android - 添加 Canvas - Android

Question

我动态创建 Canvas :

Canvas canvas = new Canvas();

但是我怎样才能将它添加到我的 LinearLayout 中呢？

LinearLayout ll = new LinearLayout(this);

Answer 1

您可以使用简单的 addView 来完成，或者如果您正在做一些更复杂的事情，例如需要一个新线程来进行图形绘制，那么您可以使用自定义 SurfaceView 将其添加到您的 xml 布局中

    <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"
    />

然后创建一个名为 MyDraw 的类，它扩展了 SurfaceView，您可以在其中调用线程进行绘制。

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);
            }
    }
}