Android自己定义组件系列——进阶实践
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上一篇《Android自己定义组件系列【5】——进阶实践（1）》中对任老师的《可下拉的PinnedHeaderExpandableListView的实现》前一部分进行了实现，这一篇我们来看看ExpandableListView的使用并实现剩下的部分。
原文出处：http://blog.csdn.net/singwhatiwanna/article/details/25546871
一、ExpandableListView的使用方法
ExpandableListView是ListView的子类，它在普通ListView的基础上进行了扩展，适配器为ExpandableListAdapter。
与Adapter相似的是。实现ExpandableListAdapter也有例如以下方式：
1、扩展BaseExpandableListAdapter实现ExpandableListAdapter
2、使用SimpleExpandableListAdapter将两个List集合包装成ExpandableListAdapter
3、使用SimpleCursorTreeAdapter将Cursor中的数据包装成SimpleCursorTreeAdapter
接下来用第一种方式来做个小样例。来看看ExpandableListView的使用
ExpandableListAdapter adapter = new BaseExpandableListAdapter() {
@Override
public boolean isChildSelectable(int arg0, int arg1) {
// TODO Auto-generated method stub
return false;
}
@Override
public boolean hasStableIds() {
// TODO Auto-generated method stub
return false;
}
@Override
public View getGroupView(int arg0, boolean arg1, View arg2, ViewGroup arg3) {
// TODO Auto-generated method stub
return null;
}
@Override
public long getGroupId(int arg0) {
// TODO Auto-generated method stub
return 0;
}
@Override
public int getGroupCount() {
// TODO Auto-generated method stub
return 0;
}
@Override
public Object getGroup(int arg0) {
// TODO Auto-generated method stub
return null;
}
@Override
public int getChildrenCount(int arg0) {
// TODO Auto-generated method stub
return 0;
}
@Override
public View getChildView(int arg0, int arg1, boolean arg2, View arg3,
ViewGroup arg4) {
// TODO Auto-generated method stub
return null;
}
@Override
public long getChildId(int arg0, int arg1) {
// TODO Auto-generated method stub
return 0;
}
@Override
public Object getChild(int arg0, int arg1) {
// TODO Auto-generated method stub
return null;
}
};能够看到BaseExpandableListApdater中的方法非常多，主要方法介绍例如以下：getGroupCount():返回组列表数量
getGroupView():返回的View作为组列表项
getChildrenCount():返回子列表项的数量
getChildView():返回的View作为特定组、特定位置的子列表项
package com.example.expandablelistviewtest; import android.app.Activity; import android.os.Bundle; import android.view.Gravity; import android.view.View; import android.view.ViewGroup; import android.widget.AbsListView; import android.widget.BaseExpandableListAdapter; import android.widget.ExpandableListAdapter; import android.widget.ExpandableListView; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.TextView; public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); ExpandableListAdapter adapter = new BaseExpandableListAdapter() { int[] logos = new int[] { R.drawable.ic_launcher, R.drawable.ic_launcher, R.drawable.ic_launcher }; private String[] groupTypes = new String[]{ "计算机语言", "人类语言", "动物语言" }; private String[][] childTypes = new String[][] { {"Java", "C++", "C", "php"}, {"汉语", "英语", "日语", "法语"}, {"咕咕", "汪汪", "喵喵"} }; // 获取指定组位置、指定子列表项处的子列表项数据 @Override public Object getChild(int groupPosition, int childPosition) { return childTypes[groupPosition][childPosition]; } @Override public long getChildId(int groupPosition, int childPosition) { return childPosition; } @Override public int getChildrenCount(int groupPosition) { return childTypes[groupPosition].length; } private TextView getTextView() { AbsListView.LayoutParams lp = new AbsListView.LayoutParams( ViewGroup.LayoutParams.MATCH_PARENT, 64); TextView textView = new TextView(MainActivity.this); textView.setLayoutParams(lp); textView.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT); textView.setPadding(36, 0, 0, 0); textView.setTextSize(20); return textView; } // 该方法决定每一个子选项的外观 @Override public View getChildView(int groupPosition, int childPosition, boolean isLastChild, View convertView, ViewGroup parent) { TextView textView = getTextView(); textView.setText(getChild(groupPosition, childPosition) .toString()); return textView; } // 获取指定组位置处的组数据 @Override public Object getGroup(int groupPosition) { return groupTypes[groupPosition]; } @Override public int getGroupCount() { return groupTypes.length; } @Override public long getGroupId(int groupPosition) { return groupPosition; } // 该方法决定每一个组选项的外观 @Override public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent) { LinearLayout ll = new LinearLayout(MainActivity.this); ll.setOrientation(0); ImageView logo = new ImageView(MainActivity.this); logo.setImageResource(logos[groupPosition]); ll.addView(logo); TextView textView = getTextView(); textView.setText(getGroup(groupPosition).toString()); ll.addView(textView); return ll; } @Override public boolean isChildSelectable(int groupPosition, int childPosition) { return true; } @Override public boolean hasStableIds() { return true; } }; ExpandableListView expandListView = (ExpandableListView) findViewById(R.id.list); expandListView.setAdapter(adapter); } }
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<ExpandableListView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content"/>
</RelativeLayout>
二、代码分析
首先看onCreate方法：
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
expandableListView = (PinnedHeaderExpandableListView) findViewById(R.id.expandablelist);
stickyLayout = (StickyLayout)findViewById(R.id.sticky_layout);
initData();
adapter = new MyexpandableListAdapter(this);
expandableListView.setAdapter(adapter);
// 展开全部group
for (int i = 0, count = expandableListView.getCount(); i < count; i++) {
expandableListView.expandGroup(i);
}
expandableListView.setOnHeaderUpdateListener(this);
expandableListView.setOnChildClickListener(this);
expandableListView.setOnGroupClickListener(this);
stickyLayout.setOnGiveUpTouchEventListener(this);
}前面几行非常easy。和上面的样例差点儿一样。我们仅仅须要再关注一下initData()方法和以下的几行监听函数。initData()中是模拟的数据。例如以下：
void initData() {
groupList = new ArrayList<Group>();
Group group = null;
for (int i = 0; i < 3; i++) {
group = new Group();
group.setTitle("group-" + i);
groupList.add(group);
}
childList = new ArrayList<List<People>>();
for (int i = 0; i < groupList.size(); i++) {
ArrayList<People> childTemp;
if (i == 0) {
childTemp = new ArrayList<People>();
for (int j = 0; j < 13; j++) {
People people = new People();
people.setName("yy-" + j);
people.setAge(30);
people.setAddress("sh-" + j);
childTemp.add(people);
}
} else if (i == 1) {
childTemp = new ArrayList<People>();
for (int j = 0; j < 8; j++) {
People people = new People();
people.setName("ff-" + j);
people.setAge(40);
people.setAddress("sh-" + j);
childTemp.add(people);
}
} else {
childTemp = new ArrayList<People>();
for (int j = 0; j < 23; j++) {
People people = new People();
people.setName("hh-" + j);
people.setAge(20);
people.setAddress("sh-" + j);
childTemp.add(people);
}
}
childList.add(childTemp);
}
}接下来我们看看监听这几个监听函数public class MainActivity extends Activity implements
ExpandableListView.OnChildClickListener,
ExpandableListView.OnGroupClickListener,
OnHeaderUpdateListener, OnGiveUpTouchEventListener {从Activity的继承关系上看。OnChildClickListener和OnGroupClickListener是ExpandableListView类的监听函数。 @Override
public boolean onGroupClick(final ExpandableListView parent, final View v,
int groupPosition, final long id) {
return false;
}
@Override
public boolean onChildClick(ExpandableListView parent, View v,
int groupPosition, int childPosition, long id) {
Toast.makeText(MainActivity.this,
childList.get(groupPosition).get(childPosition).getName(), 1)
.show();
return false;
}再来看看OnHeaderUpdateListener，这个监听函数实际上是在重写（自己定义）的ExpandableListView中自己定义的监听。 public void setOnHeaderUpdateListener(OnHeaderUpdateListener listener) {
mHeaderUpdateListener = listener;
if (listener == null) {
return;
}
mHeaderView = listener.getPinnedHeader();
int firstVisiblePos = getFirstVisiblePosition();
int firstVisibleGroupPos = getPackedPositionGroup(getExpandableListPosition(firstVisiblePos));
listener.updatePinnedHeader(firstVisibleGroupPos);
requestLayout();
postInvalidate();
}getPinnedHeader()方法创建（得到）一个列表头。然后通过updatePinnedHeader方法设置当前可见的子列表元素的组名称。
requestLayout()方法的作用是当view确定自身已经不再适合现有的区域时，该view本身调用这种方法要求parent view又一次调用他的onMeasure onLayout来对又一次设置自己位置。特别的当view的layoutparameter发生改变，而且它的值还没能应用到view上，这时候适合调用这种方法。
postInvalidate()方法的作用是实现界面刷新。
public interface OnHeaderUpdateListener {
/**
* 採用单例模式返回同一个view对象就可以
* 注意：view必须要有LayoutParams
*/
public View getPinnedHeader();
public void updatePinnedHeader(int firstVisibleGroupPos);
}从OnHeaderUpdateListener监听函数的定义上看。当触发监听后会调用两个方法的实现例如以下： @Override
public View getPinnedHeader() {
if (mHeaderView == null) {
mHeaderView = (ViewGroup) getLayoutInflater().inflate(R.layout.group, null);
mHeaderView.setLayoutParams(new LayoutParams(
LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
}
return mHeaderView;
} @Override
public void updatePinnedHeader(int firstVisibleGroupPos) {
Group firstVisibleGroup = (Group) adapter.getGroup(firstVisibleGroupPos);
TextView textView = (TextView) getPinnedHeader().findViewById(R.id.group);
textView.setText(firstVisibleGroup.getTitle());
}接下来我们须要知道什么情况下回触发这个监听函数。 protected void refreshHeader() {
if (mHeaderView == null) {
return;
}
int firstVisiblePos = getFirstVisiblePosition();
int pos = firstVisiblePos + 1;
int firstVisibleGroupPos = getPackedPositionGroup(getExpandableListPosition(firstVisiblePos));
int group = getPackedPositionGroup(getExpandableListPosition(pos));
if (group == firstVisibleGroupPos + 1) {
View view = getChildAt(1);
if (view.getTop() <= mHeaderHeight) {
int delta = mHeaderHeight - view.getTop();
mHeaderView.layout(0, -delta, mHeaderWidth, mHeaderHeight - delta);
}
} else {
mHeaderView.layout(0, 0, mHeaderWidth, mHeaderHeight);
}
if (mHeaderUpdateListener != null) {
mHeaderUpdateListener.updatePinnedHeader(firstVisibleGroupPos);
}
}能够看到再调用refreshHeader()方法的时候会触发updatePinnerHeader方法。 @Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
if (totalItemCount > 0) {
refreshHeader();
}
if (mScrollListener != null) {
mScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
}
}呵呵，这下最终恍然大悟了。在onScroll方法中调用了refreshHeader，这就是说在滑动屏幕的时候OnHeaderUpdateListener监听会触发。会不断的推断是否应该改变列名称。快凌晨1点钟了，今天就分析到这吧。明天继续。
再次声明一下，本文是为了学习Android自己定义组件，对任老师博客《可下拉的PinnedHeaderExpandableListView的实现》进行具体解读。假设有问题希望指出。
原文出处：http://blog.csdn.net/singwhatiwanna/article/details/25546871
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