Android :: Drawing Bitmaps On Screen In Game Without Slow Performance

I want to make a tile based game for android. At the moment I am drawing each tile as a separate bitmap. I have a big for loop that reads from a string and draws different tiles depending on what character it finds to draw the level. I have allowed the user to scroll the screen using scrolling gestures. However the game is too slow. It takes a long time to update the screen after the user scrolls. I presume this is because it has to draw each tile's bitmap individually. What would be a faster way to draw the level? I was thinking I could merge all the tiles into one bitmap. But I don't know how to do this.

Anyway here is my code so you can see the problem:
package org.example.tutorial2d;
import android.app.Activity;
import android.os.Bundle;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.GestureDetector.OnGestureListener;
import org.example.tutorial2d.Panel;
public class Tutorial2D extends Activity implements OnGestureListener {
GestureDetector gestureScanner; Panel main;
/** Called when the activity is first created. */
@Override public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
gestureScanner = new GestureDetector(this);
//requestWindowFeature(Window.FEATURE_NO_TITLE);
main = new Panel(this); setContentView(main); }
@Override public boolean onTouchEvent(MotionEvent me) {
return gestureScanner.onTouchEvent(me); }
@Override public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
main.handleScroll(distanceX,distanceY); return true; }
@Override public boolean onDown(MotionEvent e) { return true;
} @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { return true;
} @Override public void onLongPress(MotionEvent e){
} @Override public void onShowPress(MotionEvent e) {
} @Override public boolean onSingleTapUp(MotionEvent e) { return true; } }

And the class that does all the work:
package org.example.tutorial2d;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.drawable.Drawable;
import android.util.Log;
import android.view.View;
import org.example.tutorial2d.Point;
public class Panel extends View {
private int scrollX = 0; private int scrollY = 0;
public Panel(Context context) { super(context);
} @Override public void onDraw(Canvas canvas) {
/*Bitmap scratch; //Drawable scratch;
//scratch = getContext().getResources().getDrawable(
// R.drawable.icon); canvas.drawColor(Color.BLACK);
//scratch.draw(canvas); int origin = 0;
scratch = BitmapFactory.decodeResource(getResources(), R.drawable.horizontal5);
canvas.drawBitmap(scratch, origin, origin, null);
int width = scratch.getWidth(); int height = scratch.getHeight();
scratch = BitmapFactory.decodeResource(getResources(), R.drawable.room4entrynesw3x3);
canvas.drawBitmap(scratch, origin + width, origin - 32, null);
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