drawText注意事项

迈不过友情╰ 2023-01-18 04:10 162阅读 0赞

自定义View中写文字坑多多 总结一下：

drawText（）参数中y不是文字左上角坐标，是基线的y坐标；

drawText用于单行文字绘制，多行文字可以使用StaticLayout；

public class TextItemView extends View {
        private Paint pointPaint;
        private TextPaint textPaint;
        private Context context;
        private float fontSpacing, halfSpacing;
        private List<String> mListTexts = new ArrayList<>();
        private List<StaticLayout> mListStaticLayouts = new ArrayList<>();
    
        public TextItemView(Context context) {
            super(context);
            init(context);
        }
    
        public TextItemView(Context context, @Nullable AttributeSet attrs) {
            super(context, attrs);
            init(context);
        }
    
        private void init(Context context) {
            this.context = context;
            pointPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
            pointPaint.setColor(Color.parseColor("#666666"));
    
            textPaint = new TextPaint(Paint.ANTI_ALIAS_FLAG);
            textPaint.setColor(Color.parseColor("#666666"));
            textPaint.setTextSize(BaseUtils.dip2px(context, 16));
            Paint.FontMetrics fontMetrics = textPaint.getFontMetrics();
            fontSpacing = fontMetrics.bottom - fontMetrics.top;
            halfSpacing = fontSpacing / 2.0f;
        }
    
    
        public void setData(List<String> list) {
            mListTexts.clear();
            mListTexts.addAll(list);
            mListStaticLayouts.clear();
            invalidate();
        }
    
        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            if (mListTexts.isEmpty()) {
                return;
            }
            int y = 0;//开始 draw的Y左边
            if (mListStaticLayouts.isEmpty()) {
                int txtWidth = (int) (width - fontSpacing);//总宽 - 圆点宽 = 文字宽
                for (String s : mListTexts) {
                    StaticLayout layout = new StaticLayout(s, textPaint, txtWidth, Layout.Alignment.ALIGN_NORMAL, 1.3f, 0, true);
                    mListStaticLayouts.add(layout);
                    LogUtils.d("@@@", ", width = " + width + " , s = " + s);
                }
            }
    
            for (StaticLayout mStaticLayout : mListStaticLayouts) {
                canvas.drawCircle(halfSpacing, y + halfSpacing, 4, pointPaint);
                canvas.save();
                canvas.translate(fontSpacing, y);//偏移 腾出圆点的位置
                mStaticLayout.draw(canvas);
                int multiplier = (int) (fontSpacing * (mStaticLayout.getSpacingMultiplier() - 1.0f));
                y += (mStaticLayout.getHeight() + multiplier);
                canvas.restore();
                LogUtils.d("@@@", "y  = " + y);
            }
    
            if (reHeight != y) {//y是最后一行文字Baseline坐标，才是该控件真正高度，需要重新赋值给该View
                requestLayout();
                reHeight = y;
            }
        }
    
        private int reHeight;
        private int width;
    
        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
            width = getMeasuredWidth();
            LogUtils.d("@@@", "onSizeChanged , width = " + width);
        }
    
        @Override
        protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            int finalHeight = resolveSize(Math.max(reHeight, 1), heightMeasureSpec);
            setMeasuredDimension(widthMeasureSpec, finalHeight);
        }
    }