Regarding Android Paint drawing color

问题

DrawView.java

public class DrawView extends View implements OnTouchListener {
private Canvas mCanvas;
private Path mPath;
public Paint mPaint;
ArrayList<Path> paths = new ArrayList<Path>();
private ArrayList<Path> undonePaths = new ArrayList<Path>();

private MaskFilter mEmboss;
private MaskFilter mBlur;

private Bitmap im;

public DrawView(Context context) {
    super(context);
    setFocusable(true);
    setFocusableInTouchMode(true);
    this.setOnTouchListener(this);

    paths.clear();
    undonePaths.clear();

    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.BLUE);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(4);
    mEmboss = new EmbossMaskFilter(new float[] { 1, 1, 1 }, 0.4f, 6, 3.5f);

    mBlur = new BlurMaskFilter(8, BlurMaskFilter.Blur.NORMAL);

    mCanvas = new Canvas();
    mPath = new Path();
    // paths.add(mPath);

    im = BitmapFactory.decodeResource(context.getResources(),
            R.drawable.ic_launcher);

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawColor(Share.cColor);

    for (Path p : paths) {

        canvas.drawPath(p, mPaint);
    }

    canvas.drawPath(mPath, mPaint);

}

private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;

private void touch_start(float x, float y) {

    mPaint.setColor(Share.dColor);
    undonePaths.clear();
    mPath.reset();
    mPath.moveTo(x, y);
    mX = x;
    mY = y;

    Log.e("", "pathsize:::" + paths.size());
    Log.e("", "undonepathsize:::" + undonePaths.size());
}

private void touch_move(float x, float y) {
    float dx = Math.abs(x - mX);
    float dy = Math.abs(y - mY);
    if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
        mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
        mX = x;
        mY = y;
    }
}

private void touch_up() {
    mPath.lineTo(mX, mY);
    // commit the path to our offscreen
    mCanvas.drawPath(mPath, mPaint);
    // kill this so we don't double draw
    paths.add(mPath);
    mPath = new Path();

    Log.e("", "pathsize:::" + paths.size());
    Log.e("", "undonepathsize:::" + undonePaths.size());
}

public void onClickUndo() {

    Log.e("", "pathsize:::" + paths.size());
    Log.e("", "undonepathsize:::" + undonePaths.size());
    if (paths.size() > 0) {
        undonePaths.add(paths.remove(paths.size() - 1));
        invalidate();
    } else {

    }
    // toast the user
}

public void onClickRedo() {

    Log.e("", "pathsize:::" + paths.size());
    Log.e("", "undonepathsize:::" + undonePaths.size());
    if (undonePaths.size() > 0) {
        paths.add(undonePaths.remove(undonePaths.size() - 1));
        invalidate();
    } else {

    }
    // toast the user
}

@Override
public boolean onTouch(View arg0, MotionEvent event) {
    float x = event.getX();
    float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        touch_start(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_MOVE:
        touch_move(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_UP:
        touch_up();
        invalidate();
        break;
    }
    return true;
}

}

I am trying to draw finger paint with different colors but whenever i change the color of paint then all previous path or drawing get and draw with updated color i want to draw with different colors how can i do that ? please give me some solutions for this.

回答1:

To do this, you'd have to create a new Paint for every object drawn. This is because when the Canvas redraws, it references that same Paint object every time, so all paths will use this paint.

Firstly, I would change your paths array to contain both a Paint and a Path. You can achieve this using the Android type Pair.

ArrayList<Pair<Path, Paint>> paths = new ArrayList<Pair<Path, Paint>>();

You will also have to convert your undonePaths variable in this manner.

Then, in your touch_up() method, you need to add this new Paint object.

Paint newPaint = new Paint(mPaint); // Clones the mPaint object
paths.add(new Pair<Path, Paint>(mPath, newPaint));

Lastly, your loop has to be adjusted for this as well:

for (Pair<Path, Paint> p : paths) {
    canvas.drawPath(p.first, p.second);
}

This is quite memory intensive, so you will have to take good care to reset these items when they're no longer in use, but to have so many different colors, you must have all of these different Paint objects.

来源：https://stackoverflow.com/questions/11806208/regarding-android-paint-drawing-color