Android如何实现自定义字母选择侧边栏

这篇文章将为大家详细讲解有关Android如何实现自定义字母选择侧边栏，小编觉得挺实用的，因此分享给大家做个参考，希望大家阅读完这篇文章后可以有所收获。

具体内容如下

LetterSideBar.java

package com.zb.customview.widgets; import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Rect;import android.text.TextUtils;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View; import androidx.annotation.Nullable; import com.zb.customview.R; public class LetterSideBar extends View {     private Paint mPaint;    private int color, selectedColor;    private float textSize, spacing;    private String mChoosing = "Z";    private OnLetterSelectedListener listener;    private int width, height;     private String[] LETTERS = new String[] {"#", "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"};     public interface OnLetterSelectedListener {        //空表示取消选中        void onSelected(String letter);    }     public void setOnLetterSelectedListener(OnLetterSelectedListener listener) {        this.listener = listener;    }     public LetterSideBar(Context context) {        this(context, null);    }     public LetterSideBar(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);        if(null != attrs) {            TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.LetterSideBar);            color = ta.getColor(R.styleable.LetterSideBar_LetterSideBar_textColor, Color.BLACK);            selectedColor = ta.getColor(R.styleable.LetterSideBar_LetterSideBar_textSelectedColor, Color.RED);            textSize = ta.getDimensionPixelSize(R.styleable.LetterSideBar_LetterSideBar_textSize, sp2px(12));            spacing = ta.getDimensionPixelSize(R.styleable.LetterSideBar_LetterSideBar_spacing, dp2px(5));            ta.recycle();        }        init();    }     private void init() {        mPaint = new Paint();        mPaint.setAntiAlias(true);        mPaint.setColor(color);        mPaint.setTextSize(textSize);    }     @Override    protected void onDraw(Canvas canvas) {        drawText(canvas);        drawSelectedText(canvas, mChoosing);    }     private void drawText(Canvas canvas) {        mPaint.setColor(color);        for (int i=0; i= LETTERS.length)            return;        drawLetterAt(canvas, position, selected);    }     @Override    public boolean onTouchEvent(MotionEvent event) {        int action = event.getAction();        switch (action) {            case MotionEvent.ACTION_DOWN:            case MotionEvent.ACTION_MOVE:                float x = event.getX();                float y = event.getY();                if(isTouchInsideView(x, y)) {                    //触摸在控件内                    int position = caculatePosition(y);                    if(position >= 0 && position < LETTERS.length) {                        //合规位置                        String letter = LETTERS[position];                        if(!letter.equals(mChoosing)) { //与选中的不符 去刷新控件                            mChoosing = letter;                            performListener(mChoosing);                            invalidate();                        }                    } else {                        //不合规位置                        if(null != mChoosing) {                            mChoosing = null;                            performListener(mChoosing);                            invalidate();                        }                    }                } else if(null != mChoosing) { //点击事件不在view内部                    mChoosing = null;                    performListener(mChoosing);                    invalidate();//触摸在view之外 取消选中                }                return true;            default:                if(mChoosing != null) {                    mChoosing = null;                    performListener(mChoosing);                    invalidate();                }                break;        }        return super.onTouchEvent(event);    }     private void performListener(String letter) {        if(null != listener)            listener.onSelected(letter);    }     private boolean isTouchInsideView(float x, float y) {        //左右可以适当判断在控件内        if(x >= 0 && x <= width && y >= getPaddingTop() && y < height)            return true;        return false;    }     /**     * 计算触摸的位置     * @param y     * @return     */    private int caculatePosition(float y) {        float heightWithOutPadding = height - getPaddingTop() - getPaddingBottom();        float eachElementHeight = heightWithOutPadding / LETTERS.length;        y -= getPaddingTop();        int position = (int) (y / eachElementHeight);        return position;    }     private void drawLetterAt(Canvas canvas, int position, String letter) {         float heightForEach = ((height * 1f - getPaddingTop() - getPaddingBottom())                - (LETTERS.length - 1) * spacing) / LETTERS.length;        float spacingInUp = spacing * (position - 1);        if(spacingInUp < 0)            spacingInUp = 0;        float currentTop = getPaddingTop() + (heightForEach * position) + spacingInUp;        float currentBottom = currentTop + heightForEach;        Paint.FontMetrics fmi = mPaint.getFontMetrics();        float x = (width - getPaddingLeft() - getPaddingRight() - mPaint.measureText(letter)) / 2f + getPaddingLeft();        float baseLine = (fmi.descent + Math.abs(fmi.ascent)) / 2f - fmi.descent;        float y = (currentBottom + currentTop) / 2f + baseLine;        canvas.drawText(letter, 0, 1, x, y, mPaint);    }     @Override    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {        super.onLayout(changed, left, top, right, bottom);        if(changed) {            width = getWidth();            height = getHeight();        }    }     @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        int textWidth = (int) (getPaddingLeft() + getPaddingRight() + mPaint.measureText("A"));        Rect textBounds = new Rect();        mPaint.getTextBounds("A", 0, 1, textBounds);        int singleTextHeight = textBounds.height();        int totalHeight = (int) (27f * singleTextHeight + 26f * spacing) + getPaddingBottom() + getPaddingTop();//26个字母+1个#         int widthMode = MeasureSpec.getMode(widthMeasureSpec);        int heightMode = MeasureSpec.getMode(widthMeasureSpec);        int specWidth = MeasureSpec.getSize(widthMeasureSpec);        int specHeight = MeasureSpec.getSize(widthMeasureSpec);        int realWidth, realHeight;        if(widthMode == MeasureSpec.EXACTLY) {            realWidth = specWidth;        } else {            realWidth = textWidth;        }        if(heightMode == MeasureSpec.EXACTLY) {            realHeight = specHeight;        } else {            realHeight = totalHeight;        }        setMeasuredDimension(realWidth, realHeight);    }     protected int dp2px(int dp) {        return (int) (getContext().getResources().getDisplayMetrics().density * dp + 0.5);    }    protected int sp2px(int sp) {        return (int) (getContext().getResources().getDisplayMetrics().scaledDensity * sp + 0.5);    }}

attrs.xml

layout.xml

代码中使用

sideBar.setOnLetterSelectedListener(new LetterSideBar.OnLetterSelectedListener() {            @Override            public void onSelected(String letter) {                if(TextUtils.isEmpty(letter)) {                    P.p("取消选中");                    letterTxt.setVisibility(View.GONE);                } else {                    P.p("选中" + letter);                    letterTxt.setText(letter);                    letterTxt.setVisibility(View.VISIBLE);                }            }        });

关于"Android如何实现自定义字母选择侧边栏"这篇文章就分享到这里了，希望以上内容可以对大家有一定的帮助，使各位可以学到更多知识，如果觉得文章不错，请把它分享出去让更多的人看到。