Android中ListView下拉刷新的实现方法实例分析

2019-10-24 20:35:48

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这篇文章主要介绍了Android中ListView下拉刷新的实现方法,涉及Android操作ListView的相关技巧,具有一定参考借鉴价值,需要的朋友可以参考下

本文实例讲述了Android中ListView下拉刷新的实现方法。分享给大家供大家参考，具体如下：

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) {

if (firstVisibleItem == 0) {

isRefreshable = true;

} else {

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);

}

}

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"?>



<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:background="#000000" >



<RelativeLayout

android:id="@+id/head_contentLayout"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:paddingLeft="30dp" >



<FrameLayout

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_centerVertical="true" >



<ImageView

android:id="@+id/lvHeaderArrowIv"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_gravity="center"

android:src="@drawable/arrow" />



<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>



<LinearLayout

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_centerHorizontal="true"

android:gravity="center_horizontal"

android:orientation="vertical" >



<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" />



<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;

}

}