CircularImageView和API 16：NullPointerException错误-Java 学习之路

我在不同的API上测试我的应用程序，它似乎适用于API 17至23但我在API 16中发现，我无法加载我的自定义视图 . 我只是想在一个圆圈中显示一张照片，我从这个帖子中获取了自定义视图的代码：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;
    }
}

此行中出现错误：

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

这是logcat：

01-09 15：09：51.185 2119-2119 /？ E / AndroidRuntime：FATAL EXCEPTION：com.example.simon.customshapes.CircularImageView.getCroppedBitmap（CircularImageView.java:59）中的主要java.lang.NullPointerException，位于com.example.simon.customshapes.CircularImageView.onDraw（CircularImageView.java:51））在android.view.View.View.draw（View.java:13458）的android.view.View.getDisplayList（View.java:12409）android.view.View.getDisplayList（View.java:12453）android.view .view.draw（View.java:13182）位于android.view.View.View.Starts上的android.view.ViewGroup.DispatchDraw（ViewGroup.java：2799）的android.view.ViewGroup.drawChild（ViewGroup.java:2929） View.java:13461）在Android.view.View.View.draw（View.java:13182）的android.view.View.getDisplayList（View.java:12453）的android.view.View.getDisplayList（View.java:12409））在Android.view.View.View上的android.view.ViewGroup.DisplayList（View.java:12407）的android.view.ViewGroup.DispatchDraw（ViewGroup.java:2799）上的android.view.ViewGroup.drawChild（ViewGroup.java:2929） android.view.View.dr中的.View.getDisplayList（View.java:12453） aw（View.java:13182）位于android.view.ViewGroup.Davatch上的android.view.ViewGroup.drawChild（ViewGroup.java:2929），android.view.dvatch：Java上的android.support.v7.widget.RecyclerView.drawChild（RecyclerView.java:3588）（ViewGroup.java:2799）在Android.view.View.get.get.DisplayList上的android.sview.view.draw（View.java:13461）android.support.v7.widget.RecyclerView.draw（RecyclerView.java:3097） View.java:12409）在android.view.View.View.Go（View.java:13182）的android.view.View.View.Go（View.java:13452）的android.view.View. ）在android.view.View.DisplayList（View.java:12409）的android.view.View.Dis上的android.view.View.DavatchDraw（View.java:2806）上的android.view.View.DispatchDraw（ViewGroup.java:2806） android.view.View.DisplayList（View.java:12453），位于android.view.View.St.Th上的android.view.View.draw.（View.java:2189），android.view. ViewGroup.java:2799）在Android.view.View.getDisplayList（View.java）的android.view.View.getDisplayList（View.java:12407）：12453）在android.view.View.draw（View.java:13182）android.view.ViewGroup.drawChild（ViewGroup.java:2929）android.view.ViewGroup.dispatchDraw（ViewGroup.java:2799）at android .view.View.draw（View.java:13461）位于Android的android.view.View.getDisplayList（View.java:12409）的android.support.v4.view.ViewPager.draw（ViewPager.java:2262） . 在Android.view.design.will上安装了android.view.view.draw（View.java:13182）的view.View.getDisplayList（View.java:12453），android.support.design.widget上的android.view.ViewGroup.drawChild（ViewGroup.java:2929） .CoordinatorLayout.drawChild（CoordinatorLayout.java:1077）位于android.view.View.DisplayList上的android.view.View.getDisplayList（View.java:12407）的android.view.ViewGroup.dispatchDraw（ViewGroup.java:2799） View.java:12453）在Android.view.View.DavatchDraw（ViewGroup.java:2799）的android.view.View.draw.draw（ViewGroup.java:2929）的android.view.View.draw（View.java:13182））在android.view.View.getDisplayList（View.java:12453）的android.view.View.getDisplayList（View.java:12407）在android.view.View.draw（View.java:13182）的android.view.ViewGroup.drawChild（ViewGroup.java:2929）android.view.ViewGroup.dispatchDraw（ViewGroup.java:2799）android.view .view.getDisplayList（View.java:12407）位于android.view.View.View（View.java:13452）的android.view.View.View.Start（View.java:12453） ViewGroup.java:2929）在Android.view.FrameLayout.draw的android.view.View.Davout：事件处于android.view.View.Davout：事件处的android.view.View.Davout：事件中的android.view.View.Dava（ . View.java：13449））在android.view.View.get.DisplayList（View.java:12453）的android.view.View.getDisplayList（View.java:12453）android.view.View.draw（View.java:13182）android.view .ViewGroup.drawChild（ViewGroup.java:2929）位于android.view.View.DisplayList上的android.view.View.getDisplayList（View.java:12407）的android.view.ViewGroup.dispatchDraw（ViewGroup.java:2799） View.java:12453）在android.view.View.draw.Stild（ViewGroup.java:2929）的android.view.View.draw（View.java:13182）在...

我不能在Android API 16中绘制圆形图像视图吗？

3 回答

您可以使用MLRoundedImageView进行圆形图像查看 . MLRoundedImageView.java

public class MLRoundedImageView extends ImageView {

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

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

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

@Override
protected void onDraw(Canvas canvas) {

    Drawable drawable = getDrawable();

    if (drawable == null) {
        return;
    }

    if (getWidth() == 0 || getHeight() == 0) {
        return;
    }
    Bitmap b = ((BitmapDrawable) drawable).getBitmap();
    Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);

    int w = getWidth(), h = getHeight();

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

    final int color = 0xffa19774;
    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(Mode.SRC_IN));
    canvas.drawBitmap(sbmp, rect, rect, paint);

    return output;
}
}

然后在布局中使用这样的

<com.yourproject.MLRoundedImagView
  Layout properties here />

然后在你的活动中

MLRoundedImagView imageview = (MLRoundedImagView) findViewbyId(R.id.imageview);

回复于 2024-04-27T02:42:32+08:00

1

好吧，因为你的位图是null并且drawable不是错误所在的唯一位置在copy(Bitmap, boolean)之内 .

如果你看一下文档

如果不支持转换，或者分配器失败，则返回NULL .

尝试使用较小的图像，因为这可能是低的标志记忆 . 您还应该针对返回的可能空值添加一些警示，例如在这种情况下只绘制正常的位图 .

回复于 2024-04-27T02:42:32+08:00

使用此方法将drawable转换为位图：

public static Bitmap drawableToBitmap (Drawable drawable) {
    Bitmap bitmap = null;

    if (drawable instanceof BitmapDrawable) {
        BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;
        if(bitmapDrawable.getBitmap() != null) {
            return bitmapDrawable.getBitmap();
        }
    }

    if(drawable.getIntrinsicWidth() <= 0 || drawable.getIntrinsicHeight() <= 0) {
        bitmap = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888); // Single color bitmap will be created of 1x1 pixel
    } else {
        bitmap = Bitmap.createBitmap(drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
    }

    Canvas canvas = new Canvas(bitmap);
    drawable.setBounds(0, 0, canvas.getWidth(), canvas.getHeight());
    drawable.draw(canvas);
    return bitmap;
}

然后，而不是在原始代码中使用，以下行：

Bitmap b = ((BitmapDrawable) drawable).getBitmap();

使用此代替：

Bitmap b = drawableToBitmap(drawable);

然后它将运行没有错误 .

回复于 2024-04-27T02:42:32+08:00

CircularImageView和API 16：NullPointerException错误

3 回答

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