How to add pagelines to a EditText in android?

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隐瞒了意图╮
隐瞒了意图╮ 2021-01-14 14:07

Is it possible to show pagelines in a EditText?

I mean these lines:

\"enter

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3条回答
  • The notepad application sample from the android dev site shows you how to do this.

    http://developer.android.com/resources/samples/NotePad/index.html

    Looks like this (scroll down for code):

    Notepad

    Most of the relevant code is in this file. Pay attention to the LinedEditText inner class. It is defined within the activity. It draws the lines required.

    Inside the activity onCreate() method, setContentView(R.id.note_editor) is set as the view, it is defined like here

    Snippet extracted from here. Update: Code modified by @Pieter888 to draw lines on the entire EditText control.

    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.graphics.Rect;
    import android.util.AttributeSet;
    import android.widget.EditText;
    
    public class LinedEditText extends EditText 
    {
        private Rect mRect;
        private Paint mPaint;
    
        public LinedEditText(Context context, AttributeSet attrs) 
        {
            super(context, attrs);
            mRect = new Rect();
            mPaint = new Paint();
            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setColor(0xFF000000);
        }
    
        /**
         * This is called to draw the LinedEditText object
         * @param canvas The canvas on which the background is drawn.
         */
        @Override
        protected void onDraw(Canvas canvas) 
        {
            int height = canvas.getHeight();
            int curHeight = 0;
            Rect r = mRect;
            Paint paint = mPaint;
            int baseline = getLineBounds(0, r);
            for (curHeight = baseline + 1; curHeight < height; 
                                                     curHeight += getLineHeight())
            {
                canvas.drawLine(r.left, curHeight, r.right, curHeight, paint);
            }
            super.onDraw(canvas);
        }
    }
    
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  • 2021-01-14 14:17

    @gideon's answer above works well but has an issue when you enter more text in the edittext because more lines are not drawn accordingly. To solve this, I wrote an override for onMeasure() and called invalidate(). and more lines will be drawn when text increases.

      @Override
      protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec,heightMeasureSpec);
        invalidate();
      }
    

    The code now is:

    import android.content.Context;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.graphics.Rect;
    import android.util.AttributeSet;
    import android.widget.EditText;
    
    public class LinedEditText extends EditText 
    {
        private Rect mRect;
        private Paint mPaint;
    
        public LinedEditText(Context context, AttributeSet attrs) 
        {
            super(context, attrs);
            mRect = new Rect();
            mPaint = new Paint();
            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setColor(0xFF000000);
        }
    
        /**
         * This is called to draw the LinedEditText object
         * @param canvas The canvas on which the background is drawn.
         */
        @Override
        protected void onDraw(Canvas canvas) 
        {
            int height = canvas.getHeight();
            int curHeight = 0;
            Rect r = mRect;
            Paint paint = mPaint;
            int baseline = getLineBounds(0, r);
            for (curHeight = baseline + 1; curHeight < height; 
                                                     curHeight += getLineHeight())
            {
                canvas.drawLine(r.left, curHeight, r.right, curHeight, paint);
            }
            super.onDraw(canvas);
        }
    
     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
       super.onMeasure(widthMeasureSpec,heightMeasureSpec);
       invalidate();
          }
    }
    
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  • 2021-01-14 14:23

    @gideon's code works but more lines not be drawn

    you must just change canvas.getHeight() to getHeight() as following below:

    public class LinedEditText extends EditText
     {
    private Rect mRect;
    private Paint mPaint;
    
    public LinedEditText(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        mRect = new Rect();
        mPaint = new Paint();
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setColor(ResourcesCompat.getColor(getResources(), R.color.blue,null));
    }
    
    
    @Override
    protected void onDraw(Canvas canvas)
    {
        int height = getHeight();
        int curHeight = 0;
        Rect r = mRect;
        Paint paint = mPaint;
        int baseline = getLineBounds(0, r);
        for (curHeight = baseline + 1; curHeight < height;
             curHeight += getLineHeight())
        {
            canvas.drawLine(r.left, curHeight, r.right, curHeight, paint);
        }
        super.onDraw(canvas);
    }
    
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