Having trouble drawing circle to screen

Question

I am new to android programming and am trying to draw a circle on the screen. Eventually I'd like to have the circle move around. But for now I have been having trouble getting the circle to draw. When I run the code, it gives me an error:

"Attempt to invoke virtual method 'long android.graphics.Paint.getNativeInstance()' on a null"

My Code:

package com...

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new MyView(this));
    }

    class MyView extends View {



    private Bitmap b;
        public Paint p;

        public MyView(Context context) {
            super(context);
            Paint p = new Paint();
            p.setColor(Color.GREEN);
            b = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            canvas.drawCircle(50, 50, 10, p);
        }
    }
}

You redeclare a Paint in construct method again，and you didn't initial paint in your onDraw method. So please just initial p in your construct method. — Veer, Sep 14 '16 at 05:26

score 1 · Accepted Answer · answered Sep 14 '16 at 04:30

Problem with your code is

 public MyView(Context context) {
            super(context);
            Paint p = new Paint();// Problem is here this is local declaration
            p = new Paint() // do like this and remove above line
            p.setColor(Color.GREEN);
            b = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
        }

Having trouble drawing circle to screen

1 Answers1