Thứ Tư, 5 tháng 9, 2012

Example of Paint.setShader() with SweepGradient

0
09:58
More examples of drawing on canvas of custom View listed HERE.

Example of Paint.setShader() with SweepGradient:

Paint.setShader() with SweepGradient


Create a custom View to draw with Paint to apply SweepGradient, MyView.java.
package com.example.androiddraw;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.SweepGradient;
import android.util.AttributeSet;
import android.view.View;

public class MyView extends View {

Paint BackPaint = new Paint();
Context MyContext;

public MyView(Context context) {
super(context);
init(context);
}

public MyView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context);
}

public MyView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context);
}

private void init(Context ctx){
MyContext = ctx;
BackPaint.setStyle(Paint.Style.FILL);
BackPaint.setColor(Color.BLACK);

}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
int w = MeasureSpec.getSize(widthMeasureSpec);
int h = MeasureSpec.getSize(heightMeasureSpec);
setMeasuredDimension(w, h);
}

@Override
protected void onDraw(Canvas canvas) {

float w, h, cx, cy, radius;
w = getWidth();
h = getHeight();
cx = w/2;
cy = h/2;

if(w > h){
radius = h/4;
}else{
radius = w/4;
}

canvas.drawRect(0, 0, w, h, BackPaint);

Paint MyPaint = new Paint();
MyPaint.setStyle(Paint.Style.FILL);

float shaderCx = cx;
float shaderCy = cy;
int shaderColor0 = Color.RED;
int shaderColor1 = Color.BLUE;

MyPaint.setAntiAlias(true);
MyPaint.setShader(new SweepGradient(
shaderCx,
shaderCy,
shaderColor0,
shaderColor1));

canvas.drawCircle(cx, cy, radius, MyPaint);

};

}


MainActivity.java
package com.example.androiddraw;

import android.os.Bundle;
import android.app.Activity;

public class MainActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

MyView myView = new MyView(this);
setContentView(myView);
}

}


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