我要回家想一想~

If we want the underline, we have to draw the underline by ourselves.

So we define the new class LinedEditText to override onDraw.

public static class LinedEditText extends EditText {
    private Paint mPaint;

    // we need this constructor for LayoutInflater
    public LinedEditText(Context context, AttributeSet attrs) {
        super(context, attrs);
        initPaint();
    }
    
    private void initPaint() {
        mPaint = new Paint();
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(0x80000000);
        mPaint.setStrokeWidth(2);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        // draw underline on current page
        int left = getLeft();
        int right = getRight();
        int paddingTop = getPaddingTop();
        int paddingBottom = getPaddingBottom();
        int paddingLeft = getPaddingLeft();
        int paddingRight = getPaddingRight();
        int height = getHeight();
        int lineHeight = getLineHeight();
        int count = (height-paddingTop-paddingBottom) / lineHeight;
        // total line counts
        int linecount= getLineCount();
        if (count < linecount)
            count = linecount;

        for (int i = 0; i < count; i++) {
            int baseline = lineHeight * (i+1) + paddingTop;
            canvas.drawLine(left+paddingLeft, baseline, right-paddingRight, baseline, mPaint);
        }

        super.onDraw(canvas);
    }
}

and we use the class on layout xml

<view xmlns:android="http://schemas.android.com/apk/res/android"
    class="com.example.MyActivity$LinedEditText"
    android:id="@+id/edittext"
    android:inputType="textMultiLine"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:scrollbars="vertical"
    android:fadingEdge="vertical"
    android:gravity="top"
    android:textColor="@color/Black"
    android:textSize="16sp" />

Android - How to make all lines in an edittext underlined