Add a canvas - Android

I dynamically create a canvas with:

Canvas canvas = new Canvas();

But how can I add it to my LinearLayout?

LinearLayout ll = new Line开发者_开发问答arLayout(this);

You can either do it with a simple addView or if you are doing something more complex like needing a new thread to do your graphics painting then you can add it to your xml layout with a custom SurfaceView

    <com.util.MyDraw
    android:id="@+id/surfaceView" 
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="10px"
    android:layout_marginLeft="10px"
    android:layout_marginRight="10px"
    android:layout_below="@+id/spinner1"
    />

Then create a class called MyDraw that extends SurfaceView and in there you can call your Thread to paint.

package com.util;

public class MyDraw extends SurfaceView implements Callback {

    private MyThread myThread;
    private SurfaceHolder holder;
    private Paint paint;
    Path path;
    public LinkedList<Integer> list; {
         list = new LinkedList<Integer>();
    }

    public MyDraw(Context context) {
        super(context);
        holder = getHolder();
        holder.addCallback(this);
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(2);
        paint.setColor(Color.GREEN);
        path = new Path();
    }

    public void surfaceCreated(SurfaceHolder holder) {
        myThread = new MyThread(holder, this);
        myThread.setFlag(true);
        myThread.start();
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {}

    public void surfaceDestroyed(SurfaceHolder holder) {
        myThread.setFlag(false);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        path.rewind();
        path.reset();

        if (canvas != null) {
            canvas.drawColor(Color.BLACK);

            if (list != null && list.size() > 0) {
                path.moveTo(0, list.get(0));

                int sec;
                for(sec = 1; sec < list.size(); sec++) {
                    path.lineTo(sec, (list.get(sec)/divFactor));
                }

                canvas.drawPath(path, paint);
            }
    }
}

This replaces my earlier answer (which was totally off). A Canvas is not something to be added to a layout. (If you're familiar with J2SE, it's the Android analogue to java.awt.Graphics.)

Perhaps you want to add a view where you can do your own drawing (using a Canvas). For this, you can use a SurfaceView or you can define your own custom View class as described here.

setContentView(canvasView); //add canvas view (set canvasView as main view)
linearLayout.addView(canvasView); //linearLayout add canvasView

public class CanvasView extends View{

public CanvasView(Context c){
super(c);
}

public void onDraw(Canvas canvas){
//do your draw methods
}

}