Android中ListView下拉刷新的实现

ListView中的下拉刷新是非常常见的，也是经常使用的，看到有很多同学想要，那我就整理一下，供大家参考。那我就不解释，直接上代码了。

这里需要自己重写一下ListView,重写代码如下:

package net.loonggg.listview;

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.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

public class MyListView extends ListView implements OnScrollListener {

	private final static int RELEASE_To_REFRESH = 0;// 下拉过程的状态值
	private final static int PULL_To_REFRESH = 1; // 从下拉返回到不刷新的状态值
	private final static int REFRESHING = 2;// 正在刷新的状态值
	private final static int DONE = 3;
	private final static int LOADING = 4;

	// 实际的padding的距离与界面上偏移距离的比例
	private final static int RATIO = 3;
	private LayoutInflater inflater;

	// ListView头部下拉刷新的布局
	private LinearLayout headerView;
	private TextView lvHeaderTipsTv;
	private TextView lvHeaderLastUpdatedTv;
	private ImageView lvHeaderArrowIv;
	private ProgressBar lvHeaderProgressBar;

	// 定义头部下拉刷新的布局的高度
	private int headerContentHeight;

	private RotateAnimation animation;
	private RotateAnimation reverseAnimation;

	private int startY;
	private int state;
	private boolean isBack;

	// 用于保证startY的值在一个完整的touch事件中只被记录一次
	private boolean isRecored;

	private OnRefreshListener refreshListener;

	private boolean isRefreshable;

	public MyListView(Context context) {
		super(context);
		init(context);
	}

	public MyListView(Context context, AttributeSet attrs) {
		super(context, attrs);
		init(context);
	}

	private void init(Context context) {
		setCacheColorHint(context.getResources().getColor(R.color.transparent));
		inflater = LayoutInflater.from(context);
		headerView = (LinearLayout) inflater.inflate(R.layout.lv_header, null);
		lvHeaderTipsTv = (TextView) headerView
				.findViewById(R.id.lvHeaderTipsTv);
		lvHeaderLastUpdatedTv = (TextView) headerView
				.findViewById(R.id.lvHeaderLastUpdatedTv);

		lvHeaderArrowIv = (ImageView) headerView
				.findViewById(R.id.lvHeaderArrowIv);
		// 设置下拉刷新图标的最小高度和宽度
		lvHeaderArrowIv.setMinimumWidth(70);
		lvHeaderArrowIv.setMinimumHeight(50);

		lvHeaderProgressBar = (ProgressBar) headerView
				.findViewById(R.id.lvHeaderProgressBar);
		measureView(headerView);
		headerContentHeight = headerView.getMeasuredHeight();
		// 设置内边距，正好距离顶部为一个负的整个布局的高度，正好把头部隐藏
		headerView.setPadding(0, -1 * headerContentHeight, 0, 0);
		// 重绘一下
		headerView.invalidate();
		// 将下拉刷新的布局加入ListView的顶部
		addHeaderView(headerView, null, false);
		// 设置滚动监听事件
		setOnScrollListener(this);

		// 设置旋转动画事件
		animation = new RotateAnimation(0, -180,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		animation.setInterpolator(new LinearInterpolator());
		animation.setDuration(250);
		animation.setFillAfter(true);

		reverseAnimation = new RotateAnimation(-180, 0,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f,
				RotateAnimation.RELATIVE_TO_SELF, 0.5f);
		reverseAnimation.setInterpolator(new LinearInterpolator());
		reverseAnimation.setDuration(200);
		reverseAnimation.setFillAfter(true);

		// 一开始的状态就是下拉刷新完的状态，所以为DONE
		state = DONE;
		// 是否正在刷新
		isRefreshable = false;
	}

	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {

	}

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

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		if (isRefreshable) {
			switch (ev.getAction()) {
			case MotionEvent.ACTION_DOWN:
				if (!isRecored) {
					isRecored = true;
					startY = (int) ev.getY();// 手指按下时记录当前位置
				}
				break;
			case MotionEvent.ACTION_UP:
				if (state != REFRESHING && state != LOADING) {
					if (state == PULL_To_REFRESH) {
						state = DONE;
						changeHeaderViewByState();
					}
					if (state == RELEASE_To_REFRESH) {
						state = REFRESHING;
						changeHeaderViewByState();
						onLvRefresh();
					}
				}
				isRecored = false;
				isBack = false;

				break;

			case MotionEvent.ACTION_MOVE:
				int tempY = (int) ev.getY();
				if (!isRecored) {
					isRecored = true;
					startY = tempY;
				}
				if (state != REFRESHING && isRecored && state != LOADING) {
					// 保证在设置padding的过程中，当前的位置一直是在head，否则如果当列表超出屏幕的话，当在上推的时候，列表会同时进行滚动
					// 可以松手去刷新了
					if (state == RELEASE_To_REFRESH) {
						setSelection(0);
						// 往上推了，推到了屏幕足够掩盖head的程度，但是还没有推到全部掩盖的地步
						if (((tempY - startY) / RATIO < headerContentHeight)// 由松开刷新状态转变到下拉刷新状态
								&& (tempY - startY) > 0) {
							state = PULL_To_REFRESH;
							changeHeaderViewByState();
						}
						// 一下子推到顶了
						else if (tempY - startY <= 0) {// 由松开刷新状态转变到done状态
							state = DONE;
							changeHeaderViewByState();
						}
					}
					// 还没有到达显示松开刷新的时候,DONE或者是PULL_To_REFRESH状态
					if (state == PULL_To_REFRESH) {
						setSelection(0);
						// 下拉到可以进入RELEASE_TO_REFRESH的状态
						if ((tempY - startY) / RATIO >= headerContentHeight) {// 由done或者下拉刷新状态转变到松开刷新
							state = RELEASE_To_REFRESH;
							isBack = true;
							changeHeaderViewByState();
						}
						// 上推到顶了
						else if (tempY - startY <= 0) {// 由DOne或者下拉刷新状态转变到done状态
							state = DONE;
							changeHeaderViewByState();
						}
					}
					// done状态下
					if (state == DONE) {
						if (tempY - startY > 0) {
							state = PULL_To_REFRESH;
							changeHeaderViewByState();
						}
					}
					// 更新headView的size
					if (state == PULL_To_REFRESH) {
						headerView.setPadding(0, -1 * headerContentHeight
								+ (tempY - startY) / RATIO, 0, 0);

					}
					// 更新headView的paddingTop
					if (state == RELEASE_To_REFRESH) {
						headerView.setPadding(0, (tempY - startY) / RATIO
								- headerContentHeight, 0, 0);
					}

				}
				break;

			default:
				break;
			}
		}
		return super.onTouchEvent(ev);
	}

	// 当状态改变时候，调用该方法，以更新界面
	private void changeHeaderViewByState() {
		switch (state) {
		case RELEASE_To_REFRESH:
			lvHeaderArrowIv.setVisibility(View.VISIBLE);
			lvHeaderProgressBar.setVisibility(View.GONE);
			lvHeaderTipsTv.setVisibility(View.VISIBLE);
			lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);

			lvHeaderArrowIv.clearAnimation();// 清除动画
			lvHeaderArrowIv.startAnimation(animation);// 开始动画效果

			lvHeaderTipsTv.setText("松开刷新");
			break;
		case PULL_To_REFRESH:
			lvHeaderProgressBar.setVisibility(View.GONE);
			lvHeaderTipsTv.setVisibility(View.VISIBLE);
			lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);
			lvHeaderArrowIv.clearAnimation();
			lvHeaderArrowIv.setVisibility(View.VISIBLE);
			// 是由RELEASE_To_REFRESH状态转变来的
			if (isBack) {
				isBack = false;
				lvHeaderArrowIv.clearAnimation();
				lvHeaderArrowIv.startAnimation(reverseAnimation);

				lvHeaderTipsTv.setText("下拉刷新");
			} else {
				lvHeaderTipsTv.setText("下拉刷新");
			}
			break;

		case REFRESHING:

			headerView.setPadding(0, 0, 0, 0);

			lvHeaderProgressBar.setVisibility(View.VISIBLE);
			lvHeaderArrowIv.clearAnimation();
			lvHeaderArrowIv.setVisibility(View.GONE);
			lvHeaderTipsTv.setText("正在刷新...");
			lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);
			break;
		case DONE:
			headerView.setPadding(0, -1 * headerContentHeight, 0, 0);

			lvHeaderProgressBar.setVisibility(View.GONE);
			lvHeaderArrowIv.clearAnimation();
			lvHeaderArrowIv.setImageResource(R.drawable.arrow);
			lvHeaderTipsTv.setText("下拉刷新");
			lvHeaderLastUpdatedTv.setVisibility(View.VISIBLE);
			break;
		}
	}

	// 此方法直接照搬自网络上的一个下拉刷新的demo，此处是“估计”headView的width以及height
	private void measureView(View child) {
		ViewGroup.LayoutParams params = child.getLayoutParams();
		if (params == null) {
			params = new ViewGroup.LayoutParams(
					ViewGroup.LayoutParams.FILL_PARENT,
					ViewGroup.LayoutParams.WRAP_CONTENT);
		}
		int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0,
				params.width);
		int lpHeight = params.height;
		int childHeightSpec;
		if (lpHeight > 0) {
			childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,
					MeasureSpec.EXACTLY);
		} else {
			childHeightSpec = MeasureSpec.makeMeasureSpec(0,
					MeasureSpec.UNSPECIFIED);
		}
		child.measure(childWidthSpec, childHeightSpec);
	}

	public void setonRefreshListener(OnRefreshListener refreshListener) {
		this.refreshListener = refreshListener;
		isRefreshable = true;
	}

	public interface OnRefreshListener {
		public void onRefresh();
	}

	public void onRefreshComplete() {
		state = DONE;
		lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString());
		changeHeaderViewByState();
	}

	private void onLvRefresh() {
		if (refreshListener != null) {
			refreshListener.onRefresh();
		}
	}

	public void setAdapter(LvAdapter adapter) {
		lvHeaderLastUpdatedTv.setText("最近更新:" + new Date().toLocaleString());
		super.setAdapter(adapter);
	}

}

重写完ListView之后，在布局文件中是这么使用的，头部下拉刷新的布局文件lv_header.xml代码如下：

<?xml version="1.0" encoding="utf-8"?>
<!-- ListView的头部 -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="#000000" >

    <!-- 内容 -->

    <RelativeLayout
        android:id="@+id/head_contentLayout"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingLeft="30dp" >

        <!-- 箭头图像、进度条 -->

        <FrameLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_centerVertical="true" >

            <!-- 箭头 -->

            <ImageView
                android:id="@+id/lvHeaderArrowIv"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:src="@drawable/arrow" />

            <!-- 进度条 -->

            <ProgressBar
                android:id="@+id/lvHeaderProgressBar"
                style="?android:attr/progressBarStyleSmall"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:visibility="gone" />
        </FrameLayout>

        <!-- 提示、最近更新 -->

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            android:gravity="center_horizontal"
            android:orientation="vertical" >

            <!-- 提示 -->

            <TextView
                android:id="@+id/lvHeaderTipsTv"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="下拉刷新"
                android:textColor="@color/white"
                android:textSize="20sp" />

            <!-- 最近更新 -->

            <TextView
                android:id="@+id/lvHeaderLastUpdatedTv"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="上次更新"
                android:textColor="@color/gold"
                android:textSize="10sp" />
        </LinearLayout>
    </RelativeLayout>

</LinearLayout>

在Main.xml中进行设置，代码如下：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#000000"
    android:orientation="vertical" >

    <net.loonggg.listview.MyListView
        android:id="@+id/lv"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" />

</LinearLayout>

然后就是在MainActivity中实现，代码如下：

package net.loonggg.listview;

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

import net.loonggg.listview.MyListView.OnRefreshListener;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends Activity {
	private List<String> list;
	private MyListView lv;
	private LvAdapter adapter;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		lv = (MyListView) findViewById(R.id.lv);
		list = new ArrayList<String>();
		list.add("loonggg");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		list.add("我们都是开发者");
		adapter = new LvAdapter(list, this);
		lv.setAdapter(adapter);

		lv.setonRefreshListener(new OnRefreshListener() {

			@Override
			public void onRefresh() {
				new AsyncTask<Void, Void, Void>() {
					protected Void doInBackground(Void... params) {
						try {
							Thread.sleep(1000);
						} catch (Exception e) {
							e.printStackTrace();
						}
						list.add("刷新后添加的内容");
						return null;
					}

					@Override
					protected void onPostExecute(Void result) {
						adapter.notifyDataSetChanged();
						lv.onRefreshComplete();
					}
				}.execute(null, null, null);
			}
		});
	}
}

这里还需要为ListView设置一下Adapter,自定义的Adapter如下：

package net.loonggg.listview;

import java.util.List;

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

public class LvAdapter extends BaseAdapter {
	private List<String> list;
	private Context context;

	public LvAdapter(List<String> list, Context context) {
		this.list = list;
		this.context = context;
	}

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

	@Override
	public Object getItem(int position) {
		return list.get(position);
	}

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

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		TextView tv = new TextView(context.getApplicationContext());
		tv.setText(list.get(position));
		return tv;
	}

}

到这里就完了，代码中的解释非常详细，具体的我就不多说了，也不解释了，自己看看并研究吧！