How can I display a code drawn line over other apps?

问题

Details: I would like to add a code drawn line (like you draw with canvas/paint) and display it over other applications.

I currently have an application that allows me to display an image over other application. See my Stackoverflow answer for my code. I have implemented the permission to do so:

android.permission.SYSTEM_ALERT_WINDOW

I have tried to add a canvas/paint to the WindowManager without errors, but my app crashed. I have tried searching for an answer, but have turned up empty.

If anyone can help me figure this out, you will be greatly appreciated!

To clarify: I would like this to be drawn where I can have it over other applications and where I can still interact with other applications. Also I've added a button functionality where I turn off/on a view with WindowManager addView and WindowManager removeView, but every time I add a view, it covers the entire area and I can no longer click the button to remove the view.

回答1:

I have found a way and will share here. If you want more of the code, use the link to my Stackoverflow answer that I also linked in my question.

I guess I wasn't setting up the correct code, or at lease all of it, until now.

DrawView.java

package com.example.floatingicon;

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{
    Paint paint = new Paint();

    public DrawView(Context context){
        super(context);
        paint.setColor(Color.BLACK);
    }

    @Override
    public void onDraw(Canvas canvas){
        canvas.drawLine(240, 0, 240, 620, paint);
        canvas.drawLine(0, 200, 480, 200, paint);
    }
}

This will draw a cross on the screen

MainService.java

import com.example.floatingicon.DrawView;

public class MainService extends Service
{
    private DrawView drawView;

    @Override
    public void onCreate()
    {
        drawView = new DrawView(this);

        final WindowManager.LayoutParams paramsDraw = new WindowManager.LayoutParams(
            WindowManager.LayoutParams.WRAP_CONTENT, 
            WindowManager.LayoutParams.WRAP_CONTENT, 
            WindowManager.LayoutParams.TYPE_PHONE,
            WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE, 
            PixelFormat.TRANSLUCENT);

        paramsDraw.gravity = Gravity.TOP | Gravity.LEFT;
        paramsDraw.x=0;
        paramsDraw.y=0;

        winManager.addView(drawView, paramsDraw);
    }
}

If you add that to the already existing code, it should work just fine.

来源：https://stackoverflow.com/questions/23681162/how-can-i-display-a-code-drawn-line-over-other-apps