我认为更好的方法是创建自定义 ImageView 并覆盖 onDraw 方法。就像是:
public class CustomView extends ImageView {
public CustomView(Context context) {
super(context);
}
public CustomView(Context context, AttributeSet attrst) {
super(context, attrst);
}
public CustomView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
MyBitmapFactory bitMapFac = null;
public void setBitmapFactory(MyBitmapFactory bitMapFac)
{
this.bitMapFac = bitMapFac;
}
@Override
public void onDraw(Canvas canvas) {
canvas.drawColor(Color.TRANSPARENT);
/*instantiate a bitmap and draw stuff here, it could well be another
class which you systematically update via a different thread so that you can get a fresh updated
bitmap from, that you desire to be updated onto the custom ImageView.
That will happen everytime onDraw has received a call i.e. something like:*/
Bitmap myBitmap = bitMapFac.update(); //where update returns the most up to date Bitmap
//here you set the rectangles in which you want to draw the bitmap and pass the bitmap
canvas.drawBitmap(myBitMap, new Rect(0,0,400,400), new Rect(0,0,240,135) , null);
super.onDraw(canvas);
//you need to call postInvalidate so that the system knows that it should redraw your custom ImageView
this.postInvalidate();
}
}
最好实现一些逻辑,通过 update() 方法检查是否有新的位图要获取,这样 onDraw 内部的代码就不会每次都执行并给系统带来开销。
然后在任何需要的地方使用您的自定义视图。最简单的方法是直接在 activity_layout.xml 中声明它,如下所示:
<com.mycustomviews.CustomView
android:id="@+id/customView"
android:layout_centerInParent="true"
android:layout_height="135dp"
android:layout_width="240dp"
android:background="@android:color/transparent"/>
然后通过使用以下方式访问您的代码,就像任何其他视图一样:
customView = (CustomView) findViewById(R.id.customView);