初学Android,开发自定义的View(四)

下面是一个小例子，跟随手指的小球

创建一个继承自View的类，用来绘制圆形

package WangLi.CustomView.Space;import android.content.Context;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.view.View;public class DrawView extends View {    public float currentX = 40;    public float currentY = 50;public DrawView(Context context) {super(context);// TODO Auto-generated constructor stub}@Overridepublic void onDraw(Canvas canvas){super.onDraw(canvas);//创建画笔Paint p = new Paint();//设置画笔颜色p.setColor(Color.RED);//绘制一个小圆(作为小球)canvas.drawCircle(currentX, currentY, 15, p);}

下面是该应用的Activity类

package WangLi.CustomView.Space;import android.app.Activity;import android.os.Bundle;import android.view.View;import android.view.View.OnTouchListener;import android.widget.LinearLayout;import android.view.MotionEvent;public class CustomView extends Activity {    /** Called when the activity is first created. */    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        //获取LinearLayout布局容器        LinearLayout root = (LinearLayout)findViewById(R.id.root);        //创建DrewView组件        final DrawView draw = new DrawView(this);        //设置自定义组件的最大宽度,高度        draw.setMinimumWidth(300);        draw.setMinimumHeight(500);        //为draw组件绑定Touch事件        draw.setOnTouchListener(new OnTouchListener(){        public boolean onTouch(View view, MotionEvent event)         {        //修改draw组件的currentX,currentY两个属性        draw.currentX = event.getX();        draw.currentY = event.getY();        //通知draw组件重绘        draw.invalidate();        //返回true表明处理方法已经处理该事件        return true;        }        });        root.addView(draw);    }}

运行效果如下

这个红色的球，在手机模拟器中，鼠标按下(模拟Touch事件)就会跟着光标移动

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