问题
I am trying to draw a oval using canvas, but it never gets drawn.
Here is my code for the custom view. I have also used setWillNotDraw(false)
still nothing gets drawn on the screen.
public class Myview extends View {
Paint paint;
RectF rect;
public Myview(Context context) {
super(context);
init();
setWillNotDraw(false);
}
public Myview(Context context, AttributeSet attrs) {
super(context, attrs);
init();
setWillNotDraw(false);
}
public Myview(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init();
setWillNotDraw(false);
}
private void init() {
rect = new RectF(0.1 f, 0.1 f, getWidth(), getHeight());
paint = new Paint();
paint.setShader(new LinearGradient(0.40 f, 0.0 f, 100.60 f, 100.0 f,
Color.parseColor("#ffffff"),
Color.parseColor("#Ffffff"),
Shader.TileMode.CLAMP));
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(200, 200);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawOval(rect, paint);
}
}
Any suggestions?
回答1:
The problem is getWidth() and getHeight() is O. Change that to your requirement.
You can use the below as a reference.
public class MainActivity extends Activity
{
MyView mv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mv= new MyView(this);
setContentView(mv);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(20);
mPaint.setShader(new LinearGradient(0.40f, 0.0f, 100.60f, 100.0f,
Color.RED,
Color.RED,
Shader.TileMode.CLAMP));
}
private Paint mPaint;
public class MyView extends View{
Paint paint;
RectF rect;
public MyView(Context context) {
super(context);
rect = new RectF(20, 20, 100,100);
//canvas.drawOval(new RectF(50, 50, 20, 40), p)
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
setMeasuredDimension(200, 200);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
canvas.drawOval(rect, mPaint);
}
}
}
Change the co-ordinates and color to your requirements. The above draws a circle but you can change the co-ordinates to draw oval something like canvas.drawOval(new RectF(50, 50, 20, 40), mPaint);
回答2:
when called in init(): rect = new RectF(0.1f, 0.1f, getWidth(),getHeight());
both getWidth() & getHeight() return 0
来源:https://stackoverflow.com/questions/16605428/custom-view-canvas-ondraw-doesnt-draw-anything