IssueTracker

Artifact used: androidx.appcompat:appcompat:1.1.0-alpha04
Version used: 28
Theme used: Theme.AppCompat.Light.DarkActionBar
Devices/Android versions reproduced on: Emulator Nexus 5 API 28


We notice that, during targetSdkVersion 28, androidx.appcompat.widget.AppCompatEditText will tend to "slightly push down" the line after input, when non-English unicode (Like Chinese, Japanese, ...) is being entered.

Such behavior doesn't happen, when the code is targetSdkVersion 27 or below.


Use targetSdkVersion 27, run on emulator API 28
======================================

(Before input non-English unicode) - before-27.png
(After input non-English unicode) - after-27.png
(Confirm spacing is OK) - compare-27.png


Use targetSdkVersion 28, run on emulator API 28
======================================

(Before input non-English unicode) - before-28.png
(After input non-English unicode) - after-28.png
(Confirm spacing is problematic. Lines after input are being pushed down) - compare-28.png



This is the XML and code used by us. We inherit from `androidx.appcompat.widget.AppCompatEditText`, to paint the lines, to make the problem more obvious.

                    <com.yocto.wenote.note.LinedEditText
                        android:id="@+id/body_edit_text"
                        android:gravity="top"
                        android:paddingLeft="16dp"
                        android:paddingRight="16dp"
                        android:layout_marginBottom="12dp"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        android:background="@android:color/transparent"
                        android:scrollbars="vertical"
                        android:textSize="18sp"
                        android:singleLine="false"
                        android:lineSpacingMultiplier="1.4"
                        android:inputType="textMultiLine|textCapSentences"
                        android:textCursorDrawable="?attr/shorterCursor" />

    package com.yocto.wenote.note;
   
    import android.content.Context;
    import android.content.res.Resources;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.util.AttributeSet;
    import android.util.TypedValue;
   
    import com.yocto.wenote.R;
   
    /**
     * Created by yccheok on 24/3/2018.
     */
   
    public class LinedEditText extends androidx.appcompat.widget.AppCompatEditText {
        private final Paint mPaint = new Paint();
        private int noteLineColor;
        private static final float DEFAULT_LINE_SPACING_EXTRA = 0.0f;
        private static final float DEFAULT_LINE_SPACING_MULTIPLIER = 1.4f;
   
        private void initResource() {
            Context context = getContext();
            TypedValue typedValue = new TypedValue();
            Resources.Theme theme = context.getTheme();
            theme.resolveAttribute(R.attr.noteLineColor, typedValue, true);
            noteLineColor = typedValue.data;
        }
   
        public LinedEditText(Context context) {
            super(context);
            initResource();
            initPaint();
        }
   
        public void setNoteLineColor(int noteLineColor) {
            this.noteLineColor = noteLineColor;
        }
   
        public LinedEditText(Context context, AttributeSet attrs) {
            super(context, attrs);
            initResource();
            initPaint();
        }
   
        public LinedEditText(Context context, AttributeSet attrs, int defStyleAttr) {
            super(context, attrs, defStyleAttr);
            initResource();
            initPaint();
        }
   
        private void initPaint() {
            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setColor(noteLineColor);
            mPaint.setStrokeWidth(1);
        }
   
        @Override
        protected void onDraw(Canvas canvas) {
            int left = getLeft();
            int right = getRight();
            int paddingTop = getPaddingTop();
            int paddingBottom = getPaddingBottom();
            int paddingLeft = getPaddingLeft();
            int paddingRight = getPaddingRight();
            final int heightWithScrollY = getHeight() + getScrollY();
            int lineHeight = getLineHeight();
            int count = (heightWithScrollY-paddingTop-paddingBottom) / lineHeight;
   
            mPaint.setColor(noteLineColor);
            mPaint.setTypeface(this.getTypeface());
   
            final float originalLineHeight;
            if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.JELLY_BEAN) {
                originalLineHeight = lineHeight / getLineSpacingMultiplier();
            } else {
                originalLineHeight = lineHeight / DEFAULT_LINE_SPACING_MULTIPLIER;
            }
   
            for (int i = 0; i < count; i++) {
                float baseline = lineHeight * (i + 1) + paddingTop - mPaint.descent() - (lineHeight - originalLineHeight);
                canvas.drawLine(
                        left + paddingLeft,
                        baseline,
                        right - paddingRight,
                        baseline,
                        mPaint
                );
            }
   
            super.onDraw(canvas);
        }
   
        // https://stackoverflow.com/questions/49467579/workaround-for-edittext-ignoring-linespacingmultiplier
        @Override
        protected void onTextChanged(CharSequence text, int start, int lengthBefore, int lengthAfter) {
            super.onTextChanged(text, start, lengthBefore, lengthAfter);
   
            if (lengthBefore != lengthAfter) {
                float add;
                float mul;
   
                if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.JELLY_BEAN) {
                    add = getLineSpacingExtra();
                    mul = getLineSpacingMultiplier();
                } else {
                    add = DEFAULT_LINE_SPACING_EXTRA;
                    mul = DEFAULT_LINE_SPACING_MULTIPLIER;
                }
   
                setLineSpacing(0f, 1f);
                setLineSpacing(add, mul);
            }
        }
   
    }

Take note that, if you use `targetSdkVersion` 28, BUT run on emulator API 27, this problem will not occur too.

This issue also posted at https://stackoverflow.com/questions/55845977/incorrect-edittext-line-spacing-behavior-in-target-api-28-when-dealing-with-non

Thank you.