如何每次在将ImageView绘制到UI(在片段中)之前获取ImageView Height和Width

Question

我想将外部存储中的照片设置为(圆形(ImageView。因此，我有一个函数，要求ImageView的高度和宽度，以裁剪图片，然后将其设置为位图。

我的问题是，这个函数在加载UI之前就被调用了。我在onViewCreated中找到了第一次调用此函数的解决方案，在那里我向addOnWindowFocusChangeListener添加了一个Listener。这是第一次奏效。

片段在ViewPager中，如果我转到左边的片段，然后从中间到右边，它又不见了。

我对StackOverflow完全陌生。我感谢每一个提示，我可以做得更好

//This works for the First Time
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
View m = getView();
ViewTreeObserver n = m.getViewTreeObserver();
n.addOnWindowFocusChangeListener(new ViewTreeObserver.OnWindowFocusChangeListener() {
@Override
public void onWindowFocusChanged(final boolean hasFocus) {
// do your stuff here
ImageUtil.setPic(binding.photoRoundProfile, mCurrentPhotoPath);
}
});
}

//The function where I set the Picture into the ImageView
static public void setPic(ImageView mImageView, String pPath) {
try {
if (pPath == null) return;
File f = new File(pPath);
if (!f.exists() || f.isDirectory()) return;
// Get the dimensions of the View
int targetW = mImageView.getWidth();
if (targetW == 0) targetW = mImageView.getMeasuredWidth();
int targetH = mImageView.getHeight();
if (targetH == 0) targetH = mImageView.getMeasuredHeight();
// Get the dimensions of the bitmap
BitmapFactory.Options bmOptions = new BitmapFactory.Options();
bmOptions.inJustDecodeBounds = true;
BitmapFactory.decodeFile(pPath, bmOptions);
int photoW = bmOptions.outWidth;
int photoH = bmOptions.outHeight;
// Determine how much to scale down the image
int scaleFactor = photoW / targetW; //Math.min(photoW/targetW, photoH/targetH);
// Decode the image file into a Bitmap sized to fill the View
bmOptions.inJustDecodeBounds = false;
bmOptions.inSampleSize = scaleFactor;
bmOptions.inPurgeable = true;
Bitmap bitmap = BitmapFactory.decodeFile(pPath, bmOptions);
Bitmap orientedBitmap = ExifUtil.rotateBitmap(pPath, bitmap);
mImageView.setImageBitmap(orientedBitmap);
//mImageView.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
mImageView.setAdjustViewBounds(true);
mImageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
} catch (Exception e) {
e.printStackTrace();
}
}

有一个视频，为了更好地理解：https://www.loom.com/share/05c4174562d74c9bba8ff02c9072c866

Answer 1

我找到了解决问题的方法。我在OnPreDrawListener中找到了方法onPreDraw。每次更新ImageView时，此侦听器都会运行。因此，我添加了if语句以节省性能，而不是每次都重新绘制。

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ImageView iv= binding.photoRoundProfile;
ViewTreeObserver vto = iv.getViewTreeObserver();
vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
private int mFinalWidth = 0;
private int mFinalHeight = 0;
public boolean onPreDraw() {
if(mFinalHeight != 0 || mFinalWidth != 0)
return true;
mFinalHeight = iv.getHeight();
mFinalWidth = iv.getWidth();
Log.d("hilength","Height: " + mFinalHeight + " Width: " + mFinalWidth);
ImageUtil.setPic(binding.photoRoundProfile, mCurrentPhotoPath);
return true;
}
});
}