Android 绘图基础：Canvas、Paint、Color
自定义View 需要集成View组件，并且重写其onDraw(Canvas canvas)就可以了。
public class MyView extends View {
public MyView(Context context) {
super(context);
}
public void onDraw(Canvas canvas) {
Paint paint_circle = new Paint();
paint_circle.setAntiAlias(true);
paint_circle.setColor(Color.BLUE);
paint_circle.setStyle(Style.STROKE);
paint_circle.setStrokeWidth(10);
canvas.drawCircle(110,150,60, paint_circle);
Paint paint_string = new Paint();
paint_string.setColor(Color.BLUE);
paint_string.setTextSize(20);
canvas.drawText("Welcome to Beijing", 245, 310, paint_string);
//绘制福娃图片
canvas.drawBitmap(BitmapFactory.decodeResource(getResources(),
R.drawable.fuwa), 35, 340, paint_line);
}
}
Canvas类
Canvas类可以用来实现各种图形的绘制工作常用图形的方法如下：
- 绘制直线：canvas.drawLine(float startX, float startY, float stopX, float stopY, Paint paint);
- 绘制矩形：canvas.drawRect(float topLeftX, float topLeftY, float rightBottomX, float rightBottomY, Paint paint);
- 绘制圆形：canvas.drawCircle(float cx, float cy, float radius, Paint paint);
- 绘制字符：canvas.drawText(String text, float x, float y, Paint paint);
- 绘制图形：canvas.drawBitmap(Bitmap bitmap, float left, float top, Paint paint);
Paint类
要绘制图形，首先得调整画笔，按照自己的开发需要设置画笔的相关属性。Pain类的常用属性设置方法如下：
- setAntiAlias(); //设置画笔的锯齿效果
- setColor(); //设置画笔的颜色
- setARGB(); //设置画笔的A、R、G、B值
- setAlpha(); //设置画笔的Alpha值
- setTextSize(); //设置字体的尺寸
- setStyle(); //设置画笔的风格（空心或实心）
- setStrokeWidth(); //设置空心边框的宽度
- getColor(); //获取画笔的颜色
Bitmap、BitmapDrawable、BitmapFactory类
Bitmap代表一张位图，BitmapDrawable里面封装类一个Bitmap对象。
BitmapDrawable drawable = new BitmapDrawable(bitmap);
Bitmap bitmap = drawable.getBitmap();
bitmap.recycle();
BitmapFactory是一个工具类，提供了大量的方法。
- public static Bitmap decodeFile (String pathName)
- public static Bitmap decodeByteArray (byte[] data, int offset, int length)
- public static Bitmap decodeStream (InputStream is)
实例
- 圆角图片
/*
<com.xc.xcskin.view.XCRoundImageView
android:id="@+id/roundImageView"
android:layout_centerInParent="true"
android:layout_width="200dp"
android:layout_height="200dp"
android:src="@drawable/roundimageview"
/>
*/
public class XCRoundImageView extends ImageView{
private Paint paint ;
public XCRoundImageView(Context context) {
this(context,null);
}
public XCRoundImageView(Context context, AttributeSet attrs) {
this(context, attrs,0);
}
public XCRoundImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
paint = new Paint();
}
@Override
protected void onDraw(Canvas canvas) {
Drawable drawable = getDrawable();
if (null != drawable) {
Bitmap bitmap = ((BitmapDrawable) drawable).getBitmap();
Bitmap b = getCircleBitmap(bitmap, 14);
final Rect rectSrc = new Rect(0, 0, b.getWidth(), b.getHeight());
final Rect rectDest = new Rect(0,0,getWidth(),getHeight());
paint.reset();
canvas.drawBitmap(b, rectSrc, rectDest, paint);
} else {
super.onDraw(canvas);
}
}
private Bitmap getCircleBitmap(Bitmap bitmap, int pixels) {
Bitmap output = Bitmap.createBitmap(bitmap.getWidth(),
bitmap.getHeight(), Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Rect rect = new Rect(0, 0, bitmap.getWidth(), bitmap.getHeight());
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
int x = bitmap.getWidth();
canvas.drawCircle(x / 2, x / 2, x / 2, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;
}
}
更多内容:
1. Android 自定义View修炼-Android实现圆形、圆角和椭圆自定义图片View（使用BitmapShader图形渲染方法）
