Android实现探照灯的功能

一、前言

由于最近项目需要，急需开发一个探照灯的功能，限定三天内完成，在网上搜了一整天，尝试各种实现方法，其实无外乎使用BitmapShader和ShapeDrawable在画布上画出源图片，还有一些使用其他语言的方法，比如canavas的clip相关的方法，但是都不能满足我的项目需求。第一个方法虽然可以实现探照灯的效果，缺点是必须要有源图像，而我都项目要求是不管你在哪个界面，都要能够直接探照到背景（就相当于被探照部分变透明了，直接看到后面）。最后只能想办法自己实现了，于是第二天想出了一个可行的方案，如下：

二、思路

根据需求，总结如下：

-探照灯功能
-探照灯可移动
-探照的部分透明
-在其他应用界面仍然可用

三、实现

废话不多说，直接上代码：

-1.实现Activity透明

<style name="TranspantTheme">
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:colorBackgroundCacheHint">@null</item>
        <item name="android:windowIsTranslucent">true</item>
        <item name="android:windowAnimationStyle">@android:style/Animation</item>
        <item name="android:windowNoTitle">true</item>
        <item name="android:windowContentOverlay">@null</item>
    </style>

在配置文件中给Activity添加如上主题，即将

android:theme="@style/theApp"

改为：

android:theme="@style/TranspantTheme"

这样子启动起来的Activity就是个透明的。

-2.退出应用仍然可用（在其他应用界面仍然可用）

使用WindowManager：

 private WindowManager windowManager;
 private WindowManager.LayoutParams wmParams,wm;
 private int wmType;
 private void initView() {
      
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            wmType = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
        } else {
            wmType = WindowManager.LayoutParams.TYPE_PHONE;
        }

        windowManager = (WindowManager) this.getSystemService(Context.WINDOW_SERVICE);

        wmParams = new WindowManager.LayoutParams();
        wmParams.type = wmType;
        wmParams.screenOrientation = ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE;
        wmParams.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
        wmParams.gravity = Gravity.LEFT | Gravity.TOP;
        wmParams.x = 0;
        wmParams.y = 0;
        wmParams.width = WindowManager.LayoutParams.MATCH_PARENT;
        wmParams.height = WindowManager.LayoutParams.MATCH_PARENT;
        wmParams.format = PixelFormat.RGBA_8888;

        wm = new WindowManager.LayoutParams();
        wm.type = wmType;
        wm.screenOrientation = ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE;
        wm.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
        wm.gravity = Gravity.RIGHT | Gravity.TOP;
        wm.x = 0;
        wm.y = 0;
        wm.width = 100;
        wm.height = 100;
        wm.format = PixelFormat.RGBA_8888;
    }

先初始化好windowManager，别忘了在Activity配置文件中设置为横屏显示（受到windowManager影响）

-3.定义实现探照灯功能的View

直接上代码：

public class MyImageView extends android.support.v7.widget.AppCompatImageView{
    private Paint paint1,paint2;//两只笔
    private float x=200,y=200;
    private int screenWidth,screenHeight;

    public MyImageView(Context context) {
        super(context);
        initData();
    }

    private synchronized void initData() {
        //获取屏幕宽高
        DisplayMetrics metrics = getResources().getDisplayMetrics();
        screenWidth = metrics.widthPixels;
        screenHeight = metrics.heightPixels;
        setMyEraseSize(40);
        setColor(Color.GRAY);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        drawBackground(canvas);
        drawMyCircle(canvas);
    }

    //画圆
    private void drawMyCircle(Canvas canvas) {
        canvas.drawCircle(x,y,100,paint1);
    }

    //画背景颜色
    private void drawBackground(Canvas canvas) {
        Rect rect=new Rect(0,0,screenWidth,screenHeight);
        canvas.drawRect(rect,paint2);
    }

    public boolean onTouchEvent(MotionEvent event){
        final int x = (int) event.getX();// 获取当前触摸点的X轴坐标
        final int y = (int) event.getY(); // 获取当前触摸点的Y轴坐标
        this.x=x;this.y=y;
        invalidate(); // 重绘画布
        return true;
    }

    //设置橡皮擦大小
    public void setMyEraseSize(int size){
        paint1= new Paint();
        paint1.reset();
        paint1.setAntiAlias(true);//抗锯齿
        paint1.setDither(true);//防抖动
        paint1.setColor(Color.WHITE);
        paint1.setStrokeWidth(size);
        paint1.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
        BlurMaskFilter bmf=new BlurMaskFilter((0.5f), BlurMaskFilter.Blur.SOLID);
        paint1.setMaskFilter(bmf);
        paint1.setStyle(Paint.Style.FILL);
        paint1.setStrokeJoin(Paint.Join.ROUND);
        paint1.setStrokeCap(Paint.Cap.ROUND);
        paint1.setSubpixelText(true);
        paint1.setTextSize(50);
    }

    //设置比颜色
    public void setColor(int color){
        paint2=new Paint();
        paint2.reset();
        paint2.setAntiAlias(true);//抗锯齿
        paint2.setDither(true);//防抖动
        paint2.setStrokeWidth(5);
        paint2.setTextSize(50);
        paint2.setSubpixelText(true);
        BlurMaskFilter bmf=new BlurMaskFilter((0.5f), BlurMaskFilter.Blur.SOLID);
        paint2.setMaskFilter(bmf);
        paint2.setPathEffect(new CornerPathEffect(20));
        paint2.setStyle(Paint.Style.FILL);
        paint2.setStrokeJoin(Paint.Join.ROUND);
        paint2.setStrokeCap(Paint.Cap.ROUND);
        paint2.setColor(color);
    }
}

解析：
简单来说，其实就是采用思路：
用两只笔，一只负责画背景（黑布），一只负责橡皮擦的功能（画圆），这时由于Activity是透明的，所以就可以直接看到下一层内容，然后在手指移动时更新橡皮擦（圆形）的位置，重绘就可以了。代码很简单，相信你能看懂！！
怎么样？是不是很简单？
为了能让大家看到效果，这里接着加上这个demo的其他方法：

public class MainActivity extends Activity {
    private WindowManager windowManager;
    private WindowManager.LayoutParams wmParams,wm;
    private int wmType;
    private MyImageView myImageView;
    private ImageView view;
    private final int OVERLAY_PERMISSION_REQ_CODE = 1234;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (checkBallPermission()) startProgram();
    }

   //检查是否有悬浮窗权限
    private boolean checkBallPermission()
    {
        if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
        {
            if(!Settings.canDrawOverlays(this)) {
                Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + getPackageName()));
                startActivityForResult(intent,OVERLAY_PERMISSION_REQ_CODE);
                return false;
            }
        }
        return true;
    }

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        Log.e("SearchPrint","onActivityResult");
        if (requestCode == OVERLAY_PERMISSION_REQ_CODE) {
            if(android.os.Build.VERSION.SDK_INT>=Build.VERSION_CODES.M) {
                if (!Settings.canDrawOverlays(this))
                {
                    Toast.makeText(MainActivity.this, this.getResources().getString(R.string.ballfail), Toast.LENGTH_SHORT).show();
                    this.finish();
                }
                else {
                    startProgram();
                }
            }
        }
    }

    private void startProgram() {
        initView();
        show();
        addListener();
    }

    private void addListener() {
        view.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                hide();
                finish();
            }
        });
    }

    private void hide(){
        try{
            windowManager.removeView(myImageView);
            windowManager.removeView(view);
        }catch (Exception e){
            e.printStackTrace();
            Log.e("SearchPrint","removeView:"+e.getMessage());
        }
    }

    private void show() {
        try{
            windowManager.addView(myImageView,wmParams);
            windowManager.addView(view,wm);
        }catch (Exception e){
            e.printStackTrace();
            Log.e("SearchPrint","addView:"+e.getMessage());
        }
    }

    private void initView() {
        myImageView=new MyImageView(this);
        view=new ImageView(this);
        view.setBackgroundResource(R.drawable.exit);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            wmType = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
        } else {
            wmType = WindowManager.LayoutParams.TYPE_PHONE;
        }

        windowManager = (WindowManager) this.getSystemService(Context.WINDOW_SERVICE);

        wmParams = new WindowManager.LayoutParams();
        wmParams.type = wmType;
        wmParams.screenOrientation = ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE;
        wmParams.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
        wmParams.gravity = Gravity.LEFT | Gravity.TOP;
        wmParams.x = 0;
        wmParams.y = 0;
        wmParams.width = WindowManager.LayoutParams.MATCH_PARENT;
        wmParams.height = WindowManager.LayoutParams.MATCH_PARENT;
        wmParams.format = PixelFormat.RGBA_8888;

        wm = new WindowManager.LayoutParams();
        wm.type = wmType;
        wm.screenOrientation = ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE;
        wm.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;
        wm.gravity = Gravity.RIGHT | Gravity.TOP;
        wm.x = 0;
        wm.y = 0;
        wm.width = 100;
        wm.height = 100;
        wm.format = PixelFormat.RGBA_8888;
    }
}

四、其他

如果需要实现探照出来的是一张自定义的图片，那更简单，直接结合使用BitmapShader和ShapeDrawable，网上有不少方法，你还可以添加个从图库里面选择图片的方法，都挺简单的，由于篇幅限制，这里就不再叙述了。

原创文章，转载请加上链接https://www.jianshu.com/p/438e5c7f3ba7

转载于:https://www.jianshu.com/p/438e5c7f3ba7