我有一个简短的问题:
假设我有一个(可变的)位图需要修改(添加图像,文本等等)。
我没有乱用许多特殊的类来绘制画布(画布,画布,矩阵等),而是想到为什么不使用Android的内置类来完成这项任务,并且只有在我需要真正定制的操作时我仍然可以使用画布?
因此,举例来说,为了在位图上显示任何类型的视图(当然没有父视图),我可以调用下一个函数:
public void drawViewToBitmap(Bitmap b, View v, Rect rect) {
Canvas c = new Canvas(b);
// <= use rect to let the view to draw only into this boundary inside the bitmap
view.draw(c);
}
这样的事情可能吗?也许这甚至是它在幕后工作的方式?
我应该在绘图和画布创作之间的部分写什么?
编辑:我已经尝试了下一个代码,但它没有用:
public void drawFromViewToCanvas(final View view, final Rect rect, final Canvas canvas) {
final int widthSpec = View.MeasureSpec.makeMeasureSpec(rect.width(), View.MeasureSpec.EXACTLY);
final int heightSpec = View.MeasureSpec.makeMeasureSpec(rect.height(), View.MeasureSpec.EXACTLY);
view.measure(widthSpec, heightSpec);
// Lay the view out with the known dimensions
view.layout(0, 0, rect.width(), rect.height());
// Translate the canvas so the view is drawn at the proper coordinates
canvas.save();
canvas.translate(rect.left, rect.top);
// Draw the View and clear the translation
view.draw(canvas);
canvas.restore();
}
用法示例:
final int imageSize = 50;
rect = new Rect(35, 344 , 35 + imageSize, 344 + imageSize);
final ImageView imageView = new ImageView(mContext);
imageView.setImageBitmap(bitmap);
imageView.setScaleType(ScaleType.CENTER_CROP);
drawFromViewToCanvas(imageView, getRect(), canvas);
编辑:sony's website上有一个示例:
int measureWidth = View.MeasureSpec.makeMeasureSpec(bitmapWidth, View.MeasureSpec.EXACTLY);
int measuredHeight = View.MeasureSpec.makeMeasureSpec(bitmapHeight, View.MeasureSpec.EXACTLY);
view.measure(measureWidth, measuredHeight);
view.layout(0, 0, bitmapWidth, bitmapHeight);
view.draw(canvas);
想知道它是否有效。
答案 0 :(得分:55)
view.layout(0, 0, viewWidth, viewHeight);
除非你只知道你想要的那些宽度和高度参数,否则你可能还想先测量它:
int widthSpec = MeasureSpec.makeMeasureSpec (ViewGroup.LayoutParams.WRAP_CONTENT, MeasureSpec.UNSPECIFIED;
int heightSpec = MeasureSpec.makeMeasureSpec (400, MeasureSpec.UNSPECIFIED;
view.measure(widthSpec, heightSpec);
view.layout(0, 0, view.getMeasuredWidth(), view.getMeasuredHeight());
编辑:
如果您已经知道所需的宽度和高度:
//Lay the view out with the known dimensions
view.layout (0, 0, rect.width(), rect.height());
//Translate the canvas so the view is drawn at the proper coordinates
canvas.save();
canvas.translate(rect.left, rect.top);
//Draw the View and clear the translation
view.draw(canvas);
canvas.restore();
再次编辑:
是的,经过测试。你可以自己试试:
public class DrawingActivity extends Activity {
public void onCreate (Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//Set a Rect for the 200 x 200 px center of a 400 x 400 px area
Rect rect = new Rect();
rect.set(100, 100, 300, 300);
//Allocate a new Bitmap at 400 x 400 px
Bitmap bitmap = Bitmap.createBitmap(400, 400, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
//Make a new view and lay it out at the desired Rect dimensions
TextView view = new TextView(this);
view.setText("This is a custom drawn textview");
view.setBackgroundColor(Color.RED);
view.setGravity(Gravity.CENTER);
//Measure the view at the exact dimensions (otherwise the text won't center correctly)
int widthSpec = View.MeasureSpec.makeMeasureSpec(rect.width(), View.MeasureSpec.EXACTLY);
int heightSpec = View.MeasureSpec.makeMeasureSpec(rect.height(), View.MeasureSpec.EXACTLY);
view.measure(widthSpec, heightSpec);
//Lay the view out at the rect width and height
view.layout(0, 0, rect.width(), rect.height());
//Translate the Canvas into position and draw it
canvas.save();
canvas.translate(rect.left, rect.top);
view.draw(canvas);
canvas.restore();
//To make sure it works, set the bitmap to an ImageView
ImageView imageView = new ImageView(this);
imageView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
setContentView(imageView);
imageView.setScaleType(ImageView.ScaleType.CENTER);
imageView.setImageBitmap(bitmap);
}
}