android实战项目二实现画板效果

实现画图板的效果ontouchevent

需要有一个自定义的组件用android绘图的重点

下面是自定义的类
先重写这个view的ontouchListener方法的得到手指的坐标点
再重写view的ondraw方法 来画出手指移动的轨迹

public class MypiantView extends View {
    private List<Point> allpoints = new ArrayList<Point>();;

    // 用容器来保存所有坐标
    public MypiantView(Context context, AttributeSet attrs) {
        super(context, attrs);
        super.setBackgroundColor(Color.WHITE);
        super.setOnTouchListener(new OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {
                Point point = new Point((int) event.getX(), (int) event.getY());
                if (event.getAction() == MotionEvent.ACTION_DOWN) {
                    allpoints = new ArrayList<Point>();// 初始化
                    allpoints.add(point);
                } else if (event.getAction() == MotionEvent.ACTION_UP) {
                    allpoints.add(point);
                } else if (event.getAction() == MotionEvent.ACTION_MOVE) {
                    allpoints.add(point);
                    MypiantView.this.postInvalidate();// 重新绘制
                }
                return true;// 表示不再执行了
            }
        });

    }

    // 重写andraw方法
    @Override
    protected void onDraw(Canvas canvas) {
        Paint paint = new Paint();
        paint.setColor(Color.RED);
        if (allpoints.size() > 1) {
            // 用集合来装点，遍历每个点
            Iterator<Point> iterator = allpoints.iterator();
            Point firstPoint = null;// 开始点
            Point lastpPoint = null;// 结束点

            while (iterator.hasNext()) {
                if (firstPoint == null) {// 找到开始点
                    firstPoint = (Point) iterator.next();
                } else {
                    if (lastpPoint != null) {
                        firstPoint = lastpPoint;
                    }
                    lastpPoint = (Point) iterator.next();
                    canvas.drawLine(firstPoint.x, firstPoint.y, lastpPoint.x, lastpPoint.y, paint);// 画线
                }
            }
        }
        super.onDraw(canvas);
    }
}

再配置xml文件将自定义view导入

<?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" >  
    <org.yayun.demo.MyPaintView  
        android:id="@+id/paintView"  
        android:layout_width="fill_parent"  
        android:layout_height="fill_parent" >  
    </org.yayun.demo.MyPaintView>  
</LinearLayout> 

最后在activity中引用布局文件xml

public class MyviewDraw extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        super.setContentView(R.layout.ontouchdraw);
    }
}

最后就可以运行了成功用手指在手机屏幕上画出了一条红线！！！