Android自定义控制(五)仿新浪微博的下拉刷新

网上有很多很有名的开源框架,这里就来拉拉PullToRefresh这个框架,也就是我们平时用的下拉刷新啦,当然你问我这个有什么用啊?别人已经写好了,这里主要是学习以及练习,练习的次数多了,一切就顺其自然的会了.

废话少说,先上图,再上代码:

1.要想实现下拉刷新功能必须要有个下拉刷新的布局,是吧?

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="10dip"
        android:paddingTop="10dip" >

        <LinearLayout
            android:id="@+id/layout"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:gravity="center"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/tip"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="@string/state" />

            <TextView
                android:id="@+id/lastupdate_time"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content" />
        </LinearLayout>

        <ProgressBar
            android:id="@+id/progress"
            style="?android:attr/progressBarStyleSmall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_toLeftOf="@id/layout"
            android:layout_marginRight="20dip"
            android:visibility="gone" />

        <ImageView
            android:id="@+id/arrow"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignTop="@+id/layout"
            android:layout_marginRight="19dp"
            android:layout_toLeftOf="@+id/layout"
            android:src="@drawable/arrow_down" />

    </RelativeLayout>

</LinearLayout>

2.你要把它加入到布局里面吧!

headView=layoutInflater.from(context).inflate(R.layout.header_layout, null);
		this.addHeaderView(headView);

3.加入到布局直接显示出来也不符合需求啊,所以这一步需要隐藏布局,当然不能和前一篇博客(Android自定义控件(四)仿网易客户端上拉加载更多)一样直接隐藏,直接隐藏满足不了如图的要求,我们这里采取的是设置头部布局的高度为实际高度的负值,这样就实现了隐藏功能,当下拉的时候,还不至于一次就全部显示出来,ok这种办法能够实现图中的要求

headerHeight = headView.getMeasuredHeight();
		setHeaderViewHeight(-headerHeight);

/**
	 * 设置头部布局的高度
	 * 
	 * @param i
	 */
	private void setHeaderViewHeight(int headerHeight) {
		headView.setPadding(headView.getPaddingLeft(), headerHeight,
				headView.getPaddingRight(), headView.getPaddingBottom());
		//重绘
		headView.invalidate();
	}

4.跑起来之后,白瞎了,没实现想要的功能,也就是说没有把头部布局隐藏掉,哎,跟踪代码之后发现高度为0,郭神说过在measure之前,getMeasureWidth()和getMeasureHeight()都为零,好吧,那就先measure吧!

private void measureView(View view) {
		ViewGroup.LayoutParams lp = view.getLayoutParams();
		if (lp == null) {
			lp = new ViewGroup.LayoutParams(
					ViewGroup.LayoutParams.MATCH_PARENT,
					ViewGroup.LayoutParams.WRAP_CONTENT);
		}
		int width = ViewGroup.getChildMeasureSpec(0, 0, lp.width);
		int height;
		int tempHeight=lp.height;
		if (tempHeight > 0) {
			height = MeasureSpec.makeMeasureSpec(tempHeight,
					MeasureSpec.EXACTLY);
		} else {
			height = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
		}
		view.measure(width, height);
	}

5.隐藏成功了,下面就要实现具体的功能了,下拉刷新,松开刷新,正在刷新这三个状态,是通过手势改变状态,所以这里要实现onTouch,当然还有OnScrollListener

需要用到firstVisibleItem判断Listview向上滑动还是向下滑动,如果firstVisibleItem==0说明到达ListView的头部了,当然你还需要一个布尔值判断是否按下滑动

@Override
	public void onScroll(AbsListView view, int firstVisibleItem,
			int visibleItemCount, int totalItemCount) {
		this.firstVisibleItem=firstVisibleItem;
	}

重写onTouchEvent,通过firstVisibleItem和布尔值判断按下,抬起,滑动

@Override
	public boolean onTouchEvent(MotionEvent ev) {
		switch (ev.getAction()) {
		case MotionEvent.ACTION_DOWN:
			if (firstVisibleItem == 0) {
				isRemark = true;
				startY = (int) ev.getY();
			}
			break;

		case MotionEvent.ACTION_MOVE:
			onMove(ev);
			break;

		case MotionEvent.ACTION_UP:
			if (state==RELEASE) {
				state=REFRASH;
				reflashViewByState();
				//更新数据
				isRefreshListener.onRefresh();
			}else if (state==PULL) {
				state=NONE;
				isRemark=false;
				refreshDrawableState();
			}
			break;
		}
		return super.onTouchEvent(ev);
	}

代码不全,先解释一下,后面附上全部代码

按下时,如果firstVisibleItem为0,说明到达listview的顶部,并且可以按下,把isRemark赋值为true,滑动时改变头部布局的状态

/**
	 * 移动过程的状态变换
	 * 
	 * @param ev
	 */
	private void onMove(MotionEvent ev) {
		if (!isRemark) {
			return;
		}
		int tempY = (int) ev.getY();
		int space = tempY - startY;
		int topPadding = space - headerHeight;
		switch (state) {
		case NONE:
			if (space>0) {
				state=PULL;
				reflashViewByState();
			}
			break;

		case PULL:
			setHeaderViewHeight(topPadding);
			if (space>headerHeight+30&&scrollState==SCROLL_STATE_IDLE) {
				state=RELEASE;
				reflashViewByState();
			}
			break;

		case RELEASE:
			setHeaderViewHeight(topPadding);
			if (space<headerHeight+30) {
				state=PULL;
				reflashViewByState();
			}else if (space<=0) {
				state=NONE;
				reflashViewByState();
			}
			break;
			
		}
	}

根据滑动之后和动画前y值的变化判断滑动状态,当space大于零时,当前状态变为下拉刷新,如果space大于某个值时,当前状态变为松开可以刷新,当space大于零小于某个值时,当前状态为下拉刷新状态,当space小于零时,当前状态变为正常状态.当然状态改变时,界面也要随着改变

/**
	 *根据状态刷新当前页面
	 */
	private void reflashViewByState() {
		TextView tip = (TextView) headView.findViewById(R.id.tip);
		ImageView arrow = (ImageView) headView.findViewById(R.id.arrow);
		ProgressBar progress = (ProgressBar) headView.findViewById(R.id.progress);
		RotateAnimation anim = new RotateAnimation(0, 180,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		anim.setDuration(500);
		anim.setFillAfter(true);
		RotateAnimation anim1 = new RotateAnimation(180, 0,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		anim1.setDuration(500);
		anim1.setFillAfter(true);
		switch (state) {
		case NONE:
			setHeaderViewHeight(-headerHeight);
			arrow.clearAnimation();
			break;
			
		case PULL:
			arrow.setVisibility(View.VISIBLE);
			progress.setVisibility(View.GONE);
			tip.setText("下拉刷新");
			arrow.clearAnimation();
			arrow.setAnimation(anim1);
			break;

		case RELEASE:
			arrow.setVisibility(View.VISIBLE);
			progress.setVisibility(View.GONE);
			tip.setText("松开刷新");
			arrow.clearAnimation();
			arrow.setAnimation(anim);
			break;
			
		case REFRASH:
			setHeaderViewHeight(50);
			arrow.setVisibility(View.GONE);
			progress.setVisibility(View.VISIBLE);
			tip.setText("正在刷新");
			arrow.clearAnimation();
			break;
		}
	}

界面上主要改变的就是提示,箭头和progress,正常状态下,界面不可见,下拉刷新状态下,箭头可见并且朝下,提示信息为下拉刷新并且progress不可见,松开刷新状态,箭头朝上,progress不可见,提示信息为下拉刷新,正在加载状态箭头不可见,progress可见,提示信息改为正在刷新

当然,在变成正在加载状态时,还要加载更过数据

public interface IsRefreshListener{
		public void onRefresh();
	}
	
	public void setIsRefreshListener(IsRefreshListener isRefreshListener){
		this.isRefreshListener=isRefreshListener;
	}

加载完数据后,还要通知listview刷新结束

/**
	 * 获取完数据；
	 */
	public void reflashComplete() {
		state = NONE;
		isRemark = false;
		reflashViewByState();
		TextView lastupdatetime = (TextView) headView
				.findViewById(R.id.lastupdate_time);
		SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 hh:mm:ss");
		Date date = new Date(System.currentTimeMillis());
		String time = format.format(date);
		lastupdatetime.setText(time);
	}

自定义下拉刷新控件就这样完成了,不懂得留言吧,我尽量给你解答,自定义这东西,写多了也就知道怎么写了

下面附上自定义下拉刷新控件的全部代码:

package com.sdufe.thea.guo.view;

import java.text.SimpleDateFormat;
import java.util.Date;

import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;

import com.sdufe.thea.guo.R;

public class PullToRefreshListView extends ListView implements OnScrollListener {

	View headView;
	int headerHeight;
	int firstVisibleItem;
	int scrollState;
	boolean isRemark;
	int startY;

	int state;
	final int NONE = 0;
	final int PULL = 1;
	final int RELEASE = 2;
	final int REFRASH = 3;
	
	IsRefreshListener isRefreshListener;

	public PullToRefreshListView(Context context, AttributeSet attrs,
			int defStyle) {
		super(context, attrs, defStyle);
		initView(context);
	}

	public PullToRefreshListView(Context context, AttributeSet attrs) {
		super(context, attrs);
		initView(context);
	}

	public PullToRefreshListView(Context context) {
		super(context);
		initView(context);
	}

	private void initView(Context context) {
		headView = LayoutInflater.from(context).inflate(R.layout.header_layout,
				null);
		measureView(headView);
		headerHeight = headView.getMeasuredHeight();
		setHeaderViewHeight(-headerHeight);
		addView(headView);
		setOnScrollListener(this);
	}

	/**
	 * 计算宽高
	 * 
	 * @param view
	 */
	private void measureView(View view) {
		ViewGroup.LayoutParams lp = view.getLayoutParams();
		if (lp == null) {
			lp = new ViewGroup.LayoutParams(
					ViewGroup.LayoutParams.MATCH_PARENT,
					ViewGroup.LayoutParams.WRAP_CONTENT);
		}
		int width = ViewGroup.getChildMeasureSpec(0, 0, lp.width);
		int height;
		int tempHeight = lp.height;
		if (tempHeight > 0) {
			height = MeasureSpec.makeMeasureSpec(tempHeight,
					MeasureSpec.EXACTLY);
		} else {
			height = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
		}
		view.measure(width, height);
	}

	/**
	 * 设置头部布局的高度
	 * 
	 * @param i
	 */
	private void setHeaderViewHeight(int headerHeight) {
		headView.setPadding(headView.getPaddingLeft(), headerHeight,
				headView.getPaddingRight(), headView.getPaddingBottom());
		// 重绘
		headView.invalidate();
	}

	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {
		this.scrollState = scrollState;
	}

	@Override
	public void onScroll(AbsListView view, int firstVisibleItem,
			int visibleItemCount, int totalItemCount) {
		this.firstVisibleItem = firstVisibleItem;
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		switch (ev.getAction()) {
		case MotionEvent.ACTION_DOWN:
			if (firstVisibleItem == 0) {
				isRemark = true;
				startY = (int) ev.getY();
			}
			break;

		case MotionEvent.ACTION_MOVE:
			onMove(ev);
			break;

		case MotionEvent.ACTION_UP:
			if (state==RELEASE) {
				state=REFRASH;
				reflashViewByState();
				//更新数据
				isRefreshListener.onRefresh();
			}else if (state==PULL) {
				state=NONE;
				isRemark=false;
				refreshDrawableState();
			}
			break;
		}
		return super.onTouchEvent(ev);
	}

	/**
	 * 移动过程的状态变换
	 * 
	 * @param ev
	 */
	private void onMove(MotionEvent ev) {
		if (!isRemark) {
			return;
		}
		int tempY = (int) ev.getY();
		int space = tempY - startY;
		int topPadding = space - headerHeight;
		switch (state) {
		case NONE:
			if (space>0) {
				state=PULL;
				reflashViewByState();
			}
			break;

		case PULL:
			setHeaderViewHeight(topPadding);
			if (space>headerHeight+30&&scrollState==SCROLL_STATE_IDLE) {
				state=RELEASE;
				reflashViewByState();
			}
			break;

		case RELEASE:
			setHeaderViewHeight(topPadding);
			if (space<headerHeight+30) {
				state=PULL;
				reflashViewByState();
			}else if (space<=0) {
				state=NONE;
				reflashViewByState();
			}
			break;
			
		}
	}
	
	/**
	 * 获取完数据；
	 */
	public void reflashComplete() {
		state = NONE;
		isRemark = false;
		reflashViewByState();
		TextView lastupdatetime = (TextView) headView
				.findViewById(R.id.lastupdate_time);
		SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 hh:mm:ss");
		Date date = new Date(System.currentTimeMillis());
		String time = format.format(date);
		lastupdatetime.setText(time);
	}

	/**
	 *根据状态刷新当前页面
	 */
	private void reflashViewByState() {
		TextView tip = (TextView) headView.findViewById(R.id.tip);
		ImageView arrow = (ImageView) headView.findViewById(R.id.arrow);
		ProgressBar progress = (ProgressBar) headView.findViewById(R.id.progress);
		RotateAnimation anim = new RotateAnimation(0, 180,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		anim.setDuration(500);
		anim.setFillAfter(true);
		RotateAnimation anim1 = new RotateAnimation(180, 0,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		anim1.setDuration(500);
		anim1.setFillAfter(true);
		switch (state) {
		case NONE:
			setHeaderViewHeight(-headerHeight);
			arrow.clearAnimation();
			break;
			
		case PULL:
			arrow.setVisibility(View.VISIBLE);
			progress.setVisibility(View.GONE);
			tip.setText("下拉刷新");
			arrow.clearAnimation();
			arrow.setAnimation(anim1);
			break;

		case RELEASE:
			arrow.setVisibility(View.VISIBLE);
			progress.setVisibility(View.GONE);
			tip.setText("松开刷新");
			arrow.clearAnimation();
			arrow.setAnimation(anim);
			break;
			
		case REFRASH:
			setHeaderViewHeight(50);
			arrow.setVisibility(View.GONE);
			progress.setVisibility(View.VISIBLE);
			tip.setText("正在刷新");
			arrow.clearAnimation();
			break;
		}
	}

	public interface IsRefreshListener{
		public void onRefresh();
	}
	
	public void setIsRefreshListener(IsRefreshListener isRefreshListener){
		this.isRefreshListener=isRefreshListener;
	}
}

下面就是怎么用了

<com.sdufe.thea.guo.view.PullToRefreshListView
        android:id="@+id/pull_to_refresh"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

下面的用法就跟listview差不多了,提示一点要实现IsRefreshListener接口,在onRefresh()里面加载更多数据

package com.sdufe.thea.guo;

import java.util.ArrayList;
import java.util.List;

import com.sdufe.thea.guo.view.PullToRefreshListView;
import com.sdufe.thea.guo.view.PullToRefreshListView.IsRefreshListener;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.ArrayAdapter;

public class MainActivity extends Activity implements IsRefreshListener{

	PullToRefreshListView listView;
	ArrayAdapter<String> adapter;
	List<String> list;

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

		listView = (PullToRefreshListView) findViewById(R.id.pull_to_refresh);
		initData();
		adapter = new ArrayAdapter<String>(this,
				android.R.layout.simple_list_item_1, list);
		listView.setAdapter(adapter);
	}

	private void initData() {
		list = new ArrayList<String>();
		list.add("123456789");
		list.add("123456789");
		list.add("123456789");
	}

	@Override
	public void onRefresh() {
		list.add("爸爸");
		list.add("妈妈");
		list.add("我");
	        adapter.notifyDataSetChanged();
		listView.reflashComplete();
	}

}

今天就到此结束啦,不懂的,留言