Question

I can add a editText to the scrollview and any other component but when I try to insert a drawing canvas, nothing appears. I show the code for more information

package prueba.android.ondraw;

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.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.LinearLayout;

public class Prueba_ondrawActivity extends Activity {
    private static final String LOGTAG = "";
    @Override
    public void onCreate(Bundle savedInstanceState) {
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main); 
        LinearLayout layout = (LinearLayout) findViewById(R.id.layout);

        MyView v = new MyView(this);

        layout.addView(v);

    }
    private class MyView extends View{
        public MyView(Context context) {
            super(context);
        }
        protected void onDraw(Canvas canvas) {
            int j = 0;
            for(int i=0;i<10;i++){
                super.onDraw(canvas);
                Paint paint = new Paint();
                paint.setColor(Color.CYAN);
                paint.setAntiAlias(true);
                int ancho= canvas.getWidth();
                String ancho2 = "" + ancho;
                Log.e(LOGTAG,ancho2);
                canvas.drawRect(0, 0,200,200, paint);
                j= j+100;
            }
        }
    }
}

Main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">

    <ScrollView
        android:id="@+id/scrollView1"
        android:layout_width="150dp"
        android:layout_height="400dp"
        android:layout_marginLeft="100dp"
        android:background="#FFFFFF"
        > 
        <LinearLayout
            android:id="@+id/layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
        </LinearLayout>
    </ScrollView>

</LinearLayout>

I hope that someone can give me a solution because it can not find how to draw within the scrollview

Thanksss

Answer 1

You are seeing nothing because your custom view has no size.
Either use LayoutParams or pass in the pixel size directly. You could also implement onMeasure Some more info is here

layout.addView(v,300,300);

Also you don’t need to call super.onDraw or create a new Paint on every iteration.