android studio 开发 app ,四张图片，一张固定做为背景，另三张可以拖动，旋转，缩放的代码

你可以使用Android中的Drag and Drop API来实现拖动操作。以下是一个简单的示例：

首先在XML布局文件中添加一个ImageView来显示背景图片，然后添加另外三个ImageView来显示可拖动的图片：

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/background_img"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@drawable/background_image"/>

    <ImageView
        android:id="@+id/draggable_img1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/draggable_image1"/>

    <ImageView
        android:id="@+id/draggable_img2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/draggable_image2"/>

    <ImageView
        android:id="@+id/draggable_img3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/draggable_image3"/>

</RelativeLayout>

然后在Java代码中，将ImageView设置为可拖动，并添加旋转和缩放操作。在这个示例中，我们使用了Android中的GestureDetector和ScaleGestureDetector类来实现这些操作：

public class MainActivity extends AppCompatActivity implements View.OnTouchListener {

    private ImageView backgroundImg, draggableImg1, draggableImg2, draggableImg3;

    private int xDelta, yDelta;
    private float rotationDegrees = 0f;
    private float scale = 1f;
    private float lastTouchX, lastTouchY;

    private GestureDetector gestureDetector;
    private ScaleGestureDetector scaleGestureDetector;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        backgroundImg = findViewById(R.id.background_img);
        draggableImg1 = findViewById(R.id.draggable_img1);
        draggableImg2 = findViewById(R.id.draggable_img2);
        draggableImg3 = findViewById(R.id.draggable_img3);

        // 设置可拖动
        draggableImg1.setOnTouchListener(this);
        draggableImg2.setOnTouchListener(this);
        draggableImg3.setOnTouchListener(this);

        // 初始化GestureDetector和ScaleGestureDetector
        gestureDetector = new GestureDetector(this, new GestureListener());
        scaleGestureDetector = new ScaleGestureDetector(this, new ScaleListener());
    }

    @Override
    public boolean onTouch(View view, MotionEvent event) {
        final int x = (int) event.getRawX();
        final int y = (int) event.getRawY();

        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                // 计算偏移量
                RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
                xDelta = x - lParams.leftMargin;
                yDelta = y - lParams.topMargin;
                lastTouchX = event.getX();
                lastTouchY = event.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                // 更新位置
                RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view.getLayoutParams();
                layoutParams.leftMargin = x - xDelta;
                layoutParams.topMargin = y - yDelta;
                layoutParams.rightMargin = 0;
                layoutParams.bottomMargin = 0;
                view.setLayoutParams(layoutParams);

                // 处理旋转和缩放操作
                gestureDetector.onTouchEvent(event);
                scaleGestureDetector.onTouchEvent(event);
                break;
        }
        return true;
    }

    private class GestureListener extends GestureDetector.SimpleOnGestureListener {
        @Override
        public boolean onDown(MotionEvent e) {
            return true;
        }

        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            // 计算旋转角度
            rotationDegrees -= distanceX;
            // 旋转图片
            draggableImg1.setRotation(rotationDegrees);
            draggableImg2.setRotation(rotationDegrees);
            draggableImg3.setRotation(rotationDegrees);
            return true;
        }
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            // 计算缩放比例
            scale *= detector.getScaleFactor();
            scale = Math.max(0.1f, Math.min(scale, 5.0f));
            // 缩放图片
            draggableImg1.setScaleX(scale);
            draggableImg1.setScaleY(scale);
            draggableImg2.setScaleX(scale);
            draggableImg2.setScaleY(scale);
            draggableImg3.setScaleX(scale);
            draggableImg3.setScaleY(scale);
            return true;
        }
    }
}

这是一个简单的实现，你可以根据你的需求进行修改和扩展。