Canvas 文字对齐方式

ゝ一世哀愁。 2022-11-18 01:18 263阅读 0赞

# Canvas 文字对齐方式 #

常用的画文字的方法

`public void drawText (String text, float x, float y, Paint paint)`

x,y 并不是指定文字的中点位置，并且x,y与文字对齐方式有关（通过setTextAlign()指定，默认为left）

测试

import android.graphics.Bitmap;
    import android.graphics.Canvas;
    import android.graphics.Color;
    import android.graphics.Paint;
    import android.graphics.Rect;
    import android.graphics.RectF;
    
    /**
     * Created by talon on 2021/3/10
     * note: 根据对象绘制图片
     * 参考：https://www.jianshu.com/p/8b97627b21c4
     */
    public class DrawBitmapManager4 {
    
        private final String TAG = "DrawImageManager";
    
        public static Bitmap createBitmap() {
            // 创建一个画布
            Bitmap bitmap = Bitmap.createBitmap(800, 1000, Bitmap.Config.ARGB_8888);
            Canvas canvas = new Canvas(bitmap);
            canvas.drawBitmap(bitmap, 0, 0, null);
            // 给画布加个边框
            Rect rect = new Rect(0, 0, canvas.getWidth(), canvas.getHeight());
            Paint paint = new Paint();
            paint.setColor(Color.BLACK);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(2);
            canvas.drawRect(rect, paint);
    
            // 开始测试数据
    
            // todo 证明： setStrokeWidth这个方法，并不是往canvas内侧填充，而是往外侧增加一半，往内侧增加一半。
    //        testStrokeWidth(canvas);
            // todo  证明：文字居中方案
            setTextCenter(canvas); // 居中
            setTextLeft(canvas); // 左对齐
            setTextRight(canvas); // 右对齐
            return bitmap;
        }
    
    
        private static void testStrokeWidth(Canvas canvas) {
            // 划粗400px的线，只填充了200px
            Paint paint = new Paint();
            paint.setColor(Color.BLACK);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(400);
    
            canvas.drawLine(0, 0, 0, canvas.getHeight(), paint);
            // 划线
            paint.setColor(Color.RED);
            paint.setStrokeWidth(5);
            canvas.drawLine(210, 0, 210, canvas.getHeight(), paint);
        }
    
    
        private static void setTextCenter(Canvas canvas) {
    
            //矩形背景
            Paint bgRect = new Paint();
            bgRect.setStyle(Paint.Style.FILL);
            bgRect.setColor(Color.TRANSPARENT);
            RectF rectF = new RectF(0, 0, canvas.getWidth(), canvas.getHeight());
            canvas.drawRect(rectF, bgRect);
    
            Paint textPaint = new Paint();
            textPaint.setStyle(Paint.Style.FILL);
            textPaint.setTextSize(100);
            textPaint.setTextAlign(Paint.Align.CENTER);
    
            String text = "测Zz试";
            //计算baseline ;
            Paint.FontMetrics fontMetrics = textPaint.getFontMetrics();
            float distance = (fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom;
            float baseline = rectF.centerY() + distance;
            canvas.drawText(text, rectF.centerX(), baseline, textPaint);
    
            // 划线标记中间位置
            textPaint.setColor(Color.RED);
            textPaint.setStrokeWidth(5);
            canvas.drawLine(0, canvas.getHeight() / 2, canvas.getWidth(), canvas.getHeight() / 2, textPaint);
        }
    
        private static void setTextLeft(Canvas canvas) {
    
            //矩形背景
            Paint bgRect = new Paint();
            bgRect.setStyle(Paint.Style.FILL);
            bgRect.setColor(Color.TRANSPARENT);
            RectF rectF = new RectF(0, 0, canvas.getWidth(), canvas.getHeight());
            canvas.drawRect(rectF, bgRect);
    
            Paint textPaint = new Paint();
            textPaint.setStyle(Paint.Style.FILL);
            textPaint.setTextSize(100);
            textPaint.setTextAlign(Paint.Align.LEFT);
    
            String text = "测Zz试";
            //计算baseline ;
            Paint.FontMetrics fontMetrics = textPaint.getFontMetrics();
            float distance = (fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom;
            float baseline = rectF.centerY() + distance;
            canvas.drawText(text, rectF.left, baseline, textPaint);
    
            // 划线标记中间位置
            textPaint.setColor(Color.RED);
            textPaint.setStrokeWidth(5);
            canvas.drawLine(0, canvas.getHeight() / 2, canvas.getWidth(), canvas.getHeight() / 2, textPaint);
        }
    
    
        private static void setTextRight(Canvas canvas) {
    
            //矩形背景
            Paint bgRect = new Paint();
            bgRect.setStyle(Paint.Style.FILL);
            bgRect.setColor(Color.TRANSPARENT);
            RectF rectF = new RectF(0, 0, canvas.getWidth(), canvas.getHeight());
            canvas.drawRect(rectF, bgRect);
    
            Paint textPaint = new Paint();
            textPaint.setStyle(Paint.Style.FILL);
            textPaint.setTextSize(100);
            textPaint.setTextAlign(Paint.Align.RIGHT);
    
            String text = "测Zz试";
            //计算baseline ;
            Paint.FontMetrics fontMetrics = textPaint.getFontMetrics();
            float distance = (fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom;
            float baseline = rectF.centerY() + distance;
            canvas.drawText(text, rectF.right, baseline, textPaint);
    
            // 划线标记中间位置
            textPaint.setColor(Color.RED);
            textPaint.setStrokeWidth(5);
            canvas.drawLine(0, canvas.getHeight() / 2, canvas.getWidth(), canvas.getHeight() / 2, textPaint);
        }
    }