Android自定义控制(五)仿新浪微博的下拉刷新

网上有很多很有名的开源框架,这里就来拉拉PullToRefresh这个框架,也就是我们平时用的下拉刷新啦,当然你问我这个有什么用啊?别人已经写好了,这里主要是学习以及练习,练习的次数多了,一切就顺其自然的会了.

废话少说,先上图,再上代码:

1.要想实现下拉刷新功能必须要有个下拉刷新的布局,是吧?

[html] view plaincopy

<?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="match_parent"
android:orientation="vertical" >
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingBottom="10dip"
android:paddingTop="10dip" >
<LinearLayout
android:id="@+id/layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:gravity="center"
android:orientation="vertical" >
<TextView
android:id="@+id/tip"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/state" />
<TextView
android:id="@+id/lastupdate_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
<ProgressBar
android:id="@+id/progress"
style="?android:attr/progressBarStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toLeftOf="@id/layout"
android:layout_marginRight="20dip"
android:visibility="gone" />
<ImageView
android:id="@+id/arrow"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignTop="@+id/layout"
android:layout_marginRight="19dp"
android:layout_toLeftOf="@+id/layout"
android:src="@drawable/arrow_down" />
</RelativeLayout>
</LinearLayout>

2.你要把它加入到布局里面吧!

[java] view plaincopy

headView=layoutInflater.from(context).inflate(R.layout.header_layout, null);
this.addHeaderView(headView);

3.加入到布局直接显示出来也不符合需求啊,所以这一步需要隐藏布局,当然不能和前一篇博客( Android自定义控件(四)仿网易客户端上拉加载更多 )一样直接隐藏,直接隐藏满足不了如图的要求,我们这里采取的是设置头部布局的高度为实际高度的负值,这样就实现了隐藏功能,当下拉的时候,还不至于一次就全部显示出来,ok这种办法能够实现图中的要求

[java] view plaincopy

headerHeight = headView.getMeasuredHeight();
setHeaderViewHeight(-headerHeight);

[java] view plaincopy

/**
* 设置头部布局的高度
*
* @param i
*/
private void setHeaderViewHeight(int headerHeight) {
headView.setPadding(headView.getPaddingLeft(), headerHeight,
headView.getPaddingRight(), headView.getPaddingBottom());
//重绘
headView.invalidate();
}

4.跑起来之后,白瞎了,没实现想要的功能,也就是说没有把头部布局隐藏掉,哎,跟踪代码之后发现高度为0,郭神说过在measure之前,getMeasureWidth()和getMeasureHeight()都为零,好吧,那就先measure吧!

[java] view plaincopy

private void measureView(View view) {
ViewGroup.LayoutParams lp = view.getLayoutParams();
if (lp == null) {
lp = new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
}
int width = ViewGroup.getChildMeasureSpec(0, 0, lp.width);
int height;
int tempHeight=lp.height;
if (tempHeight > 0) {
height = MeasureSpec.makeMeasureSpec(tempHeight,
MeasureSpec.EXACTLY);
} else {
height = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
}
view.measure(width, height);
}

5.隐藏成功了,下面就要实现具体的功能了,下拉刷新,松开刷新,正在刷新这三个状态,是通过手势改变状态,所以这里要实现onTouch,当然还有OnScrollListener

需要用到firstVisibleItem判断Listview向上滑动还是向下滑动,如果firstVisibleItem==0说明到达ListView的头部了,当然你还需要一个布尔值判断是否按下滑动

[java] view plaincopy

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

重写onTouchEvent,通过firstVisibleItem和布尔值判断按下,抬起,滑动

[java] view plaincopy

@Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
if (firstVisibleItem == 0) {
isRemark = true;
startY = (int) ev.getY();
}
break;
case MotionEvent.ACTION_MOVE:
onMove(ev);
break;
case MotionEvent.ACTION_UP:
if (state==RELEASE) {
state=REFRASH;
reflashViewByState();
//更新数据
isRefreshListener.onRefresh();
}else if (state==PULL) {
state=NONE;
isRemark=false;
refreshDrawableState();
}
break;
}
return super.onTouchEvent(ev);
}

代码不全,先解释一下,后面附上全部代码

按下时,如果firstVisibleItem为0,说明到达listview的顶部,并且可以按下,把isRemark赋值为true,滑动时改变头部布局的状态

[java] view plaincopy

/**
* 移动过程的状态变换
*
* @param ev
*/
private void onMove(MotionEvent ev) {
if (!isRemark) {
return;
}
int tempY = (int) ev.getY();
int space = tempY - startY;
int topPadding = space - headerHeight;
switch (state) {
case NONE:
if (space>0) {
state=PULL;
reflashViewByState();
}
break;
case PULL:
setHeaderViewHeight(topPadding);
if (space>headerHeight+30&&scrollState==SCROLL_STATE_IDLE) {
state=RELEASE;
reflashViewByState();
}
break;
case RELEASE:
setHeaderViewHeight(topPadding);
if (space<headerHeight+30) {
state=PULL;
reflashViewByState();
}else if (space<=0) {
state=NONE;
reflashViewByState();
}
break;
}
}

根据滑动之后和动画前y值的变化判断滑动状态,当space大于零时,当前状态变为下拉刷新,如果space大于某个值时,当前状态变为松开可以刷新,当space大于零小于某个值时,当前状态为下拉刷新状态,当space小于零时,当前状态变为正常状态.当然状态改变时,界面也要随着改变

[java] view plaincopy

/**
*根据状态刷新当前页面
*/
private void reflashViewByState() {
TextView tip = (TextView) headView.findViewById(R.id.tip);
ImageView arrow = (ImageView) headView.findViewById(R.id.arrow);
ProgressBar progress = (ProgressBar) headView.findViewById(R.id.progress);
RotateAnimation anim = new RotateAnimation(0, 180,
RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
anim.setDuration(500);
anim.setFillAfter(true);
RotateAnimation anim1 = new RotateAnimation(180, 0,
RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
anim1.setDuration(500);
anim1.setFillAfter(true);
switch (state) {
case NONE:
setHeaderViewHeight(-headerHeight);
arrow.clearAnimation();
break;
case PULL:
arrow.setVisibility(View.VISIBLE);
progress.setVisibility(View.GONE);
tip.setText("下拉刷新");
arrow.clearAnimation();
arrow.setAnimation(anim1);
break;
case RELEASE:
arrow.setVisibility(View.VISIBLE);
progress.setVisibility(View.GONE);
tip.setText("松开刷新");
arrow.clearAnimation();
arrow.setAnimation(anim);
break;
case REFRASH:
setHeaderViewHeight(50);
arrow.setVisibility(View.GONE);
progress.setVisibility(View.VISIBLE);
tip.setText("正在刷新");
arrow.clearAnimation();
break;
}
}

界面上主要改变的就是提示,箭头和progress,正常状态下,界面不可见,下拉刷新状态下,箭头可见并且朝下,提示信息为下拉刷新并且progress不可见,松开刷新状态,箭头朝上,progress不可见,提示信息为下拉刷新,正在加载状态箭头不可见,progress可见,提示信息改为正在刷新

当然,在变成正在加载状态时,还要加载更过数据

[java] view plaincopy

public interface IsRefreshListener{
public void onRefresh();
}
public void setIsRefreshListener(IsRefreshListener isRefreshListener){
this.isRefreshListener=isRefreshListener;
}

加载完数据后,还要通知listview刷新结束

[java] view plaincopy

/**
* 获取完数据；
*/
public void reflashComplete() {
state = NONE;
isRemark = false;
reflashViewByState();
TextView lastupdatetime = (TextView) headView
.findViewById(R.id.lastupdate_time);
SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 hh:mm:ss");
Date date = new Date(System.currentTimeMillis());
String time = format.format(date);
lastupdatetime.setText(time);
}

自定义下拉刷新控件就这样完成了,不懂得留言吧,我尽量给你解答,自定义这东西,写多了也就知道怎么写了

下面附上自定义下拉刷新控件的全部代码:

[java] view plaincopy

package com.sdufe.thea.guo.view;
import java.text.SimpleDateFormat;
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.RotateAnimation;
import android.widget.AbsListView;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListView;
import com.sdufe.thea.guo.R;
public class PullToRefreshListView extends ListView implements OnScrollListener {
View headView;
int headerHeight;
int firstVisibleItem;
int scrollState;
boolean isRemark;
int startY;
int state;
final int NONE = 0;
final int PULL = 1;
final int RELEASE = 2;
final int REFRASH = 3;
IsRefreshListener isRefreshListener;
public PullToRefreshListView(Context context, AttributeSet attrs,
int defStyle) {
super(context, attrs, defStyle);
initView(context);
}
public PullToRefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
initView(context);
}
public PullToRefreshListView(Context context) {
super(context);
initView(context);
}
private void initView(Context context) {
headView = LayoutInflater.from(context).inflate(R.layout.header_layout,
null);
measureView(headView);
headerHeight = headView.getMeasuredHeight();
setHeaderViewHeight(-headerHeight);
addView(headView);
setOnScrollListener(this);
}
/**
* 计算宽高
*
* @param view
*/
private void measureView(View view) {
ViewGroup.LayoutParams lp = view.getLayoutParams();
if (lp == null) {
lp = new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.WRAP_CONTENT);
}
int width = ViewGroup.getChildMeasureSpec(0, 0, lp.width);
int height;
int tempHeight = lp.height;
if (tempHeight > 0) {
height = MeasureSpec.makeMeasureSpec(tempHeight,
MeasureSpec.EXACTLY);
} else {
height = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED);
}
view.measure(width, height);
}
/**
* 设置头部布局的高度
*
* @param i
*/
private void setHeaderViewHeight(int headerHeight) {
headView.setPadding(headView.getPaddingLeft(), headerHeight,
headView.getPaddingRight(), headView.getPaddingBottom());
// 重绘
headView.invalidate();
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
this.scrollState = scrollState;
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
this.firstVisibleItem = firstVisibleItem;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
if (firstVisibleItem == 0) {
isRemark = true;
startY = (int) ev.getY();
}
break;
case MotionEvent.ACTION_MOVE:
onMove(ev);
break;
case MotionEvent.ACTION_UP:
if (state==RELEASE) {
state=REFRASH;
reflashViewByState();
//更新数据
isRefreshListener.onRefresh();
}else if (state==PULL) {
state=NONE;
isRemark=false;
refreshDrawableState();
}
break;
}
return super.onTouchEvent(ev);
}
/**
* 移动过程的状态变换
*
* @param ev
*/
private void onMove(MotionEvent ev) {
if (!isRemark) {
return;
}
int tempY = (int) ev.getY();
int space = tempY - startY;
int topPadding = space - headerHeight;
switch (state) {
case NONE:
if (space>0) {
state=PULL;
reflashViewByState();
}
break;
case PULL:
setHeaderViewHeight(topPadding);
if (space>headerHeight+30&&scrollState==SCROLL_STATE_IDLE) {
state=RELEASE;
reflashViewByState();
}
break;
case RELEASE:
setHeaderViewHeight(topPadding);
if (space<headerHeight+30) {
state=PULL;
reflashViewByState();
}else if (space<=0) {
state=NONE;
reflashViewByState();
}
break;
}
}
/**
* 获取完数据；
*/
public void reflashComplete() {
state = NONE;
isRemark = false;
reflashViewByState();
TextView lastupdatetime = (TextView) headView
.findViewById(R.id.lastupdate_time);
SimpleDateFormat format = new SimpleDateFormat("yyyy年MM月dd日 hh:mm:ss");
Date date = new Date(System.currentTimeMillis());
String time = format.format(date);
lastupdatetime.setText(time);
}
/**
*根据状态刷新当前页面
*/
private void reflashViewByState() {
TextView tip = (TextView) headView.findViewById(R.id.tip);
ImageView arrow = (ImageView) headView.findViewById(R.id.arrow);
ProgressBar progress = (ProgressBar) headView.findViewById(R.id.progress);
RotateAnimation anim = new RotateAnimation(0, 180,
RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
anim.setDuration(500);
anim.setFillAfter(true);
RotateAnimation anim1 = new RotateAnimation(180, 0,
RotateAnimation.RELATIVE_TO_SELF, 0.5f,
RotateAnimation.RELATIVE_TO_SELF, 0.5f);
anim1.setDuration(500);
anim1.setFillAfter(true);
switch (state) {
case NONE:
setHeaderViewHeight(-headerHeight);
arrow.clearAnimation();
break;
case PULL:
arrow.setVisibility(View.VISIBLE);
progress.setVisibility(View.GONE);
tip.setText("下拉刷新");
arrow.clearAnimation();
arrow.setAnimation(anim1);
break;
case RELEASE:
arrow.setVisibility(View.VISIBLE);
progress.setVisibility(View.GONE);
tip.setText("松开刷新");
arrow.clearAnimation();
arrow.setAnimation(anim);
break;
case REFRASH:
setHeaderViewHeight(50);
arrow.setVisibility(View.GONE);
progress.setVisibility(View.VISIBLE);
tip.setText("正在刷新");
arrow.clearAnimation();
break;
}
}
public interface IsRefreshListener{
public void onRefresh();
}
public void setIsRefreshListener(IsRefreshListener isRefreshListener){
this.isRefreshListener=isRefreshListener;
}
}

下面就是怎么用了

[html] view plaincopy

<com.sdufe.thea.guo.view.PullToRefreshListView
android:id="@+id/pull_to_refresh"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>

下面的用法就跟listview差不多了,提示一点要实现IsRefreshListener接口,在onRefresh()里面加载更多数据

[java] view plaincopy

package com.sdufe.thea.guo;
import java.util.ArrayList;
import java.util.List;
import com.sdufe.thea.guo.view.PullToRefreshListView;
import com.sdufe.thea.guo.view.PullToRefreshListView.IsRefreshListener;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.ArrayAdapter;
public class MainActivity extends Activity implements IsRefreshListener{
PullToRefreshListView listView;
ArrayAdapter<String> adapter;
List<String> list;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (PullToRefreshListView) findViewById(R.id.pull_to_refresh);
initData();
adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, list);
listView.setAdapter(adapter);
}
private void initData() {
list = new ArrayList<String>();
list.add("123456789");
list.add("123456789");
list.add("123456789");
}
@Override
public void onRefresh() {
list.add("爸爸");
list.add("妈妈");
list.add("我");
adapter.notifyDataSetChanged();
listView.reflashComplete();
}
}

今天就到此结束啦,不懂的,留言

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