Android 实现带字母索引的侧边栏功能

概述之前已经用自定义View做出如下这样一个效果了这两天需要重新拿来使用，发现效果虽然做出来了，不过思路不太对，就重新参考写了一个，用法也更为简单了

之前已经用自定义view做出如下这样一个效果了

这两天需要重新拿来使用，发现效果虽然做出来了，不过思路不太对，就重新参考写了一个，用法也更为简单了

首要的自然是需要继承VIEw绘制出侧边栏，并向外提供一个监听字母索引变化的方法

/** * 作者：叶应是叶 * 时间：2017/8/20 11:38 * 描述： */public class LetterIndexVIEw extends VIEw { public interface OntouchingLetterChangedListener {  voID onHit(String letter);  voID onCancel(); } private OntouchingLetterChangedListener touchingLetterChangedListener; private Paint paint; private boolean hit; private final String[] letters = {"↑","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","#"}; private final int DEFAulT_WIDTH; public LetterIndexVIEw(Context context) {  this(context,null); } public LetterIndexVIEw(Context context,@Nullable AttributeSet attrs) {  this(context,attrs,0); } public LetterIndexVIEw(Context context,@Nullable AttributeSet attrs,int defStyleAttr) {  super(context,defStyleAttr);  paint = new Paint();  paint.setAntiAlias(true);  paint.setTextAlign(Paint.Align.CENTER);  paint.setcolor(color.parsecolor("#565656"));  DEFAulT_WIDTH = dptopx(context,24); } @OverrIDe protected voID onMeasure(int wIDthMeasureSpec,int heightmeasureSpec) {  setMeasuredDimension(getWIDthSize(wIDthMeasureSpec),getDefaultSize(getSuggestedMinimumHeight(),heightmeasureSpec)); } private int getWIDthSize(int wIDthMeasureSpec) {  int wIDthMode = MeasureSpec.getMode(wIDthMeasureSpec);  int wIDthSize = MeasureSpec.getSize(wIDthMeasureSpec);  switch (wIDthMode) {   case MeasureSpec.AT_MOST: {    if (wIDthSize >= DEFAulT_WIDTH) {     return DEFAulT_WIDTH;    } else {     return wIDthSize;    }   }   case MeasureSpec.EXACTLY: {    return wIDthSize;   }   case MeasureSpec.UnspecIFIED:   default:    return DEFAulT_WIDTH;  } } @OverrIDe public boolean dispatchtouchEvent(MotionEvent event) {  switch (event.getAction()) {   case MotionEvent.ACTION_DOWN:    hit = true;    onHit(event.getY());    break;   case MotionEvent.ACTION_MOVE:    onHit(event.getY());    break;   case MotionEvent.ACTION_UP:   case MotionEvent.ACTION_CANCEL:    hit = false;    if (touchingLetterChangedListener != null) {     touchingLetterChangedListener.onCancel();    }    break;  }  invalIDate();  return true; } @OverrIDe protected voID onDraw(Canvas canvas) {  if (hit) {   //字母索引条背景色   canvas.drawcolor(color.parsecolor("#bababa"));  }  float letterHeight = ((float) getHeight()) / letters.length;  float wIDth = getWIDth();  float textSize = letterHeight * 5 / 7;  paint.setTextSize(textSize);  for (int i = 0; i < letters.length; i++) {   canvas.drawText(letters[i],wIDth / 2,letterHeight * i + textSize,paint);  } } private voID onHit(float offset) {  if (hit && touchingLetterChangedListener != null) {   int index = (int) (offset / getHeight() * letters.length);   index = Math.max(index,0);   index = Math.min(index,letters.length - 1);   touchingLetterChangedListener.onHit(letters[index]);  } } public voID setontouchingLetterChangedListener(OntouchingLetterChangedListener ontouchingLetterChangedListener) {  this.touchingLetterChangedListener = ontouchingLetterChangedListener; } private int dptopx(Context context,float dpValue) {  float scale = context.getResources().getdisplayMetrics().density;  return (int) (dpValue * scale + 0.5f); }}

在侧边栏时，中间会显示当前滑动指向的字母，这其实是一个TextVIEw，在主布局文件中添加，通过IndexControl来控制TextVIEw的可见性，并指示ListVIEw滑动到指定项

/** * 作者：叶应是叶 * 时间：2017/8/20 11:39 * 描述： */public class IndexControl { private final ListVIEw ListVIEw; private final TextVIEw tv_hint; private final Map<String,Integer> letterMap; public IndexControl(ListVIEw contactsListVIEw,LetterIndexVIEw letterIndexVIEw,TextVIEw tv_hint,Map<String,Integer> letterMap) {  this.ListVIEw = contactsListVIEw;  this.tv_hint = tv_hint;  this.letterMap = letterMap;  letterIndexVIEw.setontouchingLetterChangedListener(new LetterChangedListener()); } private class LetterChangedListener implements LetterIndexVIEw.OntouchingLetterChangedListener {  @OverrIDe  public voID onHit(String letter) {   tv_hint.setVisibility(VIEw.VISIBLE);   tv_hint.setText(letter);   int index = -1;   if ("↑".equals(letter)) {    index = 0;   } else if (letterMap.containsKey(letter)) {    index = letterMap.get(letter);   }   if (index < 0) {    return;   }   index += ListVIEw.getheaderVIEwsCount();   if (index >= 0 && index < ListVIEw.getCount()) {    ListVIEw.setSelectionFromtop(index,0);   }  }  @OverrIDe  public voID onCancel() {   tv_hint.setVisibility(VIEw.INVISIBLE);  } }}

这里也提供代码下载：LetterIndexView

总结

以上所述是小编给大家介绍的AndroID 实现带字母索引的侧边栏功能，希望对大家有所帮助，如果大家有任何疑问，欢迎给我留言，小编会及时回复大家的！

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