android 自定义View之将字体绘制在Rect中间

最新推荐文章于 2024-09-01 22:51:15 发布

原创最新推荐文章于 2024-09-01 22:51:15 发布 · 2.2k 阅读

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本文介绍了如何在Android中创建一个自定义View `NTextView`，该View能够在指定的矩形区域`Rect`内将文字绘制在中间。通过设置`Paint`对象的属性和计算文字的基线，实现了文字的垂直居中对齐，并使用`canvas.drawText()`方法在矩形中心绘制文字。

@SuppressLint("ViewConstructor")

public class NTextView extends View {


    private String TAG="NtextView";

    public NTextView(Context context) {
        super(context);
    }

    public NTextView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

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

    @Override
    public void onDraw (Canvas canvas) {
        Rect targetRect = new Rect(50, 50, 1000, 200);
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setStrokeWidth(3);
        paint.setTextSize(80);
        String testString = "测试：ijkJQKA:1234";
        paint.setColor(Color.CYAN);
        canvas.drawRect(targetRect, paint);
        paint.setColor(Color.RED);
        Paint.FontMetricsInt fontMetrics = paint.getFontMetricsInt();
        int baseline = (targetRect.bottom + targetRect.top - fontMetrics.bottom - fontMetrics.top) / 2;
        int baseline2=targetRect.bottom-((targetRect.bottom-targetRect.top-fontMetrics.bottom+fontMetrics.top)/2+fontMetrics.bottom);


        Log.i(TAG, "onDraw: "+baseline2);
        Log.i(TAG, "onDraw: "+baseline);
        Log.i(TAG, "onDraw: bottom"+targetRect.bottom+"  top"+targetRect.top +" fBottom"+fontMetrics.bottom+"  ftop"+fontMetrics.top);
        // 下面这行是实现水平居中，drawText对应改为传入targetRect.centerX()
        paint.setTextAlign(Paint.Align.CENTER);
        canvas.drawText(testString, targetRect.centerX(), baseline, paint);
    }
}