Invalidate not calling onDraw()

Question

I am trying to call onDraw() whenever drawCircle() is pressed. I know that it is being called (by onClick in xml) because I get the message: "drawCircle pressed". The problem however, is that invalidate is not calling onDraw() which would draw a circle at a random place on the canvas, with a random color. I have tried placing the invalidate in DrawView and having drawCircle in my activity call that method but it also does not work. Any ideas why invalidate is not calling onDraw?

Thanks

In my XML I have defined my View:

<View
    android:layout_width="fill_parent"
    android:layout_height="1dp"
    android:background="#cccccc"
    android:paddingBottom="100dp"
    android:paddingTop="20dp" />

<com.example.genraterandomcircle.DrawView
    android:id="@+id/drawView1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_above="@+id/generateBtnId"
    android:background="#000000" />

<Button
    android:id="@+id/generateBtnId"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/drawView1"
    android:layout_alignParentBottom="true"
    android:layout_marginLeft="25dp"
    android:onClick="drawCircle"
    android:text="@string/generateBtnStr" />

<Button
    android:id="@+id/clearBtnId"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignBaseline="@+id/generateBtnId"
    android:layout_alignBottom="@+id/generateBtnId"
    android:layout_alignRight="@+id/drawView1"
    android:layout_marginRight="50dp"
    android:onClick="clearCircles"
    android:text="@string/clearBtnStr" />

GenerateCircles.java:

package com.example.genraterandomcircle;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;

public class GenerateCircles extends Activity
{

    DrawView dv;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.layout_generate_circles);
        dv = new DrawView(this);
    }

    public void drawCircle(View v)
    {
        System.out.println("drawCircle pressed");

        dv.invalidate();
    }

    public void clearCircles(View v)
    {
        System.out.println("clear pressed");
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.generate_circles, menu);
        return true;
    }

}

The DrawView Class:

package com.example.genraterandomcircle;

import java.util.Random;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
import android.widget.Button;

public class DrawView extends View
{
    Canvas c;
    Paint p = new Paint(Paint.ANTI_ALIAS_FLAG);
    Random random = new Random();
    Bitmap bm;

    public DrawView(Context context)
    {
        super(context);
        init(context);
    }

    public DrawView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        init(context);
    }

    public DrawView(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
        init(context);
    }

    private void init(Context context)
    {

        p.setColor(Color.BLACK);
        bm = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
        c = new Canvas(bm);

        System.out.println("hi there");
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        super.onDraw(canvas);
        //canvas.drawColor(Color.BLACK);
        canvas.drawBitmap(bm, canvas.getWidth() / 2, 0, null);

        p.setColor(Color.rgb(random.nextInt(255), random.nextInt(255), random.nextInt(255)));
        canvas.drawCircle(random.nextInt(canvas.getWidth()), random.nextInt(canvas.getHeight()),
                    random.nextInt(canvas.getWidth() / 4), p);

    }
}

Answer 1

instead of

dv = new DrawView(this); 

in your onCreate use:

dv = (DrawView)findViewById(R.id.drawView1);

your not using the drawview that is in the layout that you set to the content view