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.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.AbsListView.OnScrollListener;

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);
        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 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);
    }

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

    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        if (firstVisibleItem == 0) {
            isRefreshable = true;
        } else {
            isRefreshable = false;
        }

    }

}

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的代码如下：

<?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！