我参考了这个链接：How do I make a dotted/dashed line in Android?,并使用了DashPathEffect.但这对我不起作用？为什么？我的代码：

public class NoteEditText extends EditText {
    private Paint mPaint;

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

    public NoteEditText(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaint = new Paint();
        mPaint.setStrokeWidth(1);
        mPaint.setStyle(Paint.Style.FILL_AND_STROKE);
        mPaint.setColor(Color.DKGRAY);
        PathEffect effects = new DashPathEffect(new float[]{5,5,5,5},1);  
        mPaint.setPathEffect(effects);
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        int height = this.getHeight();
        int lineHeight = this.getLineHeight();
        int lineNum = height / lineHeight;
        L.l("line count: " + lineNum);
        for (int i = 0; i < lineNum; i++) {
            int y = (i + 1) * lineHeight;
            canvas.drawLine(0, y, this.getWidth() - 1, y, mPaint);
        }
    }
}

解决方法:

硬件加速不支持方法setPathEffect.默认情况下它已打开(我认为自Android 4.0以来)

http://developer.android.com/guide/topics/graphics/hardware-accel.html#unsupported

您可以使用以下代码段关闭构造函数内的硬件加速：

setLayerType(View.LAYER_TYPE_SOFTWARE, null);