将按钮添加到图形 Canvas

Question

我正在使用这个问题的答案：Drawing on Canvas and save image 来创建一个 canvas 来绘制图像。

我目前正在单击一个按钮时打开一个名为 DrawImage 的 FragmentActivity。在此 activity 中，我希望 MyDrawView 与一个浮动操作按钮一起显示，该按钮允许用户在单击时保存他们的绘图。

这就是我目前显示 canvas 的方式，它有效，但我不知道如何在其上添加按钮。有什么想法吗？

DrawImage

public class DrawImage extends FragmentActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        View drawImageCanvas = new MyDrawView(this.getApplicationContext());
        setContentView(drawImageCanvas);
    }
}

MyDrawView（与 link 相同）

public class MyDrawView extends View {

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

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

    mPath = new Path();
    mBitmapPaint = new Paint(Paint.DITHER_FLAG);

    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(0xFF000000);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(3);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    mCanvas = new Canvas(mBitmap);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);

    canvas.drawPath(mPath, mPaint);
}

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

private void touch_start(float x, float y) {
    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
    mPath.reset();
}

@Override
public boolean onTouchEvent(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;
}

public void clear(){
    mBitmap.eraseColor(Color.TRANSPARENT);
    invalidate();
    System.gc();
}
}

Answer 1

您正在将 contentView 设置为 MyDrawView 视图，因此布局中将不再有任何视图（按钮）。这样添加按钮是不可能的。

解决方法是将MyDrawView移动到xml文件(fragment_draw_image.xml)并设置内容v

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.example.misah.test.MyDrawView
        android:id="@+id/myView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Save Drawing"/>

</RelativeLayout>

然后 setContentView(R.layout.fragment_draw_image); 在布局中，您有绘图视图和位于其顶部的按钮，以及您想要的任何其他内容。

已编辑：

也将此构造函数添加到 MyDrawView，您可以从 xml:

使用它

public MyDrawView(Context c) {
    super(c);
    init();
}

public MyDrawView(Context context, @Nullable AttributeSet attrs) {
    super(context, attrs);
    init();
}

public MyDrawView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init();
}

public MyDrawView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    super(context, attrs, defStyleAttr, defStyleRes);
    init();
}

并将您在构造函数中所做的一切添加到初始化方法（绘图等）

Answer 2

JVM 找不到您的自定义 class MyDrawView。必须把包名点MyDrawView放在XML文件中(fragment_draw_image.xml)

将按钮添加到图形 Canvas

Add Button to Graphics Canvas

android

android-view

android-fragmentactivity

android-graphics