Absolutely, this feature is totally achievable in Android Studio using Java! Let me break down the key components, implementation approaches, and relevant official resources to help you build this:

1. Replace EditText with Draggable/Resizable Elements #

Since standard EditText can’t handle drag/resize out of the box, you’ll need to create custom views for both text boxes and images, then handle touch gestures manually:

Custom Draggable/Resizable Text Box #

Extend AppCompatEditText and add touch event handling for dragging and scaling:

public class DraggableEditText extends AppCompatEditText {
    private float lastTouchX, lastTouchY;
    private boolean isDragging = false;
    private ScaleGestureDetector scaleDetector;
    private float scaleFactor = 1.0f;

    public DraggableEditText(Context context) {
        super(context);
        init();
    }

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

    private void init() {
        setBackgroundResource(R.drawable.text_box_border); // Add a visible border
        setSingleLine(false);
        scaleDetector = new ScaleGestureDetector(getContext(), new ScaleListener());
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        scaleDetector.onTouchEvent(event);

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                lastTouchX = event.getRawX();
                lastTouchY = event.getRawY();
                isDragging = true;
                requestFocus(); // Ensure editability when tapped
                return true;
            case MotionEvent.ACTION_MOVE:
                if (isDragging) {
                    float dx = event.getRawX() - lastTouchX;
                    float dy = event.getRawY() - lastTouchY;
                    setX(getX() + dx);
                    setY(getY() + dy);
                    lastTouchX = event.getRawX();
                    lastTouchY = event.getRawY();
                    return true;
                }
                break;
            case MotionEvent.ACTION_UP:
                isDragging = false;
                break;
        }
        return super.onTouchEvent(event);
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            scaleFactor *= detector.getScaleFactor();
            scaleFactor = Math.max(0.5f, Math.min(scaleFactor, 2.0f)); // Limit scale range
            setScaleX(scaleFactor);
            setScaleY(scaleFactor);
            return true;
        }
    }
}

Custom Draggable/Resizable Image #

Similarly, extend ImageView to support drag, resize, and gallery selection:

public class DraggableImageView extends AppCompatImageView {
    // Reuse the same touch/scale logic as DraggableEditText
    // Add gallery selection via Intent:
    public void pickImageFromGallery(Activity activity, int requestCode) {
        Intent intent = new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        activity.startActivityForResult(intent, requestCode);
    }
}

2. Multi-Page Support with ViewPager #

Use ViewPager to manage multiple document pages, each page being a custom ViewGroup (like FrameLayout) that holds your draggable elements:

• Create a PagerAdapter that dynamically adds/removes pages
• Add a button to trigger adapter.addItem() and notify the adapter of data changes

3. Undo/Redo Functionality #

Implement an action stack system to track user operations:

1. Create an interface for editable actions:

public interface EditAction {
    void undo();
    void redo();
}

2. Create concrete action classes (e.g., AddTextAction, MoveElementAction, DeleteElementAction)
3. Maintain two stacks in your activity:

private Stack<EditAction> undoStack = new Stack<>();
private Stack<EditAction> redoStack = new Stack<>();

// Example: When adding a text box
public void addTextToCanvas(ViewGroup canvas) {
    DraggableEditText newText = new DraggableEditText(this);
    canvas.addView(newText);
    undoStack.push(new AddTextAction(canvas, newText));
    redoStack.clear(); // Clear redo stack after new action
}

// Undo button click handler
public void onUndoClick(View view) {
    if (!undoStack.isEmpty()) {
        EditAction action = undoStack.pop();
        action.undo();
        redoStack.push(action);
    }
}

4. Export to PDF #

Use Android’s built-in PdfDocument class to render each page’s elements into a PDF:

private void generatePdf(List<ViewGroup> documentPages) {
    PdfDocument pdfDoc = new PdfDocument();
    PdfDocument.PageInfo pageInfo = new PdfDocument.PageInfo.Builder(595, 842, 1).create(); // A4 size

    for (ViewGroup page : documentPages) {
        PdfDocument.Page pdfPage = pdfDoc.startPage(pageInfo);
        Canvas canvas = pdfPage.getCanvas();

        // Draw each element on the PDF page
        for (int i = 0; i < page.getChildCount(); i++) {
            View element = page.getChildAt(i);
            canvas.save();
            canvas.translate(element.getX(), element.getY());
            canvas.scale(element.getScaleX(), element.getScaleY());
            element.draw(canvas);
            canvas.restore();
        }

        pdfDoc.finishPage(pdfPage);
    }

    // Save the PDF to external storage
    try {
        File pdfFile = new File(getExternalFilesDir(null), "custom_document.pdf");
        FileOutputStream fos = new FileOutputStream(pdfFile);
        pdfDoc.writeTo(fos);
        pdfDoc.close();
        fos.close();
        Toast.makeText(this, "PDF saved!", Toast.LENGTH_SHORT).show();
    } catch (IOException e) {
        e.printStackTrace();
        Toast.makeText(this, "PDF save failed", Toast.LENGTH_SHORT).show();
    }
}

All the tools you need are well-documented in Android’s official guides:

• Custom Views: Learn about touch event handling and gesture detection in the Custom View Development Guide
• PdfDocument: Detailed usage instructions in the PdfDocument Class Reference
• ViewPager: Dynamic page management in the ViewPager Guide
• Gesture Detection: Scale and drag gestures via ScaleGestureDetector

内容的提问来源于stack exchange，提问作者BlackMirror