Android编程动态创建视图View的方法

在Android开发中，在Activity中关联视图View是一般使用setContentView方法，该方法一种参数是使用XML资源直接创建：setContentView (int layoutResID)，指定layout中的一个XML的ID即可，这种方法简单。另一个方法是setContentView(android.view.View)，参数是指定一个视图View对象，这种方法可以使用自定义的视图类。

在一些场合中，需要对View进行一些定制处理，比如获取到Canvas进行图像绘制，需要重载View::onDraw方法，这时需要对View进行派生一个类，重载所需要的方法，然后使用setContentView(android.view.View)与Activity进行关联，具体代码举例如下：

public class temp extends Activity {
    /** 在Activity中关联视图view */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new DrawView(this));
    }
    /*自定义类*/
    private class DrawView extends View {
        private Paint paint;
        /**
         * Constructor
         */
        public DrawView(Context context) {
            super(context);
            paint = new Paint();
            // set's the paint's colour
            paint.setColor(Color.GREEN);
            // set's paint's text size
            paint.setTextSize(25);
            // smooth's out the edges of what is being drawn
            paint.setAntiAlias(true);
        }

        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            canvas.drawText("Hello World", 5, 30, paint);
            // if the view is visible onDraw will be called at some point in the
            // future
            invalidate();
        }
    }
}

第二个例子，动态绘图

public class MyAndroidProjectActivity extends Activity {
    /** Called when the activity is first created. */
    /*
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }*/
	static int times = 1;
	 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new DrawView(this));
 
    }
    private class DrawView extends View {
    	Paint vPaint = new Paint();
        private int i = 0;
        public DrawView(Context context) {
            super(context);

        }

        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            System.out.println("this run " + (times++) +" times!");

            // 设定绘图样式
            vPaint.setColor( 0xff00ffff ); //画笔颜色
            vPaint.setAntiAlias( true );   //反锯齿
            vPaint.setStyle( Paint.Style.STROKE );

            // 绘制一个弧形
            canvas.drawArc(new RectF(60, 120, 260, 320), 0, i, true, vPaint );

            // 弧形角度
            if( (i+=10) > 360 )
                i = 0;

            // 重绘, 再一次执行onDraw 程序
            invalidate();
        }
    }
        
}