Android开发之细说ListView上拉加载，下拉刷新过程

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

 

第一步：制作一个旋转的箭头动画indeterminate_drawable.xml

<?xml version="1.0" encoding="utf-8"?>
<rotate xmlns:android="http://schemas.android.com/apk/res/android"
android:drawable="@drawable/indicate_rotate"
android:fromDegrees="0"  从0度开始旋转
android:pivotX="50%"     参照点自身X轴一半
android:pivotY="50%"     自身Y轴一半
android:toDegrees="360"/>   旋转360度

第二步：下拉加载布局文件layout_header.xml

<?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="wrap_content"
    android:gravity="center_horizontal"
    android:orientation="horizontal" >
    
    <RelativeLayout android:layout_width="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_marginBottom="10dp"
        android:layout_height="wrap_content">
        
        <ImageView android:layout_width="wrap_content"
            android:layout_centerInParent="true"
            android:id="@+id/iv_arrow"
            android:background="@drawable/indicator_arrow"
            android:layout_height="wrap_content"/>
        
        <ProgressBar android:layout_width="30dp"
            android:layout_centerInParent="true"
            android:layout_height="30dp"
            android:visibility="invisible"    初始化不可见
            android:id="@+id/pb_rotate"
            android:indeterminateDuration="1000"    旋转周期1秒
               android:indeterminateDrawable="@drawable/indeterminate_drawable"   设置刚刚自定义的旋转箭头动画
            />
        
    </RelativeLayout>
    
    <LinearLayout android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_marginBottom="10dp"
        android:gravity="center"
        android:layout_marginLeft="15dp"
        android:orientation="vertical">
        <TextView android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="20sp"
            android:id="@+id/tv_state"
            android:textColor="#aa000000"
            android:text="下拉刷新"/>
        <TextView android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="14sp"
            android:id="@+id/tv_time"
            android:textColor="@android:color/darker_gray"
            android:text="最后刷新："/>
        
    </LinearLayout>

</LinearLayout>

第三步：上拉加载布局文件layout_footer.xml

<?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="wrap_content"
    android:gravity="center_horizontal"
    android:orientation="horizontal" >
    
    <RelativeLayout android:layout_width="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_marginBottom="10dp"
        android:layout_height="wrap_content">
        
        <ImageView android:layout_width="wrap_content"
            android:layout_centerInParent="true"
            android:id="@+id/iv_arrow"
            android:background="@drawable/indicator_arrow"
            android:layout_height="wrap_content"/>
        
        <ProgressBar android:layout_width="30dp"
            android:layout_centerInParent="true"
            android:layout_height="30dp"
            android:visibility="invisible"
            android:id="@+id/pb_rotate"
            android:indeterminateDuration="1000"
               android:indeterminateDrawable="@drawable/indeterminate_drawable"
            />
        
    </RelativeLayout>
    
    <LinearLayout android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:layout_marginBottom="10dp"
        android:gravity="center"
        android:layout_marginLeft="15dp"
        android:orientation="vertical">
        <TextView android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="20sp"
            android:id="@+id/tv_state"
            android:textColor="#aa000000"
            android:text="下拉刷新"/>
        <TextView android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="14sp"
            android:id="@+id/tv_time"
            android:textColor="@android:color/darker_gray"
            android:text="最后刷新："/>
        
    </LinearLayout>

</LinearLayout>

第四步：自定义一个带下拉刷新，上拉加载的listView

package com.zaizai.dropdownrefresh.view;

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


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

import com.zaizai.dropdownrefresh.R;

public class RefreshListView extends ListView implements OnScrollListener {

    private View headerView;//headerView
    private ImageView ivArrow;
    private ProgressBar pbRotate;
    private TextView tvState, tvTime;
    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() {
        //设置滚动监听事件
        setOnScrollListener(this);
        initHeaderView();
        initRotateAnimation();
        initFooterView();
    }


    /**
     * 初始化headerView
     */
    private void initHeaderView() {
        headerView = View.inflate(getContext(), R.layout.layout_header, null);
        ivArrow = (ImageView) headerView.findViewById(R.id.iv_arrow);
        pbRotate = (ProgressBar) headerView.findViewById(R.id.pb_rotate);
        tvState = (TextView) headerView.findViewById(R.id.tv_state);
        tvTime = (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(); //获得View的高度
        headerView.setPadding(0, -headerViewHeight, 0, 0);  //将View隐藏，在下拉时在显示
        //将其放在第一个view位置
        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(); //获得底部view的高度
        footerView.setPadding(0, -footerViewHeight, 0, 0);   //将其隐藏
        addFooterView(footerView);  //设置为最底部的View
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN: {
                //获得按下的Y值
                downY = (int) ev.getY();
                break;
            }
            case MotionEvent.ACTION_MOVE: {

                if (currentState == REFRESHING) {
                    //正在加载数据未完成，此时拖动不处理
                    break;
                }
                //下拉的距离
                int deltaY = (int) (ev.getY() - downY);

                int paddingTop = -headerViewHeight + deltaY;
                //下拉的距离大于0且第一个条目已经出现
                if (paddingTop > -headerViewHeight && getFirstVisiblePosition() == 0) {
                    /*根据下拉的距离重新定位headerView*/
                    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;
                        //更新headerView状态
                        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;
            }
            default: {
                break;
            }
        }
        return super.onTouchEvent(ev);
    }

    /**
     * 根据currentState来更新headerView状态
     */
    private void refreshHeaderView() {
        switch (currentState) {
            case PULL_REFRESH:
                tvState.setText("下拉刷新");
                ivArrow.startAnimation(downAnimation);
                break;
            case RELEASE_REFRESH:
                tvState.setText("松开刷新");
                ivArrow.startAnimation(upAnimation);
                break;
            case REFRESHING:
                ivArrow.clearAnimation();//因为向上的旋转动画有可能没有执行完
                ivArrow.setVisibility(View.INVISIBLE);
                pbRotate.setVisibility(View.VISIBLE);
                tvState.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;
            pbRotate.setVisibility(View.INVISIBLE);
            ivArrow.setVisibility(View.VISIBLE);
            tvState.setText("下拉刷新");
            tvTime.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) {
    }

}

第五步：自定义listView使用

package com.zaizai.dropdownrefresh;

import android.os.Handler;
import android.os.SystemClock;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.BaseAdapter;
import android.widget.TextView;

import com.zaizai.dropdownrefresh.view.RefreshListView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    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) {
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        super.onCreate(savedInstanceState);
        initView();
        initData();
    }

    private void initView() {

        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 RefreshListView.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;
        }

    }
}