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我正在尝试实现一个应用程序，该应用程序使用android.permission.SYSTEM_ALERT_WINDOW. 它在屏幕上显示一条直线（ImageView），可以拖动（单指）、缩放（双指缩放）和旋转（双指）。

在此chatHead 代码ImageView的帮助下，我可以在屏幕上拖动。但是我无法在此服务上应用缩放和旋转，但缩放和旋转在应用于扩展的正常活动时效果很好（使用这个问题的第二个答案）。ImageViewAppCompatActivity

我在下面提供我的完整代码以供参考。

HomeActivity.java

从HomeActivity我打电话给Service(LineService)和AppCompatActivity(LineActivity)。我无法viewTransformation()从LineActivityin实现该功能，LineService因为它是一个Service. 有没有其他方法可以在LineService.

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.provider.Settings;
import android.view.View;
import android.widget.Button;

public class HomeActivity extends Activity {

    public final static int REQUEST_CODE = 5463&0xffffff00;
    Button buttonLineService;
    Button buttonLineActivity;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        buttonLineService = findViewById(R.id.buttonLineService);
        buttonLineActivity = findViewById(R.id.buttonLineActivity);

        checkDrawOverlayPermission();

        buttonLineService.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(getApplicationContext(), LineService.class);
                startService(i);
                finish();
            }
        });
        buttonLineActivity.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(getApplicationContext(), LineActivity.class);
                startActivity(i);
                finish();
            }
        });
    }
        public void checkDrawOverlayPermission() {
            /** check if we already  have permission to draw over other apps */
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && !Settings.canDrawOverlays(HomeActivity.this)) {
//            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O &&
//                    (AppOpsManager.OPSTR_SYSTEM_ALERT_WINDOW.equals(op) &&
//                            packageName.equals(mContext.getPackageName()))) {
                /** if not construct intent to request permission */
                Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
                        Uri.parse("package:" + getPackageName()));
                /** request permission via start activity for result */
                startActivityForResult(intent, REQUEST_CODE);
            }
        }

    @Override
    protected void onActivityResult(int requestCode, int resultCode,  Intent data) {
        /** check if received result code
         is equal our requested code for draw permission  */
        if (requestCode == REQUEST_CODE) {
       // ** if so check once again if we have permission */
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && Settings.canDrawOverlays(this)) {
                // continue here - permission was granted
            }
        }
    }
}

活动主页.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".HomeActivity">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="100dp"
    android:orientation="vertical"
    android:layout_centerHorizontal="true">

    <Button
        android:id="@+id/buttonPermission"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Provide Overlay Permission"/>

    <Button
        android:id="@+id/buttonLineService"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Open Line Service"/>

    <Button
        android:id="@+id/buttonLineActivity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Open Line Activity"/>

</LinearLayout>

</RelativeLayout>

LineService.java

import android.annotation.SuppressLint;
import android.app.Service;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.os.Build;
import android.os.IBinder;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.ImageView;

public class LineService extends Service {

    private WindowManager windowManager;
    private ImageView line;

    @Override
    public IBinder onBind(Intent intent) {
        // Not used
        return null;
    }

    @SuppressLint("ClickableViewAccessibility")
    @Override
    public void onCreate() {
        super.onCreate();

        windowManager = (WindowManager) getSystemService(WINDOW_SERVICE);

        line = new ImageView(this);
        line.setImageResource(R.drawable.line);

        final WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT,
                Build.VERSION.SDK_INT >= Build.VERSION_CODES.O ? WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY : WindowManager.LayoutParams.TYPE_PHONE,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                PixelFormat.TRANSLUCENT);

        params.gravity = Gravity.CENTER;
        params.x = 0;
        params.y = 100;

        windowManager.addView(line, params);


        line.setOnTouchListener(new View.OnTouchListener() {
            private int initialX;
            private int initialY;
            private float initialTouchX;
            private float initialTouchY;

            @Override
            public boolean onTouch(View v, MotionEvent event) {

                if (event.getPointerCount() == 2) {

                } else {
                    switch (event.getAction()) {
                        case MotionEvent.ACTION_DOWN:
                            initialX = params.x;
                            initialY = params.y;
                            initialTouchX = event.getRawX();
                            initialTouchY = event.getRawY();
                            return true;
                        case MotionEvent.ACTION_UP:
                            return true;
                        case MotionEvent.ACTION_MOVE:
                            params.x = initialX + (int) (event.getRawX() - initialTouchX);
                            params.y = initialY + (int) (event.getRawY() - initialTouchY);
                            windowManager.updateViewLayout(line, params);
                            return true;
                    }
                }
                return false;
            }
        });
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        if (line != null) windowManager.removeView(line);
    }
}

LineActivity.java

import android.annotation.SuppressLint;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.graphics.PointF;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.widget.ImageView;

public class LineActivity extends AppCompatActivity {

    private ImageView line;

    float[] lastEvent = null;
    float d = 0f;
    float newRot = 0f;
    private boolean isZoomAndRotate;
    private boolean isOutSide;
    private static final int NONE = 0;
    private static final int DRAG = 1;
    private static final int ZOOM = 2;
    private int mode = NONE;
    private PointF start = new PointF();
    private PointF mid = new PointF();
    float oldDist = 1f;
    private float xCoOrdinate, yCoOrdinate;

    @SuppressLint("ClickableViewAccessibility")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_test_line);

        final WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT,
                Build.VERSION.SDK_INT >= Build.VERSION_CODES.O ? WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY : WindowManager.LayoutParams.TYPE_PHONE,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
                PixelFormat.TRANSLUCENT);

        params.gravity = Gravity.CENTER;
        params.x = 0;
        params.y = 100;

        line = findViewById(R.id.imageview_trash);

        line.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                ImageView view = (ImageView) v;
                view.bringToFront();
                viewTransformation(view, event);
                return true;
            }
        });
    }

    private void viewTransformation(View view, MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                xCoOrdinate = view.getX() - event.getRawX();
                yCoOrdinate = view.getY() - event.getRawY();

                start.set(event.getX(), event.getY());
                isOutSide = false;
                mode = DRAG;
                lastEvent = null;
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                oldDist = spacing(event);
                if (oldDist > 10f) {
                    midPoint(mid, event);
                    mode = ZOOM;
                }

                lastEvent = new float[4];
                lastEvent[0] = event.getX(0);
                lastEvent[1] = event.getX(1);
                lastEvent[2] = event.getY(0);
                lastEvent[3] = event.getY(1);
                d = rotation(event);
                break;
            case MotionEvent.ACTION_UP:
                isZoomAndRotate = false;
                if (mode == DRAG) {
                    float x = event.getX();
                    float y = event.getY();
                }
            case MotionEvent.ACTION_OUTSIDE:
                isOutSide = true;
                mode = NONE;
                lastEvent = null;
            case MotionEvent.ACTION_POINTER_UP:
                mode = NONE;
                lastEvent = null;
                break;
            case MotionEvent.ACTION_MOVE:
                if (!isOutSide) {
                    if (mode == DRAG) {
                        isZoomAndRotate = false;
                        view.animate().x(event.getRawX() + xCoOrdinate).y(event.getRawY() + yCoOrdinate).setDuration(0).start();
                    }
                    if (mode == ZOOM && event.getPointerCount() == 2) {
                        float newDist1 = spacing(event);
                        if (newDist1 > 10f) {
                            float scale = newDist1 / oldDist * view.getScaleX();
                            view.setScaleX(scale);
                            view.setScaleY(scale);
                        }
                        if (lastEvent != null) {
                            newRot = rotation(event);
                            view.setRotation((float) (view.getRotation() + (newRot - d)));
                        }
                    }
                }
                break;
        }
    }

    private float rotation(MotionEvent event) {
        double delta_x = (event.getX(0) - event.getX(1));
        double delta_y = (event.getY(0) - event.getY(1));
        double radians = Math.atan2(delta_y, delta_x);
        return (float) Math.toDegrees(radians);
    }

    private float spacing(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (int) Math.sqrt(x * x + y * y);
    }

    private void midPoint(PointF point, MotionEvent event) {
        float x = event.getX(0) + event.getX(1);
        float y = event.getY(0) + event.getY(1);
        point.set(x / 2, y / 2);
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();
        Intent i = new Intent(getApplicationContext(), HomeActivity.class);
        startActivity(i);
        finish();
    }
}

activity_test_line.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".LineActivity">

    <ImageView
        android:id="@+id/imageview_trash"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/line" />

</LinearLayout>

行.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <gradient
        android:startColor="#FFFF0000"
        android:endColor="#80FF00FF"
        android:angle="45"/>
    <padding android:left="200dp"
        android:top="200dp"
        android:right="200dp"
        android:bottom="200dp" />
    <corners android:radius="8dp" />
    <size android:width="200dp"
        android:height="5dp"/>
</shape>
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