[移动开发]android 实现划线绘制效果

在android设备中查看检测屏幕是否触摸正常时，通常会采用在页面使用手指触摸，那我们就来完成一下这个效果。

如图所示：

首先页面的布局很简单只需要一个全屏的布局即可，这个我们还增加了一个title，代码如下：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/dd">

    <LinearLayout
        android:id="@+id/ll_title"
        android:layout_width="match_parent"
        android:layout_height="45dp"
        android:orientation="vertical">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center"
            android:textColor="#0099ff"
            android:text="划线测试 手指抬起不清除"/>
    </LinearLayout>

    <LinearLayout
        android:id="@+id/ll_bg"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

    </LinearLayout>
</RelativeLayout>

接下来就是对应的activity代码，实现了一个自定义的view,使用到了手指的触摸，然后实现canvas绘图效果，在处理一下当触摸按下时的动作逻辑，让标题VISIBLE或者GONE即可全屏显示，又能显示标题。

/**
* @Author: glc
* @Date: 2022/02/23
* @Time: 14:46
* @Description: 划线测试 手抬起不清除
*/
public class LineActivity2 extends AppCompatActivity {
private int width;
private int height;
private LinearLayout llbg;
private LinearLayout llTitle;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        WindowManager windowManager = getWindowManager();
        width = windowManager.getDefaultDisplay().getWidth();
        height = windowManager.getDefaultDisplay().getHeight();
        setContentView(R.layout.activity_line2);
        llbg=findViewById(R.id.ll_bg);
        llTitle=findViewById(R.id.ll_title);
        llbg.addView(new Drawl(this));
    }

    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.ANTI_ALIAS_FLAG);//创建一个画笔
            bitmap = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888); //设置位图的宽高
            canvas=new Canvas();
            canvas.setBitmap(bitmap);

            paint.setStyle(Paint.Style.STROKE);//设置非填充
            paint.setStrokeWidth(30);//笔宽15像素
            paint.setColor(Color.RED);//设置为红笔
            paint.setAntiAlias(true);//锯齿不显示
            paint.setDither(true);
            paint.setStrokeJoin(Paint.Join.ROUND);//设置图像的结合方式
            paint.setStrokeCap(Paint.Cap.ROUND);//设置画笔为圆形样式

        }

        //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();
                llTitle.setVisibility(GONE);
            }
            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();
                llTitle.setVisibility(GONE);
            }
            if(event.getAction()==MotionEvent.ACTION_UP){
                llTitle.setVisibility(VISIBLE);

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


    }

}