Android下拉列表选项框及指示箭头动画

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);  }}