延迟绘制图像的时间

Question

我正在为Android开发一个应用。目标是绘制图像。它可以工作，但是当我在图像上绘画（运行代码时）时，触摸输入会延迟。

我看到了很多绘制图像的方法，并尝试复制它们的示例，但是触摸输入仍然会有所延迟。

下面是我班上的代码

如果您需要更多信息，请问我。

谢谢。

public class ImageActivity extends Activity implements View.OnClickListener,
    View.OnTouchListener {

private ImageView photo;
private ImageButton cancel;
private ImageButton savePicture;

private Bitmap bmp;
private Bitmap alteredBitmap;
private Canvas canvas;
private Paint paint;
private Matrix matrix;
private float downx = 0;
private float downy = 0;
private float upx = 0;
private float upy = 0;
private String photoPath;
private File photoFile;
private CreateFileImage createFileImage = new CreateFileImage();

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_image);

    Intent i = getIntent();
    Bundle extra = i.getExtras();
    photoPath = extra.getString("photoPath");

    photo = this.findViewById(R.id.photo);
    isStoragePermissionGranted();

    cancel = this.findViewById(R.id.cancel);
    savePicture = this.findViewById(R.id.save);

    savePicture.setOnClickListener(this);
    cancel.setOnClickListener(this);
    photo.setOnTouchListener(this);
}

public void onClick(View v) {

    if (v == cancel) {
        Intent i = new Intent();
        setResult(RESULT_CANCELED, i);
        finish();

    } else if (v == savePicture) {

        if (alteredBitmap != null) {
            ContentValues contentValues = new ContentValues(3);
            contentValues.put(MediaStore.Images.Media.DISPLAY_NAME, "Draw On Me");

            Uri imageFileUri = getContentResolver().insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, contentValues);
            try {
                OutputStream imageFileOS = getContentResolver().openOutputStream(imageFileUri);
                alteredBitmap.compress(Bitmap.CompressFormat.JPEG, 90, imageFileOS);
                Toast t = Toast.makeText(this, "Saved!", Toast.LENGTH_SHORT);
                t.show();

            } catch (Exception e) {
                Log.v("EXCEPTION", e.getMessage());
            }
        }
    }
}


private void setPhoto(){
    Uri imageFileUri = Uri.parse(photoPath);
    try {
        BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
        File imageFile = new File(photoPath);
        bmpFactoryOptions.inJustDecodeBounds = true;
        bmp = BitmapFactory.decodeFile(imageFile.getAbsolutePath());

        bmpFactoryOptions.inJustDecodeBounds = false;
        bmp = BitmapFactory.decodeFile(imageFile.getAbsolutePath());

        alteredBitmap = Bitmap.createBitmap(bmp.getWidth(), bmp
                .getHeight(), bmp.getConfig());

        canvas = new Canvas(alteredBitmap);
        paint = new Paint();
        paint.setColor(Color.RED);
        paint.setStrokeWidth(10);
        paint.setAntiAlias(true);
        paint.setDither(true);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setXfermode(null);
        paint.setAlpha(0xff);
        matrix = new Matrix();
        canvas.drawColor(0xFFAAAAAA);
        canvas.drawBitmap(bmp, matrix, paint);

        photo.setImageBitmap(alteredBitmap);
        photo.setOnTouchListener(this);
    } catch (Exception e) {
        Log.v("ERROR", e.toString());
    }
}

private Path mPath;
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
private void touchStart(float x, float y){
    mPath = new Path();

    mPath.reset();
    mPath.moveTo(x, y);

    mX = x;
    mY = y;
}


public boolean onTouch(View v, MotionEvent event) {
    int action = event.getAction();
    switch (action) {
        case MotionEvent.ACTION_DOWN:
            downx = getPointerCoords(event)[0];
            downy = getPointerCoords(event)[1];
            touchStart(downx, downy);
//                photo.invalidate();
            break;
        case MotionEvent.ACTION_MOVE:
            upx = getPointerCoords(event)[0];//event.getX();
            upy = getPointerCoords(event)[1];//event.getY();
            canvas.drawLine(downx, downy, upx, upy, paint);
            downx = upx;
            downy = upy;
//                photo.invalidate();
            break;
        case MotionEvent.ACTION_UP:
            upx = getPointerCoords(event)[0];//event.getX();
            upy = getPointerCoords(event)[1];//event.getY();
            canvas.drawLine(downx, downy, upx, upy, paint);
            photo.invalidate();
            break;
        default:
            break;
    }
    return true;
}

final float[] getPointerCoords(MotionEvent e)
{
    final int index = e.getActionIndex();
    final float[] coords = new float[] { e.getX(index), e.getY(index) };
    Matrix matrix = new Matrix();
    photo.getImageMatrix().invert(matrix);
    matrix.postTranslate(photo.getScrollX(), photo.getScrollY());
    matrix.mapPoints(coords);
    return coords;
}

public void isStoragePermissionGranted() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
                == PackageManager.PERMISSION_GRANTED &&
                checkSelfPermission(Manifest.permission.READ_EXTERNAL_STORAGE)
                        == PackageManager.PERMISSION_GRANTED) {
            Log.v("Permission", "Permission EXTERNAL_STORAGE is granted");
            setPhoto();
        } else {

            Log.v("Permission", "Permission EXTERNAL_STORAGE is revoked");
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.READ_EXTERNAL_STORAGE}, 1);
        }
    } else { //permission is automatically granted on sdk<23 upon installation
        Log.v("Permission", "Permission EXTERNAL_STORAGE is granted");
        setPhoto();
    }
}

@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if (grantResults.length > 0
            && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
        setPhoto();
    }
}
}

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