android-canvas | 易学教程

Canvas does not draw in Custom View

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问题 I created a Custom View CircleView like this: public class CircleView extends LinearLayout { Paint paint1; public CircleView(Context context) { super(context); init(); } public CircleView(Context context, AttributeSet attrs) { super(context, attrs); init(); } public void init() { paint1 = new Paint(); paint1.setColor(Color.RED); } protected void onDraw(Canvas canvas) { //super.onDraw(canvas); canvas.drawCircle(50, 50, 25, paint1); this.draw(canvas); } } Then I included it on my Activity's

Android: Drawing to canvas, way to make bottom left correspond to (0,0)?

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I'm trying to write a graph class I can use in Android(I'm aware pre-made ones exist), but converting all of my coordinates would be a pain. Is there an easy way to make the screen coordinates start at the bottom left? No, I don't know of a way to move 0,0 to the bottom left and get what you would typically think of as "normal" coordinates. But combining scale() and translate() might do the trick to achieve the same effect. canvas.translate(0,canvas.getHeight()); // reset where 0,0 is located canvas.scale(1,-1); // invert You can flip your Canvas with something like canvas.scale(1, -1) and

Strange crash drawing on canvas on Android 4.0.3. A/libc: Fatal signal 11 (SIGSEGV)

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I'm using a low cost tablet with Android 4.0.3. Here the log: 06-11 23:36:04.653: D/SynopticElement(1583): Size changed to 200x200 06-11 23:36:04.693: D/dalvikvm(1583): GC_FOR_ALLOC freed 62K, 12% free 7275K/8199K, paused 33ms 06-11 23:36:04.713: D/SynopticElement(1583): Size changed to 190x190 06-11 23:36:04.733: D/dalvikvm(1583): GC_FOR_ALLOC freed 9K, 12% free 7583K/8583K, paused 22ms 06-11 23:36:04.743: A/libc(1583): Fatal signal 11 (SIGSEGV) at 0xc52c9d4c (code=1) Debugging my code: canvas.scale(getWidth(), getWidth()); //I'm drawing a custom component Paint frameBackgroundPainter = new

How to get the size of the screen size in a canvas in android?

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问题 I am able to get the screen size in the normal activity but I need to get the screen size in a canvas view & manipulate in accordance with it.Any snippet on it will be helpful.Thanks. 回答1: i got widthPixels heightPixels use ing this. DisplayMetrics metrics = getBaseContext().getResources().getDisplayMetrics(); int w = metrics.widthPixels; int h = metrics.heightPixels; 来源： https://stackoverflow.com/questions/9124797/how-to-get-the-size-of-the-screen-size-in-a-canvas-in-android

Android - Canvas drawLine inside ImageView

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I've one ImageView in which I want to draw a Line. I've done the follow: mImagenCampo = (ImageView) findViewById(R.id.imagen_campo); crearPunto(mArea9M, mPaloIzq,v.getWidth(), mPaloIzq,Color.WHITE); And the function is: private void crearPunto(float x, float y, float xend, float yend, int color) { BitmapDrawable bmpDraw = (BitmapDrawable) mImagenCampo.getDrawable(); Bitmap bmp = bmpDraw.getBitmap().copy(Config.RGB_565, true); Canvas c = new Canvas(bmp); Paint p = new Paint(); p.setColor(color); c.drawLine(x, y, xend, yend, p); mImagenCampo.setImageBitmap(bmp); } My problem is that the line is

Drawing bitmap without scaling on Android

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问题 I was trying to drawbitmap on a canvas. In the emulator, it seems that the image is blurred. Is it likely that the android automatically scaled the bitmap? I did try to disable the scaling such as < supports-screens android:smallScreens="false" android:normalScreens="true" android:largeScreens="false" android:xlargeScreens="false" android:anyDensity="true" /> blur means if I have a pixel in the bitmap, I am seeing like 2x2 pixel. soemtimes a pixel is missing. so I assumed that Android

android canvas draw circles and get touch events

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问题 i have been trying to make such a demo where i need to draw many(hundreds of) circle shapes on canvas (or any other way if possible) , after drawing the canvas i need to zoom and move it .. and also want to capture the click(touch) event of each shape separately .. so i know i can get canvas touch event and get x and y positions and check which which circle is touched but i have to draw many circles and as well after zooming and moving the circle's x and y pos is changes so plz help me.. Give

onClickListener in Canvas

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Im developing an application which having Images as a Index on selection of particular image that activity will begin but I dont know how to set onClickListener or onTouchListener in Canvas heres my code public class DrawView extends View implements OnTouchListener { LinearLayout mLayout; Bitmap index; Bitmap book; Bitmap bird; Bitmap game; Bitmap mail; Bitmap music; Bitmap torch; Paint paint; public DrawView(Context context) { super(context); setFocusable(true); setFocusableInTouchMode(true); this.setOnTouchListener(this); index = BitmapFactory.decodeResource(getResources(), R.drawable.photo1

Add noise effect to a drawing

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I'm in the process of creating a custom view for my android application and would like to add a noise overlay over my drawings. My drawings are pretty standard, arcs, bezier curves, etc. What would be the way to go with creating a noise overlay over arbitrary shapes, drawn with canvas? Use a tileable transparent noise png and cover the canvas with it. 来源： https://stackoverflow.com/questions/6994289/add-noise-effect-to-a-drawing

Android: draw arc within canvas api with a gradient fill color

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I want to draw an arc using canvas using a gradient fill. How can achieve this? Hey I stole this from here: Draw an arc with a SweepGradient in Android but it works fine, I used a LinearGradient instead. Shader gradient = new SweepGradient (0,getMeasuredHeight()/2, Color.RED, Color.WHITE); lightRed.setShader(gradient); canvas.drawArc(rectf, -90, 360, false, lightRed); In my cause i I had to draw someone like this: Maybe you too. So, let's think! How does Sweep Gradient works? If you draw rect via this: private val colors = intArrayOf(ContextCompat.getColor(context, R.color.progress_from_color)