Develop Reference

CustomView not showing inside ScrollView

New Android programmer here.
I'm trying to display an .png image as a bitmap on Android. The only way I have been able to display the converted image at all is with a custom class that extends View. However, my image is too large to be displayed entirely on the screen and I would like to be able to scroll with it. But when I define a ScrollView and put the Canvas with the Bitmap into it, I get a blank screen. I had no luck setting this up with the layout file, so it is all done in the Activity class.
This is where the Activity is created:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ScrollView scroll = new ScrollView(this);
scroll.addView(new CustomView(this));
setContentView(scroll);
}
And this is my CustomView class:
private class CustomView extends View{
public CustomView(Context context) {
super(context);
}
#Override
protected void onDraw(Canvas canvas){
Bitmap bitmapMap = BitmapFactory.decodeResource(getResources(),R.drawable.resourceimage);
canvas.drawBitmap(bitmapMap,0,0,null);
this.setWillNotDraw(false);
}
}
And if I replace this line of code in my Activity: setContentView(scroll)
with this line: setContentView(new CustomView(this)), I can see the image, albeit not the entire image. So, is there a way to set this up in the layout files instead? Or is there something I'm missing that I need to declare in the ScrollView class?
EDIT: I would prefer not to use ImageView, because I would like to change the image in specific locations, and using bitmap seemed to be the easiest way to accomplish that, via x and y coordinates.

Your custom view needs to override the onMeasure method and properly set the measured width and height so that the parent views (in this case the ScrollView) can know how much space to allocate for the child.

controll bitmap image manually

I,m taking my first step into movement of bitmaps. From bits on the internet i,ve created this simple code. The bitmap moves across the screen from top left to top right it goes off the screen and back on at 0,0. What i want to do is add a button or method to manually move the image. I,m only using this single class and have noticed it does not use the main_activity xml Or does it?? If someone could show me on this 1 direction i can duplicate for the other directions. If youd like to add code so doesnt go off screen would be a bonus
public class MainActivity extends Activity {
int x=0;
int y=0;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new myView(this)); }
private class myView extends View{
public myView(Context context) {
super(context); }
#Override
protected void onDraw(Canvas canvas) {
Bitmap myBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.richinch);
if (x < canvas.getWidth()){x +=10;}
else {x=0;}
canvas.drawBitmap(myBitmap, x, y, null);
invalidate();
}}}
Ive added this to the code and read a little on OnTouch listener. How would i add that to the region or Rectangle this would be very helpfull so effectively i,m using the Bitmap as a button if was button id know with onclick, Basicall im trying to make 2 Bitmap buttons to move the image Left Right for now.Eventually all directions. Please use names im using unless creating summit eg int etc
Paint green = new Paint();
green.setColor(Color.RED);
green.setStyle(Paint.Style.FILL);
////creating the shape////
Rect rect= new Rect();
rect.set(0, 0,x+50, x+50);
canvas.drawRect(rect,green);
Region region = new Region(0, 950, 100, 1030);

I am not exactly sure what you want to achieve, but if you would like to make an animation, avoid using onDraw() and just let ObjectAnimator do the "moving" for you. Here's a detailed tutorial on it.
The minimum code you need:
ObjectAnimator animation = ObjectAnimator.ofFloat(yourObject, "x", xDest);
animation.setDuration(500); // milliseconds
animation.start();

You are not using any xml
this part here:
setContentView(new myView(this)); is where you would add your xml file setContentView(R.layout.mainxml)
If you want to move around a bitmap with the touch of your finger check out these tutorials. They do exactly this and you will learn to use a SurfaceView
http://www.eis4u.com/2012/02/13/playing-with-graphics-in-android-part-i/
http://www.eis4u.com/2012/02/13/playing-with-graphics-in-android-part-ii/
http://www.eis4u.com/2012/02/13/playing-with-graphics-in-android-part-iii/

Setting background image in a custom view

I have created a class which extends View class.
public class SplashScreen extends View
and i use it by setting contentview
View splash = new SplashScreen(this);
setContentView(splash);
I need to set background image but I can't use layout. I think I need to do canvas drawing but I don't know how to do.
protected void onDraw(Canvas canvas) {
ballBounds.set(ballX-ballRadius, ballY-ballRadius, ballX+ballRadius, ballY+ballRadius);
paint.setColor(Color.LTGRAY);
// canvas.drawImage(R.drawable.background_image); (Ps: I know there is no function such as drawImage)"
canvas.drawOval(ballBounds, paint);}

If you want to just set the background you can do
public SplashScreen(Context context, AttributeSet attrs) {
super(context, attrs);
setBackgroundResource(R.drawable.background);
}

you can add image on canvas as:
Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.pic180);
Matrix matrix=new Matrix();
matrix.postScale(0.8f, 0.8f);
matrix.postRotate(45);
Bitmap dstbmp=Bitmap.createBitmap(bmp,0,0,bmp.getWidth(),
bmp.getHeight(),matrix,true);
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(dstbmp, 10, 10, null);

Don't you just want to change SplachScreen type to activity? Then setContentView change to whatever your layout is and if you want that splach screen appear before your application, make it first in Manifest and in splashscreen end, destroy activity and start your application menu activity. Then you won't need View class and less work finding where is problem

Canvas and drawing image in layout

I have a code where I draw image:
class Panel extends View {
public Panel(Context context) {
super(context);
}
#Override
public void onDraw(Canvas canvas) {
Bitmap _scratch = BitmapFactory.decodeResource(getResources(), R.drawable.calvin_logo_small);
canvas.drawColor(Color.WHITE);
canvas.drawBitmap(_scratch, x-point, y-point, null);
}
}
How can I draw this image in my activity, but I don't want to change may layout. I have layout: setContentView(R.layout.main); This is possible to draw in this lauout with canvas? I have this activity and this layout have a lot of components. I only want image in place where I click with canvas. This is idea. I start application where start activity with my setContentView(R.layout.main);. After that I click on the screen and canvas draw picture in place where I clicked. This is possible to do?

Your code should work. Just override the onTouchEvent() for the view, store the co-ordinates of the touch event in field variables and invalidate() the view so that onDraw() would be called. Use the co-ordinates in onDraw() to render the image as you've already done.
To improve performance, you can cache the bitmap if it's not going to change.

Android: Drawing a canvas to an ImageView

I'm new to android programming and what I'm trying to figure out is this;
In my layout i have a TextView, ImageView, and Button, all on a vertically oriented LinearLayout.
I want to be able to dynamically draw circles in the ImageView, without disturbing the rest of my layout(textview/button). I'm trying to create a canvas, and use the drawcircle function within canvas to set the location of the circle. And then draw that canvas to my imageview in some way. I cannot get this to work, is there a trick to this? Or is my method fundamentally wrong? How would i go about drawing circles to the ImageView without recreating my entire layout?
Thanks!

I had the same challenge and came to the conclusion that overwriting onDraw will at least in the general case not work. My blog explains the reasons. What worked very well for me is the following:
Create a new image bitmap and attach a brand new canvas to it.
Draw the image bitmap into the canvas.
Draw everything else you want into the canvas.
Attach the canvas to the ImageView.
Here is a code snippet for this:
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.drawable.BitmapDrawable;
ImageView myImageView = ...
Bitmap myBitmap = ...
Paint myRectPaint = ...
int x1 = ...
int y1 = ...
int x2 = ...
int y2 = ...
//Create a new image bitmap and attach a brand new canvas to it
Bitmap tempBitmap = Bitmap.createBitmap(myBitmap.getWidth(), myBitmap.getHeight(), Bitmap.Config.RGB_565);
Canvas tempCanvas = new Canvas(tempBitmap);
//Draw the image bitmap into the cavas
tempCanvas.drawBitmap(myBitmap, 0, 0, null);
//Draw everything else you want into the canvas, in this example a rectangle with rounded edges
tempCanvas.drawRoundRect(new RectF(x1,y1,x2,y2), 2, 2, myPaint);
//Attach the canvas to the ImageView
myImageView.setImageDrawable(new BitmapDrawable(getResources(), tempBitmap));

ImageView imageView=(ImageView) findViewById(R.id.image);
Bitmap bitmap = Bitmap.createBitmap(100, 100, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.BLACK);
canvas.drawCircle(50, 50, 10, paint);
imageView.setImageBitmap(bitmap);

I think that a better approach would be to create a custom ImageView and Override the onDraw method. Something like:
public class CustomView extends ImageView {
public CustomView(Context context) {
super(context);
}
public CustomView(Context context, AttributeSet attrst) {
super(context, attrst);
}
public CustomView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
MyBitmapFactory bitMapFac = null;
public void setBitmapFactory(MyBitmapFactory bitMapFac)
{
this.bitMapFac = bitMapFac;
}
#Override
public void onDraw(Canvas canvas) {
canvas.drawColor(Color.TRANSPARENT);
/*instantiate a bitmap and draw stuff here, it could well be another
class which you systematically update via a different thread so that you can get a fresh updated
bitmap from, that you desire to be updated onto the custom ImageView.
That will happen everytime onDraw has received a call i.e. something like:*/
Bitmap myBitmap = bitMapFac.update(); //where update returns the most up to date Bitmap
//here you set the rectangles in which you want to draw the bitmap and pass the bitmap
canvas.drawBitmap(myBitMap, new Rect(0,0,400,400), new Rect(0,0,240,135) , null);
super.onDraw(canvas);
//you need to call postInvalidate so that the system knows that it should redraw your custom ImageView
this.postInvalidate();
}
}
It would be a good idea to implement some logic that checks if there is a fresh bitmap to acquire via the update() method, so that the code inside onDraw won't execute every time and put overhead to the system.
And then use your custom view wherever you need it. The easiest way would be to declare it directly inside the activity_layout.xml as such:
<com.mycustomviews.CustomView
android:id="#+id/customView"
android:layout_centerInParent="true"
android:layout_height="135dp"
android:layout_width="240dp"
android:background="#android:color/transparent"/>
And then access is in your code like any other view by using:
customView = (CustomView) findViewById(R.id.customView);

If you have a xml with layout with all your elements arranged in vertical orienttion. You can achieve what you want by making a class in your package which extends Class View and override its onDraw method. draw circle in it as you want . then instead of adding imageView in the layout add this your own view in the xml layout.like the following
< LinearLayout >
< TextView> < /TextView>
< Button> < /Button>
<com.prac.MyView> </ com.prac.MyView>
< /LinearLayout>
Check the following link for 2D graphics. Its a great tutorial to read.
http://organicandroid.blogspot.com/2010/08/starting-to-play-with-graphics.html
Hope this help : )

There are a couple of ways to do what you want, but using an ImageView the way you describe isn't one of them. One possibility is to have the ImageView display an animated Drawable. You can then focus on having your Drawable implementation draw the circles. Another is to create a new Bitmap every time you want the image to change and set the ImageView to display the new Bitmap. The usual way of doing this, though, is to create a custom View subclass. The API Demos sample project has an example of a custom view, and you can find lots tutorials with Google.