LetterView.java

package com.justwayward.reader.view;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.support.annotation.Nullable;
import android.text.TextUtils;
import android.util.AttributeSet;
import android.widget.TextView;

/**
 * @author yuyh.
 * @date 17/1/30.
 */

public class LetterView extends TextView {

    // 颜色画板集
    private static final int[] colors = {
            0xff1abc9c, 0xff16a085, 0xfff1c40f, 0xfff39c12, 0xff2ecc71,
            0xff27ae60, 0xffe67e22, 0xffd35400, 0xff3498db, 0xff2980b9,
            0xffe74c3c, 0xffc0392b, 0xff9b59b6, 0xff8e44ad, 0xffbdc3c7,
            0xff34495e, 0xff2c3e50, 0xff95a5a6, 0xff7f8c8d, 0xffec87bf,
            0xffd870ad, 0xfff69785, 0xff9ba37e, 0xffb49255, 0xffb49255
    };


    private Paint mPaintBackground;
    private Paint mPaintText;
    private Rect mRect;

    private String text;

    private int charHash;

    public LetterView(Context context) {
        this(context, null);
    }

    public LetterView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public LetterView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

        init();

        setText(getText().toString());
    }

    private void init() {
        mPaintText = new Paint(Paint.ANTI_ALIAS_FLAG);
        mPaintText.setColor(Color.WHITE);

        mPaintBackground = new Paint(Paint.ANTI_ALIAS_FLAG);

        mRect = new Rect();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, widthMeasureSpec); // 宽高相同
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (null != text) {
            // 画圆
            canvas.drawCircle(getWidth() / 2, getWidth() / 2, getWidth() / 2, mPaintBackground);
            // 写字
            mPaintText.setTextSize(getWidth() / 2);
            mPaintText.setStrokeWidth(3);
            mPaintText.getTextBounds(text, 0, 1, mRect);
            // 垂直居中
            Paint.FontMetricsInt fontMetrics = mPaintText.getFontMetricsInt();
            int baseline = (getMeasuredHeight() - fontMetrics.bottom - fontMetrics.top) / 2;
            // 左右居中
            mPaintText.setTextAlign(Paint.Align.CENTER);
            canvas.drawText(text, getWidth() / 2, baseline, mPaintText);
        }
    }

    public void setText(String content) {
        if (TextUtils.isEmpty(content)) {
            content = " ";
        }
        this.text = String.valueOf(content.toCharArray()[0]);
        this.text = text.toUpperCase();
        charHash = this.text.hashCode();
        int color = colors[charHash % colors.length];
        mPaintBackground.setColor(color);
        invalidate();
    }
}