【移动应用开发技术】Android如何实现带字母索引的侧边栏功能

【移动应用开发技术】Android如何实现带字母索引的侧边栏功能

这篇文章主要介绍了Android如何实现带字母索引的侧边栏功能，具有一定借鉴价值，感兴趣的朋友可以参考下，希望大家阅读完这篇文章之后大有收获，下面让在下带着大家一起了解一下。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,

attrs,

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

<

listV