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Draw a rounded rectangle with RectF and canvas?

I am trying to draw a rounded rectangle using RectF and canvas.drawRoundRect (). See my code below:

package com.example.test;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.RelativeLayout;
import android.graphics.RectF;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Create main RL params
        RelativeLayout.LayoutParams rlMainlayoutParams 
                = new RelativeLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);

        // Create main relative layout
        RelativeLayout rlMain = new RelativeLayout(this);
        rlMain.setLayoutParams(rlMainlayoutParams);
        //rlMain.setBackgroundResource(R.drawable.bgndlogin);
        rlMain.setBackgroundColor(Color.WHITE);

        RectF rectf = new RectF(200, 400, 200, 400);
        CustomRectangle customRectangle = new CustomRectangle(this, rectf, 5, 5, "#FFFF00");

        //
        rlMain.addView(customRectangle);

        setContentView(rlMain);
    }

    //!< Draw the log in rectangle shaped panel
    public class CustomRectangle extends View {
        Paint paint;
        float left_side, top_side;
        String color;
        RectF rectf;

        //!< Constructor for the log in rectangle shaped panel
        public CustomRectangle(Context context, RectF rectf, float left_side, float top_side, String color) {
            super(context);

            this.rectf = rectf;
            this.left_side= left_side;
            this.top_side = top_side;
            this.color = color;

        }

        //!< Implement to draw the rectangle
        @Override
        public void onDraw(Canvas canvas) {
            paint = new Paint();
            paint.setColor(Color.parseColor(color));
            paint.setStrokeWidth(3);
            //paint.setAlpha(61);

            canvas.drawRoundRect(rectf, left_side, top_side, paint);

        }
    }

}

The program starts, but nothing works, I just get my white background screen. Any ideas as to why?

Note. I create my relative layout programmatically and not using XML for scaling.

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4 answers

Actually, your RectFrepresenting Pointnot Rectangle, so you cannot see Rect...

RectF rectF = new RectF(left, top, right, bottom);

and there RectFis

RectF rectf = new RectF(200, 400, 200, 400); // representing Point

here left = right = 200and top = bottom = 400which represents aPoint

Rect width = 200 height = 400, RectF

RectF rectf = new RectF(0, 0, 200, 400);

width = 400 and height = 200, RectF

RectF rectf = new RectF(0, 0, 400, 200);
+11

. , , , , : RectF rectf = new RectF(0, 0, 480, 854);

0

. . , , .

package com.example.test;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.RelativeLayout;
import android.graphics.RectF;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Create main RL params
        RelativeLayout.LayoutParams rlMainlayoutParams 
                = new RelativeLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT);

        // Create main relative layout
        RelativeLayout rlMain = new RelativeLayout(this);
        rlMain.setLayoutParams(rlMainlayoutParams);
        //rlMain.setBackgroundResource(R.drawable.bgndlogin);
        rlMain.setBackgroundColor(Color.WHITE);

        RectF rectf = new RectF(0, 0, 200, 300);
        CustomRectangle customRectangle = new CustomRectangle(this, rectf, 15, 15, "#FFFF00");

        //
        rlMain.addView(customRectangle);

        setContentView(rlMain);
    }

    //!< Draw the log in rectangle shaped panel
    public class CustomRectangle extends View {
        Paint paint;
        float left_side, top_side;
        String color;
        RectF rectf;

        //!< Constructor for the log in rectangle shaped panel
        public CustomRectangle(Context context, RectF rectf, float left_side, float top_side, String color) {
            super(context);

            this.rectf = rectf;
            this.left_side= left_side;
            this.top_side = top_side;
            this.color = color;

        }

        //!< Implement to draw the rectangle
        @Override
        public void onDraw(Canvas canvas) {
            paint = new Paint();
            paint.setColor(Color.parseColor(color));
            paint.setStrokeWidth(3);
            //paint.setAlpha(61);

            canvas.drawRoundRect(rectf, left_side, top_side, paint);

        }
    }

}
0

Android Docs

RectF . (, , ).

RectF rectf = new RectF(left, top, right, bottom);

RectF .

,
 width = | - |   = | top-bottom |

If the width and height are 0, as in the question, this will not represent a representation or an object,
which in logic is not possible for the object to exist with a height, width and depth of 0.

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