Develop Reference

Android - add image from a class to a layout

So basicaly the theory is this: i want to create a class that holds a bitmap, which is loaded from a resource. then i want to create a new object of that class and add it to a layout.
So far i've managed to do everything except idk, how to add the bitmap to a layout.
And i want it to be displayed on an existing layout.
bitmap class:
class BitmapView extends View
{
public BitmapView(Context context)
{
super(context);
}
#Override
public void onDraw(Canvas canvas) {
Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.wave);
// canvas.drawColor(Color.BLACK);
canvas.drawBitmap(bmp, 10, 10, null);
}
}
and i call it with setContentView(new BitmapView(this));
but this draws the picture over the whole screen. i want it to display the background that was set in a previous layout. Also is there any way i can set bitmap size?
Thanks

Use an Imageview for displaying bitmap
ImageView imgView=new ImageView(context);
imgView.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT));
imgView.setBitmapImage(bitmap); //Your bitmap goes here.
setContentView(imgView);

use setImageBitmap(bmp). Put an ImageView inside your layout. Reference it with ImageView im = (ImageView) findViewById(R.id.myBitmapId);. When you create your bitmap simply do im.setImageBitmap(bmp);

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.

Put a Image over an activity

How I can put an image over an activity (something like the image below) but with the buttons and other widgets under this image receiving the touch events?
image http://images.macworld.com/appguide/images/android/558/2908791394402692/5582908791394402692_1.jpg

You can create a transparent Activity like this How do I create a transparent Activity on Android? and make a Layout with a fullscreen ImageView

I solve the problem override the draw function.
public class TutorialLinearLayout extends LinearLayout {
public TutorialLinearLayout(Context context) {
super(context);
}
#Override
public void draw(Canvas canvas) {
super.draw(canvas);
Bitmap tutorial = BitmapFactory.decodeResource(getResources(), R.drawable.tutorial);
canvas.drawBitmap(tutorial, 0, 0, null);
tutorial.recycle();
}
}

Drawing Bitmap in Android?

My project is about image processing in android.I have a bitmap that I have loaded from a resource file (an PNG image). I want to draw it. But I couldn't.
Here my code snippet:
mB = BitmapFactory.decodeResource(getResources(), R.drawable.picture);
Canvas c = new Canvas(mB);
Paint p = new Paint();
c.drawBitmap(mB,0,0,p);
it didn't work. Is the code true? .Is there any thing more that I must do?

You should use an ImageView instead and load it by
imageView.setImageResource(R.drawable.picture);
If you want to manually draw it with a Canvas, you have to use a canvas that is passed into a draw() method and implement a Custom View.
Update to add example CustomView:
public class CustomView extends View {
private Paint mPaint;
private Drawable mDrawable;
public CustomView(Context context, AttributeSet attrs) {
super(context, attrs);
mPaint = new Paint();
mDrawable = context.getResources().getDrawable(R.drawable.some_drawable);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
mDrawable.draw(canvas);
}
}

There are a couple of things you are missing.
First, I think you're misunderstanding the Canvas(Bitmap b) constructor. The Bitmap passed in there is one that the Canvas will draw into. This could be just a new Bitmap that you constructed.
Second, it is recommended that you use the Canvas that is passed to you in your View's onDraw method. Presumably that View is one from your Activity, either fetched from your XML layout via findViewById or constructed and passed to setContentView in the Activity's onCreate() method.
So, you are going to have to subclass View and override the onDraw method to get your drawing done. Something like:
public class MyView extends View {
#Override
public void onDraw (Canvas c) {
Bitmap mB = BitmapFactory.decodeResource(this.getContext().getResources(), R.drawable.picture);
c.drawBitmap(mB, 0, 0, null);
}
}
Then, in your Activity, you'll need to create an instance of your new View and pass it to the Activity via setContentView:
public class MyActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mv = new MyView(this);
setContentView(mv);
}
You can instead call the setContentView(View v, ViewGroup.LayoutParameters lp) overload if you want to set up the LayoutParameters.
I haven't tested any of this, but it should at least get you on the right path.

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.