安卓 - 在画布上绘制视图

Android -Draw a view on canvas

本文关键字：绘制 视图 安卓      更新时间：2023-10-16

我尝试使用画布在Android中绘制手指颜料。我已经使用油漆为当前路径着色。使用撤消重做选项删除并显示路径。但是撤消重做效果很好。如果我使用另一种颜色进行绘图，则我使用红色进行绘画，所有以前的路径都更改为当前颜色。

import java.util.ArrayList;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
public class CustomView extends View implements OnTouchListener {
    public Canvas mCanvas;
    private Path mPath;
    public Paint mPaint, mBitmapPaint;
    Bitmap mBitmap;
    Canvas canvas;
    TabletActivity tabletActivity;
    public ArrayList<Path> paths = new ArrayList<Path>();
    public ArrayList<Path> undonePaths = new ArrayList<Path>();
    private Bitmap im;
    public CustomView(Context context) {
        super(context);
        setFocusable(true);
        setFocusableInTouchMode(true);
        this.setOnTouchListener(this);
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(Color.RED);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(6);
        mCanvas = new Canvas();
        mPath = new Path();
        im = BitmapFactory.decodeResource(context.getResources(),
                                          R.drawable.ic_launcher);
        DisplayMetrics metrics = getContext()
                                    .getResources()
                                    .getDisplayMetrics();
        int w = metrics.widthPixels;
        int h = metrics.heightPixels;
        mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        mBitmapPaint = new Paint(Paint.DITHER_FLAG);
        // mBitmapPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC))
        // ;
    }
    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
    }
    @Override
    protected void onDraw(Canvas canvas) {
        // mPath = new Path();
        // canvas.drawPath(mPath, mPaint);
        // canvas.drawColor(Color.TRANSPARENT);
        canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
        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) {
        undonePaths.clear();
        mPath.reset();
        mPath.moveTo(x, y);
        mX = x;
        mY = y;
    }
    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();
    }
    public void onClickUndo() {
        if (paths.size() > 0) {
            undonePaths.add(paths.remove(paths.size() - 1));
            invalidate();
        } else {
        }
    // toast the user
    }
    public void onClickRedo() {
        if (undonePaths.size() > 0) {
            paths.add(undonePaths.remove(undonePaths.size() - 1));
            invalidate();
        } else {
        }
        // toast the user
    }

    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;
    }
}

正如user603125所说，目前你只有一个绘画对象，你用这个油漆绘制所有路径。请记住，在onDraw中，您每次都重新绘制所有路径。为了解决这个问题，你必须跟踪每条路径使用的颜色，例如在地图中，并做这样的事情：

private Map<Path, Color> mPathColors = new HashMap<Path, Color>(); // map for path colors
private Color mCurrentColor; // color to paint current path with (has to be set somewhere)
...
protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
    for (Path p : paths) {
        mPaint.setColor(mPathColors.get(p);
        canvas.drawPath(p, mPaint);
    }
    mPaint.setColor(mCurrentColor);
    canvas.drawPath(mPath, mPaint);
}

touch_up()将当前颜色写入地图，如下所示：

private void touch_up() {
   ...
   paths.add(mPath);
   mPathColors.put(mPath, mCurrentColor);
   ...
}

您正在使用相同的绘制对象来绘制上一个路径以及当前路径。

    @Override
protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
    mPaint.setColor(Color.YELLOW);
    for (Path p : paths) {
        canvas.drawPath(p, mPaint);
    }
    mPaint.setColor(Color.RED);
    canvas.drawPath(mPath, mPaint);
}
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