我是Android中的新手,我发现了一些与上下文有关的事情。
所以我有一个实用程序类,它包含一个实用程序方法,可以创建并返回 Bitmap 图像,这是我的类的代码:
public class ImgUtility {
/**
* Method that create the images related to the difficulty of a recepy
* @param context
* @param difficulty that represent the number of chef_hat_ok into the final image
* @return a Bitmap representing the difficult of a recepy
*/
public static Bitmap createRankingImg(Context context, int difficulty) {
// Create a Bitmap image starting from the star.png into the "/res/drawable/" directory:
Bitmap myBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.chef_hat_ok);
// Create a new image bitmap having width to hold 5 star.png image:
Bitmap tempBitmap = Bitmap.createBitmap(myBitmap.getWidth() * 5, myBitmap.getHeight(), Bitmap.Config.RGB_565);
/* Attach a brand new canvas to this new Bitmap.
The Canvas class holds the "draw" calls. To draw something, you need 4 basic components:
1) a Bitmap to hold the pixels.
2) a Canvas to host the draw calls (writing into the bitmap).
3) a drawing primitive (e.g. Rect, Path, text, Bitmap).
4) a paint (to describe the colors and styles for the drawing).
*/
Canvas tempCanvas = new Canvas(tempBitmap);
// Draw the image bitmap into the cavas:
tempCanvas.drawBitmap(myBitmap, 0, 0, null);
tempCanvas.drawBitmap(myBitmap, myBitmap.getWidth(), 0, null);
tempCanvas.drawBitmap(myBitmap, myBitmap.getWidth() * 2, 0, null);
tempCanvas.drawBitmap(myBitmap, myBitmap.getWidth() * 3, 0, null);
tempCanvas.drawBitmap(myBitmap, myBitmap.getWidth() * 4, 0, null);
return tempBitmap;
}
}
正如您所看到的,此类包含 createRankingImg(),它将上下文对象作为参数并使用它来创建图像。此对象用于从资源中检索图像(进入 BitmapFactory.decodeResource()方法)。什么将Context对象直接表示为Android应用程序?
我知道要在活动类中获取上下文,我可以使用 getResources()方法。
我的问题是我必须将一个上下文放到一个代表Fragment的类中。
我有这样的事情:
public class ScreenSlidePageFragment extends Fragment {
.......................................................................
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@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
.....................................................................
.....................................................................
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switch (mPageNumber + 1) {
case 1:
imgSlideView.setImageResource(R.drawable.carbonara);
((TextView) rootView.findViewById(android.R.id.text1)).setText(getString(R.string.carbonara));
ImageView difficultyContainerImageView1 = (ImageView) rootView.findViewById(R.id.difficultyContainer);
difficultyContainerImageView1.setImageDrawable(new BitmapDrawable(getResources(), ImgUtility.createRankingImg(getApplicationContext(), 3)));
break;
.....................................................................
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}
return rootView;
}
我的问题是,在前一个片段类中,我调用方法:
ImgUtility.createRankingImg(getResources(), 3)
传递 getResources()输出(我认为给我上下文,IDE会给我以下错误消息:
错误的第一个参数类型。发现:' android.content.res.Resources', 必需:' android.content.Context'
所以在我看来,在一个扩展 Fragment 而不是 Activity 的类中, getResources()方法会返回一个资源对象而不是 Context 对象(与Activity类一样)。这是真的吗?为什么呢?
如何在扩展Fragment的类中获取Context?究竟什么代表了Android应用中的Context?我错过了什么?我该如何解决这个问题呢?
答案 0 :(得分:0)
创建一个以Context作为参数的初始函数,以便您可以从activity类传递上下文对象。