16.7挑戰練習：優化照片顯示

(1)新建dialog_photo.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

    <ImageView
        android:id="@+id/crime_photo_detail"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

</LinearLayout>
 

public class PhotoDetailFragment extends DialogFragment {

    private static final String ARG_File = "file";
    private ImageView mPhotoView;

    public static PhotoDetailFragment newInstance(File file) {
        Bundle args = new Bundle();
        args.putSerializable(ARG_File, file);

        PhotoDetailFragment fragment = new PhotoDetailFragment();
        fragment.setArguments(args);
        return fragment;
    }

    @NonNull
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        File file = (File) getArguments().getSerializable(ARG_File);

        View v = LayoutInflater.from(getActivity())
                .inflate(R.layout.dialog_photo, null);
        mPhotoView = (ImageView) v.findViewById(R.id.crime_photo_detail);

        Bitmap bitmap = PictureUtils.getScaledBitmap(
                file.getPath(), getActivity());
        mPhotoView.setImageBitmap(bitmap);

        return new AlertDialog.Builder(getActivity())
                .setView(v)
                //.setTitle(R.string.date_picker_title)
                .setPositiveButton(android.R.string.ok, null)
                .create();

    }
}
 

(3)修改CrimeFragment.java

private static final int REQUEST_PHOTO = 3;
private static final String DIALOG_PHOTO = "DialogPhoto";

mPhotoView = (ImageView) v.findViewById(R.id.crime_photo);
        mPhotoView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (mPhotoFile == null || !mPhotoFile.exists()) {
                    mPhotoView.setImageDrawable(null);
                } else {

                    FragmentManager manager = getFragmentManager();
                    PhotoDetailFragment dialog = PhotoDetailFragment.newInstance(mPhotoFile);
                    dialog.setTargetFragment(CrimeFragment.this, REQUEST_PHOTO);
                    dialog.show(manager, DIALOG_PHOTO);

                }

            }
        });
        updatePhotoView();
 

16.8 挑戰練習：優化縮圖載入

修改CrimeFragment.java

(1)updatePhotoView,呼叫頻寬高參數的getScaledBitmap

private void updatePhotoView(int width, int height) {
        if (mPhotoFile == null || !mPhotoFile.exists()) {
            mPhotoView.setImageDrawable(null);
        } else {
            Bitmap bitmap = PictureUtils.getScaledBitmap(
                    mPhotoFile.getPath(), width, height); // change this one
            mPhotoView.setImageBitmap(bitmap);
        }
    }

mPhotoObserver = mPhotoView.getViewTreeObserver();
        mPhotoObserver.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                updatePhotoView(mPhotoView.getWidth(), mPhotoView.getHeight());
            }
        });

        return v;

else if (requestCode == REQUEST_PHOTO) {

                    updatePhotoView(mPhotoView.getWidth(), mPhotoView.getHeight());
        }

上述程式碼執行無誤，可以達到效果，但是OnGlobalLayoutListener的原理還沒有太搞懂，只知道可以通過這個方式獲取檢視的寬和高，待以後深入學習後再加補充。