[筆記] imageView.setScaleType

這陣子要寫一個放大圖片的功能，
使用ImageView來實作，
不過使用下面的程式碼，
圖片始終沒有達到放大的效果：


Bitmap image = null;
Bitmap resizedBitmap= null;
int w = imageW;
int h = imageH;

image =  BitmapFactory.decodeByteArray(baos.toByteArray(), 0, baos.size());
Matrix matrix = new Matrix();
matrix.postScale(2.0f, 2.0f);
resizedBitmap = Bitmap.createBitmap(image, 0, 0, image.getWidth(), image.getHeight(), matrix, true);
//imageView.setScaleType(ImageView.ScaleType.CENTER);
imageView.setImageBitmap(resizedBitmap);



xml大致如下：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/scale_view"
    android:layout_width="match_parent"
    android:layout_height="match_parent"

    >
    <ImageView android:id="@+id/spotlight"
            android:layout_width="320dp" 
            android:layout_height="180dp"
            android:scaleType="fitCenter" //這行也要拿掉，不必要.
            android:adjustViewBounds="true"
            android:layout_alignLeft="@id/mainView"

            />
</RelativeLayout>



最後發現需要加上：
imageView.setScaleType(ImageView.ScaleType.CENTER);
如此才會按圖片的size居中顯示，
當圖片長/寬超過View的長/寬，
則截取圖片的居中部分顯示.

(圖晚點補上好了




其他相關的scale方式還有：

Enum Values
ImageView.ScaleType	CENTER	Center the image in the view, but perform no scaling.
ImageView.ScaleType	CENTER_CROP	Scale the image uniformly (maintain the image's aspect ratio) so that both dimensions (width and height) of the image will be equal to or larger than the corresponding dimension of the view (minus padding).
ImageView.ScaleType	CENTER_INSIDE	Scale the image uniformly (maintain the image's aspect ratio) so that both dimensions (width and height) of the image will be equal to or less than the corresponding dimension of the view (minus padding).
ImageView.ScaleType	FIT_CENTER	Scale the image using CENTER.
ImageView.ScaleType	FIT_END	Scale the image using END.
ImageView.ScaleType	FIT_START	Scale the image using START.
ImageView.ScaleType	FIT_XY	Scale the image using FILL.
ImageView.ScaleType	MATRIX	Scale using the image matrix when drawing.

Ref：ImageView.ScaleType