android :在布局大小内拖动视图(场景大小)

public class MainActivity extends AppCompatActivity implements View.OnTouchListener {
    private float lastX, lastY;
    private View draggableView;

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

        draggableView = findViewById(R.id.draggable_view);
        draggableView.setOnTouchListener(this);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                lastX = event.getRawX();
                lastY = event.getRawY();
                break;
            case MotionEvent.ACTION_MOVE:
                float deltaX = event.getRawX() - lastX;
                float deltaY = event.getRawY() - lastY;

                float newX = v.getX() + deltaX;
                float newY = v.getY() + deltaY;

                // 边界检测
                newX = Math.max(0, Math.min(newX, v.getParent().getWidth() - v.getWidth()));
                newY = Math.max(0, Math.min(newY, v.getParent().getHeight() - v.getHeight()));

                v.setX(newX);
                v.setY(newY);

                lastX = event.getRawX();
                lastY = event.getRawY();
                break;
        }
        return true;
    }
}