如何在自定义View的画布中设置位图图像？

Question

我的主类中有一个Bitmap对象。我需要将这个位图发送到我的自定义视图类，以便将其设置为在canvas上进一步处理的背景。

例如，有一个名为setPicture的方法，它将位图作为参数接收。那么，如何在画布上绘制这个位图呢？

请参考下面的代码：

public class TouchView extends View {

 final int MIN_WIDTH = 75;
 final int MIN_HEIGHT = 75;
 final int DEFAULT_COLOR = Color.RED;
 int _color;
 final int STROKE_WIDTH = 2;

private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
private float x, y;
private boolean touching = false;

public TouchView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    // TODO Auto-generated constructor stub
    init();
}

public TouchView(Context context, AttributeSet attrs) {
    super(context, attrs);
    // TODO Auto-generated constructor stub
    init();
}

public TouchView(Context context) {
    super(context);
    // TODO Auto-generated constructor stub
    init();
}

private void init() {
    setMinimumWidth(MIN_WIDTH);
    setMinimumHeight(MIN_HEIGHT);
    _color = DEFAULT_COLOR;
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    // TODO Auto-generated method stub
    setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec),
            MeasureSpec.getSize(heightMeasureSpec));
}

@Override
protected void onDraw(Canvas canvas) {
    // TODO Auto-generated method stub
    super.onDraw(canvas);

    if (touching) {
        paint.setStrokeWidth(STROKE_WIDTH);
        paint.setColor(_color);
        paint.setStyle(Paint.Style.FILL);
        canvas.drawCircle(x, y, 75f, paint);
    }
}

public void setPicture (Bitmap bitmap) {

        ///////
         This method must receive my bitmap to draw it on canvas!!!!!!!!!!!!!!!
        ///////


}

public void setColor(int color) {
    _color = color;
}

@Override
public boolean onTouchEvent(MotionEvent motionEvent) {
    // TODO Auto-generated method stub

    switch (motionEvent.getAction()) {
    case MotionEvent.ACTION_MOVE:
    case MotionEvent.ACTION_DOWN:
        x = motionEvent.getX();
        y = motionEvent.getY();
        touching = true;
        break;
    default:
        touching = false;
    }
    invalidate();
    return true;
}

}

我应该如何将这个位图发送到onDraw？

Answer 1

在您的onDraw()方法中，

只管去做

canvas.drawBitmap(myBitmap, 0, 0, null);

myBitmap是您的位图变量。

0,0是指要绘制的坐标，也就是左上角。

还有其他Apis可用，用于绘制特定区域等。

More info can be found here in the api docs.

或者:改为扩展ImageView，并使用setImageBitmap(Bitmap src);方法来实现。

Answer 2

将位图转换为可绘制的，并使用View类的setBackgroundDrawable方法。

public void setPicture (Bitmap bitmap) {
    setBackgroundDrawable(new BitmapDrawable(bitmap));
}

Answer 3

decodedString = Base64.decode(datadtlimgsItem.getImageStr(), Base64.DEFAULT);
            decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length);
            decodedByte = Util.resize(decodedByte, 1500, 1500);
            mDrawingView.addBitmap(decodedByte);

 public void addBitmap(Bitmap bitmap){
        canvasBitmap = bitmap;
        invalidate();
    }
// set bitmap on draw canvas in your custom view class
 @Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);

    if (canvasBitmap == null){

        canvasBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    }
    drawCanvas = new Canvas(canvasBitmap);
}