I am new for android. I want to add image button in onDraw. I wonder if I can do like this. I don't have compile error. But simulator says, "Unfortunately MyApp has stopped."
My second question is how can I add button at x, y location in screen?
There is no location parameters in addView.
protected class MyLayout extends LinearLayout {
ImageButton button;
public MyLayout(Context context) {
super(context);
setWillNotDraw(false);
button = new ImageButton(context);
button.setImageBitmap(buttonBitmap); // buttonBitmap is loaded in onCreate
}
public void onDraw(Canvas canvas) {
addView(button);
}
}
I would not be adding a button to a custom linearlayout in the onDraw() override function. onDraw is called periodically (for example when the element is resized). So you will be adding the same button EACH time onDraw() is called. And you will get an error if you add the same item more than once.
What exactly are you trying to do? If you want to just add a button to a linear layout, you can do so without extending a layout.
Related
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.
Is important to use the setContentView(R.layout.name.xml) in android?
In the following code, I want to draw a line in relativeLayout Object without using the setContentView(R.layout.name.xml). It can compile Successfully. But it stops execution time.
Draw.java
class Draw extends View {
Paint paint;
public Draw(Context context) {
super(context);
paint = new Paint();
}
#Override
protected void onDraw(Canvas canvas) {
paint.setColor(Color.RED);
canvas.drawLine(10,10,100,100,paint);
super.onDraw(canvas);
}}
MainActivity.java
class MainActivity extends Activity {
Draw draw;
#Override
public void onCreate(Bundle s){
super.onCreate(s);
RelativeLayout relativeLayout = new RelativeLayout(this);
draw = new Draw(this);
relativeLayout.addView(draw,200,200);
}
}
setContentView() in Android must be called in the onCreate() method before getting any references to any views in the Activity.
Without setContentView() your activity won't be inflated with or assigned a layout.
As a result your app won't start because the start activity has no layout or UI to display.
So, always include a setContentView(), passing the layout as the parameter, in the onCreate() method of your activity.
Hope that helps.
What method setContentView does is not just setting resource of layout, but something more important. If it's a new activity, it will generate the window decor, apply the theme to your activity and so on. So you see, you cannot just dismiss this and replacing it with your code.
try add this code at the end of onCreate method
setContentView(relativeLayout);
My problem is that I don't know how to change position of a canvas drawable on click of
my button that it's located in the main activity and not to surfaceview so the code to work should be on surfaceview here is what I've got
public class JumpOnClick extends Activity implements OnClickListener{
DrawingSurface ds;
FrameLayout frm;
Button btnC;
int color=0xfff00000;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ds=new DrawingSurface(this);
setContentView(R.layout.activity_jump_on_click);
frm=(FrameLayout)findViewById(R.id.frameLayout);
frm.addView(ds);
btnC=(Button)findViewById(R.id.buttonColor);
btnC.setOnClickListener(this);
}
#Override
public void onClick(View v) {
// how to connect actions in here for my sprites on my surfaceview
// for example AnimatedSprite a = new AnimatedSprite();
// if(b == null)
//b=BitmapFactory.decodeStream(res.openRawResource(R.drawable.explosion));
// a.Initialize(b, 120, 159, 7, 20, true);
// mSprites.add(a);
}
}
if I understand correctly,
define two static float variables in your surfaceview class respectively x and y, and when you do your drawing in your surfaceview just use this variables as position parameters in your surfaceview's draw method. And then back in your activity in your onClick method of the button just change these x,y variables, as you can access them without any need to create object.
I believe that you need to add layout rules to your button to place it in the Surfaceview (Actually a button cant be added to a SurfaceView, you need to create an illusion with a Layout in your Activity and place the button to this Layout).
You can check this simple solution at this video https://www.youtube.com/watch?v=8qE9TQjQ5no&t=31s
that is placing buttons to a SurfaceView at the top and bottom using a Relativelayout. My opinion is with that technique you wont need the ontouchevent method neither the x,y position, you will need that if you create a button in the ondraw method (then wont be a button but a bitmap image)...My opinion is to stick with the first solution if the position is the problem so it can act as a button with the onclicklistener.
I have a FrameLayout that contains several ImageView. On the main activity, I record the touch events in order to move my FrameLayout and the images inside with the finger (drag).
For doing so, I am calling canvas.translate(x,y) inside the onDraw of the framelayout which is called by a invalidate() in the activity touch event handler.
Everything works like a charm except that after the translate, I am not able to click on my ImageView. In fact, the click listener of each image is still at the original place before the translate.
I have read that I should manually update the layout of each image after the translate but how to do that ? If I change the margin with the translate value, the images are going two times further ...
I would really appreciate any help on that one.
Cheers.
Here is the frameLayout where I translate the canvas in the onDraw() method (the ImageView are added to that FrameLayout in my main Activity).
public class TopView extends FrameLayout {
public float mPosX = 0;
public float mPosY = 0;
public TopView(Context context)
{
super(context);
FrameLayout.LayoutParams lp = new FrameLayout.LayoutParams(1920, 3200, Gravity.CENTER);
this.setLayoutParams(lp);
setWillNotDraw(false);
}
#Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.translate(this.mPosX, this.mPosY);
}
}
You can use setPadding(this.mPosX,this.mPosY,0,0) in the the constructor. It should work.
I am trying to create a "hidden edit view" which will give me the functionality of text editing within a 3rd party GUI on Android. I figured that the easiest way to make it not draw would be to just override onDraw() with a no-op; however it's having no effect. I've added a log statement to check that it is being called. Does anyone have an idea why it's still being drawn?
private class HiddenEditText extends EditText
{
public HiddenEditText(Context context)
{
super(context);
}
#Override
protected void onDraw(Canvas canvas)
{
Log.e("DBG", "onDraw()");
}
}
// ...
EditText EditTextGreen = new HiddenEditText(this);
EditTextGreen.setFocusable(true);
EditTextGreen.setLayoutParams(new TableLayout.LayoutParams(TableLayout.LayoutParams.FILL_PARENT, TableLayout.LayoutParams.WRAP_CONTENT));
layout.addView(EditTextGreen, 0);
Another way of achieving this result, is to specify the background of the EditText as transparent:
<EditText android:background="#android:color/transparent" ...
The background is drawn by View.draw(). onDraw() is invoked by View.draw(), so you need to follow Mannaz' advice and set the background to a transparent color or just set it to null.