Android GradientDrawable类的详解，设置activity的背景颜色渐变效果[整理后的源码]

最新推荐文章于 2024-11-05 15:13:53 发布

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最新推荐文章于 2024-11-05 15:13:53 发布

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文章标签： android float import class path

本文链接：https://blog.youkuaiyun.com/go_to_learn/article/details/7530997

本文详细介绍了如何在Android中使用GradientDrawable类来创建背景颜色渐变效果。通过示例代码展示了如何设置线性、径向和扫掠渐变，并调整圆角大小，以实现不同类型的渐变背景。

import android.app.Activity;
import android.content.Context;
import android.graphics.*;
import android.graphics.drawable.*;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.*;

public class RoundRects extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new SampleView(this));
    }
    
    private static class SampleView extends View {
        private Path    mPath;
        private Paint   mPaint;
        private Rect    mRect;
        private GradientDrawable mDrawable;

        public SampleView(Context context) {
            super(context);
            setFocusable(true);

            mPath = new Path();
            mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
            mRect = new Rect(0, 0, 120, 120);
            
            mDrawable = new GradientDrawable(GradientDrawable.Orientation.TL_BR,
                                             new int[] { 0xFFFF0000, 0xFF00FF00,
                                                 0xFF0000FF });
            mDrawable.setShape(GradientDrawable.RECTANGLE);
            mDrawable.setGradientRadius((float)(Math.sqrt(2) * 60));
        }
        
        static void setCornerRadii(GradientDrawable drawable, float r0,
                                   float r1, float r2, float r3) {
            drawable.setCornerRadii(new float[] { r0, r0, r1, r1,
                                                  r2, r2, r3, r3 });
        }
        
        @Override protected void onDraw(Canvas canvas) {
            
            mDrawable.setBounds(mRect);

            float r = 16;
            
            canvas.save();
            canvas.translate(10, 10);
            mDrawable.setGradientType(GradientDrawable.LINEAR_GRADIENT);
            setCornerRadii(mDrawable, r, r, 0, 0);
            mDrawable.draw(canvas);
            canvas.restore();
            
            canvas.save();
            canvas.translate(10 + mRect.width() + 10, 10);
            mDrawable.setGradientType(GradientDrawable.RADIAL_GRADIENT);
            setCornerRadii(mDrawable, 0, 0, r, r);
            mDrawable.draw(canvas);
            canvas.restore();
            
            canvas.translate(0, mRect.height() + 10);
    
            canvas.save();
            canvas.translate(10, 10);
            mDrawable.setGradientType(GradientDrawable.SWEEP_GRADIENT);
            setCornerRadii(mDrawable, 0, r, r, 0);
            mDrawable.draw(canvas);
            canvas.restore();
            
            canvas.save();
            canvas.translate(10 + mRect.width() + 10, 10);
            mDrawable.setGradientType(GradientDrawable.LINEAR_GRADIENT);
            setCornerRadii(mDrawable, r, 0, 0, r);
            mDrawable.draw(canvas);
            canvas.restore();
            
            canvas.translate(0, mRect.height() + 10);
            
            canvas.save();
            canvas.translate(10, 10);
            mDrawable.setGradientType(GradientDrawable.RADIAL_GRADIENT);
            setCornerRadii(mDrawable, r, 0, r, 0);
            mDrawable.draw(canvas);
            canvas.restore();
            
            canvas.save();
            canvas.translate(10 + mRect.width() + 10, 10);
            mDrawable.setGradientType(GradientDrawable.SWEEP_GRADIENT);
            setCornerRadii(mDrawable, 0, r, 0, r);
            mDrawable.draw(canvas);
            canvas.restore();
            
        }
    }
}