大家好，我是小典，我来为大家解答以上问题。android:drawableright，android的drawable类很多人还不知道，现在让我们一起来看看吧！
一、相关概念
1、Drawable就是一个可画的对象，其可能是一张位图（BitmapDrawable），也可能是一个图形（ShapeDrawable），还有可能是一个图层（LayerDrawable），咱们根据画图的需求，创建相应的可画对象
2、Canvas画布，绘图的目的区域，用于绘图
3、Bitmap位图，用于图的处理
4、Matrix矩阵
二、Bitmap
1、从资源中获取Bitmap
Java代码
Resources res = getResources();
Bitmap bmp = BitmapFactory.decodeResource(res, R.drawable.icon);
2、Bitmap → byte[]
Java代码
public byte[] Bitmap2Bytes(Bitmap bm) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
bm.compress(Bitmap.CompressFormat.PNG, 100, baos);
return baos.toByteArray();
}
3、byte[] → Bitmap
Java代码
public Bitmap Bytes2Bimap(byte[] b) {
if (b.length != 0) {
return BitmapFactory.decodeByteArray(b, 0, b.length);
} else {
return null;
}
}
4、Bitmap缩放
Java代码
public static Bitmap zoomBitmap(Bitmap bitmap, int width, int height) {
int w = bitmap.getWidth();
int h = bitmap.getHeight();
Matrix matrix = new Matrix();
float scaleWidth = ((float) width / w);
float scaleHeight = ((float) height / h);
matrix.postScale(scaleWidth, scaleHeight);
Bitmap newbmp = Bitmap.createBitmap(bitmap, 0, 0, w, h, matrix, true);
return newbmp;
}
5、将Drawable转化为Bitmap
Java代码
public static Bitmap drawableToBitmap(Drawable drawable) {
// 取 drawable 的长宽
int w = drawable.getIntrinsicWidth();
int h = drawable.getIntrinsicHeight();
// 取 drawable 的颜色格式
Bitmap.Config config = drawable.getOpacity() != PixelFormat.OPAQUE ? Bitmap.Config.ARGB_8888
: Bitmap.Config.RGB_565;
// 建立对应 bitmap
Bitmap bitmap = Bitmap.createBitmap(w, h, config);
// 建立对应 bitmap 的画布
Canvas canvas = new Canvas(bitmap);
drawable.setBounds(0, 0, w, h);
// 把 drawable 内容画到画布中
drawable.draw(canvas);
return bitmap;
}
6、获得圆角图片
Java代码
public static Bitmap getRoundedCornerBitmap(Bitmap bitmap, float roundPx) {
int w = bitmap.getWidth();
int h = bitmap.getHeight();
Bitmap output = Bitmap.createBitmap(w, h, Config.ARGB_8888);
Canvas canvas = new Canvas(output);
final int color = 0xff424242;
final Paint paint = new Paint();
final Rect rect = new Rect(0, 0, w, h);
final RectF rectF = new RectF(rect);
paint.setAntiAlias(true);
canvas.drawARGB(0, 0, 0, 0);
paint.setColor(color);
canvas.drawRoundRect(rectF, roundPx, roundPx, paint);
paint.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
canvas.drawBitmap(bitmap, rect, rect, paint);
return output;
}
7、获得带倒影的图片
Java代码
public static Bitmap createReflectionImageWithOrigin(Bitmap bitmap) {
final int reflectionGap = 4;
int w = bitmap.getWidth();
int h = bitmap.getHeight();
Matrix matrix = new Matrix();
matrix.preScale(1, -1);
Bitmap reflectionImage = Bitmap.createBitmap(bitmap, 0, h / 2, w,
h / 2, matrix, false);
Bitmap bitmapWithReflection = Bitmap.createBitmap(w, (h + h / 2),
Config.ARGB_8888);
Canvas canvas = new Canvas(bitmapWithReflection);
canvas.drawBitmap(bitmap, 0, 0, null);
Paint deafalutPaint = new Paint();
canvas.drawRect(0, h, w, h + reflectionGap, deafalutPaint);
canvas.drawBitmap(reflectionImage, 0, h + reflectionGap, null);
Paint paint = new Paint();
LinearGradient shader = new LinearGradient(0, bitmap.getHeight(), 0,
bitmapWithReflection.getHeight() + reflectionGap, 0x70ffffff,
0x00ffffff, TileMode.CLAMP);
paint.setShader(shader);
// Set the Transfer mode to be porter duff and destination in
paint.setXfermode(new PorterDuffXfermode(Mode.DST_IN));
// Draw a rectangle using the paint with our linear gradient
canvas.drawRect(0, h, w, bitmapWithReflection.getHeight()
+ reflectionGap, paint);
return bitmapWithReflection;
}
三、Drawable
1、Bitmap转换成Drawable
Java代码
Bitmap bm=xxx; //xxx根据自己的情况获取
BitmapDrawable bd= new BitmapDrawable(getResource(), bm);
因为BtimapDrawable是Drawable的子类，最终直接使用bd对象即可。
2、Drawable缩放
Java代码
public static Drawable zoomDrawable(Drawable drawable, int w, int h) {
int width = drawable.getIntrinsicWidth();
int height = drawable.getIntrinsicHeight();
// drawable转换成bitmap
Bitmap oldbmp = drawableToBitmap(drawable);
// 创建操作图片用的Matrix对象
Matrix matrix = new Matrix();
// 计算缩放比例
float sx = ((float) w / width);
float sy = ((float) h / height);
// 设置缩放比例
matrix.postScale(sx, sy);
// 建立新的bitmap，其内容是对原bitmap的缩放后的图
Bitmap newbmp = Bitmap.createBitmap(oldbmp, 0, 0, width, height,
matrix, true);
return new BitmapDrawable(newbmp);
}
本文到此讲解完毕了，希望对大家有帮助。