分层图像加画布

Question

我正在尝试将两张图片放在一起。顶部是透明的。在它们之上，我正在尝试添加一个透明画布，以便用户可以绘制、键入，以及他们需要做的任何事情，并且底部的两个图像是可见的。

所以我可以让两个图像显示或只是画布。每次我尝试显示画布时，它似乎都在[覆盖它们的两个图像中的 p 上。

这是我目前所拥有的......

 public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);        
    setContentView(new MyView(this));

..... some code to set up the paint
}

private Paint       mPaint;
private MaskFilter  mEmboss;
private MaskFilter  mBlur;

public class MyView extends View {

        private static final float MINP = 0.25f;
        private static final float MAXP = 0.75f;

        private Bitmap  mBitmap;
        private Canvas  mCanvas;
        private Path    mPath;
        private Paint   mBitmapPaint;                

        public MyView(Context c) {
            super(c);                       

            // Creating a new relative layout add the definition again.       
            RelativeLayout relativeLayout = new RelativeLayout(TwoPicksOnEachOther.this);                   
            // Setting the orientation to vertical         
            ////relativeLayout.setOrientation(LinearLayout.VERTICAL);                   

            // Creating Fish  image       
            final ImageView iv = new ImageView(TwoPicksOnEachOther.this);         
            iv.setImageResource(R.drawable.fish2);
            // relative layout parameters
            RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(     
                    RelativeLayout.LayoutParams.FILL_PARENT, 
                    RelativeLayout.LayoutParams.FILL_PARENT);        
            //iv.setId(1);                          
            relativeLayout.addView(iv,lp);        

            // Creating transparent image with boat.
            final ImageView iv2 = new ImageView(TwoPicksOnEachOther.this);
            iv2.setImageResource(R.drawable.ctdeasytwo);
            //iv2.setId(2);
            RelativeLayout.LayoutParams lp2 = new RelativeLayout.LayoutParams(     
                    RelativeLayout.LayoutParams.FILL_PARENT, 
                    RelativeLayout.LayoutParams.FILL_PARENT);
            relativeLayout.addView(iv2,lp2);     

            mBitmap = Bitmap.createBitmap(480, 800, Bitmap.Config.ARGB_8888); 
            //mBitmap = BitmapFactory.decodeResource(getResources(),
            //        R.drawable.ctdeasytwo);                      
            mCanvas = new Canvas(mBitmap);
           // mCanvas.drawBitmap(mBitmap, 10, 10, null);
            mPath = new Path();
            mBitmapPaint = new Paint(Paint.DITHER_FLAG);

        }

        @Override
        protected void onDraw(Canvas canvas) {
            canvas.drawColor(Color.TRANSPARENT);

            canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);  

            canvas.drawPath(mPath, mPaint);
        }

................... More code to manage touch events.

现在我怀疑画布不是相对布局的一部分。这可能是问题吗？如果是，我不能做 relativeLayout.addView(mCanvas,lp);

有什么建议吗？

Answer 1

抱歉，我等了八个小时才回答我自己的问题。

我能够解决问题。我创建了一个类。

public class newClass extends View { 
public newClass (Context context){ super(context); } 
... 
@Override protected void onDraw(Canvas canvas) { 
canvas.drawColor(Color.TRANSPARENT); } 

然后我要做的就是

final newClass myCanvas = new newClass (this); 

relativeLayout.addView(myCanvas,lp2); 

工作正常...

Answer 2

通过执行以下操作（仅显示部分代码），我设法做了类似的事情（在透明画布上绘制背景位图）：

public class MyView extends View {
    public MyView(Context c) {
        super(c);
        Bitmap tmpBitmap;

        // Create the background bitmap and convert it to a drawable object
        mBackBitmap = Bitmap.createBitmap(tmpBitmap, 0, 0, tmpBitmap.getWidth(), tmpBitmap.getHeight(), aMatrix, false);
        mBackBitmapDrawable = new BitmapDrawable(mBackBitmap);
        // Set the drawable object as the background
        setBackgroundDrawable(mBackBitmapDrawable);
        // Create an empty bitmap for the canvas
        mBitmap = Bitmap.createBitmap(tmpBitmap.getWidth(), tmpBitmap.getHeight(), Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        //Log.d("MyView", "onDraw");
        // Use transparent background
        canvas.drawColor(Color.TRANSPARENT);
        canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
        canvas.drawPath(mPath, mPaint);
    }
}

希望对你有帮助。

Answer 3

你可以参考这个 Image in Canvas with touch events