android - CircularImageView 和 API 16 : NullPointerException error

Question

我在不同的 API 上测试我的应用程序，它似乎可以在 API 17 到 23 上工作，但我发现在 API 16 中，我无法加载我的自定义 View 。我只想在一个圆圈中显示一张照片，并且我已经从此线程中获得了自定义 View 的代码:How to create a circular ImageView in Android?

我的代码粘贴在这里:

public class CircularImageView extends ImageView {

    public CircularImageView(Context context) {
        super(context);
    }

    public CircularImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public CircularImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onDraw(Canvas canvas) {

        Drawable drawable = getDrawable();

        int w = getWidth();

        if (drawable == null) {
            return;
        }

        if (getWidth() == 0 || getHeight() == 0) {
            return;
        }
        Bitmap b = ((BitmapDrawable) drawable).getBitmap();

        Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);

        Bitmap roundBitmap = getCroppedBitmap(bitmap, w);
        canvas.drawBitmap(roundBitmap, 0, 0, null);

    }

    public static Bitmap getCroppedBitmap(Bitmap bmp, int radius) {
        Bitmap sbmp;

        if (bmp.getWidth() != radius || bmp.getHeight() != radius) {
            float smallest = Math.min(bmp.getWidth(), bmp.getHeight());
            float factor = smallest / radius;
            sbmp = Bitmap.createScaledBitmap(bmp, (int) (bmp.getWidth() / factor), (int) (bmp.getHeight() / factor), false);
        } else {
            sbmp = bmp;
        }

        Bitmap output = Bitmap.createBitmap(radius, radius,
                Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(output);

        final Paint paint = new Paint();
        final Rect rect = new Rect(0, 0, radius, radius);

        paint.setAntiAlias(true);
        paint.setFilterBitmap(true);
        paint.setDither(true);
        canvas.drawARGB(0, 0, 0, 0);
        paint.setColor(Color.parseColor("#BAB399"));
        canvas.drawCircle(radius / 2 + 0.7f,
                radius / 2 + 0.7f, radius / 2 + 0.1f, paint);
        paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
        canvas.drawBitmap(sbmp, rect, rect, paint);

        return output;
    }
}

错误发生在这一行:

    if (bmp.getWidth() != radius || bmp.getHeight() != radius) 

这是日志猫:

01-09 15:09:51.185 2119-2119/? E/AndroidRuntime: FATAL EXCEPTION: main java.lang.NullPointerException at com.example.simon.customshapes.CircularImageView.getCroppedBitmap(CircularImageView.java:59) at com.example.simon.customshapes.CircularImageView.onDraw(CircularImageView.java:51) at android.view.View.draw(View.java:13458) at android.view.View.getDisplayList(View.java:12409) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.draw(View.java:13461) at android.view.View.getDisplayList(View.java:12409) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.getDisplayList(View.java:12407) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.support.v7.widget.RecyclerView.drawChild(RecyclerView.java:3588) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.draw(View.java:13461) at android.support.v7.widget.RecyclerView.draw(RecyclerView.java:3097) at android.view.View.getDisplayList(View.java:12409) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2806) at android.view.View.draw(View.java:13461) at android.view.View.getDisplayList(View.java:12409) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.getDisplayList(View.java:12407) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.draw(View.java:13461) at android.support.v4.view.ViewPager.draw(ViewPager.java:2262) at android.view.View.getDisplayList(View.java:12409) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.support.design.widget.CoordinatorLayout.drawChild(CoordinatorLayout.java:1077) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.getDisplayList(View.java:12407) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.getDisplayList(View.java:12407) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.getDisplayList(View.java:12407) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.draw(View.java:13461) at android.widget.FrameLayout.draw(FrameLayout.java:467) at android.view.View.getDisplayList(View.java:12409) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at android.view.ViewGroup.dispatchDraw(ViewGroup.java:2799) at android.view.View.getDisplayList(View.java:12407) at android.view.View.getDisplayList(View.java:12453) at android.view.View.draw(View.java:13182) at android.view.ViewGroup.drawChild(ViewGroup.java:2929) at a

我无法在 Android API 16 中绘制圆形 ImageView 是否有原因？

Answer 1

好吧，因为您的位图为空，并且可绘制对象并不是唯一可能出现错误的地方，即在 copy(Bitmap, boolean) 内.

如果你查看文档

If the conversion is not supported, or the allocator fails, then this returns NULL.

尝试使用较小的图像，因为这可能是内存不足的迹象。您还应该针对可能返回的空值添加一些防范措施，例如在这种情况下只需绘制普通位图。