android - 如何堆叠 Canvas 和按钮？

Question

我想编写以下应用程序。有一个 Canvas 和一个垂直堆叠在 LinearView 中的 Button。当按钮第一次在 Canvas 中绘制圆时按下，然后如果再次按下圆圈消失。圆圈必须出现以其空间为中心。

有什么想法吗？

谢谢，

JG

Answer 1

这应该可行

自定义 View 类

public class DrawView extends View {
    private Canvas viewCanvas;

    public DrawView(Context context) {
        super(context);
        setLayoutParams(new LayoutParams(LinearLayout.LayoutParams.FILL_PARENT
            ,LinearLayout.LayoutParams.FILL_PARENT)); 
    }

    public DrawView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override 
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint p = new Paint();
        p.setColor(Color.RED);
        canvas.drawCricle(getWidth()/2,getHeight()/2,50,null);
        viewCanvas = canvas;
    }

    public clearCircle(){
        viewCanvas.drawColor(Color.BLACK);
    }
}

Activity 类应该是这样的

public class KeyboardTopDemo extends Activity {
    private FrameLayout container;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ss);

        container = (FrameLayout)findViewById(R.id.sc);        
        container.addView(new DrawView(this));
    }

    public void clearHandler(View target){
        container.getChildAt(0).clearCircle();
    }
}

这是布局xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" android:layout_height="fill_parent" 
    android:orientation="vertical">
    <FrameLayout android:orientation="vertical" android:layout_width="fill_parent" 
        android:layout_height="0dip" android:id="@+id/sc" 
        android:scrollbars="horizontal" android:layout_weight="1.0">
        <ImageView android:layout_width="fill_parent" 
            android:layout_height="fill_parent" android:src="@drawable/chips"/>
    </FrameLayout>
    <Button android:layout_width="fill_parent" android:layout_height="wrap_content" 
        android:text="Clear" android:onClick="clearHandler"/>     
</LinearLayout>