Question

I am new to Android. When i run this code, only one circle is displayed. If i remove view1, then view2 is displayed. but they are never displayed together!!! why is that?
Any help would be appreciated.

thanks

package com.dots;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
public class Dots1Activity extends Activity
{
    private static final String TAG = "DotsActivity";
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.HORIZONTAL);
        TextView label = new TextView(this);
        LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
             LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
        label.setText("Click the circle!");
        CustomDrawableView view1 = new CustomDrawableView(this, 100, 100, 50, Color.RED);
        CustomDrawableView view2 = new CustomDrawableView(this, 200, 200, 25, Color.GREEN);
        CustomDrawableView view3 = new CustomDrawableView(this, 300, 300, 10, Color.WHITE);
        ll.addView(label, layoutParams);
        ll.addView(view1, layoutParams);
        ll.addView(view2, layoutParams);
        ll.addView(view3, layoutParams);
        setContentView(ll);
    }

}

 class CustomDrawableView extends View implements OnClickListener{
     private Context context;
    private int x, y, radius, color;
    public CustomDrawableView(Context context, int x, int y, int radius, int color) {
        super(context);
        this.context = context;
        this.x = x;
        this.y =y;
        this.radius = radius;
        this.color = color;
        setOnClickListener(this);
    }

    protected void onDraw(Canvas canvas) 
    {
        super.onDraw(canvas);
        this.setBackgroundColor(Color.LTGRAY);
        Paint paint = new Paint (Paint.ANTI_ALIAS_FLAG);
        paint.setColor(color);
        canvas.drawCircle(x, y, radius, paint);

    }

    public void onClick(View v) {
        Toast.makeText(this.context, 
                x+"-"+y+"-"+radius, 
                Toast.LENGTH_SHORT).show();  
    }
}

Answer 1

ll.setOrientation(LinearLayout.HORIZONTAL);

They are put next to each other. You can’t see them, because your display isn’t width naught. Put them in a HorizontalScrollView or make them aper VERTICAL.

---

I’m not sure if this takes effect here, but i found this on the Android Documentation:

Note that the framework will not draw
views that are not in the invalid
region. To force a view to draw, call
invalidate().

Try if this solves your problem (for the moment I guess).

---

About your Code

Something i noticed: The implemented interface for the onClickListener is View.OnClickListener:

class CustomDrawableView extends View implements View.OnClickListener{ [...] }

How to solve the Problem

I looked around on the Android Docs and found this. They mantioned the method onMeasure(), which:

Measure the view and its content to
determine the measured width and the
measured height.

So I added it to your custom CustomDrawableView-class. Unfortuandly, you can’t pass the super.onMeasure()-method simple integers, you’ll need to decode them first, using the View.MeasureSpec-class:

protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
        super.onMeasure(View.MeasureSpec.makeMeasureSpec(100, View.MeasureSpec.EXACTLY),
                View.MeasureSpec.makeMeasureSpec(100, View.MeasureSpec.EXACTLY));
    }

In the Example, I set both width and height to 100px. Also, I did some other improvements on your code:

Dots1Activity-class

import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.widget.LinearLayout;
import android.widget.TextView;

public class Dots1Activity extends Activity
{
    private static final String TAG = "DotsActivity";
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        LinearLayout ll = new LinearLayout(this);
        ll.setOrientation(LinearLayout.VERTICAL);
        TextView label = new TextView(this);
        LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(
             LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT);
        label.setText("Click the circle!");
        CustomDrawableView view1 = new CustomDrawableView(this, 50, 50, 50, Color.RED);
        CustomDrawableView view2 = new CustomDrawableView(this, 75, 75, 25, Color.GREEN);
        CustomDrawableView view3 = new CustomDrawableView(this, 85, 85, 10, Color.WHITE);
        ll.addView(label, layoutParams);
        ll.addView(view1, layoutParams);
        ll.addView(view2, layoutParams);
        ll.addView(view3, layoutParams);
        setContentView(ll);
    }

}

CustomDrawableView-class

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.View;
import android.widget.Toast;

class CustomDrawableView extends View implements View.OnClickListener{
     private Context context;
    private int x, y, radius, color;
    public CustomDrawableView(Context context, int x, int y, int radius, int color) {
        super(context);
        this.context = context;
        this.x = x;
        this.y =y;
        this.radius = radius;
        this.color = color;
        setOnClickListener(this);
    }

    protected void onDraw(Canvas canvas) 
    {
        super.onDraw(canvas);
        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setColor(color);
        canvas.drawCircle(x, y, radius, paint);
    }

    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec){
        super.onMeasure(View.MeasureSpec.makeMeasureSpec(100, View.MeasureSpec.EXACTLY),
                View.MeasureSpec.makeMeasureSpec(100, View.MeasureSpec.EXACTLY));
    }

    public void onClick(View v) {
        Toast.makeText(this.context, 
                x+"-"+y+"-"+radius, 
                Toast.LENGTH_SHORT).show();  
    }
}

This code compiles, shows all the circles and the onClick-Event works, too.

Although I have to say it was a bit of a challenge and I’m grateful for it.