感谢红橙Darren博主
package com.rzm.commonlibrary.views;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;
import com.rzm.commonlibrary.R;
/**
* Created by renzhenming on 2018/3/24.
* 实现根据字母分类排序的列表，多用于地址选择或者手机通讯录
*/
public class AlphabetView extends View{
//普通模式绘制的画笔
private final Paint mPaint;
//触摸时绘制用的画笔
private final Paint mTouchPaint;
//默认字母大小
private int mTextSize = 16;
//默认字母颜色
private int mTextColor = Color.BLACK;
//触摸时字母颜色
private int mTouchTextColor = Color.RED;
//控件的高度
private int mViewHeight;
//26个字母
private String mLetters[] = {"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 int mItemHeight;
//当前触摸的字母
private String mCurrentTouchLetter;
//当前是否在触摸
private boolean mCurrentIsTouch = false;
//抬起之后是否清除当前选中的高亮颜色
private boolean mClearAfterUp = true;
public AlphabetView(Context context) {
this(context,null);
}
public AlphabetView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs,-1);
}
public AlphabetView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
//获取自定义属性
TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.AlphabetView);
mTextColor = typedArray.getColor(R.styleable.AlphabetView_textColor, mTextColor);
mTouchTextColor = typedArray.getColor(R.styleable.AlphabetView_touchTextColor, mTouchTextColor);
mTextSize = typedArray.getDimensionPixelSize(R.styleable.AlphabetView_textSize, mTextSize);
typedArray.recycle();
//设置画笔用于绘制字母
/**
* 为什么使用两个画笔而不是单独的使用一个然后切换颜色的设置，因为paint是有一个
* 设置颜色的方法的setColor,我们看一下setColor的源码，发现是native方法实现的，
* private static native void nSetColor(long paintPtr, @ColorInt int color);
* 如果在onDraw中频繁的切换颜色性能会降低，所以这就是通常使用几种颜色定义几个画笔
* 的原因
*/
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(mTextColor);
mPaint.setTextSize(sp2px(mTextSize));
mTouchPaint = new Paint();
mTouchPaint.setAntiAlias(true);
mTouchPaint.setDither(true);
mTouchPaint.setColor(mTouchTextColor);
mTouchPaint.setTextSize(sp2px(mTextSize));
}
private float sp2px(int sp){
return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,sp,getResources().getDisplayMetrics());
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
//根据布局中设置的宽度模式确定宽度
int width =0;
int mode = MeasureSpec.getMode(widthMeasureSpec);
if (mode == MeasureSpec.EXACTLY){
width = MeasureSpec.getSize(widthMeasureSpec);
}
if (mode == MeasureSpec.AT_MOST){
//计算宽度,两边的padding加上文字宽度，这个文字随意，不过最好是26个字母中最宽的
float textWidth = mPaint.measureText("");
width = (int) (getPaddingLeft() + getPaddingRight()+textWidth);
}
//获取设置的高度
mViewHeight = MeasureSpec.getSize(heightMeasureSpec);
setMeasuredDimension(width, mViewHeight);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
//获取每个字母占的高度
mItemHeight = (getHeight()-getPaddingTop() - getPaddingBottom())/mLetters.length;
//绘制26个字母
for (int i = 0; i < mLetters.length; i++) {
//得到每个字母的中心位置,防止给布局设置了paddingTop，所以这里+上
int letterCenterY = i* mItemHeight + mItemHeight /2+getPaddingTop();
//得到每个字母的中心位置
Paint.FontMetrics fontMetrics = mPaint.getFontMetrics();
int dy = (int) ((fontMetrics.bottom - fontMetrics.top)/2 - fontMetrics.bottom);
//根据字母中心位置求字母的基线
//baseline = center + (FontMetrics.bottom - FontMetrics.top)/2 - FontMetrics.bottom;
int baseLine = letterCenterY+dy;
//获取每一个字母绘制的x坐标
float letterWidth = mPaint.measureText(mLetters[i]);
//确保每一个字母都在中间位置
int x = (int) (getWidth()/2 - letterWidth/2);
//开始绘制
/**
* text 需要绘制的文字
x 绘制文字原点X坐标
y 绘制文字原点Y坐标
xy指的时文字左下角的坐标，也就是基线和文字最左边下方的交点
paint 画笔
*/
if (mLetters[i].equals(mCurrentTouchLetter)){
canvas.drawText(mLetters[i],x,baseLine,mTouchPaint);
}else{
canvas.drawText(mLetters[i],x,baseLine,mPaint);
}
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
case MotionEvent.ACTION_MOVE:
//当前触摸的位置,相对与控件的位置而不是相对于屏幕
float startY = event.getY();
//计算当前字母的位置
int position = (int)startY/mItemHeight;
//防止当触摸超出控件范围的时候，设定position值，防止数组越界
if (position <0){
position = 0;
}
if (position > mLetters.length - 1){
position = mLetters.length - 1;
}
//滑动过程中如果滑动的位置和上一次相同，就不再处理，减少invalidate的次数
if (mLetters[position].equals(mCurrentTouchLetter)){
return true;
}
//记录当前触摸的弥足
mCurrentTouchLetter = mLetters[position];
mCurrentIsTouch = true;
if (mTouchListener != null){
mTouchListener.onTouch(mCurrentTouchLetter,mCurrentIsTouch);
}
break;
case MotionEvent.ACTION_UP:
//抬起时设置为false
mCurrentIsTouch = false;
if (mTouchListener != null){
mTouchListener.onTouch(mCurrentTouchLetter,mCurrentIsTouch);
}
if (mClearAfterUp){
//将当前触摸的字母设置为null,up之后重绘界面，清除高亮状态
mCurrentTouchLetter = null;
}
break;
}
invalidate();
return true;
}
/**
* 设置手指触摸抬起之后，是否恢复高亮状态为正常状态，默认为true
* @param mClearAfterUp
*/
public void setClearAfterUp(boolean mClearAfterUp) {
this.mClearAfterUp = mClearAfterUp;
}
// 设置触摸监听
private OnAlphabetTouchListener mTouchListener;
public void setOnAlphabetTouchListener(OnAlphabetTouchListener touchListener) {
this.mTouchListener = touchListener;
}
public interface OnAlphabetTouchListener {
void onTouch(String letter, boolean isTouch);
}
}
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