null) {
            adapter = new SortAadapter(this, android.R.layout.simple_list_item_1);

            // ListView适配器
            listPopupWindow.setAdapter(adapter);

            // 选择item的监听事件
            listPopupWindow.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int pos, long id) {
                    Toast.makeText(getApplicationContext(), adapter.getItem(pos), Toast.LENGTH_SHORT).show();
                    chooseText.setText(adapter.getItem(pos));

                    listPopupWindow.dismiss();
                }
            });

            listPopupWindow.setOnDismissListener(new PopupWindow.OnDismissListener() {
                @Override
                public void onDismiss() {
                    //旋转0度是复位ImageView
                    arrowImageView.animate().setDuration(500).rotation(0).start();
                }
            });
        }

        // ListPopupWindow的锚,弹出框的位置是相对当前View的位置
        listPopupWindow.setAnchorView(view);

        listPopupWindow.setVerticalOffset(dip2px(this,5));

        // 对话框的宽高
        listPopupWindow.setWidth(view.getWidth());

        listPopupWindow.setModal(true);

        listPopupWindow.show();
        arrowImageView.animate().setDuration(500).rotation(180).start();
    }

    public static int dip2px(Context context, float dipValue) {
        float sDensity = context.getResources().getDisplayMetrics().density;
        final float scale = sDensity;
        return (int) (dipValue * scale + 0.5f);
    }
}

布局文件：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:id="@+id/linearLayout"
        android:layout_width="wrap_content"
        android:layout_height="24dp"
        android:background="@drawable/round_corner_line_radius_3dp"
        android:orientation="horizontal"
        android:paddingLeft="8dp"
        android:paddingRight="8dp"
        android:layout_centerInParent="true">

        <TextView
            android:id="@+id/chooseText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:text="分类"
            android:textColor="@android:color/holo_orange_dark"
            android:textSize="12dp" />

        <ImageView
            android:id="@+id/arrow"
            android:layout_width="14dp"
            android:layout_height="14dp"
            android:layout_gravity="center_vertical"
            android:layout_marginLeft="8dp"
            android:src="@drawable/icon" />

    </LinearLayout>

</RelativeLayout>

LinearLayout的背景需要一个圆角背景res/drawable/round_corner_line_radius_3dp.xml：

<?xml version="1.0" encoding="UTF-8"?>
<shape
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape= "rectangle">

    <stroke android:color="@android:color/holo_orange_dark"
        android:width="2px"/>

    <solid  android:color="@android:color/transparent"/>
    <corners android:radius="3dp" />

</shape>  

箭头icon.png：

附：
1，《Android第三方开源下拉框：NiceSpinner》链接：http://blog.csdn.net/zhangphil/article/details/51554001