【Android高级】全部自己实现的下拉刷新功能

        很早之前就接触过下拉刷新的第三方库，貌似大一就用过了，当时也只是用用。

        后来很久没有用了，上次用的使用的时候，顺便把源码也看了看，当时也只是看看。

        现在时间还算充裕，始终感觉有口气憋着，于是打算靠自己把下拉刷新的功能也出来，这次真要写写了。

        写的过程其实不太算顺利，开始把问题想复杂了，嵌套了好多view，导致后面的触摸事件搞得特别复杂，虽然最后能下拉刷出来，但那个效果真的不能再烂了。把我搞得心累的。。。

        缓了缓之后，我尝试了一种新思路，直接继承listView，把下拉头放在ListView的headView里面，在开发过程中也遇到不少问题，但想尽一切办法还是基本搞出来了。在项目开发过程中主要遇到下面三个问题：

（1）初始化的适合就要把adpter传进去，不然动画和headView加载会失效。

（2）headView通过headView.setPadding(0, (int) -headHeight, 0, 0);即padding控制滑动位置。

（3）要自定义函数获取listView滚动的高度

  public int getMyScrollY() {
 

   View c = this.getChildAt(0);
    

   if (c == null) {
    return 0;
    }
   

   int firstVisiblePosition = this.getFirstVisiblePosition();
  

   int top = c.getTop();
    

    return -top + firstVisiblePosition * c.getHeight();


  }

下面是源码部分：

【自定义的CustomListView】

public class CustomListView extends ListView {
enum State {
None, Load, Over, Refresh_Down, List_Down, List_Up
}

public interface CustomPullRereshListener {
public void pullUpToRrefreshing();

}

public void setCustomPullRereshListener(CustomPullRereshListener customPullRereshListener) {
this.customPullRereshListener = customPullRereshListener;
}

CustomPullRereshListener customPullRereshListener;

View headView;

float headHeight;
Handler handler;

ImageView rotateImageView;
TextView rotateTextView;

public CustomListView(Context context, AttributeSet attrs) {
super(context, attrs);

headView = (View) LayoutInflater.from(context).inflate(R.layout.head_lay, this, false);
headView.measure(0, 0);

Log.i("tag", headView.getMeasuredHeight() + "--" + headView.getMeasuredWidth() + "--" + headView.getX() + "--" + headView.getY());
rotateImageView = (ImageView) headView.findViewById(R.id.rotate_img);
rotateTextView = (TextView) headView.findViewById(R.id.rotate_tv);

headHeight = headView.getMeasuredHeight();

handler = new Handler();

addHeaderView(headView, null, false);

headView.setPadding(0, (int) -headHeight, 0, 0);
headView.invalidate();
this.setHeaderDividersEnabled(false);
}

public void initAdapter(BaseAdapter adapter) {
setAdapter(adapter);

}

float current_Y;
float bef_Y;
float start_Y;
float index;

State nowState;

@Override
public void onWindowFocusChanged(boolean hasWindowFocus) {
super.onWindowFocusChanged(hasWindowFocus);
}

float radio;

public int getMyScrollY() {
View c = this.getChildAt(0);
if (c == null) {
return 0;
}
int firstVisiblePosition = this.getFirstVisiblePosition();
int top = c.getTop();
return -top + firstVisiblePosition * c.getHeight();
}

@Override
public boolean onTouchEvent(MotionEvent event) {

switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:

current_Y = event.getY();
bef_Y = current_Y;
start_Y = current_Y;
radio = 1;
nowState = State.None;
stateChange(nowState);
return true;
case MotionEvent.ACTION_MOVE:

current_Y = event.getY();
index = current_Y - bef_Y;

if (index > 20 && index < 100) {
if (getMyScrollY() == 0) {
nowState = State.Refresh_Down;
}
}

if (nowState == State.Refresh_Down) {
radio = Math.abs(current_Y - start_Y) / 300 + 1;
scrollBy(0, -(int) (index / (radio)));
headView.setPadding(0, (int) (index / radio), 0, 0);
bef_Y = current_Y;
return true;
}

break;

case MotionEvent.ACTION_UP:

if (nowState == State.Refresh_Down) {
nowState = State.Load;

stateChange(nowState);

if (customPullRereshListener != null) {
customPullRereshListener.pullUpToRrefreshing();
} else {
refreshComplete();
}
return true;
}

break;
}

return super.onTouchEvent(event);

}

public void refreshComplete() {
handler.postDelayed(new Runnable() {
@Override
public void run() {

if (nowState == State.Load) {
nowState = State.Over;
stateChange(nowState);
scrollTo(0, 0);
headView.setPadding(0, (int) -headHeight, 0, 0);

}

}
}, 1000);
}

private void stateChange(State state) {

switch (state) {
case Load:

rotateTextView.setText("正在加载......");
RotateAnimation rotateAnimation = new RotateAnimation(0, 360, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
rotateAnimation.setDuration(360);
rotateAnimation.setFillAfter(false);
rotateAnimation.setRepeatCount(Animation.INFINITE);
rotateAnimation.setRepeatMode(Animation.RESTART);
rotateAnimation.setInterpolator(new LinearInterpolator());//不停顿
rotateImageView.setAnimation(rotateAnimation);
rotateAnimation.start();
rotateImageView.invalidate();
break;
case Over:

rotateImageView.getAnimation().cancel();
rotateTextView.setText("加载完毕");

break;
case None:
rotateTextView.setText("下拉刷新");
break;

}

}

}


【在Activity中使用】

public class MainAct extends Activity {

HttpExecutor httpExecutor;
String urlsArray[] = {
"http://cdn.duitang.com/uploads/item/201207/18/20120718215150_QyFQZ.jpeg",
"http://p4.qqgexing.com/shaitu/2012/07/04/15/4ff3f5c978a47.jpg",
"http://pic28.nipic.com/20130425/11851724_233351407130_2.jpg",
"http://pic20.nipic.com/20120502/9783151_111254241000_2.jpg",
"http://imglf1.ph.126.net/EeL25lsX85z6c96AwavoTA==/6598268234330966851.jpg",
"http://img2.duitang.com/uploads/item/201302/20/20130220145320_esamB.thumb.600_0.jpeg",
"http://img.hb.aicdn.com/13f25a84dccc639761eefb17f24c9e6e5a465589194d2-KfLLqS_fw580",//7

"http://pica.nipic.com/2008-01-19/2008119114919476_2.jpg",
"http://pic10.nipic.com/20101104/2318721_221323551000_2.jpg",
"http://pic33.nipic.com/20130928/4420504_005335593000_2.jpg",
"http://pic.nipic.com/2008-06-26/20086261061382_2.jpg",
"http://pic4.nipic.com/20090724/3058848_003738705_2.jpg",
"http://pic28.nipic.com/20130407/10942662_171131527000_2.jpg",
"http://pic10.nipic.com/20101022/5974539_102012063985_2.jpg",//7

"http://pic1a.nipic.com/2008-09-03/20089314315569_2.jpg",
"http://pic31.nipic.com/20130703/4383073_091911237144_2.jpg",
"http://pic23.nipic.com/20120831/10705080_091651720189_2.jpg",
"http://pic27.nipic.com/20130310/10753400_160550558169_2.jpg",
"http://pic25.nipic.com/20121108/10222425_165949609136_2.jpg",
"http://img3.redocn.com/20140313/20140312_ac2c4a0c509fcf1f6a16pMm5444bqKJa.jpg",
"http://pica.nipic.com/2007-10-12/20071012214217571_2.jpg",
"http://pic.58pic.com/58pic/13/85/97/97g58PICJtn_1024.jpg",
"http://pic12.nipic.com/20110125/5860366_200110540150_2.jpg"};//9

ArrayList<String> urls = new ArrayList<String>();

CustomListView pullToRefreshListView;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.new_cutom_view_lay);
httpExecutor = new HttpExecutor(new Handler());
pullToRefreshListView = (CustomListView) findViewById(R.id.container_lay);

final MyAdapter myAdapter = new MyAdapter();

pullToRefreshListView.initAdapter(myAdapter);

pullToRefreshListView.setCustomPullRereshListener(new CustomListView.CustomPullRereshListener() {
@Override
public void pullUpToRrefreshing() {
loadDataToList();
myAdapter.notifyDataSetChanged();

pullToRefreshListView.refreshComplete();
}
});

pullToRefreshListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

Log.i("tag", "pos:" + position);
}
});

}

public void loadDataToList() {
for (int i = 0; i < urlsArray.length; i++) {
urls.add(urlsArray[i]);
}
}

class MyAdapter extends BaseAdapter {
@Override
public int getCount() {
return urls.size();
}

@Override
public Object getItem(int position) {
return urls.size();
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {

MyHolder myHolder;
if (convertView == null) {
convertView = LayoutInflater.from(getApplicationContext()).inflate(R.layout.list_item_lay, null);
myHolder = new MyHolder();
myHolder.imageView = (ImageView) convertView.findViewById(R.id.item_img);
myHolder.textView = (TextView) convertView.findViewById(R.id.item_tv);
convertView.setTag(myHolder);
}
myHolder = (MyHolder) convertView.getTag();
myHolder.imageView.setImageResource(R.drawable.loading);//BitmapFactory.decodeResource(getResources(), R.drawable.loading));
myHolder.textView.setText("loading...");
myHolder.imageView.setTag(urls.get(position));
myHolder.textView.setTag(urls.get(position) + "_tv");

httpExecutor.loadImage(urls.get(position), myHolder, position);
return convertView;
}
}

}