接下来几篇文章将对任老师的博文《可下拉的PinnedHeaderExpandableListView的实现》分步骤来详细实现，来学习一下大神的代码并记录一下。
原文出处：http://blog.csdn.net/singwhatiwanna/article/details/25546871
先看一下最终效果：
新建一个activity_main.xml文件
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<com.example.testexpandablelistview.ui.StickyLayout
android:id="@+id/sticky_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="0dp"
android:orientation="vertical">
<LinearLayout
android:id="@+id/header"
android:layout_width="match_parent"
android:layout_height="100dp"
android:gravity="center"
android:background="#78a524"
android:orientation="vertical">
</LinearLayout>
<LinearLayout
android:id="@+id/content"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
</LinearLayout>
</com.example.testexpandablelistview.ui.StickyLayout>
</RelativeLayout>上面的StickyLayout类就是我们自定义的LinearLayout,思路其实很简单，先获取StickyLayout中的header和content两个View，代码如下： private void initData(){
//使用getIdentifier()方法可以方便的获各应用包下的指定资源ID。
//详细请看：http://blog.sina.com.cn/s/blog_5da93c8f0100zlrx.html
int headerId = getResources().getIdentifier("header", "id", getContext().getPackageName());
int contentId = getResources().getIdentifier("content", "id", getContext().getPackageName());
if(headerId != 0 && contentId != 0){
mHeader = findViewById(headerId);
mContent = findViewById(contentId);
mOriginalHeaderHeight = mHeader.getMeasuredHeight();
mHeaderHeight = mOriginalHeaderHeight;
//是一个距离，表示滑动的时候，手的移动要大于这个距离才开始移动控件。
mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
Log.d(TAG, "mTouchSlop = " + mTouchSlop);
}else{
throw new NoSuchElementException("Did your view with "header" or "content" exist?");
}
}再处理屏幕的监听函数 @Override
public boolean onInterceptTouchEvent(MotionEvent event) {
int intercepted = 0;
int x = (int) event.getX();
int y = (int) event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mLastXIntercept = x;
mLastYIntercept = y;
mLastX = x;
mLastY = y;
intercepted = 0;
break;
case MotionEvent.ACTION_MOVE:
int deltaX = x - mLastXIntercept;
int deltaY = y - mLastYIntercept;
if(mStatus == STATUS_EXPANDED && deltaY <= -mTouchSlop){
intercepted = 1;
}else if(mGiveUpTouchEventListener != null){
if(mGiveUpTouchEventListener.giveUpTouchEvent(event) && deltaY >= mTouchSlop){
intercepted = 1;
}
}
break;
case MotionEvent.ACTION_UP:{
intercepted = 0;
mLastXIntercept = mLastYIntercept = 0;
break;
}
default:
break;
}
Log.d(TAG, "intercepted = " + intercepted);
//如果为1则返回true,传递给当前的onTouchEvent。如果为0则返回false,传递给子控件
return intercepted != 0;
}onInterceptTouchEvent是在ViewGroup里面定义的，用于拦截手势事件，每个手势事件都会先调用onInterceptTouchEvent,如果该方法返回true则拦截到事件，当前的onTouchEvent会触发，如果返回false则传递给子控件。 @Override
public boolean onTouchEvent(MotionEvent event) {
int x = (int) event.getX();
int y = (int) event.getY();
Log.d(TAG, "x=" + x + " y=" + y + " mlastY=" + mLastY);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_MOVE:
int deltaX = x - mLastX;
int deltaY = y - mLastY;
Log.d(TAG, "mHeaderHeight=" + mHeaderHeight + " deltaY=" + deltaY + " mlastY=" + mLastY);
mHeaderHeight +=deltaY;
setHeaderHeight(mHeaderHeight);
break;
case MotionEvent.ACTION_UP:
int destHeight = 0;
if(mHeaderHeight <= mOriginalHeaderHeight * 0.5){
destHeight = 0;
mStatus = STATUS_COLLAPSED;
}else{
destHeight = mOriginalHeaderHeight;
mStatus = STATUS_EXPANDED;
}
//慢慢滑向终点
this.smoothSetHeaderHeight(mHeaderHeight, destHeight, 500);
break;
default:
break;
}
mLastX = x;
mLastY = y;
return true;
}滑动的时候将事件传递给onTouchEvent滑动事件中setHeaderHeight改变了上面的header部分的高度，当抬起时会判断是否改变了原始高度的一般，再慢慢滑向终点。
/*
* 改变header的高度
*/
private void setHeaderHeight(int height) {
if(height < 0){
height = 0;
} else if (height > mOriginalHeaderHeight) {
height = mOriginalHeaderHeight;
}
if(mHeaderHeight != height || true){
mHeaderHeight = height;
mHeader.getLayoutParams().height = mHeaderHeight;
mHeader.requestLayout();
}
} public void smoothSetHeaderHeight(final int from, final int to, long duration) {
final int frameCount = (int) (duration / 1000f * 30) + 1;
final float partation = (to - from) / (float) frameCount;
new Thread("Thread#smoothSetHeaderHeight") {
public void ruan(){
for(int i = 0; i < frameCount; i++) {
final int height;
if(i == frameCount - 1){
height = to;
}else{
height = (int)(from + partation * i);
}
post(new Runnable() {
@Override
public void run() {
setHeaderHeight(height);
}
});
try {
sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
}上面的View.post(Runnable)方法的作用是将Runnable对象添加到UI线程中运行，从而改变header部分的高度。StickyLayout类的完整代码如下：
package com.example.testexpandablelistview.ui;
import java.util.NoSuchElementException;
import android.annotation.TargetApi;
import android.content.Context;
import android.os.Build;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.widget.LinearLayout;
/**
* 自定义LinearLayout
* @author 转自：http://blog.csdn.net/singwhatiwanna/article/details/25546871
*
*/
public class StickyLayout extends LinearLayout{
private static final String TAG = "StickyLayout";
public interface OnGiveUpTouchEnventListener{
public boolean giveUpTouchEvent(MotionEvent event);
}
private View mHeader; //上面部分，下面成为Header
private View mContent; //下面部分
private OnGiveUpTouchEnventListener mGiveUpTouchEventListener;
private int mTouchSlop; //移动的距离
//header的高度 单位：px
private int mOriginalHeaderHeight; //Header部分的原始高度
private int mHeaderHeight; //Header部分现在的实际高度（随着手势滑动会变化）
private int mStatus = STATUS_EXPANDED; //当前的状态
public static final int STATUS_EXPANDED = 1; //展开状态
public static final int STATUS_COLLAPSED = 2; //闭合状态
//分别记录上次滑动的坐标
private int mLastX = 0;
private int mLastY = 0;
//分别记录上次滑动的坐标（onInterceptTouchEvent)
private int mLastXIntercept = 0;
private int mLastYIntercept = 0;
/*
* 构造函数1
*/
public StickyLayout(Context context){
super(context);
}
/*
* 构造函数2
*/
public StickyLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
/* 构造函数3
* TargetApi 标签的作用是使高版本的api代码在低版本sdk不报错
*/
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public StickyLayout(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
/**
* onWindowFocusChanged方法用于监听一个activity是否加载完毕，Activity生命周期中，
* onStart, onResume, onCreate都不是真正visible的时间点，真正的visible时间点是onWindowFocusChanged()函数被执行时。
*/
@Override
public void onWindowFocusChanged(boolean hasWindowFocus) {
super.onWindowFocusChanged(hasWindowFocus);
//如果是activity加载完毕，mHeader和mContent未被初始化，则执行初始化方法。
if(hasWindowFocus && (mHeader == null || mContent == null)){
initData();
}
}
private void initData(){
//使用getIdentifier()方法可以方便的获各应用包下的指定资源ID。
//详细请看：http://blog.sina.com.cn/s/blog_5da93c8f0100zlrx.html
int headerId = getResources().getIdentifier("header", "id", getContext().getPackageName());
int contentId = getResources().getIdentifier("content", "id", getContext().getPackageName());
if(headerId != 0 && contentId != 0){
mHeader = findViewById(headerId);
mContent = findViewById(contentId);
mOriginalHeaderHeight = mHeader.getMeasuredHeight();
mHeaderHeight = mOriginalHeaderHeight;
//是一个距离，表示滑动的时候，手的移动要大于这个距离才开始移动控件。
mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
Log.d(TAG, "mTouchSlop = " + mTouchSlop);
}else{
throw new NoSuchElementException("Did your view with "header" or "content" exist?");
}
}
@Override
public boolean onInterceptTouchEvent(MotionEvent event) {
int intercepted = 0;
int x = (int) event.getX();
int y = (int) event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
mLastXIntercept = x;
mLastYIntercept = y;
mLastX = x;
mLastY = y;
intercepted = 0;
break;
case MotionEvent.ACTION_MOVE:
int deltaX = x - mLastXIntercept;
int deltaY = y - mLastYIntercept;
if(mStatus == STATUS_EXPANDED && deltaY <= -mTouchSlop){
intercepted = 1;
}else if(mGiveUpTouchEventListener != null){
if(mGiveUpTouchEventListener.giveUpTouchEvent(event) && deltaY >= mTouchSlop){
intercepted = 1;
}
}
break;
case MotionEvent.ACTION_UP:{
intercepted = 0;
mLastXIntercept = mLastYIntercept = 0;
break;
}
default:
break;
}
Log.d(TAG, "intercepted = " + intercepted);
//如果为1则返回true,传递给当前的onTouchEvent。如果为0则返回false,传递给子控件
return intercepted != 0;
}
@Override
public boolean onTouchEvent(MotionEvent event) {
int x = (int) event.getX();
int y = (int) event.getY();
Log.d(TAG, "x=" + x + " y=" + y + " mlastY=" + mLastY);
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
break;
case MotionEvent.ACTION_MOVE:
int deltaX = x - mLastX;
int deltaY = y - mLastY;
Log.d(TAG, "mHeaderHeight=" + mHeaderHeight + " deltaY=" + deltaY + " mlastY=" + mLastY);
mHeaderHeight +=deltaY;
setHeaderHeight(mHeaderHeight);
break;
case MotionEvent.ACTION_UP:
int destHeight = 0;
if(mHeaderHeight <= mOriginalHeaderHeight * 0.5){
destHeight = 0;
mStatus = STATUS_COLLAPSED;
}else{
destHeight = mOriginalHeaderHeight;
mStatus = STATUS_EXPANDED;
}
//慢慢滑向终点
this.smoothSetHeaderHeight(mHeaderHeight, destHeight, 500);
break;
default:
break;
}
mLastX = x;
mLastY = y;
return true;
}
public void smoothSetHeaderHeight(final int from, final int to, long duration) {
final int frameCount = (int) (duration / 1000f * 30) + 1;
final float partation = (to - from) / (float) frameCount;
new Thread("Thread#smoothSetHeaderHeight") {
public void ruan(){
for(int i = 0; i < frameCount; i++) {
final int height;
if(i == frameCount - 1){
height = to;
}else{
height = (int)(from + partation * i);
}
post(new Runnable() {
@Override
public void run() {
setHeaderHeight(height);
}
});
try {
sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}.start();
}
/*
* 改变header的高度
*/
private void setHeaderHeight(int height) {
if(height < 0){
height = 0;
} else if (height > mOriginalHeaderHeight) {
height = mOriginalHeaderHeight;
}
if(mHeaderHeight != height || true){
mHeaderHeight = height;
mHeader.getLayoutParams().height = mHeaderHeight;
mHeader.requestLayout();
}
}
}
MainActivity.javapackage com.example.testexpandablelistview;
import android.app.Activity;
import android.os.Bundle;
import com.example.testexpandablelistview.ui.StickyLayout;
public class MainActivity extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
运行效果：
原文地址：http://blog.csdn.net/singwhatiwanna/article/details/25546871