我在画布上的撤消和重做操作有问题。如果我在 Ondraw() 方法中不使用 canvas.drawbitmap,我注意到下面的代码可以工作,但我需要绘制位图,以便我可以保存画布图像并加载图像。请帮助我。下面是我的代码。
import java.util.ArrayList;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Cap;
import android.graphics.Paint.Join;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.graphics.PorterDuff.Mode;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import com.akinslove.drawingapp.activities.DrawingCanvasActivity;
public class DrawView extends View {
// for bitmap
private Bitmap mainBitmap;
private Canvas mainCanvas;
private Paint mainbitmapPaint;
// for canvas
private Path currentPath;
private Paint currentpathPaint;
private ArrayList<Path> paths = new ArrayList<Path>();
private ArrayList<Path> undonePaths = new ArrayList<Path>();
public DrawView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initialiseMyComponents();
}
public DrawView(Context context, AttributeSet attrs) {
super(context, attrs);
initialiseMyComponents();
}
public DrawView(Context context) {
super(context);
initialiseMyComponents();
}
private void initialiseMyComponents() {
currentPath = new Path();
currentpathPaint = new Paint();
currentpathPaint.setColor(Color.BLACK);
currentpathPaint.setStrokeWidth(10);
currentpathPaint.setStyle(Style.STROKE);
currentpathPaint.setStrokeJoin(Join.ROUND);
currentpathPaint.setStrokeCap(Cap.ROUND);
currentpathPaint.setAntiAlias(true);
mainbitmapPaint = new Paint();
}
@Override
protected void onDraw(Canvas canvas) {
for (Path p : paths){
canvas.drawPath(p, currentpathPaint);
}
canvas.drawPath(currentPath, currentpathPaint);
**//I wish to use the below line of code
canvas.drawBitmap(mainBitmap, 0, 0, mainbitmapPaint);**
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
if (mainBitmap == null) {
mainBitmap = Bitmap.createBitmap(w, h, Config.ARGB_8888);
mainCanvas = new Canvas(mainBitmap);
mainCanvas.drawColor(Color.WHITE);
}
}
float lastX;
float lastY;
@Override
public boolean onTouchEvent(MotionEvent event) {
int action = event.getAction();
float x = event.getX();
float y = event.getY();
switch (action) {
case MotionEvent.ACTION_DOWN:
undonePaths.clear();
DrawingCanvasActivity.IMAGEDRAWN = true;
currentPath.moveTo(x, y);
lastX = x;
lastY = y;
invalidate();
break;
case MotionEvent.ACTION_MOVE:
currentPath.quadTo(lastX, lastY, (lastX + x) / 2, (lastY + y) / 2);
mainCanvas.drawPath(currentPath, currentpathPaint);
lastX = x;
lastY = y;
invalidate();
break;
case MotionEvent.ACTION_UP:
currentPath.lineTo(x, y);
mainCanvas.drawPath(currentPath, currentpathPaint);
// kill this so we don't double draw
paths.add(currentPath);
currentPath = new Path();
currentPath.rewind();
invalidate();
break;
}
return true;
}
// method to get bitmap
public Bitmap getMainBitmap() {
return mainBitmap;
}
// method to set bitmap
public void setMainBitmap(Bitmap mpt) {
mainBitmap = mpt;
mainCanvas = new Canvas(mainBitmap);
postInvalidate();
}
public void onClickUndo () {
if (paths.size()>0)
{
undonePaths.add(paths.remove(paths.size()-1));
invalidate();
}
}
public void onClickRedo (){
if (undonePaths.size()>0)
{
paths.add(undonePaths.remove(undonePaths.size()-1));
invalidate();
}
}
}