代碼解析
IPinnedHeader.java
該接口的設(shè)計目的主要是建立一個顯示在頂部的標(biāo)頭并添加其狀態(tài)屬性。該狀態(tài)屬性主要用于輔助屏幕滾動時設(shè)置相關(guān)行為。代碼的解析如下：
import android.view.View;
/**
* Adapter interface. The list adapter must implement this interface.
*/
public interface IPinnedHeader {
/**
* Pinned header state: don't show the header.
*/
//頂部已經(jīng)顯示該標(biāo)頭時或者當(dāng)ListView中item的數(shù)量為0時，不動態(tài)載入標(biāo)頭布局。此時頂部標(biāo)頭的狀態(tài)為@PINNED_HEADER_GONE
public static final int PINNED_HEADER_GONE = 0;
/**
* Pinned header state: show the header at the top of the list.
*/
//標(biāo)頭的狀態(tài)為可見
public static final int PINNED_HEADER_VISIBLE = 1;
/**
* Pinned header state: show the header. If the header extends beyond
* the bottom of the first shown element, push it up and clip.
*/
//頂部的標(biāo)頭的下一行是另一個標(biāo)頭時，頂部標(biāo)頭的狀態(tài)為@PINNED_HEADER_PUSHED_UP
public static final int PINNED_HEADER_PUSHED_UP = 2;
/**
* Computes the desired state of the pinned header for the given
* position of the first visible list item. Allowed return values are
* {@link #PINNED_HEADER_GONE}, {@link #PINNED_HEADER_VISIBLE} or
* {@link #PINNED_HEADER_PUSHED_UP}.
*/
//獲取頂部標(biāo)頭狀態(tài)
int getPinnedHeaderState(int position);
/**
* Configures the pinned header view to match the first visible list item.
*
* @param header pinned header view.
* @param position position of the first visible list item.
* @param alpha fading of the header view, between 0 and 255.
*/
//配置頂部標(biāo)頭
void configurePinnedHeader(View header, int position);
}
代碼解析
IIndexBarFilter.java
該接口的設(shè)計用于輔助左邊索引條的檢索，按下索引條時，顯示相應(yīng)位置的預(yù)覽字母。手指離開時，Listview顯示相應(yīng)位置的內(nèi)容。
public interface IIndexBarFilter {
void filterList(float sideIndexY,int position,String previewText);
}
代碼解析
PinnedHeaderListView .java
該類用于建立ListView，并實(shí)現(xiàn)頂部實(shí)現(xiàn)分組標(biāo)頭的功能。
/*
* A ListView that maintains a header pinned at the top of the list. The
* pinned header can be pushed up and dissolved as needed.
*/
public class PinnedHeaderListView extends ListView implements IIndexBarFilter {
// interface object that configure pinned header view position in list view
IPinnedHeader mAdapter;
// view objects
View mHeaderView,mIndexBarView,mPreviewTextView;
// flags that decide view visibility
boolean mHeaderVisibility=false;
boolean mPreviewVisibility=false;
// initially show index bar view with it's content
boolean mIndexBarVisibility=true;
// context object
Context mContext;
// view height and width
int mHeaderViewWidth,
mHeaderViewHeight,
mIndexBarViewWidth,
mIndexBarViewHeight,
mIndexBarViewMargin,
mPreviewTextViewWidth,
mPreviewTextViewHeight;
// touched index bar Y axis position used to decide preview text view position
float mIndexBarY;
public PinnedHeaderListView(Context context) {
super(context);
this.mContext = context;
}
public PinnedHeaderListView(Context context, AttributeSet attrs) {
super(context, attrs);
this.mContext = context;
}
public PinnedHeaderListView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
this.mContext = context;
}
//為ListView配置適配器
@Override
public void setAdapter(ListAdapter adapter) {
this.mAdapter = (PinnedHeaderAdapter)adapter;
super.setAdapter(adapter);
}
public void setPinnedHeaderView(View headerView) {
this.mHeaderView = headerView;
// Disable vertical fading when the pinned header is present
// TODO change ListView to allow separate measures for top and bottom fading edge;
// in this particular case we would like to disable the top, but not the bottom edge.
//FadingEdge用于暗示ListView上方或者下方還有更多內(nèi)容。因?yàn)檫@里頂部標(biāo)頭滾定，所以將其長度設(shè)置為0
if (mHeaderView != null) {
setFadingEdgeLength(0);
}
}
public void setIndexBarView(View indexBarView) {
mIndexBarViewMargin = (int)mContext.getResources().getDimension(R.dimen.index_bar_view_margin);
this.mIndexBarView = indexBarView;
}
public void setPreviewView(View previewTextView) {
this.mPreviewTextView=previewTextView;
}
//重寫@onMeasure方法，測量ListView中各組件的大小。
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (mHeaderView != null) {
measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec);
mHeaderViewWidth = mHeaderView.getMeasuredWidth();
mHeaderViewHeight = mHeaderView.getMeasuredHeight();
}
if (mIndexBarView != null && mIndexBarVisibility) {
measureChild(mIndexBarView, widthMeasureSpec, heightMeasureSpec);
mIndexBarViewWidth = mIndexBarView.getMeasuredWidth();
mIndexBarViewHeight = mIndexBarView.getMeasuredHeight();
}
if (mPreviewTextView != null && mPreviewVisibility) {
measureChild(mPreviewTextView, widthMeasureSpec, heightMeasureSpec);
mPreviewTextViewWidth = mPreviewTextView.getMeasuredWidth();
mPreviewTextViewHeight = mPreviewTextView.getMeasuredHeight();
}
}
//重寫@onLayout方法，將測量后的組件放置在指定位置。
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
if (mHeaderView != null) {
mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
configureHeaderView(getFirstVisiblePosition());
}
if (mIndexBarView != null && mIndexBarVisibility) {
mIndexBarView.layout(getMeasuredWidth()- mIndexBarViewMargin - mIndexBarViewWidth, mIndexBarViewMargin
, getMeasuredWidth()- mIndexBarViewMargin, getMeasuredHeight()- mIndexBarViewMargin);
}
if (mPreviewTextView != null && mPreviewVisibility) {
mPreviewTextView.layout(mIndexBarView.getLeft()-mPreviewTextViewWidth, (int)mIndexBarY-(mPreviewTextViewHeight/2)
, mIndexBarView.getLeft(), (int)(mIndexBarY-(mPreviewTextViewHeight/2))+mPreviewTextViewHeight);
}
}
public void setIndexBarVisibility(Boolean isVisible) {
if(isVisible) {
mIndexBarVisibility=true;
}
else {
mIndexBarVisibility=false;
}
}
private void setPreviewTextVisibility(Boolean isVisible) {
if(isVisible) {
mPreviewVisibility=true;
}
else {
mPreviewVisibility=false;
}
}
public void configureHeaderView(int position) {
if (mHeaderView == null) {
return;
}
int state = mAdapter.getPinnedHeaderState(position);
switch (state) {
case IPinnedHeader.PINNED_HEADER_GONE:
mHeaderVisibility = false;
break;
case IPinnedHeader.PINNED_HEADER_VISIBLE:
if (mHeaderView.getTop() != 0) {
mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
}
mAdapter.configurePinnedHeader(mHeaderView, position);
mHeaderVisibility = true;
break;
case IPinnedHeader.PINNED_HEADER_PUSHED_UP:
View firstView = getChildAt(0);
int bottom = firstView.getBottom();
// int itemHeight = firstView.getHeight();
int headerHeight = mHeaderView.getHeight();
int y;
if (bottom < headerHeight) {
y = (bottom - headerHeight);
}
else {
y = 0;
}
if (mHeaderView.getTop() != y) {
mHeaderView.layout(0, y, mHeaderViewWidth, mHeaderViewHeight + y);
}
mAdapter.configurePinnedHeader(mHeaderView, position);
mHeaderVisibility = true;
break;
}
}
//由于ListView是ViewGroup的子類，須重寫dispathDraw方法
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);// draw list view elements (zIndex == 1)
if (mHeaderView != null && mHeaderVisibility) {
drawChild(canvas, mHeaderView, getDrawingTime()); // draw pinned header view (zIndex == 2)
}
if (mIndexBarView != null && mIndexBarVisibility) {
drawChild(canvas, mIndexBarView, getDrawingTime()); // draw index bar view (zIndex == 3)
}
if (mPreviewTextView != null && mPreviewVisibility) {
drawChild(canvas, mPreviewTextView, getDrawingTime()); // draw preview text view (zIndex == 4)
}
}
//重寫onTouchEvent方法
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (mIndexBarView != null && ((IndexBarView)mIndexBarView).onTouchEvent(ev)) {
setPreviewTextVisibility(true);
return true;
}
else {
setPreviewTextVisibility(false);
return super.onTouchEvent(ev);
}
}
@Override
public void filterList(float indexBarY, int position,String previewText) {
this.mIndexBarY=indexBarY;
if(mPreviewTextView instanceof TextView)
((TextView)mPreviewTextView).setText(previewText);
setSelection(position);
}
}
