作业如下：在android屏幕上面任意画线 2011-12-1，从网上看到了，参考了，修改了，成功了，给大家分享下

package feng.f121.drawline;//本人创建的包名，每人有每人的不同的包

import java.security.PublicKey;

import android.R.integer;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;

//新建一个类继承View

public class Drawl extends View{

private int mov_x;//声明起点坐标
private int mov_y;
private Paint paint;//声明画笔
private Canvas canvas;//画布
private Bitmap bitmap;//位图
private int blcolor;
public Drawl(Context context) {
super(context);
paint=new Paint(Paint.DITHER_FLAG);//创建一个画笔
bitmap = Bitmap.createBitmap(480, 854, Bitmap.Config.ARGB_8888); //设置位图的宽高
canvas=new Canvas();
canvas.setBitmap(bitmap);

paint.setStyle(Style.STROKE);//设置非填充
paint.setStrokeWidth(5);//笔宽5像素
paint.setColor(Color.RED);//设置为红笔
paint.setAntiAlias(true);//锯齿不显示

}

//画位图
@Override
protected void onDraw(Canvas canvas) {
//super.onDraw(canvas);
canvas.drawBitmap(bitmap,0,0,null);
}
//触摸事件
@Override
public boolean onTouchEvent(MotionEvent event) {
if (event.getAction()==MotionEvent.ACTION_MOVE) {//如果拖动
canvas.drawLine(mov_x, mov_y, event.getX(), event.getY(), paint);//画线
invalidate();
}
if (event.getAction()==MotionEvent.ACTION_DOWN) {//如果点击
mov_x=(int) event.getX();
mov_y=(int) event.getY();
canvas.drawPoint(mov_x, mov_y, paint);//画点
invalidate();

}
mov_x=(int) event.getX();
mov_y=(int) event.getY();
return true;
}


}

在Activity中

public class DrawLine extends Activity {
private Drawl bDrawl;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
bDrawl=new Drawl(this);
setContentView(bDrawl);//将view视图放到Activity中显示
}