I'm extending ImageView in order to manually scale an image within the view. I want to scale an image to fill the width of the custom view, and then draw it to the canvas, however, I'm unable to get the view width using this.getWidth()
It just returns 0, as the view has not yet been drawn and so has dimensions 0 by 0.
Currently I have the following in my main.xml:
<com.android.myapp.BackgroundView
android:id="#+id/background_view"
android:layout_height="fill_parent"
android:layout_width="fill_parent"
android:src="#drawable/background"
android:dither="true"
/>
The custom class is as follows:
public class BackgroundView extends ImageView {
private Paint paint;
private Bitmap background;
public BackgroundView(Context context) {
super(context);
paint = new Paint();
loadBitmap();
}
public BackgroundView(Context context, AttributeSet attrs) {
super(context, attrs);
paint = new Paint();
loadBitmap();
}
public void loadBitmap() {
BitmapDrawable src = (BitmapDrawable) this.getDrawable();
background = src.getBitmap();
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawBitmap(background, 0, 0, paint);
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}
}
My Main.java class is:
public class Main extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
I can't use
Bitmap.createScaledBitmap(background, view.getWidth(), view.getHeight(), false)
as the view hasn't yet been drawn, how would I go about scaling the image to fill the view/screen width at this point?
Thanks in advance.
I believe what you want to do could also be achieved by using ImageView directly in conjunction with the scaleType attribute. Either use fitXY or centerCrop, depending on your needs.
But to answer the question, you can only use getWidth() and getHeight() after layout() has been called. So you should be able to use the values inside your onDraw method.
Also you could use another drawBitmap method so you wouldn't have to create a new bitmap in memory.
Related
I am trying to draw a single line in Android using canvas
My class :
public class LineDrawer extends View {
public LineDrawer(Context context) {
super(context);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Paint paint = new Paint();
paint.setColor(Color.BLACK);
paint.setStyle(Paint.Style.FILL_AND_STROKE);
paint.setStrokeWidth(10);
float left = 20;
float top = 20;
float right = 50;
float bottom = 100;
canvas.drawLine(left, top, right, bottom, paint);
}
}
My Main Activity :
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
LineDrawer lineDrawer = new LineDrawer(this);
setContentView(R.layout.activity_Main);
}
}
I cannot find where is the problem , I try all the solutions in the internet but nothing happen , still a blank activity..
Should I import some code ?
lineDrawer is created but not added anywhere. Just creating a view is not enough, you need to add it to the current displayed views to be taken into account and drawn. You have two options:
Add it to your XML layout. You will have to add the following constructor to your custom view.
public LineDrawer(Context context, AttributeSet attrs) {
super(context, attrs);
}
Use addView(). Anyway, given how simple is your example, I'll use first (common) method.
As an additional comment, the Paint paint object should be created on view initialization, as is a costly operation. See in the original documentation for more information about this.
seems I have a problem to understand how offset works. When I use the code below it create me 5 arrowheads, but why? I create one and the use twice offset. So i thought i get 3 arrow heads.
public class legende extends View {
private Paint paint;
private Path arrowPath;
public legende(Context context) {
super(context);
init();
}
public void init(){
paint = new Paint();
arrowPath = new Path();
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int width = 1500;
int height = 5000;
setMeasuredDimension(width, height);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
arrowPath.moveTo(420, 300);
arrowPath.lineTo(430, 300);
arrowPath.lineTo(420, 310);
arrowPath.lineTo(410, 300);
arrowPath.close();
canvas.drawPath(arrowPath, paint);
arrowPath.offset(0,200);
canvas.drawPath(arrowPath, paint);
arrowPath.offset(0,380);
canvas.drawPath(arrowPath, paint);
}
}
EDIT
Looks like, the problem is, that onDraw is called twice, but i don't know why.
This is how I use it in my fragment activity:
hScrollView.addView(new legende(getActivity()));
scrollView.addView(hScrollView);
relativeLayout.addView(scrollView);
Looks like you´ve got a non thread safe implementation of the onDraw method.
This guy worked it out by using a thread safe implementation: Custom View not drawing properly
Maybe you should copy the path to a local object inside the onDraw and then alter and paint.
I would like to add TextView and EditView into my custom LinearLayout programmatically.
But I don't know how.
Something like this (that doesn't work):
<com.custom.FavoritesViewer
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:visibility="gone"
android:id="#+id/favoritesViewer">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello"/>
</com.custom.FavoritesViewer>
and my custom layout
public class FavoritesViewer extends LinearLayout {
private Bitmap fullImage;
private int canvasWidth;
private int canvasHeight;
private final Paint paint = new Paint();
public FavoritesViewer(Context context, AttributeSet attrs) {
super(context, attrs);
setWillNotDraw(false);
initializeCanvasSize(context);
}
private void initializeCanvasSize(Context context) {
final Pair<Integer, Integer> screenSize = Utils.getScreenSize(context);
canvasWidth = screenSize.first;
canvasHeight = screenSize.second;
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(canvasWidth, canvasHeight / 3);
}
#Override
protected void onDraw(Canvas cvs) {
if (fullImage == null) {
fullImage = Bitmap.createBitmap(canvasWidth, canvasHeight / 3, Bitmap.Config.ARGB_8888);
final Canvas canvas = new Canvas(fullImage);
paint.reset();
paint.setColor(Color.parseColor("#AA000000"));
canvas.drawRect(0, 0, canvasWidth, canvasHeight / 3, paint);
}
cvs.drawBitmap(fullImage, 0, 0, null);
}
}
So I have a canvas (like background) and I would like to add some standart Views on top. I cannot add it on onDraw.
Is it any way to add View into custom Layout?
EDITTED
I need to implement some special UI with buttons. I want to wrap this in one component. I draw that UI on canvas and somehow should add buttons (It's enough for me to add simple ImageButton, not to draw an image and emulate button's behaviour). That's why I selected Layout as container and need to add Views programmatically.
As long as you call through to super (probably super.onDraw()), I imagine the parent class will draw the views you add as expected. It looks like you're just overriding onDraw, which would prevent the parent LinearLayout class from rendering it's content (like the TextView).
Try commenting out your onDraw method first, and see if the LinearLayout behaves as expected.
Also, what's the goal of the Custom Layout? There may be a better way to achieve your goal.
If i use the ImageView , i can see the image on my activity , however i can't see when i draw it with a canvas. am i missing something ?. The drawable has the dimensions 479px*100px. I can see onDraw function is being called using a breakpoint inside it.
public View getScrollingImage(){
View temp = new View(this){
BitmapDrawable cloud= (BitmapDrawable) MainActivity.this.getResources().getDrawable(R.drawable.cartoon_clouds);
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawBitmap(cloud.getBitmap(), 0,0, null);
invalidate();
}
};
//ImageView temp = new ImageView(this);
//temp.setImageDrawable(this.getResources().getDrawable(R.drawable.cartoon_clouds));
temp.setLayoutParams(new LayoutParams(LayoutParams.MATCH_PARENT,LayoutParams.MATCH_PARENT,1.0f));
return temp;
}
adding it to view by ,
mainLayout.addView(getScrollingImage());
I am on Android 4.0.4.
Got this working by overriding the onMeasure function in view , got this from Android: Drawing on Canvas in Scrollview
Thanks stackOverflow.
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(cloud.getBitmap().getWidth(),
cloud.getBitmap().getHeight());
}
In my application,I am setting an image in my imageview. I just need to place a marker on that imageview. I am doing it with onDraw function in my custom image view class.The problem is,for example if I take x position and y position as 40 respectively.The marker position shown above image in my mobile is different when compared with running same application on tablet.
I want a solution such that when I give coordinates then the position of marker on image in mobile and tablet appears same.
Here is the code my main activity:
public class PointOnImageActivity extends Activity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_point_on_image);
CustomImag ev= new CustomImag(this);
ev.setBackgroundResource(R.drawable.stad);// set background
setContentView(ev);
}
}
Here is the code of my custom imageview class:
public class CustomImag extends ImageView
{
public CustomImag(Context context)
{
super(context);
}
#Override
public void onDraw(Canvas canvas)
{
super.onDraw(canvas);
Paint mPaint = new Paint();
mPaint.setColor(Color.RED);
canvas.drawCircle(40,40,10,mPaint);
}
}
that's because 40 is pixel value, you actually need 40dp instead. so you can convert 40dp to px value dynamically, like this:
int pxValue1 = (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 40, context.getResources()
.getDisplayMetrics());
int pxValue2 = (int)TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 10, context.getResources()
.getDisplayMetrics());
canvas.drawCircle(pxValue,pxValue,pxValue2,mPaint);
You have to position your custom View according to the screen dimensions. This way, no matter what size screen displays your app, your positioning will be relative.
In your onDraw(Canvas) method, you can get the screen dimensions and draw the circle using them. In the following example(which is mostly your code), I place the red circle at screen_width / 4 and screen_height / 4:
public class MyCustomImageViewActivity extends Activity{
CustomImag ev;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ev = new CustomImag(this);
ev.setBackgroundResource(R.drawable.stad);// set background
setContentView(ev);
}
public class CustomImag extends ImageView {
Paint mPaint;
public CustomImag(Context context) {
super(context);
mPaint = new Paint();
}
#Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
Point point = new Point();
getWindowManager().getDefaultDisplay().getSize(point);
mPaint.setColor(Color.RED);
canvas.drawCircle(point.x / 4, point.y / 4, 10, mPaint);
}
}
}