Question

这是我在指定位置的图像上绘制矩形的代码。绘制了矩形，但我的问题是现在我的图像没有显示。

Bitmap bitmap = Bitmap.createBitmap(50, 50, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
imageView.setImageBitmap(bitmap);

Paint paint = new Paint();
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.FILL_AND_STROKE);
paint.setStrokeWidth(50);
float left = 20;
float topy = 20;
float right = 50;
float bottom = 50;
canvas.drawRect(left, topy, right, bottom, paint);

请告诉我的代码有什么问题吗？

Answer 1

试试这个

    Bitmap bm = new BitmapFactory().decodeResource(getResources(), your_image_id, Bitmap.Config.ARGB_8888);
    Bitmap bitmap = Bitmap.createBitmap(bm);
    Canvas canvas = new Canvas(bitmap);


    Paint paint = new Paint();
    paint.setColor(Color.RED);
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setStrokeWidth(50);
    float left = 20;
    float topy = 20;
    float right = 50;
    float bottom = 50;
    canvas.drawRect(left, topy, right, bottom, paint);

imageView.setImageBitmap(bitmap);

Answer 2

您已将StrokeWidth设为50。这是非常巨大的。删除它或减少。否则代码可以绘制矩形。

我尝试了以下代码。

Bitmap bitmap = Bitmap.createBitmap(50, 50, Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(bitmap);
button.setImageBitmap(bitmap);

Paint paint = new Paint();
paint.setColor(Color.BLACK); // canvas background fill 
canvas.drawPaint(paint); // just to check how big rectangle draw on canvas
    //you can remove 2 above lines. its my testing
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.FILL_AND_STROKE);
paint.setStrokeWidth(5); //5 instead of 50
float left = 20;
float topy = 20;
float right = 50;
float bottom = 50;
canvas.drawRect(left, topy, right, bottom, paint);

修改

您可以尝试以下布局

<LinearLayout android:id="@+id/linearParentHolder" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_alignParentTop="true" android:gravity="center" > <RelativeLayout android:id="@+id/relativeHolder" android:layout_width="wrap_content" android:layout_height="wrap_content" android:gravity="center" > <ImageView android:id="@+id/imgMainImage" android:layout_width="wrap_content" android:layout_height="wrap_content" android:adjustViewBounds="true" android:contentDescription="@string/app_name" android:scaleType="fitCenter" /> <com.customview.CustomRectangleOverlayView android:id="@+id/photoSortrView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBottom="@+id/imgMainImage" android:layout_alignLeft="@+id/imgMainImage" android:layout_alignRight="@+id/imgMainImage" android:layout_alignTop="@+id/imgMainImage" /> </RelativeLayout> </LinearLayout>

其中，两个视图位于RelativeLayout中。一个是图像视图，第二个是用于绘制矩形的自定义视图。您的ImageView将与第二个重叠。第二种观点具有透明度因此，这看起来就像是在原始图像上绘制矩形。

Answer 3

你需要先将图像变为可变图像，然后在其上绘制矩形并使其变为不可变 -

bitmap3=mutableimage3.copy(Bitmap.Config.ARGB_4444,true);// mutable image.

bitmap3=mutableimage3.copy(Bitmap.Config.ARGB_4444,false);//immutable

位图图像问题android

3 个答案: