Develop Reference

Draw a line in Android without setting it as content

Just a newbie here.
Is it possible to draw a line over a layout?
I have an XML file(activity_main) and it contains a layout which is ImageLayout that I took from github. The layout contains an image and several buttons.
What I want to do is to draw a line between two points on the layout. In order to draw a line, people usually create a Draw class and extends View. On the MainActivity, they would setContent the Draw class. I have already setContent my XML file. How would I draw a line from this point?
EDIT:
I heard about the class Path, I think it is better than using onDraw because I would be connecting(drawing lines between) several points in my layout.
Enlighten me about it if you could

Subclass the container ViewGroup and override its dispatchDraw() method. I am providing example of subclassed LinearLayout, however, this would work with any other ViewGroup.
public class MyLinearLayout extends LinearLayout {
private Paint paint;
public MyLinearLayout(Context context) {
super(context);
initPaint();
}
public MyLinearLayout(Context context, AttributeSet attrs) {
super(context, attrs);
initPaint();
}
public MyLinearLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initPaint();
}
private void initPaint() {
paint = new Paint();
paint.setColor(Color.RED);
paint.setStrokeWidth(10);
}
#Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(canvas);
canvas.drawLine(0, 0, canvas.getWidth(), canvas.getHeight(), paint);
}
}

Use this in your layout to do an horizontal line:
android:layout_width="fill_parent"
android:layout_height="2dp"
android:background="#c0c0c0"/>

Draw on SurfaceView outside onDraw() Event

I have a custom class DrawingView which extends SurfaceView. All the drawing is currently happening in the onTouchEvent()-Event. So how can I draw something on my SurfaceView outside the onTouchEvent?
I defined the DrawingView like this in my activity_main.xml:
<com.example.standardbenutzer.adelpath.DrawingView
android:id="#+id/surface"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_centerInParent="true"/>
and I tried this in my MainActivity:
DrawingView dV = (DrawingView)findViewById(R.id.surface);
Canvas canv = dV.surfaceHolder.lockCanvas();
Paint paint = new Paint();
paint.setColor(Color.WHITE);
canv.drawPoint(5,5,paint);
dV.surfaceHolder.unlockCanvasAndPost(canv);
But I get:
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.standardbenutzer.adelpath/com.example.standardbenutzer.adelpath.MainActivity}: java.lang.NullPointerException
Any tips here how i can draw on a surfaceView outside the onTouchEvent ?
So my DrawingView which extends SurfaceView now implements the SurfaceHolder.Callback interface.
So in the different constructors i add the Callback event like this:
public DrawingView(Context context) {
super(context);
surfaceHolder.addCallback(this);
}
public DrawingView(Context context, AttributeSet attrs){
super(context, attrs);
surfaceHolder.addCallback(this);
}
public DrawingView(Context context, AttributeSet attrs, int defStyle){
super(context, attrs, defStyle);
surfaceHolder.addCallback(this);
}
And in the onSurfaceCreated Event i render the image like this:
#Override
public void surfaceCreated(SurfaceHolder holder){
render(holder);
}
But this is still inside the DrawingView class. How can i move the drawing part outside the DrawingView class to my main activity? E.G. i want to render my image on button click. I still found nothing on google how i can do this. Maybe it isn't the right way to use a surfaceview? Are there alternatives?

How to set scaleType and adjustViewBounds in Custom ImageView

I've created a custom ImageView class, as I wanted to override the onDraw method for my Canvas; however, the XML attributes scaleType="centerInside" and adjustViewBounds="true" are not being inherited by my custom ImageView class. If I switch to the default ImageView, everything works fine - but how can I have it work in my custom Image View?
In the class below, I'm simply retrieving a bitmap from my application class and drawing it to the canvas; however, when using my CustomImageView - the image is massive and not scaled properly. Any idea how to fix this? Thanks!
Custom ImageView XML:
<com.project.app.controls.CustomImageView
android:id="#+id/myImage"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:adjustViewBounds="true"
android:scaleType="centerInside"/>
Custom ImageView Class:
public class CustomImageView extends ImageView {
ProjectApp wApp;
Paint paint;
public CustomImageView(Context context, AttributeSet attrs) {
super(context, attrs);
wApp = ProjectApp.createInstance();
paint = new Paint();
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
canvas.drawBitmap(wApp.photoTaken, 0, 0, null);
}
}

public CustomImageView(Context context, AttributeSet attrs) {
super(context, attrs);
wApp = ProjectApp.createInstance();
paint = new Paint();
setAdjustViewBounds(true);
setScaleType(ImageView.ScaleType.CENTER_INSIDE);
}

I think you want to use fitXY instead so the image will be bound by the constraints of the CustomImageView's layout params (and its parent in this case).
android:scaleType="fitXY"

Custom EditText with rectangle drawn around it not compatible with gravity

I am trying to create a custom EditText class with a rectangle drawn around it. I got that to work rather easily. But then I also wanted the text to be centered and therefore I set gravity = center. However that made the rectangle around the box disappear. Is the gravity property changing the bounding box? How can I retrieve the correct bounding box?
The class is as follows:
public static class LetterBox extends EditText {
private Paint mPaint = new Paint();
public LetterBox(Context context) {
super(context);
this.setupPaint();
}
public LetterBox(Context context, AttributeSet attrs) {
super(context,attrs);
this.setupPaint();
super.setGravity(Gravity.CENTER);
}
public LetterBox(Context context, AttributeSet attrs, int defStyle) {
super(context,attrs,defStyle);
this.setupPaint();
super.setGravity(Gravity.CENTER);
}
#Override
protected void onDraw(Canvas canvas) {
canvas.drawRect(0,0,getMeasuredWidth()-1,getMeasuredHeight()-1,mPaint);
super.onDraw(canvas);
}
private void setupPaint() {
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setColor(Color.BLACK);
}
}

I have implemented your code and it is working as expected. The only thing I had to change was remove the static modifier from the class. Did you intend to use static?

Paint over the specific area in Android

I want to draw over the specific Line, Rectangle or Bitmap using Canvas. If i draw over the Bitmap, it will take the square shape empty background also.
So i want to draw over that particular Bitmap area only.

create a bitmap with "bmp1" name from your desire image
create a custom view
create a class and extend View like this
class MyCustomView extends View{
private Rect m_ImageRect;
private Rect m_TextRect ;
//you need these constructor
//you can init paint object or anything on them
public MyCustomView (Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
m_Context = context;
}
public MyCustomView (Context context, AttributeSet attrs)
{
super(context, attrs);
m_Context = context;
}
public MyCustomView (Context context)
{
super(context);
m_Context = context;
}
//then override on draw method
#Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
//here frist create two rectangle
//one for your image and two for text you want draw on it
m_ImageRect = canvas.getClipBounds();
m_TextRect = canvas.getClipBounds();
//it gives you an area that can draw on it,
//the width and height of your rect depend on your screen size device
canvas.drawBitmap(your bitmap(bmp1), null, m_ImageRect , paint);
canvas.save();
canvas.clipRect(m_TextRect);
canvas.drawText("your text", the x position you want to start draw,
the y position you want to start draw, m_paintText);
canvas.restore();
}
}
at the end put the custom view on your layout,and set field on it to send value to view for draw every thing you want
i hope it's help you,if this is not what you want!
post your code so maybe i can help you more

Seems like you need clipping. See exampls: http://www.example8.com/category/view/id/15543 , Understanding Android Canvas Clipping , http://jtomlinson.blogspot.com/2008/10/clipping.html
With clipping you can specify, which regions should be 'editable'.