6.下拉刷新

下拉刷新-------

1.addHeaderView必须在setAdapter之前调用

2.将paddingTop设置一个headerView高度的负值去隐藏它

 

getHeight()和getMeasuredHeight()的区别：

getMeasuredHeight():获取测量完的高度，只要在onMeasure方法执行完，就可以用

                    它获取到宽高，在自定义控件内部多使用这个

使用view.measure(0,0)方法可以主动通知系统去测量，然后就

可以直接使用它获取宽高

getHeight()：必须在onLayout方法执行完后，才能获得宽高

view.getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

@Override

public void onGlobalLayout() {

  headerView.getViewTreeObserver().removeGlobalOnLayoutListener(this);

  int headerViewHeight = headerView.getHeight();//直接可以获取宽高

}

});

3.setSelection(position);将对应位置的item放置到屏幕顶端

 

RefreshListView

 

public class RefreshListView extends ListView implements OnScrollListener{
	private View headerView;//headerView
	private ImageView iv_arrow;
	private ProgressBar pb_rotate;
	private TextView tv_state,tv_time;
	private View footerView;
	private int footerViewHeight;
	
	private int headerViewHeight;//headerView高
	
	private int downY;//按下时y坐标
	
	private final int PULL_REFRESH = 0;//下拉刷新的状态
	private final int RELEASE_REFRESH = 1;//松开刷新的状态
	private final int REFRESHING = 2;//正在刷新的状态
	private int currentState = PULL_REFRESH;
	
	private RotateAnimation upAnimation,downAnimation;
	
	private boolean isLoadingMore = false;//当前是否正在处于加载更多
	public RefreshListView(Context context) {
		super(context);
		init();
	}
	public RefreshListView(Context context, AttributeSet attrs) {
		super(context, attrs);
		init();
	}
	
	private void init(){
		setOnScrollListener(this);
		initHeaderView();
		initRotateAnimation();
		initFooterView();
	}
	/**
	 * 初始化headerView
	 */
	private void initHeaderView() {
		headerView = View.inflate(getContext(), R.layout.layout_header, null);
		iv_arrow = (ImageView) headerView.findViewById(R.id.iv_arrow);
		pb_rotate = (ProgressBar) headerView.findViewById(R.id.pb_rotate);
		tv_state = (TextView) headerView.findViewById(R.id.tv_state);
		tv_time = (TextView) headerView.findViewById(R.id.tv_time);
		
		headerView.measure(0, 0);//主动通知系统去测量该view;
		headerViewHeight = headerView.getMeasuredHeight();
		headerView.setPadding(0, -headerViewHeight, 0, 0);
		
		addHeaderView(headerView);
	}
	
	/**
	 * 初始化旋转动画
	 */
	private void initRotateAnimation() {
		upAnimation = new RotateAnimation(0, -180, 
				RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		upAnimation.setDuration(300);
		upAnimation.setFillAfter(true);
		downAnimation = new RotateAnimation(-180, -360, 
				RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		downAnimation.setDuration(300);
		downAnimation.setFillAfter(true);
	}
	
	private void initFooterView() {
		footerView = View.inflate(getContext(), R.layout.layout_footer, null);
		footerView.measure(0, 0);//主动通知系统去测量该view;
		footerViewHeight = footerView.getMeasuredHeight();
		footerView.setPadding(0, -footerViewHeight, 0, 0);
		addFooterView(footerView);
	}
	
	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		switch (ev.getAction()) {
		case MotionEvent.ACTION_DOWN:
			downY = (int) ev.getY();
			break;
		case MotionEvent.ACTION_MOVE:
			
			if(currentState==REFRESHING){
				break;
			}
			
			int deltaY = (int) (ev.getY() - downY);
			
			int paddingTop = -headerViewHeight + deltaY;
			if(paddingTop>-headerViewHeight && getFirstVisiblePosition()==0){
				headerView.setPadding(0, paddingTop, 0, 0);
//				Log.e("RefreshListView", "paddingTop: "+paddingTop);
				
				if(paddingTop>=0 && currentState==PULL_REFRESH){
					//从下拉刷新进入松开刷新状态
					currentState = RELEASE_REFRESH;
					refreshHeaderView();
				}else if (paddingTop<0 && currentState==RELEASE_REFRESH) {
					//进入下拉刷新状态
					currentState = PULL_REFRESH;
					refreshHeaderView();
				}
				
				
				return true;//拦截TouchMove，不让listview处理该次move事件,会造成listview无法滑动
			}
			
			
			break;
		case MotionEvent.ACTION_UP:
			if(currentState==PULL_REFRESH){
				//隐藏headerView
				headerView.setPadding(0, -headerViewHeight, 0, 0);
			}else if (currentState==RELEASE_REFRESH) {
				headerView.setPadding(0, 0, 0, 0);
				currentState = REFRESHING;
				refreshHeaderView();
				
				if(listener!=null){
					listener.onPullRefresh();
				}
			}
			break;
		}
		return super.onTouchEvent(ev);
	}
	
	/**
	 * 根据currentState来更新headerView
	 */
	private void refreshHeaderView(){
		switch (currentState) {
		case PULL_REFRESH:
			tv_state.setText("下拉刷新");
			iv_arrow.startAnimation(downAnimation);
			break;
		case RELEASE_REFRESH:
			tv_state.setText("松开刷新");
			iv_arrow.startAnimation(upAnimation);
			break;
		case REFRESHING:
			iv_arrow.clearAnimation();//因为向上的旋转动画有可能没有执行完
			iv_arrow.setVisibility(View.INVISIBLE);
			pb_rotate.setVisibility(View.VISIBLE);
			tv_state.setText("正在刷新...");
			break;
		}
	}
	
	/**
	 * 完成刷新操作，重置状态,在你获取完数据并更新完adater之后，去在UI线程中调用该方法
	 */
	public void completeRefresh(){
		if(isLoadingMore){
			//重置footerView状态
			footerView.setPadding(0, -footerViewHeight, 0, 0);
			isLoadingMore = false;
		}else {
			//重置headerView状态
			headerView.setPadding(0, -headerViewHeight, 0, 0);
			currentState = PULL_REFRESH;
			pb_rotate.setVisibility(View.INVISIBLE);
			iv_arrow.setVisibility(View.VISIBLE);
			tv_state.setText("下拉刷新");
			tv_time.setText("最后刷新："+getCurrentTime());
		}
	}
	
	/**
	 * 获取当前系统时间，并格式化
	 * @return
	 */
	private String getCurrentTime(){
		SimpleDateFormat format = new SimpleDateFormat("yy-MM-dd HH:mm:ss");
		return format.format(new Date());
	}
	
	private OnRefreshListener listener;
	public void setOnRefreshListener(OnRefreshListener listener){
		this.listener = listener;
	}
	public interface OnRefreshListener{
		void onPullRefresh();
		void onLoadingMore();
	}
	
	/**
	 * SCROLL_STATE_IDLE:闲置状态，就是手指松开
	 * SCROLL_STATE_TOUCH_SCROLL：手指触摸滑动，就是按着来滑动
	 * SCROLL_STATE_FLING：快速滑动后松开
	 */
	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {
		if(scrollState==OnScrollListener.SCROLL_STATE_IDLE 
				&& getLastVisiblePosition()==(getCount()-1) &&!isLoadingMore){
			isLoadingMore = true;
			
			footerView.setPadding(0, 0, 0, 0);//显示出footerView
			setSelection(getCount());//让listview最后一条显示出来
			
			if(listener!=null){
				listener.onLoadingMore();
			}
		}
	}
	@Override
	public void onScroll(AbsListView view, int firstVisibleItem,
			int visibleItemCount, int totalItemCount) {
	}
}

　　

MainActivity

 

public class MainActivity extends Activity {
	private RefreshListView refreshListView;
	
	private ArrayList<String> list = new ArrayList<String>();
	private MyAdapter adapter;
	
	private Handler handler = new Handler(){
		public void handleMessage(android.os.Message msg) {
			//更新UI
			adapter.notifyDataSetChanged();
			refreshListView.completeRefresh();
		};
	};
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		initView();
		initData();
	}
	
	private void initView() {
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		setContentView(R.layout.activity_main);
		refreshListView = (RefreshListView) findViewById(R.id.refreshListView);
	}
	
	private void initData() {
		for (int i = 0; i < 15; i++) {
			list.add("listview原来的数据 - "+i);
		}
		
		
//		final View headerView = View.inflate(this, R.layout.layout_header, null);
		//第一种方法
//		headerView.getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() {
//			@Override
//			public void onGlobalLayout() {
//				headerView.getViewTreeObserver().removeGlobalOnLayoutListener(this);
//				int headerViewHeight = headerView.getHeight();
//				
//				
//				Log.e("MainActivity", "headerViewHeight: "+headerViewHeight);
//				headerView.setPadding(0, -headerViewHeight, 0, 0);
//				refreshListView.addHeaderView(headerView);//
//			}
//		});
		//第二种方法
//		headerView.measure(0, 0);//主动通知系统去测量
//		int headerViewHeight = headerView.getMeasuredHeight();
//		Log.e("MainActivity", "headerViewHeight: "+headerViewHeight);
//		headerView.setPadding(0, -headerViewHeight, 0, 0);
//		refreshListView.addHeaderView(headerView);//
		
		
		
		adapter = new MyAdapter();
		refreshListView.setAdapter(adapter);
		
		refreshListView.setOnRefreshListener(new OnRefreshListener() {
			@Override
			public void onPullRefresh() {
				//需要联网请求服务器的数据，然后更新UI
				requestDataFromServer(false);
			}
			@Override
			public void onLoadingMore() {
				requestDataFromServer(true);
			}
		});
		
	}
	/**
	 * 模拟向服务器请求数据
	 */
	private void requestDataFromServer(final boolean isLoadingMore){
		new Thread(){
			public void run() {
				SystemClock.sleep(3000);//模拟请求服务器的一个时间长度
				
				if(isLoadingMore){
					list.add("加载更多的数据-1");
					list.add("加载更多的数据-2");
					list.add("加载更多的数据-3");
				}else {
					list.add(0, "下拉刷新的数据");
				}
				
				//在UI线程更新UI
				handler.sendEmptyMessage(0);
			};
		}.start();
	}
	
	class MyAdapter extends BaseAdapter{
		@Override
		public int getCount() {
			return list.size();
		}
		@Override
		public Object getItem(int position) {
			return null;
		}
		@Override
		public long getItemId(int position) {
			return 0;
		}
		@Override
		public View getView(int position, View convertView, ViewGroup parent) {
			TextView textView = new TextView(MainActivity.this);
			textView.setPadding(20, 20, 20, 20);
			textView.setTextSize(18);
			
			textView.setText(list.get(position));
			
			return textView;
		}
		
	}
}