Android ListView 刪除動畫

　　Android 的ListView在刪除條目時，被刪除的條目直接消失，比較生硬，在此實現一下刪除動畫，大家一起探討；主要實現原理即是通過Animator來實現被刪除條目的動畫效果，然后在動畫結束時通過Adapter先刪除要刪除的條目,然后在遍歷所有的ListView的child並恢復被Animator改變的屬性；

　　以下是Activity代碼；主界面只有一個ListView，通過Adapter提供數據，界面如下，當點擊某一項時，將播放動畫，並刪除點擊的項目；

package app.com.listviewdeleteanimation;

import android.animation.Animator;
import android.animation.AnimatorSet;
import android.animation.ObjectAnimator;
import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;


public class MainActivity extends ActionBarActivity implements ListView.OnItemClickListener{
    /**
      *  Adapter 提供數據，提供remove方法，可以刪除指定的條目；
      *
      **/
    public class Adapter extends BaseAdapter{
        private Context mContext;
        private ArrayList<String> mItems;

        public Adapter(Context c,String [] data) {
            super();

            mContext = c;

            mItems = new ArrayList<String>();
            for (String item : data){
                mItems.add(item);
            }
        }

        public void remove(int position){
            if(position < mItems.size()){
                mItems.remove(position);
            }

            notifyDataSetChanged();
        }

        @Override
        public int getCount() {
            return mItems.size();
        }

        @Override
        public int getItemViewType(int position) {
            // current menu type
            return position;
        }

        @Override
        public String getItem(int position) {
            return mItems.get(position);
        }

        @Override
        public boolean isEmpty() {
            return mItems.isEmpty();
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            if (convertView == null) {
                convertView = LayoutInflater.from(mContext).inflate(
                        android.R.layout.simple_list_item_1, parent, false);
            }

            TextView tv = (TextView) convertView;

            tv.setText(getItem(position));

            return convertView;
        }
    }

    private ListView mListView;
    private Adapter mAdapter;

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

        mListView = (ListView)findViewById(R.id.listView);

        mAdapter = new Adapter(this, new String[] {"1","2","3","4","5","6","7",});

        mListView.setAdapter(mAdapter);
        mListView.setOnItemClickListener(this);
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, final int position, long id){
        // 獲得ListView第一個View的position
        int firstVisiblePosition = mListView.getFirstVisiblePosition();
        // 存儲所有的Animator，利用AnimatorSet直接播放
        ArrayList<Animator> animators = new ArrayList<Animator>();

　　　　 // 獲得要刪除的View
        View itemToDelete = mListView.getChildAt(position - firstVisiblePosition);

        int viewHeight = itemToDelete.getHeight();
        int dividerHeight = mListView.getDividerHeight();

        ObjectAnimator hideAnimator = ObjectAnimator.ofFloat(itemToDelete, "alpha",1f, 0f);

        animators.add(hideAnimator);

        int delay = 0;
        int firstViewToMove = position + 1;
        for (int i=firstViewToMove;i < mListView.getChildCount(); ++i){
            View viewToMove = mListView.getChildAt(i);

            ObjectAnimator moveAnimator = ObjectAnimator.ofFloat(viewToMove, "translationY", 0, -dividerHeight-viewHeight);
            moveAnimator.setInterpolator(new AccelerateDecelerateInterpolator());
            moveAnimator.setStartDelay(delay);

            delay += 100;

            animators.add(moveAnimator);
        }

        AnimatorSet set = new AnimatorSet();
        set.addListener(new Animator.AnimatorListener() {
            @Override
            public void onAnimationStart(Animator animation) {}
            @Override
            public void onAnimationEnd(Animator animation) {
                mAdapter.remove(position);
                // 動畫結束后，恢復ListView所有子View的屬性
                for (int i=0;i<mListView.getChildCount();++i){
                    View v = mListView.getChildAt(i);

                    v.setAlpha(1f);
                    v.setTranslationY(0);
                }

            }
            @Override
            public void onAnimationCancel(Animator animation) {}
            @Override
            public void onAnimationRepeat(Animator animation) {}
        });

        set.playTogether(animators);
        set.start();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}