Question

我试图在画布上绘画，然后onClick将其更改为位图图像，然后使其可拖动。我可以在画布上成功绘画但是如何将此图形转换为图像然后使其可拖动？我不介意是否可以在不转换为图像的情况下拖动绘图。有人可以帮忙吗。

public class MainActivity extends AppCompatActivity implements ColorPickerDialog.OnColorChangedListener {

    protected DrawView canvasView;
    private ImageButton blackCircle;
    private Button pens,select;
    private Paint mPaint;
    Bitmap viewCapture = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mPaint = new Paint();

        canvasView = (DrawView) findViewById(R.id.canvas_view);//The drawing mechanism
        colorChanged(mPaint.getColor());

        blackCircle = (ImageButton) findViewById(R.id.black_circle);           
        blackCircle.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                canvasView.setPathColor(Color.BLACK));
                blackCircle.setPressed(true);
            }
        });

        select = (Button) findViewById(R.id.ic_select);
        select.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v) {

                canvasView.setVisibility(View.VISIBLE);
                canvasView.setPathColor(0);
                //Drag the drawn image
                setContentView(R.layout.activity_main);
                relativeLayout = (RelativeLayout) findViewById(R.id.main);
                drawingView = new DrawingView(MainActivity.this);
                relativeLayout.addView(drawingView);

                //Create a bitmap image of current drawing
                canvasView.setDrawingCacheEnabled(true);
                viewCapture = Bitmap.createBitmap(canvasView.getDrawingCache());
                canvasView.setDrawingCacheEnabled(false);
            }
        });

    }// End of Create();

    private void clearCanvas(View v) {
        canvasView.clear();
    }       

@Override
public void colorChanged(int color) {
    mPaint.setColor(color);
    canvasView.setPathColor(mPaint.getColor());
}


/**************   OnTouch ***************/

class DrawingView extends View{
    float x,y;

    public DrawingView(Context context){
        super(context);
        viewCapture = BitmapFactory.decodeResource(context.getResources(), R.id.main);
    }

    public boolean onTouchEvent(MotionEvent event){
        switch(event.getAction()){
            case MotionEvent.ACTION_DOWN:
            break;
            case MotionEvent.ACTION_MOVE:
                x =(int)event.getX();
                y =(int)event.getY();
                invalidate();
            break;
            case MotionEvent.ACTION_UP:
                x =(int)event.getX();
                y =(int)event.getY();
                invalidate();
            break;
        }
        return true;
    }

    @Override
    public void onDraw(Canvas canvas) {
        Paint paint = new Paint();
        paint.setStyle(Paint.Style.FILL);
        paint.setColor(Color.CYAN);
        canvas.drawBitmap(viewCapture, x, y, paint); 
    }
  }
}//End of Class


public class DrawView extends View {

private Paint drawPaint, canvasPaint;
private Canvas drawCanvas;
private Bitmap canvasBitmap;
private SparseArray<Path> paths;

public DrawView(Context context) {
    super(context);
    setupDrawing();
}

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

public DrawView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    setupDrawing();
}

private void setupDrawing() {
    paths = new SparseArray<>();
    drawPaint = new Paint();
    drawPaint.setColor(Color.BLACK);
    drawPaint.setAntiAlias(true);
    drawPaint.setStrokeWidth(9);
    drawPaint.setStyle(Paint.Style.STROKE);
    drawPaint.setStrokeJoin(Paint.Join.ROUND);
    drawPaint.setStrokeCap(Paint.Cap.ROUND);
    canvasPaint = new Paint(Paint.DITHER_FLAG);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    drawCanvas = new Canvas(canvasBitmap);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
    for (int i=0; i<paths.size(); i++) {
        canvas.drawPath(paths.valueAt(i), drawPaint);
    }
}

@Override
public boolean onTouchEvent(MotionEvent event) {
    int index = event.getActionIndex();
    int id = event.getPointerId(index);

    Path path;
    switch (event.getActionMasked()) {
        case MotionEvent.ACTION_DOWN:
        case MotionEvent.ACTION_POINTER_DOWN:
            path = new Path();
            path.moveTo(event.getX(index), event.getY(index));
            paths.put(id, path);
            break;

        case MotionEvent.ACTION_MOVE:
            for (int i=0; i<event.getPointerCount(); i++) {
                id = event.getPointerId(i);
                path = paths.get(id);
                if (path != null) path.lineTo(event.getX(i), event.getY(i));
            }
            break;

        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_POINTER_UP:
            path = paths.get(id);
            if (path != null) {
                drawCanvas.drawPath(path, drawPaint);
                paths.remove(id);
            }
            break;
        default:
            return false;
    }
    invalidate();
    return true;
}

public void setPathColor(int color) {
    drawPaint.setColor(color);
}

public void clear() {
    canvasBitmap.eraseColor(Color.TRANSPARENT);
    paths.clear();
    invalidate();
    System.gc();
 }
}

Answer 1

对于接下来的步骤，我假设您想让用户拖动刚用DrawView创建的图片。因此，我将介绍另一个View，它可以显示位图并设置其位置和尺寸，就像DrawView一样。（实现此目标的最佳方法取决于您使用的ViewGroup的类型）

从画布上创建位图，如converting a canvas into bitmap image in android

使用setBackground(Drawable)将位图设置为新View的背景，并根据需要切换两个View的可见性。

要使新的View可拖动，请使用View.OnTouchListener并根据MotionEvent s更改位置

另一种选择：只需使用标志来拖动DrawView即可指示用户是可以拖动还是在其上绘制。您已经覆盖onTouchEvent()，现在首先检查该标志，如果将其设置为“拖动”，然后评估两个MOVE之间的差异并相应地调整位置。

如何将画布图形转换为图像然后在屏幕上拖动？

1 个答案: