Android自定义字母选择侧边栏

本文实例为大家分享了android自定义字母选择侧边栏的具体代码，供大家参考，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; i++) {
            drawletterat(canvas, i, letters[i]);
        }
    }
 
    private void drawselectedtext(canvas canvas, string selected) {
        if(textutils.isempty(selected))
            return;
        mpaint.setcolor(selectedcolor);
        int position = -1;
        for(int i=0; i<letters.length; i++) {
            if(selected.equals(letters[i])) {
                position = i;
                break;
            }
        }
        if(position < 0 || position >= 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

<declare-styleable name="lettersidebar"> 
<attr name="lettersidebar_textcolor" format="color"/> 
<attr name="lettersidebar_textselectedcolor" format="color"/> 
<attr name="lettersidebar_textsize" format="dimension"/> 
<attr name="lettersidebar_spacing" format="dimension"/> 
</declare-styleable>

layout.xml

<com.zb.customview.widgets.lettersidebar
        android:id="@+id/lettersidebar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:lettersidebar_textsize="14sp"
        app:lettersidebar_textcolor="#ffffff"
        android:padding="10dp"
        app:lettersidebar_textselectedcolor="#ff0000"
        app:lettersidebar_spacing="2dp"
        app:layout_constraintright_torightof="parent"
        app:layout_constrainttop_totopof="parent"
        app:layout_constraintbottom_tobottomof="parent"
        android:background="#a4a4a4"/>

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);
                }
            }
        });

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。