Android自定义ListView实现下拉刷新
时间：2021-09-04 09:49:29 | 栏目：Android代码 | 点击：次
首先呈上效果图
当今APP，哪个没有点滑动刷新功能，简直就太落伍了。正因为需求多，因此自然而然开源的也就多。但是若想引用开源库，则很麻烦，比如PullToRefreshView这个库，如果把开源代码都移植到项目中，这是件很繁琐的事，如果用依赖功能的话，对于强迫症的我，又很不爽。现在也有各种自定义ListView实现PullToRefreshListView的控件，无非就是在header加入一个控件，通过setPadding的方式来改变显示效果。效果已经太out了，如意中发现google自带的swiperefreshlayout实现的效果挺不错，但是我发现这个控件在部分手机上的效果不一样，估计和v7包相关。因此就有了这篇文章自定义这个喜欢的效果。
首先大概描述一下实现原理：
1、重写ListView的onTouchEvent，在方法中根据手指滑动的距离与临界值判断，决定当前的状态，分为四个状态：RELEASE_TO_REFRESH、PULL_TO_REFRESH、REFRESHING、DONE四个状态，分别代表释放刷新、拉动刷新、正在刷新、默认状态。
2、重写ListView的onDraw方法，根据不同的状态值，显示不同的图形表示。
3、根据滑动距离不同，显示不同的透明度、圆弧角度值、整体图形的坐标等等。
4、图形的变化分为两种：1、手动触发，滑动一点距离就更新一点坐标。比如PULL_TO_REFRESH状态，适合在onTouchEvent中的ACTION_MOVE中触发。2、动画自动触发，比如REFRESHING状态和DONE状态，适合在onTouchEvent中的ACTION_UP方法中触发，手指一松开就自动触发动画效果。
5、必须在设置了刷新监听器才可以滑动，否则就是一个普通的LIstView。
代码很简单，只有两个文件，并且有很详细的注释：
PullToRefreshListView类：
package cc.wxf.view.pull;
import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.AbsListView;
import android.widget.ListView;
/**
* Created by ccwxf on 2016/3/30.
*/
public class PullToRefreshListView extends ListView implements AbsListView.OnScrollListener {
public final static int RELEASE_TO_REFRESH = 0;
public final static int PULL_TO_REFRESH = 1;
public final static int REFRESHING = 2;
public final static int DONE = 3;
// 达到刷新条件的滑动距离
public final static int TOUCH_SLOP = 160;
// 判断是否记录了最开始按下时的Y坐标
private boolean isRecored;
// 记录最开始按下时的Y坐标
private int startY;
// ListView第一个Item
private int firstItemIndex;
// 当前状态
private int state;
// 是否可刷新，只有设置了监听器才能刷新
private boolean isRefreshable;
// 刷新标记
private PullMark mark;
private OnRefreshListener refreshListener;
private OnScrollButtomListener scrollButtomListener;
public PullToRefreshListView(Context context) {
super(context);
init(context);
}
public PullToRefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}
private void init(Context context) {
//关闭硬件加速，否则PullMark的阴影不会出现
setLayerType(View.LAYER_TYPE_SOFTWARE, null);
setOnScrollListener(this);
mark = new PullMark(this);
state = DONE;
isRefreshable = false;
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (scrollButtomListener != null) {
if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
if (view.getLastVisiblePosition() == view.getAdapter().getCount() - 1) {
scrollButtomListener.onScrollToButtom();
}
}
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
firstItemIndex = firstVisibleItem;
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
mark.onDraw(canvas);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = MeasureSpec.getSize(widthMeasureSpec);
mark.setCenterX(width / 2);
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
if (!isRefreshable) {
return super.onTouchEvent(event);
}
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
handleActionDown(event);
break;
case MotionEvent.ACTION_UP:
handleActionUp();
break;
case MotionEvent.ACTION_MOVE:
handleActionMove(event);
break;
default:
break;
}
return super.onTouchEvent(event);
}
private void handleActionMove(MotionEvent event) {
int tempY = (int) event.getY();
if (!isRecored && firstItemIndex == 0) {
isRecored = true;
startY = tempY;
}
if (state != REFRESHING && isRecored) {
if (state == RELEASE_TO_REFRESH) {
setSelection(0);
if ((tempY - startY < TOUCH_SLOP) && (tempY - startY) > 0) {
state = PULL_TO_REFRESH;
}
}
if (state == PULL_TO_REFRESH) {
setSelection(0);
if (tempY - startY >= TOUCH_SLOP) {
state = RELEASE_TO_REFRESH;
} else if (tempY - startY <= 0) {
state = DONE;
}
}
if (state == DONE) {
if (tempY - startY > 0) {
state = PULL_TO_REFRESH;
}
}
mark.change(state, tempY - startY);
}
}
private void handleActionUp() {
if (state == PULL_TO_REFRESH) {
state = DONE;
mark.changeByAnimation(state);
} else if (state == RELEASE_TO_REFRESH) {
state = REFRESHING;
mark.changeByAnimation(state);
onRefresh();
}
isRecored = false;
}
private void handleActionDown(MotionEvent event) {
if (firstItemIndex == 0 && !isRecored) {
isRecored = true;
startY = (int) event.getY();
}
}
private void onRefresh() {
if (refreshListener != null) {
refreshListener.onRefresh();
}
}
public void startRefresh() {
state = REFRESHING;
mark.changeByAnimation(state);
onRefresh();
}
public void stopRefresh() {
state = DONE;
mark.changeByAnimation(state);
}
public void setOnRefreshListener(OnRefreshListener refreshListener) {
this.refreshListener = refreshListener;
isRefreshable = true;
}
/**
* 刷新监听器
*/
public interface OnRefreshListener {
public void onRefresh();
}
public void setOnScrollButtomListener(OnScrollButtomListener scrollButtomListener) {
this.scrollButtomListener = scrollButtomListener;
}
/**
* 滑动到最低端触发监听器
*/
public interface OnScrollButtomListener {
public void onScrollToButtom();
}
}
刷新标志类：
package cc.wxf.view.pull;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.os.Handler;
/**
* Created by ccwxf on 2016/3/30.
*/
public class PullMark {
//背景面板的半径、颜色
private static final int RADIUS_PAN = 40;
private static final int COLOR_PAN = Color.parseColor("#fafafa");
//面板阴影的半径、颜色
private static final int RADIUS_SHADOW = 5;
private static final int COLOR_SHADOW = Color.parseColor("#d9d9d9");
//面板中间的圆弧的半径、颜色、粗度、开始绘制角度
private static final int RADIUS_ARROWS = 20;
private static final int COLOR_ARROWS = Color.GREEN;
private static final int BOUND_ARROWS = 6;
private static final int START_ANGLE = 0;
// 开始绘制角度的变化率、总体绘制角度、总体绘制透明度
private static final int RATIO_SATRT_ANGLE = 3;
private static final int ALL_ANGLE = 270;
private static final int ALL_ALPHA = 255;
// 动画的高度渐变比率、时间刷新间隔
private static final float RATIO_TOUCH_SLOP = 7f;
private static final long RATIO_ANIMATION_DURATION = 10;
private PullToRefreshListView listView;
// 中点的X、Y坐标、初始隐藏时的Y坐标
private float doneCenterY = -(RADIUS_PAN + RADIUS_SHADOW) / 2;
private float centerX;
private float centerY = doneCenterY;
// 开始绘制的角度、需要绘制的角度、透明度
private int startAngle = START_ANGLE;
private int sweepAngle = startAngle;
private int alpha;
// 弧度变化比率，根据总体高度与总体弧度角度的比例决定
private float radioAngle = ALL_ANGLE * 1.0f / PullToRefreshListView.TOUCH_SLOP;
// 透明度变化比率，根据总体高度与总体透明度的比例决定
private float radioAlpha = ALL_ALPHA * 1.0f / PullToRefreshListView.TOUCH_SLOP;
// PullToRefreshListView的状态
private int state;
// 当前手指滑动的距离
private float mTouchLength;
// 是否启动旋转动画
private boolean isRotateAnimation = false;
// 画笔
private Paint mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private Handler handler = new Handler();
public PullMark(PullToRefreshListView listView) {
this.listView = listView;
}
/**
* 设置绘制的中点X坐标，在PullToRefreshListView的onMeasure中实现
* @param centerX
*/
public void setCenterX(int centerX){
this.centerX = centerX;
}
/**
* 表示一次普通的数据变化，在onTouchEvent中的ACTION_MOVE中触发
* @param state
* @param mTouchLength
*/
public void change(int state, float mTouchLength){
this.state = state;
this.mTouchLength = mTouchLength;
// 改变绘制的Y坐标
centerY = doneCenterY + mTouchLength;
// 改变绘制的透明度
alpha = (int) (mTouchLength * radioAlpha);
if(alpha > ALL_ALPHA){
alpha = ALL_ALPHA;
}else if(alpha < 0){
alpha = 0;
}
//改变绘制的起始角度
startAngle = startAngle + RATIO_SATRT_ANGLE;
if(startAngle >= 360){
startAngle = 0;
}
//改变绘制的弧度角度
sweepAngle = (int) (mTouchLength * radioAngle);
if(sweepAngle > ALL_ANGLE){
sweepAngle = ALL_ANGLE;
}else if(sweepAngle < 0){
sweepAngle = 0;
}
listView.invalidate();
}
/**
* 表示一次动画的变化，在onTouchEvent的ACTION_UP中或者手动startRefresh以及手动stopRefresh中触发
* @param state
*/
public void changeByAnimation(final int state){
this.state = state;
if(state == PullToRefreshListView.DONE){
//结束旋转动画（关闭正在刷新的效果）
isRotateAnimation = false;
}
//慢慢变化到起始位置
handler.postDelayed(new RunnableMove(state), RATIO_ANIMATION_DURATION);
}
/**
* 启动移动的处理
*/
public class RunnableMove implements Runnable{
private int state;
private int destination;
private float slop;
public RunnableMove(int state) {
this.state = state;
if(state == PullToRefreshListView.DONE){
destination = 0;
slop = RATIO_TOUCH_SLOP;
}else if(state == PullToRefreshListView.REFRESHING){
destination = PullToRefreshListView.TOUCH_SLOP;
slop = RATIO_TOUCH_SLOP * 5;
}
}
@Override
public void run() {
if(mTouchLength > destination){
mTouchLength -= slop;
change(state, mTouchLength);
handler.postDelayed(this, RATIO_ANIMATION_DURATION);
}else{
if(state == PullToRefreshListView.DONE){
// 直接将坐标初始化，否则会有一点点误差
centerY = doneCenterY;
listView.invalidate();
}else if(state == PullToRefreshListView.REFRESHING){
//启动旋转的动画效果
isRotateAnimation = true;
handler.postDelayed(new RunnableRotate(), RATIO_ANIMATION_DURATION);
}
}
}
}
/**
* 旋转动画的处理
*/
public class RunnableRotate implements Runnable{
@Override
public void run() {
if(isRotateAnimation){
//启动动画旋转效果
startAngle = startAngle + RATIO_SATRT_ANGLE;
if(startAngle >= 360){
startAngle = 0;
}
listView.invalidate();
handler.postDelayed(this, RATIO_ANIMATION_DURATION);
}else{
//回到初始位置
handler.postDelayed(new RunnableMove(state), RATIO_ANIMATION_DURATION);
}
}
}
/**
* 绘制刷新图标的标志
* @param mCanvas
*/
public void onDraw(Canvas mCanvas){
//绘制背景圆盘和阴影
mPaint.setStyle(Paint.Style.FILL);
mPaint.setColor(COLOR_PAN);
mPaint.setShadowLayer(RADIUS_SHADOW, 0, 0, COLOR_SHADOW);
mCanvas.drawCircle(centerX, centerY, RADIUS_PAN, mPaint);
//绘制圆弧
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setColor(COLOR_ARROWS);
mPaint.setStrokeWidth(BOUND_ARROWS);
mPaint.setAlpha(alpha);
mCanvas.drawArc(new RectF(centerX - RADIUS_ARROWS, centerY - RADIUS_ARROWS, centerX + RADIUS_ARROWS, centerY + RADIUS_ARROWS),
startAngle, sweepAngle, false, mPaint);
}
}
使用的时候，必须要设置了监听器才能有效的滑动：
final PullToRefreshListView listView = (PullToRefreshListView) findViewById(R.id.listView);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, new String[]{
"测试1","测试2","测试3","测试4","测试5","测试6",
});
listView.setAdapter(adapter);
listView.setOnRefreshListener(new PullToRefreshListView.OnRefreshListener() {
@Override
public void onRefresh() {
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
listView.stopRefresh();
}
}, 2000);
}
});
两个源代码文件就搞定了，demo工程就不提供了，很简单的。